1.0.0 Building as a System

CHAPTER 1.0 INDEX

1.0.1 Building : A system for inhabitation

1.0.2 Categories of Building Systems

1.0.3 How Building Systems emerge

1.0.4 Building User and the Environment

1.0.0 BUILDING AS A SYSTEM

1.0.1 BUILDING : A SYSTEM FOR INHABITATION

Keywords: Parts / Components / System / a unique personality / a coherent character / a man-made system / natural system / a physical system / conceptual or non physical system / universe / user / independent or mutually less related systems / intense coherence / biological system / built-in capacities or reserves / strategical planning / synergetic devices / consume energy / byproducts.

A building is a very complex entity made up of many parts, components and systems. Some Parts of the building come together to form a Component. Parts and Components function in unison to form a System. A system has twofold identity: a unique personality of what it does, and a coherent character of how it carries out its functions. The 'first identity makes a system substantially self-sufficient', but the 'second identity makes it a participant of a larger system'.

A building is a man-made system compared to many natural systems (such as weather, ecological, solar etc.). It is a physical system unlike many 'conceptual' or nonphysical systems (such as information, taxation etc.). Buildings are physical entities composed of many elemental units. Buildings have systems of form and size, which render subsystems like scaling, modulation, proportion, hierarchy, patterns, etc. These subsystems in reference to the Universe provide orientation, siting, location, etc., and in association of the User offer left-right positioning, sense of vertical and equilibrium, anthropometric functions and sensorial values.

A building can be perceived as a very large and complex system consisting of many different types of systems and subsystems. The systems are customarily categorised in terms of what they do: such as Structural, Architectural, Interior, Electrical, Mechanical, Air-conditioning etc. Some of these are fairly independent or mutually less related systems, and so can be installed, replaced or removed without many of the consequential effects. However, other systems have very intense coherence, and so once installed cannot be easily removed or replaced without affecting other systems.

Buildings have emulated the biological system of live beings. Buildings are designed with not only built-in capacities or reserves, but designed to be responsive, through strategical planning and synergetic devices. Buildings consume energy to be a functional system, and as consequence of it, generate byproducts.

1.0.2 CATEGORIES OF BUILDING SYSTEMS

Keywords: system for inhabitation / structural and nonstructural system swap their roles.

A building can be defined as a system for inhabitation. The building or the shell can be built exclusively out of structural systems, but for inhabitation many other subsystems must be incorporated into it. These incorporated subsystems have no or a very little structural role, though may depend on the structure to be operative. All subsystems of the buildings cannot be typecasted neatly as structural versus nonstructural entities. There are several reasons for this. Structural and Nonstructural systems swap their roles under specific conditions. For example a door or a window frame of opening systems may carry some loads in an earthquake like a situation. Inversely, a structural system may become latent or redundant, as for example a retaining wall of a swimming pool filled in on both sides may not be required to act as a retaining structure. In both types of swapping of roles, the changeover may be temporary, permanent, reversible or nonreversible.

Keywords: STRUCTURAL SYSTEMS / constancy / subsystems repositioned or removed / NONSTRUCTURAL SYSTEMS / TYPES OF NONSTRUCTURAL SYSTEMS / Protective systems / Filler systems / Independent systems / building as a composite system / CONSIDERATIONS FOR A BUILDING AS A COMPOSITE SYSTEM / Identity elemental units / Location, position, and orientation / Schedules and conditions of occurrence / Nature of interrelationships / Design compulsions / Technological relevance / User considerations / User relevance / Environmental concerns / Operational aspects / Social values / Economics / Occupation and Inhabitation factors.

STRUCTURAL SYSTEMS: A structural system by its intrinsic nature, composition, position, or arrangement, provides a whole that stays stable, in equilibrium, or constant (yet may be mobile like a ship, spacecraft etc.). The structural subsystems of a building system must exist in the required location or be available at the required moment and duration to achieve the distinctive constancy. The stability of a building is disturbed, when the structural subsystems are repositioned or removed. Structural systems of the building seem to be well integrated, because by being together they achieve constancy, which is fundamental to a structure's being.

NON STRUCTURAL SYSTEMS: Non structural systems of a building apparently have no role to play in the constancy of the building. Subsystems within a building that do not affect the constancy of a building may be called nonstructural systems (e.g. partition walls, doors, windows, finishes, etc.). Non structural systems though useless in structural sense, are not totally dispensable. Many nonstructural systems protect the structural elements, like plaster, walls, claddings etc. Some nonstructural systems achieve their own stability by depending on the structural systems, e.g. a stretched net or a sail. Nonstructural systems need not be integrated with the structure so are replaceable or relocatable.

TYPES OF NON STRUCTURAL SYSTEMS used in a building:

1 Protective systems: that cover the structural systems and non structural systems, e.g. plasters, waterproofing, roofing.

2 Filler systems: fill up the gaps or spaces between structural subsystems, e.g. non load-bearing walls, joints.

3 Independent systems are complete systems by themselves that independently provide peculiar functionality, e.g. air conditioning, illumination, communication.

CONSIDERATIONS FOR A BUILDING AS A COMPOSITE SYSTEM:

Identity elemental units such as parts, components and subsystems.

Location, position, and orientation of the elemental units within the system (the building).

Schedules and conditions of occurrence or being relevant for the elemental units within the system (the building).

Nature of interrelationships between the elemental units, such as: synergy, coordinated behaviour, dependency, autonomy, and also: order, patterns, sequence, proportion, modulation system etc. involved.

Design compulsions such as minimum standards, codes, laws, regulations.

Technological relevance: Materials, specifications, experience, skills that are required.

User considerations: anthropometric and ergonomics, safety aspects such as hazards, risk management, sensual qualities, aesthetics.

User relevance in terms of novelty, tradition, vogue.

Environmental concerns: ecological value, disposal mode.

Operational aspects: repair, maintenance, replacement, accidental and malicious damage.

Social values such as acceptability, relevance, validity.

Economics such as value, cost, price.

Occupation and Inhabitation factors: life span, adaptability.

1.0.3 HOW BUILDING SYSTEMS EMERGE

1.0.4 BUILDING, USER AND THE ENVIRONMENT

Keywords: Invent a novel entity / Improvise important subsystems / Upgrade the working of the system / Adopt subsystems / Universalize systems Provide distinct intra connectivity / Facilitate networking capabilities / Provide for greater integration.

Building as system emerges at many levels and modes, some of these are:

Invent a novel entity using none or few of the existing subsystems, to replace several existing subsystems.

A window like opening system consists of many sub systems like grills, glass, railing, filters (jalis, nets), awnings, weather sheds, ventilation, safety and security hardware etc., but a comprehensive device can replace all such sub systems.

Improvise important subsystems to substantially transform the physical nature of the main system.

Installing an elevator or air-conditioning system into an old building completely transforms its nature.

Upgrade the working of the system by rationally relocating and time scheduling the various subsystems.

Adopt subsystems as offered by others such as: designers, innovators, inventors, vendors, through facilitation and customization.

Universalize systems by following standards, codes and protocols. Follow international practices such for Quality -QMS, Environment -EMS, etc.

Provide distinct intra connectivity between subsystems through a distinctive network or an ancillary subsystem.

Facilitate networking capabilities between systems with a view to achieve a larger system, through provision of nodes, interfaces.

Provide for greater integration between physical and nonphysical subsystems.

Keywords: technological up-gradation of building as a system / efficient system / comprehensive system / spatial rearrangement / rescheduling / use and environmental relevance / greater productivity / use of nonphysical systems / Changes in buildings / Intentional changes / Circumstantial changes / Environmental changes / User on occupation customises the building / Building begins to affect the user / Environment moulds the building / Building impacts the environment.

A building as a complex system is designed to function in an environment and inhabited by a user. A building affects and gets affected by the user and environment. (For detailed discussion, refer: notes on Alterations and Renovations) The building's innumerable systems are permanent, replaceable or up-gradable. The technological up-gradation of building as a system occurs through:

Replacement by an efficient system.

Elimination of several sub systems by adoption of a comprehensive system.

Integration of several systems by spatial rearrangement or rescheduling.

Regrouping the systems by their user and environmental relevance or affinities so that systems operate with greater productivity.

Greater use of nonphysical systems instead of action elements, sensing mechanisms, control elements, decision elements, connecting elements, distancing elements, converters etc. (for more see: 2.0.2).

Changes in buildings are:

Intentional changes such as: functional, technological upgrading, styling.

Circumstantial changes such as: due to ageing, wear and tear of use, over-use, under-use, non use, and mis-use).

Environmental changes: some major categories are listed here:

1 User on occupation customises the building by self-help, but changing only the familiar and easily removable subsystems. The user has to hire semiskilled crafts-persons, or retain specialists or professionals like architects, interior designers, engineers, etc. for altering partially integrated or coordinated subsystems.

2 Building begins to affect the user, through its awe, form, discipline, flexibility, unyielding rigidity, historical values, location conditions or setting, economics considerations, perceived stability, and expected life, etc.

3 Environment moulds the building, nominally at a very consistent pace and in a predictable manner. Some changes are of imperceptible measures and often ignored till the cumulative effect is beyond remedial correction. The environment also changes the building at an inconsistent rate and unpredictably, so all precautions prove useless.

4 Building impacts the environment in many ways. It causes changes in the surroundings by its presence, operations, and ultimately on its demise, demolition and disposal. A benign presence is one that disturbs the environment for small time scale and over minor extent, compared to very long lasting and extensive disturbances to the balanced state. A building has nine lives like a cat. A building reincarnates itself in spite of disintegration of many of its sub systems. A building may lose its original form and functional identity, yet continue to be relevant as a shell for a different nature of occupation.

2.0 PARTS COMPONENTS AND SYSTEMS

2.0.2 Parts, Components, Tools and Devices

CHAPTER 2.0 INDEX

2.0.1 Objects

2.0.3 Systems

2.0.4 Elements of Systems

2.0.5 Systems Approach

2.0.6 Designing Systems

2.0.1 OBJECTS

2.0.2 PARTS, COMPONENTS, TOOLS AND DEVICES

Keywords: PHYSICAL OBJECTS / simple objects / complex objects / Intrinsic qualities of physical objects / extrinsic marks of physical objects / NON PHYSICAL ENTITIES / Intrinsic qualities of non physical entities / Extrinsic marks of nonphysical entities.

PHYSICAL OBJECTS have a peculiar size and shape. Simpler ones consist of one or few materials. Simple objects are useful on their own, or be useful when placed with others. When a simple object is useful by being in company of other objects, it by itself becomes dysfunctional or inoperative but the assemblage does not get affected significantly. However, there are complex objects, that are so well integrated in the assemblage that their absence can make the entity completely useless.

Intrinsic qualities of physical objects: size shape and constituent materials. Intrinsic qualities allow standardised manufacturing, use, disposal and recycling processes.

Extrinsic marks of physical objects: position, orientation, nature of relationships, duration etc. Extrinsic qualities become apparent only when a physical object is connected to another one.

NONPHYSICAL ENTITIES are like: process, programme, reports (feedback, feed-forward), expression, etc. A nonphysical entity may contain very essential and less essential section within it. For example in a computer programme, there could be sections that are not very essential, compared to sub processes like 'routines' which are not only key features but are accessed frequently.

Intrinsic qualities of nonphysical entities: extent, duration, form and constituent elements.

Extrinsic marks of nonphysical entities are the frequency of reference, protocol of access etc.

Keywords: PARTS / placement, location and function / elemental unit / active to passive interactions / determined by the design / indeterminable behaviour / COMPONENTS / unique composition / role within the system / static / dynamic / a part is also a component / Categories of Components / Action elements / Sensing mechanisms / Control elements / Decision elements / Connecting elements / Distancing elements / Converters / TOOLS AND DEVICES / use of their own / end use / machine / automatises a process / using multiple tools and devices and by combining several strategies / replaceable component.

PARTS: In our day to day life, we use many different types of objects. At a very simple level an object is made up of only one or few materials. Such objects though have variety of sizes and shapes, serve similar purposes. For this reason parts are always replaceable, and similar parts are affected similarly. When we recognize an object as a part, we know that a whole range of nearly similar objects, worthy of being a 'part', are available. A part has universal character, but when assembled into a component, it acquires a different personality, due to the placement, location and function. A part is that elemental unit to which the whole can be reduced or resolved.

A screw, nail, handle, razor blade, button, are examples of parts. These are destined to become members of a larger entity -the component. Cement, sand, water and bricks, as parts, form a masonry wall, which in turn is component of a building. Parts like a tube, tyres, air, rims, together create a component -the wheel. The wheel with many other components makes up a system of movement.

Within a composition, parts exhibit an active to passive interactions with other parts, as determined by the design. But parts dealing with the environment (including the user) often show indeterminable behaviour.

COMPONENTS: A component is unique composition of many parts, to serve a specific purpose, and must remain steadfast to the specific function to be relevant. Components have a specific identity, compared to Parts, which have a universal character. A component is more intimately linked to the larger composition-the system, than a part is. Components are conceived to be within a larger composition or system, and derive their identity on the nature of their role within the system. Some components remain static and so are useful, but many others are dynamic and only for that reason, become members of the functional system. Components manifest at very specific location and occasion, so can be easily identified and separated. A part is also a component where it becomes exclusive due to the placement, location or function. Components show reactivity to presence or elimination of energy by becoming dormant, active to hyperactive.

Some Categories of Components are:

Action elements: These trigger an action (like tools, devices), such as commands in computer or machine codes: start, stop, redo, wait, seek, words, phrases or expressions that excite, incite, inspire, tranquillize, annoy or hurt.

Sensing mechanisms: These require a feed-forward or generate feedback, so have state device or switch, and a communication node.

Control elements: Control elements operate within a designed range of effectivity, which whenever is breached it activates a sensing mechanism.

Decision elements: A decision element is mix of sensing mechanism and a control element, the logic for decision making is preset, but could involve a linear, looped, fuzzy or random process.

Connecting elements: These elements connect several components for synchronous movement or action, transfer of energy, electrical charge, messaging and communication. Examples include wires, levers, cranks, shafts, axles, ties, circuits, etc.

Distancing elements: These distance two components in space or delay a process in time. Compaction, diffusion, acceleration, deceleration, are the characteristic of such elements. A washer, spacer, gasket, sprocket wheels, timer belts, are examples of such components.

Converters: These elements convert movements from linear to planner, circular, or read a pattern, create a pattern, scale, focus, de-focus, enlarge and compress it. Examples include measuring devices, pantographs, digital printers, plotters, monitors, keyboards, projectors, etc.

A PA system has several physical components like power supply, microphones, cables, amplifiers, speakers, etc. A computer system has physical components like processors, memory modules etc., as well as nonphysical components like software. A publication or report includes components in the form of indices, links, references, conditions of use, intellectual rights -copyright, patent. A DNA has genetic modules (code) as the components. A programming language consists of code components that trigger certain activity or keep a check on it.

TOOLS AND DEVICES: A knife, screwdrivers, pliers, scissor, axe, etc. consist of several parts, so are components, but have use of their own, and may not be destined to become members of a larger entity. Such components with a definite end use are tools and devices. Tools and devices, as a component, become part of the larger system such as a machine.

A machine automatises a process, and so allows heavier, lighter, measured and intricate use of force then a human possibly could do. The same process or the style of working can be employed using different types of tools. Thus a press can bend, puncture, or cut a piece of metal by change of tools. A machine is rational unaffected by moods or emotions. Tools and devices by becoming parts of machines help a number of processes. The efficiency is enhanced by using multiple tools and devices and by combining several strategies to output a complex object, such as done by an automated lathe, turning, drilling machine or a forging press. Tools and devices are expected to wear, and so are replaceable components.

2.0.3 SYSTEMS

Keywords: SYSTEMS / purposive entities / a complex whole / scheduled in time / appropriately located in space / TYPES OF SYSTEMS / SMALL SYSTEMS / finite entity / LARGE SYSTEMS / infinite entity / groups of subsystems / SIMPLE SYSTEMS / man-made systems / natural systems / COMPLEX SYSTEMS / interdependent / independent / sea current system / active systems / biological entities / dynamic systems / synergetic systems / PHYSICAL SYSTEMS / exploit material based qualities / use configuration related characteristics / NONPHYSICAL SYSTEMS / ethereal / metaphysical / arrangement / sustain larger physical or nonphysical systems / core / periphery / Simple nonphysical systems / complex nonphysical systems.

SYSTEMS: Systems are purposive entities qualifying the togetherness of parts, components and subsystems. A system is a set of contributing elements and a culture (manner) that allows it function as a unified whole. A system is also a group of interacting, interrelated, interdependent, as well as distanced and independent elements forming a complex whole. A system also consists of components which are connected together in order to facilitate the flow of information, matter or energy, or by togetherness project cohesion, holistic unity, commonality, universalism.

Systems have their elemental units scheduled in time and appropriately located in space. For every change in the constitution, composition (form and size) and position of an elemental unit there is a corresponding change in the system. Though, some changes are insignificant, and are ignored. Elemental units of a system due to their scheduling, positional value, or designed inactiveness, are often not relevant to others. A system, however, composed of such apparently irrelevant elements is relevant as a whole.

TYPES OF SYSTEMS: Systems can be primarily classified by their size, complexity and nature.

SMALL SYSTEMS: A small system has linear (sequential) architecture of arrangement or relationships. A Small system persists for a limited time, and dominates small extent of space, so is a finite entity.

LARGE SYSTEMS are in the form of 2D or 3D matrix, or looped with entwined structures. Its spread in time and space is infinite and so such systems could be an infinite entity, such as for example the atomospheric or economic system. A large system consists of several groups of sub systems, some of which outlast others.

SIMPLE SYSTEMS: A simple system is composed of few elemental parts and components, which are essentially interrelated. All man-made systems are simpler, for the basic reason that these are always finite and logical, in comparison to natural systems. Simple systems are static or dormant in particular time segments. A simple system consists of the physical or non physical entities, but rarely both.

COMPLEX SYSTEMS: Complex systems are composed of several sub systems, only some of which are directly interrelated, yet all function towards a unified whole. In a complex system some of the subsystems are intentionally designed to be interdependent and other are isolated in time or space, to make them independent. Complex systems include, both physical and non physical entities, but a nonphysical system due to its nature seems very complex one. Systems seem to be complex when the change causing intrinsic or extrinsic elements cannot be easily or adequately identified. A sea currents' system, is one such complexity, where the al Nino causing elements have not been yet identified. Active systems exchange energy and efficiently deliver a product or an advantage. Some complex or High-end systems emulate biological entities. But man-made systems are not capable of procreation, like the biological systems. Dynamic systems have an intensity ranging from dormancy to a high vibrancy. Synergetic systems have inbuilt capacities to adjust to the environment so are self-regulating, but dynamic systems.

Systems are physical, nonphysical or both. Examples of Physical systems are: equipments, utilities, buildings, etc.; Nonphysical systems are: banking, software, defence, healthcare, marketing systems, environment, solar, etc.

PHYSICAL SYSTEMS: Physical systems are of various sizes, shapes, materials and configurations, and each combination serves a peculiar need. Physical systems exploit materials-based qualities like: constitution, mass, weight, capacities, performance, etc. and use configurations related characteristics such as: geometry or the structural arrangement. Some physical systems generate information which in turn support non physical subsystems like software or programme. Physical systems are finite. Their elements are 'domains' bound (territorial). As a result a physical system can be considered to be static and dealt accordingly. A physical system, like the human body, is continuously affected by the environment, and is a complex entity. Such systems display multiple functionality.

NONPHYSICAL SYSTEMS: Nonphysical systems are both ethereal and metaphysical. Ethereal systems can be experienced, but have no material body or affirm to a conceptual structure, so are difficult to define. Metaphysical systems are abstract systems with ideas or concepts organized in some manner or arrangement (algorithms) to serve specific ends. The arrangement is based on relevance of occurrence, action sequence, affinity, etc. of the elements. Such systems may show a strategy (a long term plan), a tactic (a short term or immediate), or an action-reaction response programme. Output of such conceptual systems sustains either larger nonphysical or physical system. Non physical system like the environment, has no physical territory or a finite edge, but can be sensed in terms of core (or themes) effect, and overlapping zones with other systems representing the periphery and the weaker or diffused effect.

Simple Nonphysical Systems have distinctive elemental units (e.g. taxation system) structured to provide a facility, strategy, solution, explanation, conclusion, etc.

Complex Nonphysical Systems are extremely persistent (omnipresent and pervasive), or not fully comprehensible in the nominal time and space scale of the perceiver (e.g. solar system). The simplest element of a nonphysical system is -the core or nucleus, an area where effects of other systems are least effective.

2.0.4 ELEMENTS OF SYSTEMS

Keywords: ORDER / recognition of order / primary orders / selection / processes of assembly and manufacture / degree of coordination / formation of concept / CORE or NUCLEUS / PERIPHERY / exchange information / transfer energy / INTERVENING ZONES / convergent areas / gaps and interludes / DOMAINS / internal and external / nodes for dependency or connectivity.

ORDER: Order is an inherent characteristic of all systems. Order begins to emerge as soon as parts and components are selected for inclusion in system. Initially systems have order that is alogical and loosely definable, and it may or may not be apparent. But it is noticeable when the system begins to perform. At this stage, in simple system the order is obvious, logical and definable. But in nonphysical system the order can be elusive due to the scale and complexity. Yet recognition of order in a system helps in many ways:

It helps the definition of a system.

It endows self sufficiency, so that the system can become an ever replaceable component.

It provides nodes for dependency so that the system becomes integrated whole.

In all systems the primary orders are: selection (inclusion and exclusion) of parts, components, etc. and the process of assembly or manufacture. However, in complex systems there are many levels and categories of orders.

'Every human effort follows some intrinsic logic'. Parts of an entity, even before being manufactured and even before physically placed together, have some degree of coordination. The coordination begins within the thought processes of the designer along with the formation of concept for the object.

Another important characteristic of systems is their domain or territory. This is very apparent in physical system, but nonphysical systems seem infinite with no edges. However, metaphysical systems have a zone where they are adequately active in comparison to sections where such systems are diffused, i.e., partially effective.

Recognition of order in system, is both subjective and objective. Subjective involvement allows the system author to see through the nascent logic, or blinds in recognising the order. Objective evaluation of the system by an uninvolved person rides over personal biases. Objective evaluation can occur for an operational system.

CORE OR NUCLEUS: Nonphysical systems have a strong focus from which other subsystems emanate or converge to. In very pervasive nonphysical systems a core or nucleus like a focus is the zone where one establishes conceptual mooring or base to start the encounter with the system. For a human being encounter with the atmosphere as a system begins at the surface of the earth, i.e. technically at the optimum sea level. The core is considered a multi faceted entity because most of the subsystems have a bearing here. The core distinguishes two directions: inward and outward.

PERIPHERY: Periphery zones are well defined in systems that are holistic or as sub system has a semblance of independence. The periphery zones or edges are recognised when a subsystem touches other subsystems at few locations spatially or on certain occasions temporally. During rest of the conditions the periphery is not perceptible. The periphery is well delineated in systems that exchange information or transfer energy at specific nodes and through protocol.

INTERVENING ZONES: Intervening zones are the convergent areas formed by overlapping subsystems and also by gaps or interludes between subsystems. The convergence and gaps-interludes occur, both in time and space. A holistic entity, has no intervening zones, and the subsystem have little or separate identity. A loosely conglomerated system like transit, courier, etc. consist of several modulated units, occurring across different regions, or across technologies. Here planned or recognised gaps and interludes give all subsystems a component like 'replaceable' identity. The gaps and interludes are not completely devoid, but are full of metaphysical things, as in case of solar system. Systems flourishing at different historic times or across geographical regions can have concepts, ideas, etc. that are common, making them universal.

DOMAINS: Physical systems have a finite edge and so reflect a domain. A domain marks what is internal and external to the system. It indicates how a system is part of the larger system. It identifies nodes for dependency or connectivity of the system.

2.0.5 SYSTEMS APPROACH

Keywords: COMPONENT APPROACH / working whole / two major external variables / environment / user interfaces / man made systems / natural systems / parts to whole / SYSTEMS APPROACH / manufacturing activity / physical systems / conceptual systems / operations / test run / model or prototype / surveys / whole systems / fuzzy systems / SYSTEMS' THINKING / systems theory / organization and interdependence of relationships / SE: SYSTEMS ENGINEERING design, execution and operations / OR: OPERATIONS RESEARCH.

COMPONENT APPROACH: During the Industrial revolution period (1850 onwards), component approach was recognised as a way of combining and organizing a working whole out of parts and components. It helped evaluation of parts in terms of the whole. The component approach helped understanding of systems of small size and limited utility (like industrial plants).

Later (after the world war I) it was recognised that systems are much more versatile and complex. Systems could be any organized effort like roads, buildings, health care, taxation, etc. Postwar planning and development taught that systems were affected by two major external variables. Systems were required to accommodate the environment and offer user interfaces. There was also realization that man made systems were 'put together' and non changing entities, compared to natural systems that were much more persistent, though very changing. Parts to whole, the simplistic component approach, was now a very inadequate definition for systems.

SYSTEMS APPROACH: Systems approach, which began with manufacturing activity, was soon applied to all types of human activities. It was realized that there are physical systems consisting of materials-objects, distinct from conceptual systems formed of nonmaterial entities.

Physical systems were tested on actual operations or test run in parts, or as a model or prototype. Conceptual systems require surveys to check the presumptions or derivations. Physical systems are objective, and variables like environment and the user interfaces are external to it. The conceptual systems are very much governed by the external factors, and often have no distinct boundaries.

Systems were recognised to be whole systems, when endowed with very distinctive environments, and to be fuzzy systems, where the outer boundaries are indistinct.

SYSTEM'S THINKING: When large production plants, military efforts, structural entities etc. were being developed in early 20^th C, these were each considered as set of problems. The approach to the problem and the possible solutions were perceived as a system. Systems theory was the word early investigators used to describe the field which focussed on organization and interdependence of relationships. A system was perceived as a family of relationships among the members acting as a whole. 'The joining and integrating of the web of relationships create emergent properties of the whole'.

System's thinking is a style of thinking / reasoning and problem solving. It starts from the recognition of system properties in a given problem. The problems have physical as well as abstract bearings. It was realized that a system is as strong as its subsystems are, and subsystems can gain strength from conceptual clarity of what the whole should be. A system was perceived as composed of regularly interacting or interrelating groups of activities/parts which, when taken together, form a new whole. In most cases this whole has properties which cannot be found in the constituent elements.

SE: SYSTEMS ENGINEERING: The systems approach was now scientific pursuit: for planning and validation of systems as a matter of relationships. It was now recognised that systems need attention at three distinct levels: Design, Execution and Operations.

OR: OPERATIONS RESEARCH: Another parallel discipline Operations Research emerged with exclusive concern for the planning, assessment and control of operating systems. Both, SE and OR overlap, but together provide a comprehensive method of systems approach.

2.0.6 DESIGNING SYSTEMS

Keywords: Innovators or designers / lay person / the process of creation / documentation / NATURE OF DESIGN EFFORT / personal and impulsively formed systems / holistic / planned systems / CLOSED ENDED SYSTEMS holistic systems / prime or unique effort / compact and rigid / HOLISTIC APPROACH / a complete and self contained system / work of art / OPEN ENDED SYSTEMS / multilateral effort or multi trial endeavours / large number of people / different time and locations / common measurements and standards for materials and procedures / wasteful / built-in reserves / DESIGN OF A SYSTEM / governing aspects / DESIGN APPROACH / holistic / components / Redesign or re-engineering / Reverse engineering / Simultaneous or Concurrent design / NATURE OF OUTPUT / PRESENTATION TOOLS AND METHODS / approval, test, execution and operations / intellectual property rights / public domain system / SCALE AND NATURE OF DETAILS / Conceptual systems / explicit idea level details / Executable systems / NASCENT -FIRST EVER EFFORT or ROUTINE APPLICATION / fail-safe / exact definition / HUMAN AND OTHER RESOURCES AVAILABLE / TECHNOLOGY INVOLVED / conceptual systems / material systems / tactical corrections / strategic forethought / CODES AND UNIVERSAL CONFIRMATION / Dimensional coordination / Size and shape modulated parts / universal codes and regulations / greater acceptance / common platforms / HUMAN CENTRED DESIGN / ENVIRONMENTAL CONCERNS / Environmental Management Systems EMS ISO 1400x.

Innovators or designers may perceive an entity, or select its constituents by instinct, but must discover the logic behind it and justify their actions intellectually. A lay person devising entities solely through creative impulses lacks such a prowess. Designers continuously refine their capacity to improvise and innovate, by registering the process of creation or design decisions. It allows them to selectively improvise the smallest section of the entity.

The initial impulses of design, the dreams, intuitions or inspirations thin out or get wiped out completely with passage of time. These often need to be recalled in a different time and space context. Documentation of every aspect of design process is very necessary. Such expertise helps a designer to handle extensive or more complex dreams, intuitions or inspirations.

NATURE OF DESIGN EFFORT: A system reflects the nature of effort used in its formation. Personal and impulsively formed systems tend to be holistic, with few or no sub systems. On the other hand, planned systems whether personal or evolved through multilateral effort, and over a longer period of maturation, consist of many sub sets.

CLOSED ENDED SYSTEMS: These are also called holistic systems. Close-ended systems result from prime or unique effort. Spontaneous and one-man creations tend to be closed systems, unless a conscious effort is made to make it an open system. Closed systems are improvise-able only by its author or inventor. Closed-ended systems have few sub systems, and equally rare are the components. The few components are very specific and not easily replaceable. Closed systems as a result are compact and rigid. Closed ended systems become useless when faced with even minor changes in their environment or working.

HOLISTIC APPROACH: Design effort that conceives a complete and self-contained system initially is called a Holistic approach, i.e. whole to the part. Holistic approach entails germination of an intuition as a complete system. Such creations are akin to a work of art, often not functional, and not necessarily reproducible. However, such impulsive concepts may be detailed later on to become component systems.

OPEN-ENDED SYSTEMS: Open-ended systems evolve from multilateral effort or multi trial endeavours, and so have sub systems. Where large number of people are involved in design and execution, and where these processes are likely to take place at different time and locations, the system automatically becomes open ended. The subsystems for a variety of reasons are conceived as substantially independent systems. The subsystems are often designed or manufactured by different vendors. The success of the open-ended systems depends on the adaptation of common measurements and standards for materials and procedures. To accommodate all these, open-ended systems tend to be open or loose, and have a skeleton type frame structure (infrastructure). Open-ended systems many times are wasteful, because every subsystem has built-in reserves or additional safe capacities, though such individual reserves make systems more persistent. Open-ended systems allow replacements, improvisations and up-gradations of their subsystems and components.

DESIGN OF A SYSTEM: Design of a system, governing aspects are:

DESIGN APPROACH: The design approach determines the nature of system being evolved. The design approaches include: Holistic (whole to the part), Components (parts to the whole), Redesign or re-engineering, Reverse engineering, Simultaneous or Concurrent Design. (For more on this topic refer to notes on: Interior Design Practice and Office Management Section III = Chapter 8 at www.gautamshah.in ).

NATURE OF OUTPUT: The nature of system being conceived, physical ('real''material') or nonphysical (conceptual), governs the design process of a system. The nature of output, are: Construct forming, Strategic, Tactical planning, Assessment exercise, Executable scheme, Operational methodology, Corrective interventions like supportive additions, reformations, Reductive changes like curtailing, partitioning, miniaturization, condensation, Scheduling, Sequencing, Algorithms, etc.

PRESENTATION TOOLS AND METHODS: In what form the system will be presented for approval, test, execution and operations, such as: Report, instructions, drawings, images, digital data files, graphics, metaphoric, etc. determines its constitution. Systems that involve intellectual property rights may not be very revealing, but a public domain system has to be transparent.

SCALE AND NATURE OF DETAILS: The scale and nature of details are determined by the type of system. Conceptual systems have very explicit idea level details such as the domain of the system, definitions of subsystems, subsystem to subsystem relationships, dependencies, external nodes, etc. Whereas Executable systems have information of materials and processes, sequences of execution, siting of the system within the larger whole.

NASCENT -FIRST EVER EFFORT OR ROUTINE APPLICATION: First-ever systems ventures into unknown territories, and so these are conceived with extra efforts to make them fail-safe. This results into over explicit or very exact definition, making it ironclad, with no scope for improvisation. Routine application systems are more open, flexible though with very little wasteful features.

HUMAN AND OTHER RESOURCES AVAILABLE: Design of a system is an effort requiring both human and other resources. The human resources include the human-power and expertise. Other resources include, materials, time, plant, equipment, tools, and finance.

TECHNOLOGY INVOLVED: Involvement of technological features is as important in conceptual systems (nonphysical) as much as it is with material systems (physical systems). First-ever systems (novel) involve use of unproven technologies and unknown circumstances. Where as routine systems (traditional) are based on familiar grounds. Both types of systems could be of open architecture, in the first instance openness allows tactical corrections, in the second case it is as strategic forethought.

CODES AND UNIVERSAL CONFIRMATION: Designers prefer to design parts, components and systems that have dimensional coordination. Dimensional coordination also allows creation of geometric compositions. Size and shape modulated parts allow easy replacement. Affirmation to universal codes and regulations though restricts the design creativity but allows greater acceptance in the society. 'Common platforms' achieve greater economy.

HUMAN CENTRED DESIGN: Human centred design approach focuses on serving human needs in all endeavours by redefining and developing concepts and employing technologies. When human needs are genuinely served in all their manifestations it becomes an all-inclusive design system. It becomes a universal system above the racial, geopolitical and other barriers. It becomes a nondiscriminatory system.

ENVIRONMENTAL CONCERNS: Environmental concerns are now being recognised by International Standards Organization, ISO, through their recommendations for ISO 1400x : EMS, Environmental Management Systems. These standards are similar to ISO 900x series of standards dealing with QMS, Quality Management Systems.

3.0 BARRIER SYSTEMS

3.0.2 Man made Barricades

CHAPTER 3.0 INDEX

3.0.0 Barrier Systems

3.0.1 Natural Barriers

3.0.3 Make-believe Barriers

3.0.4 Other Barricades

3.0.5 Barricades for Physically Impaired Persons

3.0.6 Barriers for Performing Arts

3.0.0 BARRIER SYSTEMS

Keywords: obstructing and intervening entities / configuration, position and occurrence / context or the surroundings / intended and unintended things / extensive / opaque to transparent / lattice / membrane / barricades / separator.

Barriers are obstructing and intervening entities. Barriers through their configuration, position and occurrence affect things passing by, touching, or going through them. Barriers rarely operate on their own, so are distinguished by the context or the surroundings where they operate. Barriers operate as multi functional entity doing many intended and unintended things.

Barriers change the environment on both the sides. Barriers have a capacity to obstruct, absorb, filter and reflect, and so cause distinctly different conditions on the other side. However, barriers are often so extensive that the modified environment is not recognised, as the perceiver has no idea of, what the original (one beyond the barriers or without the barriers in position) experiences were. Barrier systems, as a result, are evident at the joints, thresholds, ends, edges, cut sections, or at the gaps.

Barriers are selectively opaque to transparent for various energies and objects. A lattice may allow a rat or insect to pass through but not a cat or dog. A membrane filter can allow gas but not any particulate matter. A barrier system, by deflecting, reflecting, by absorbing within its own body, does not let certain things to pass through them.

A barrier is a separator that not only divides an entity. It allows a new set of cultures to flourish on both the sides. However man-made barriers are not powerful enough to cause extensive changes in the environmental system within which they occur.

3.0.1 NATURAL BARRIERS

Keywords: NATURAL BARRIERS / extensive / long lasting / territorial / temporal / start and end of natural barriers / overlapped / ATMOSPHERIC BARRIERS.

NATURAL BARRIERS: Natural barriers are like rivers, mountains, ridges, valleys or atmosphere. Natural barriers are very extensive in space, and long lasting in time. Natural barriers are territorial, affect macro or micro regions, and also temporal in terms of occurrence like, eternal, seasonal, diurnal, etc. The start and end of natural barriers are not always within the relevant time and space scale. Natural barriers start or become effective somewhere and imperceptibly end or become ineffective somewhere. Natural barriers as a result are often not experienced because the other side experience (without the barrier) is not possible due to their large spread. Natural barriers are overlapped by other natural barrier systems, so have no distinct definition.

ATMOSPHERIC BARRIERS SYSTEMS: Atomospheric barrier systems are natural barriers formed by the constituents of the atmosphere such as: air, moisture, breeze, winds, radiation, temperature, etc. For example, air or its gases control the level of radiation penetration, the moisture checks the amount of dust in the air, and presence of dust and other particles helps distribution of illumination. The atmospheric barriers are very extensive, consisting of over lapping layers, and so do not have the sharp edge definition. Some of these barriers are very acute and causative, while others are mild and almost irrelevant. Atmospheric barriers are so common and omnipresent that we many times take them for granted. Some effects of the atmospheric barriers are so fast or short lived that it becomes very difficult to notice or learn any thing about them.

3.0.2 MAN-MADE BARRICADES

Keywords: PHYSICAL BARRICADES / contrived structures / conditions, properties of materials / METAPHYSICAL BARRICADES / indicative and unreal / make-believe / INDICATIVE BARRIERS / signs, signals, symbols / taboos, beliefs, customs / class of beings.

Man-made barriers are finite in size, designed for specific function and alterable. Man-made barriers occur as barricading elements such as: Curbs, embankments, Guard, Railing, Fender, Shield, Buffers, Balustrades, Fence, Parapet, Rampart, Bumper, Cushions.

PHYSICAL BARRICADES: Physical barriers are contrived structures (peculiarly shaped, sized and formed) that exploit conditions, properties of materials (strength, weight, bulk, ductility, etc.), and energy reactivity.

METAPHYSICAL BARRICADES: Metaphysical barricades are indicative and unreal, or Make-believe. A society by a tacit understanding accepts certain words, signs metaphors, and indications as allowable and non allowable actions (warnings, danger, caution, etc.). When such commonly acceptable norms are displayed, they function almost like a real barricade. Signs like Caution, Danger, 'Do not trespass', 'keep off the grass', etc. operate as barriers.

INDICATIVE BARRICADES: Indicative barricades occur as signs, signals, symbols etc. Unreal barriers arise as a response to our accumulated experiences, in the form of taboos, beliefs, customs etc. Indicative barriers are effective only for that class of beings, who not only know the meaning, but are willing to abide by it.

3.0.3 MAKE-BELIEVE BARRIERS

Keywords: unreal and metaphysical / MAKE BELIEVE EFFECTS AND BARRIERS / predictable effects / mirrors / echoes and reverberations / predictable space dimensions / mould the visible space / stage like make believe and or indicative effects / dramatic or melodramatic / delusion / Maha Bharat / Lakshagriha.

Make-believe barriers exploit the instinctive associations and conditioning of physiological and mental faculties. Man-made barrier systems are often unreal and metaphysical.

MAKE BELIEVE EFFECTS AND BARRIERS: We are generally conditioned by predictable effects of the traditional or known materials. However, when we discover that any peculiar configuration or additional input creates an experience that is different from the one that is predictable, we get a tool for a make believe effect. Mirrors play a very important role in creation of duplicate spaces. Glasses provide a transparent wall compared with a nominally solid opaque structure. Rooms other than square or rectangular shape provide an unusual experience. Echoes and reverberation of sound provide predictable space dimensions, but different perception gives unusual experience of the space. Lights and shadows mould the visible space. Ionized air endows a garden like freshness in an otherwise stifled space.

In real life we do use the stage like make-believe and indicative effects. We use these to create situations that are called 'dramatic or melodramatic'. Discotheques, Night Clubs, Amusement Parks, etc., are places where such make-believe effects are extensively exploited. Make-believe effects occur because we are conditioned by certain predictable responses of materials, texture, colour, illumination frequency and schedules of occurrence etc. When these predictable effects fail to arrive in the nominal context, or arrive in spite of a different situation a delusion occurs. Make-believe effects are almost magical or ethereal, and defy logic or reason.

Indian epic Maha Bharat mentions Lakshagriha, a palace where solid looking floors were water surfaces, and water surfaces were real floors. We perceive a dark space to be quiet and cold, but in a 'maze' of an amusement area, the reverse experience is provided. We perceive load-bearing walls to be opaque, so a glass wall seems different.

3.0.4 OTHER BARRICADES

3.0.5 BARRICADES FOR PHYSICALLY IMPAIRED PERSONS

Keywords: SENSUAL VARIATIONS AS BARRICADES / VISUAL BARRICADES / optical qualities / sensory variation / BARRICADES CONSUMING ENERGY / machines / PROTECTIVE BARRICADES / planned deflection and distortion / noncollapsible barricade / collapsible barricade / SOFT BARRICADES / HARD BARRICADES / TRANSPARENT, TRANSLUCENT AND OPAQUE BARRIERS / NOTIONAL BARRICADES / representative form of a barricade / Notional barricades are not recognised / NEED FOR BARRICADES.

SENSUAL VARIATIONS AS BARRICADES: A non physical barrier could also occur through sensory variation. A subtle shift in texture, gradient, colour, illumination level, view, temperature, audio perception changes the behaviour of the user and can become an effective barrier.

VISUAL BARRICADES: Visual barricades use colours in terms of their brightness and other optical qualities such as fluorescence, reflection and background-foreground contrasting. Visual barricades also include use of illumination or brightness, blinking (dynamic) lights, iridescence.

BARRICADES CONSUMING ENERGY: Barricades bar or control the exchange between its two faces. Barricades, themselves are variously affected by the exchange occurring through them. Some barricading systems use energy, to cause specific changes during the exchange process and also to revert to the nominal status. Barricading systems capable of using energy are machines, or a live beings, if additionally can reproduce or self sustain.

PROTECTIVE BARRICADES: Protective barricades are designed to resist the most unfavourable combination of imposed loads (impact, wind, etc.). Such barricades allow planned deflection and distortion, with or without a collapse. A noncollapsible barricade is resilient enough to revert to the original position, whereas the collapsible barricade at a predetermined stage becomes ineffective. These conditions are included through a structural configuration, material technologies and through machine devices (operating on feed forward and feed back).

SOFT BARRICADES: These recover after an impact, but do not bounce-back the striking object. Rubber flaps or plastic stripes on warehouses doors are flexible barriers.

HARD BARRICADES: These are used to divert (bounce back) the force of the impact. On express highways the shape and height of the railings and curbs are so designed that a vehicle on striking slides along it rather than thrown-back into the fast-moving traffic.

TRANSPARENT, TRANSLUCENT OR OPAQUE BARRIERS: A glass barricade could be transparent for light but not for other objects. A large aperture grill could be 'transparent' for light, air and view, 'translucent' for an infant, pet etc., but 'opaque' for a fat man. A vertical or horizontal Venetian blind could be 'transparent' or 'translucent' from a particular position and could be 'opaque' from another position. A smoke glass is 'opaque' for view from outside but 'transparent' for view from inside. Fast-moving air in an 'air curtain system' is a transparent barricade.

NOTIONAL BARRICADES: These are used for ceremonial purposes or as a representative form of a barricade. A wrought iron chain, a rope around a monument, podium, dais or rostrum, a red ribbons for inauguration, yellow tape of police investigation teams, are all notional barricades. Similarly signs and symbols (danger, do not enter, slow, stop) can also be used for barricading. If the users are knowledgeable, and are ready to accept a set social behavioural norm, than indicative (non physical) barricades are as effective as physical barricades. However, it should be possible for the user to recognize, feel and experience the presence of such barricades. Where such opportunities for recognition are not available, non physical barricades fail to be effective. Notional barricades are not recognised in a crowded area or in a chaotic situation. Similarly where barricades are required as protection against unknown elements, notional barriers are not effective.

NEED FOR BARRICADES: Barricades are required at all places of hazards such as: construction sites (for the safety of workers, visitors, and trespassers), works in public areas (such as trenches, excavations), place near electrical equipments (with exposed parts that could be live, and installations with voltage of over 440 volts), any area where explosives are used or stored, to define the radius of any cranes or such equipments, etc. Barricades serve as warning (through visual and other sensorial recognition) and also as a protective element. Barricades also denote territories, ownership and right of ways.

Keywords: exclusive route / barricades have distinguishing elements / visually impaired persons / visually deficient person / colour blind person.

Persons with physical deficiencies require barricades for: extra support to the body, as a facility to ease the movement and as a guidance for the route. The barricades however must not create an exclusive route for the physically impaired. The barricades have distinguishing elements such as: shape, size (height, width), materials and their surfaces, nature of sensorial qualities available in the defined zones.

Barricades for visually impaired persons are required at two levels. The main barricade is like that required for a normal person. The barricade for the visually impaired persons should be continuous and have same texture, size, shape and feel throughout its spread. For the visually impaired person, a secondary set of barricade system is required at near the floor level to strike the walking stick. Even where, primary barricades are not ordinarily required due to the absence of a height-related hazard, a secondary barricade (at floor level) helps in directing a visually impaired person to a specific destination. Visually deficient persons require colour contrast from their background or neighbouring elements, Ramps or steps on passages must be indicated by colour, illumination and textural difference. A colour blind person may not read a colour but recognises the later two elements.

3.0.6 BARRIERS FOR PERFORMING ARTS

Keywords: nonphysical or indicative barrier system / performing arts / real barriers / indicative barriers / acute or important sections / stage / here / beyond / mime acts / sage Bharat Muni / Natya Shastra / stage barriers / real life barriers / permanent / longer lasting / experienced dynamically.

The best and perhaps the most imaginative use of non physical or indicative barrier systems occurs in the performing arts. Here a performer wishing to express different experiences on a stage or arena has limited time, space and means. As a result the performance space or the stage is extended beyond its physical limits by exploiting both, the real barriers and indicative barriers. Since it is not possible to accommodate the entire set of physical barriers, only the acute or important sections are highlighted through frames, outlines, edges, cleavages, thresholds.

The sets, stage property, curtains, side wings, lighting, audio-video effects, etc. are used for creating a variety of spaces ('here' and 'beyond'). A cleavage in side wings or a gap between two stage properties could signify a door, window, opening, corridor or a passage. The stage thus becomes a place where a multiplicity of spaces 'Here' and a series of connected spaces supposed to exist 'Beyond' occur. Whatever is lacking in such definitions is further reinforced by the actors. The acting makes the audience feel as if the actor is actually dealing with or reacting to a real barrier. Mime acts are such explorations with unreal barriers.

Stage set barriers are experienced by the audience from a limited and fixed angle view. Sage Bharat Muni in his treatise on Natya Shastra (Canons on Dramatics) says actor turning back to the audience is out of the scene or dead. Even in Roman Amphi theatres the actors on the front section are active and by retreating to the backside become inactive. Stage barriers serve a very limited purpose effective for a short period, and last only for a scene, dialogue or the expression. However, real life barriers are rather permanent or at least are longer lasting, seen or experienced dynamically, that is from all sides.

3.1 BARRICADES IN BUILDINGS

3.1.1 Barrier Systems in Buildings

CHAPTER 3.1 INDEX

3.1.2 Varieties of Barriers in Buildings

3.1.3 Environmental Barricades

3.1.4 Railings and Parapets

3.1.5 Fences

3.1.6 Guard Rails

3.1.7 Hand Rails

3.1.8 Components of Railings and Parapets

3.1.9 Materials for Barricades

3.1.1 BARRIER SYSTEMS IN BUILDINGS

3.1.2 VARIETIES OF BARRIERS IN BUILDINGS

Keywords: man-made barriers / control of environment / hazards / control of movement / barriers protect / barricades serve purposes / Types of barriers in buildings / operational ability.

A building is formed by a number of man-made barriers. The barriers in a building are designed mainly for the control of environment, followed by barriers against hazards and for control of movement.

The barriers protect a building from environmental effects, shocks, vibrations, other effects of energy, malicious abuse, use and age related wear and tear. In a building, barricades serve purposes like: restrict, control or direct movements of people and vehicles, indicate routes, provide defence against impact and risks from elements like fire, extreme temperatures, radiation, light, noise, wind, lightening, fast-moving objects, etc.

Types of barriers in buildings are: walls, roofs, floors, doors, windows, curtains, awnings, ceilings, panelling, etc. Building related barriers are well integrated into the fabric of the building and rarely function alone. Barriers in the building derive their operational ability by being part of the larger system.

Keywords: SAFETY BARRICADES / Types of safety barricades /height related hazards / physically handicapped or infirm person / situational conditions / downward end of a ramp or slopping terrain / height for safety barricades / HEIGHT FACTORED BARRICADES / effective height / nature of surroundings / configuration / gaps in the balustrades / WIDTH FACTORED BARRICADES / barricades of greater widths / greater width with greater bulk / wider barricades / PEDESTRIAN CONTROL BARRICADES / tallest user / barbed wire fencing / notional barricades / ANIMAL BARRICADES / capacity to leap / run depth / traps at gates / wicket gates / TRAFFIC SAFETY BARRICADES / CROWD MANAGEMENT BARRICADES / safety / security / temporary / permanent / height safety standards / resist horizontal thrust / SECURITY BARRICADES / prevent access or exit / entry by terrorist / high speed impact / Berlin wall / BARRICADES FOR VEHICLE CONTROL / guard rails / BARRICADES FOR OPENINGS / fall related hazards / controlling the entry or exit / environmental controls / control vision in and out / effective sill level / barricades within the doors.

SAFETY BARRICADES: Types of safety barricades are: Height related hazards, isolation of dangerous zones, exposure to effects of radiations, against high speed movements, security from anti social persons, theft, animals, etc.

Height related hazards require barricades. Nominally a fall of 600 mm is difficult to negotiate (climb up or down), so even for a normal adult it is considered a hazard. A provision of an intermediate step or support is required. For physically disable and infirm people a barricade may be necessary even when the height difference is only 25 mm. For situational conditions such as at the downward end of a ramp or slopping terrain, a fall of less than 300 mm requires a safety barricade. In buildings for human habitation a 900-mm minimum to 1100 mm optimum height for safety barricades like parapets, balustrades, etc., is prescribed on balconies, stair sides, and terrace edges of are prescribed. The height is often compromised to 790 mm or less by, alternatively, providing wider widths, for drama, cinema or assembly hall balcony fronts, to prevent visual obstruction to the view of the front edge of the stage.

HEIGHT FACTORED BARRICADES: These are preventive barricades of specific height to control the crossover movement. Effective height actually available for the barricade is determined by the nature of the surroundings. A very steep gradient in front, and difficult to negotiate terrain (moats, pits, trenches) can also act as a barricade.

Effective height of a barricade system is affected by its configuration. A horizontal mid-bar or any such element can accommodate a toe of a user, to reduce the effective height of the available barricade. To prevent children less than five from falling, gaps in the balustrades (balcony and stairs) must not allow a 100-mm diameter sphere to pass through.

WIDTH FACTORED BARRICADES: As shown earlier in case of safety barriers, width of the barricade compensates the height requirement. Barricades of greater widths are also required, when a structure is required to resist horizontal stresses and thrusts, as in case of retaining walls and dams. Walls and partitions of greater width with greater bulk (low density) are created as insulation system for heat, x ray or other radiations. Wider barricades cut off the view of areas immediately close-below, an ideal provision for stepped floor balconies in sea shore resorts.

PEDESTRIAN CONTROL BARRICADES: Pedestrian barricades should be taller than approximately 2/5 the height of the tallest user, as for example for a mid-road verge. Security barricades should be taller than tallest persons to be barricaded. Often the effective width of the barricade structure controls the actual height required. Barbed wire fencing of Y and T, 'shapes are used in jails and defence installations. Pedestrian control can be effected by notional barricades, like a thin rope, a horizontal pipe, a small ledge, a floor marking.

ANIMAL BARRICADES: The barricades should take in to consideration, animals' the capacity to leap and also the 'run depth' available in the surroundings. Animals are confined by a variety of methods including water-filled moats, dry moats, and wire-mesh fences. Animal traps at gates have gaps to trap the animal's feet, and width to prevent a 'non run' leap. Wicket gates are intentionally made of narrow width and have a nonlinear passageway to prevent vehicles like cycles and animals.

TRAFFIC SAFETY BARRICADES: Traffic safety barricades are meant to be safe, stable (wide based, secured or resilient enough to revert to the original position) and visible. Traffic barricades direct the flow of traffic, prevent unauthorized entry or exit from the designated areas or lanes.

CROWD MANAGEMENT BARRICADES: Crowd management barricades are designed for the safety and security of people, control the direction of their travel and to control their numbers. Such barricades are temporary (occasional) and permanent. The barricades are designed with the height safety standards (the nominal balustrade height and leap over prevention), but in addition have a capacity to resist horizontal thrust. Such barricades are in place at the famous temple of Tirupati Balaji, South India, and at Ambaji Temple, Gujarat.

SECURITY BARRICADES: A security barricade is meant to prevent access or exit to a specific area, such as a hazardous zone, protection from theft, and forceful entry by terrorist. Security barricades may be designed to withstand assaults such as high speed impacts like a high speed or armoured vehicle. Some of the most important security barriers include: fort walls, the Great Wall of China, Dykes in Holland, Wall dividing East and West Berlin in Germany and quadruped sections on Bombay sea shores.

BERLIN WALL: During the period from 1961 to 1989, East Germany built a barrier to close off the migration after about 2.5 million skilled workers, professionals, and intellectuals to west Germany. This barrier, the Berlin Wall, was first erected on the night of Aug. 12-13, 1961. The original wall, built of barbed wire and cinder blocks, was subsequently replaced by a series of concrete walls up to 5 mts high, that were topped with barbed wire and guarded with watchtowers, gun emplacements, and mines. By the 1980s this system of walls, electrified fences, and fortifications extended 45 km through Berlin, dividing the two parts of the city, and extended a further 120 km around West Berlin, separating it from the rest of East Germany.

The Berlin Wall came to symbolize the Cold War's division of East from West Germany and of eastern from western Europe. Yet, about 5,000 East Germans managed to cross the Berlin Wall (by various means) and reach West Berlin safely, while another 5,000 were captured by East German authorities in the attempt and 191 more were killed during the actual crossing of the wall.

During October 1989 during the wave of democratization swept through eastern Europe and on November 9 the East German government had to open the country's borders with West Germany (including West Berlin). East Germans could travel freely now to the West.

BARRICADES FOR VEHICLE CONTROL: Guard rails are used to prevent vehicles from veering off a road into oncoming traffic, crashing against solid objects (like a bridge pillar) or falling into a ravine. Guard rails are designed with an objective to keep the vehicle upright while it is deflected along the guard rail. Vehicle barriers are generally taller than ½ the diameter of the wheel. A tall guard rail of ideal height for a car, though may not keep a truck from toppling over it, whereas a thin vehicle like a motorbike may slip under a high rail. Vehicle barriers on bridge sides, auto-ways, should be capable of resisting (strength) and deflecting (shape) the impact of cars, lorries, etc.

One-way streets and gates have small stepped fall at entry points to prevent exit of the vehicles. Wharfs, boats and ships use rubber buffers or tyres as preventive barriers against impact and rubbing.

BARRICADES FOR OPENINGS: Barricades are required in openings like Doors, Windows, Gaps, etc. These are required for fall related hazards and for controlling the entry or exit of human beings, animals, pets, flies and insects, and mosquitoes. Barriers are also required for environmental controls, such as heat, solar radiation, breezes, odours, audio. Barriers such as the louvres are required in openings to control vision in and out.

Barricades for a fall-related hazard are required if the sill level is lower than height required for a balustrade in a similar position. Barricades are also required if a piece of furniture against an opening like a window is likely to reduce the effective sill level. Barricades within the doors are required in nursery areas, stair ways, etc. where infants are likely to crawl.

TAPE OR ROPE BARRICADES: Cloth, plastic or fibre tapes and ropes are used as a visual boundary or indicative barrier by police and military to isolate sensitive zones.

3.1.3 ENVIRONMENTAL BARRICADES

Keywords: aspects of environment affect simultaneously / composite systems / WIND BARRICADES / deflect the direction / diffuse the velocity / natural terrain / man-made formations / Projections / wind catcher ducts / terrace parapets / SUN SHADING BARRICADES / vertical or horizontal / inclined positions / dual shading / Brise de soleil / RADIATION BARRICADES / Natural radiation barricades / Man made radiation barricades / NOISE CONTROL BARRICADES / stage podiums / parabolic overhangs / background noise / contoured planes to deflect / low density surfaces treatments, baffles or cavities / frequency generators / sound attenuation / BARRICADES IN TOILETS AND OTHER UTILITY AREAS / shower over-sprays.

Different aspects of environment affect simultaneously, and so a variety of barrier systems are required. Environmental barriers are often composite systems serving many different purposes.

WIND BARRICADES: Wind barricades are used on regular heavy wind as well as storm prone locations, such as sea fronts, valleys etc. to deflect the direction and diffuse the velocity of the breeze. These barricades primarily depend on the quality of natural terrain and man-made formations such as sand dues, walls, screens, vegetation, walls etc. Projections like galleries, chhajjas, screens, are also used for diverting the flow of winds in the buildings. The breeze is also diverted to interior areas of rooms by wind catcher ducts. Tropical houses have terrace parapets with a grill or lattice design to let the air pass through. Louvred doors and windows control the breeze.

SUN SHADING BARRICADES: Sun shading barricades are shading devices, usually vertical or horizontal, and often in inclined positions. Locations above 23 N or S of equator receive no sun rays from respectively North and South faces. However, all location under (within) 23 N or S of equator, receive some sun rays, and to curtail it sun shading devices of horizontal flat or inclined shape are required. In the same locations, East and West faces, in early part of morning and later part of the afternoon, receive horizontal rays, but with Southern inclination. These require a dual shading consisting of horizontal and vertical (on a south side of the opening) elements. Sun shading devices such as Brise de soleil are used.

RADIATION BARRICADES: Radiation barricades are used against radiation sources, such as furnaces, open fires, oil wells and oil storage tank yards. Such barricades could be natural or man made. Natural radiation barricades are in the form of hills, contours, dunes, slopes, trees, hedges, foliage, plants, grass, climbers etc. Man-made radiation barricades are protection walls, embankments, ramparts, retaining walls and dykes.

NOISE CONTROL BARRICADES: These are created against super highways, railway tracks, airport runways, open mines, stone crushing plants and sites with pile drivers. These barricades are made of dense vegetation, fibre boxes (grass), and hollowed or staggered construction. Stage podiums have parabolic overhangs to direct sound away from the stage and thus avoid the feedback in sound amplification system. Telephone booths in public spaces like malls, road sides, railway stations have specifically designed envelopes to prevent the background noise. Cinema and performance auditoria are designed with optimum 1/4 to 1/3 audience occupation, as the bodies of audiences and their clothing absorb sound. Noise control barricades are in form of contoured planes to deflect and amplify the sound, low density surfaces treatments, baffles or cavities to absorb select frequencies of sound, or frequency generators to produce sound attenuation.

BARRICADES IN TOILETS AND OTHER UTILITY AREAS: Barricades in toilets are required to curtail the shower over-sprays. Barriers are also placed besides WCs, bathing areas and toilets for isolation.

3.1.4 RAILINGS AND PARAPETS

Keywords: rail / opaque structure of masonry / height related hazards / architectonic element / resting the hands / RAILINGS / top rail / hand rail / foot rail / mid rails / PARAPETS / coping / corbel / embattled parapets / perforated parapets / panelled parapets / curbs / vehicle parapets / projections and depressions / vehicular impacts / parapets for railway bridges.

Railings and parapets serve many common functions. It is their nature of construction that places them in separate categories. Railings are lattice type barricades built from rails. A rail can be defined as any long member, usually of round section, fixed to posts. A parapet is usually an opaque structure of masonry but could have members like balustrades. Railings and parapets have been used as architectonic element, and placed against height related hazards. Railings and parapets are invariably smaller than the human height, because most such elements are used for resting the hands on it.

RAILINGS: Railings are placed: on sides of stairs, ramps, escalators, at the edges of terraces, balconies, to demarcate zones, to segregate movement channels, to regulate queuing people, as barricade for animals, and to prevent crawling infants and children from moving into unprotected areas. Railings are placed on inclined or slippery floors to prevent slip-fall. Railings are placed in vast grounds for people or groups to anchor themselves. Railings have posts, a top rail for holding -the hand rail, a rail for foot -the foot rail, and mid rails.

PARAPETS: Parapets are upward extensions of the wall, sometimes with a coping at the top and corbel below. Parapets have other sub elements such as: hand rail, Baluster or balustrade, banisters, volute, turn out, gooseneck, rosettes, easing, starting easing, over easing, core rail, newels, fillets, tandem caps, colonnettes. Parapets may be plain, embattled, perforated or panelled. Embattled parapets are placed on fort walls, are sometimes panelled, but have but pierce for styling, view beyond and for throwing defensive projectiles. Perforated parapets are pierced in various shapes such as circles, trefoils, quarter-foils. Panelled parapets are ornamented by a series of oblong or square panels. Parapets are placed at floor and terrace edges, sides of stairs, ladders, ramps, escalators, near wells, tanks and other water bodies.

Parapets are also used for deflecting winds, provide privacy to floor level activities, add weight to the edge to prevent liftoff forces. Parapets serve many other purposes, besides protection, such as: to shield a view, as a noise barrier, barriers against splashes of stormwater, missiles or flying objects. Parapets are often inevitable structural component (functioning as a beam) along the edge of a bridge or similar structures. Parapets that are small in size are called curbs. Curbs are also used as dividers.

The word Parapet comes from the Italian parapetto (parare = to cover/defend and petto =breast). The German term Brustwehr has the same significance. Building Act of 1707 in London banned projected wooden eaves on buildings to reduce fire risks, and instead 450 mm thick brick parapets with the roof set behind were made mandatory. This was continued in many Georgian houses, as it gave the appearance of a flat roof which accorded the classical proportions.

Vehicle parapets on traffic face must be free of projections and depressions. Longitudinal rails must be placed on the traffic side over the supporting posts and present a smooth face to traffic free from sharp edges, except at joints in longitudinal direction. Even here all projections or depressions must not exceed 20 mm. The range of possible vehicular impacts onto a parapet is extremely large in terms of vehicle type, approach angle, speed and other road conditions. The performance of a parapet is defined in terms of containment level based on a standardised impact configuration. Parapets for Railway overbridge must have a minimum height of 1800 mm.

The building act of 1707 in London and other towns of England banned the projected wooden eaves to prevent spread of fire along the wall, to the roof structure. A 18" thick parapet was required and the roof edge was set back. The roof was set back little more to provide drainage of rain water. The parapet which was completely absent in earlier houses began to be treated by crenellation. (During medieval ages, provision of crenelles required permission.) The parapet style was continued in Georgian houses giving an appearance of a flat edge roof. The parapets over the roofs were made taller, shaped, decorated and pierced.

3.1.5 FENCES

Keywords: fences of vegetation / timber fencings / chainlink fence / hurricane fences / white picket fence / turf / barbed wire fencing / woven wire fences / expanded metal lattices / electrified fences / fence wire / barbs / straight head, inward or outward bend / extended coil of barbed wire / concentration camps.

Fences are barriers to confine or exclude people or animals, to define boundaries, or to decorate. Fences of vegetation such as plants, hedges, climbers, cactus and dry thorny shrubs are used in farms and fields. Timber, earth, stone, and metals are widely used for fencing. In 19^thC North America, many varieties of timber fencings were developed, such as the split rail laid zigzag, the post rail, and the picket. Other common fences are chainlink fence, hurricane fences, and white picket fences. In comparatively low rainfall areas like East Europe and in W. USA, turf was dumped to create fences.

The first patents on barbed wire fencings were taken out in the United States in 1867. However, it was in 1874, when its production by machines, made its use widespread. Woven wire fences and expanded metal lattices, affixed to wood, steel, or concrete posts, proved economical and durable. Electrified fences, frequently a single strand of barbed wire, are sometimes used for temporary confinement of animals. A mild shock is given to the animal at intervals of a few seconds if it is in contact with the fence.

Fence wire usually consists of two longitudinal wires twisted together to form cable and having wire barbs wound around either or both of the cable wires at regular intervals. The varieties of barbed wires are numerous, with cables being single or double, round, half-round, or flat and having a range of gauges. The twisted double cable provides extra strength and permits contraction and expansion without breakage. Barbs are diagonally cut in order to provide sharper points; they may consist of one or two pieces (two or four points) and are generally spaced at intervals of 100 to 130 mm.

Barbed wire fences have straight head, inward or outward bend at the top to make the crossover difficult. Armed forces place extended coils of barbed wire on ground without any posts. During world war II barbed wire fence posts were spiked to prevent air craft landing. Hitler's concentration camps are grim-reminder of fencing used for forceful confinement. Germany was first divided by barbed wire fencing, which however did not prevent people escaping through it, so were replaced with massive RCC walls. Yet nations of the world put up barbed wire fences to demarcate boundaries, as it provides a cheap and fast way of erection.

3.1.6 GUARD RAILS

Keywords: strong band / guard rails in buildings / walkway or footpath along a wall / environmental guard rails.

A guardrail is effectively one strong band (long metal strips tied together to a support post) that transfers the side force of a veering car to multiple posts beyond the impact area or directly into a ground anchor at the end of the guardrail emplacement. A guard rail is a system designed to keep people or vehicles from (in most cases unintentionally) straying into dangerous or off-limits areas. A secondary objective is to keep the vehicle upright while it is deflected along the guardrail. This is rather difficult to achieve as a guardrail of the ideal height for a car might not keep a truck from toppling over it, while a motorbike might slip under a higher-placed rail. Guard rails are likely to cause many motor able, as this has to face many different conditions. So transportation engineers are increasingly discourage the use of a guardrail, for the guardrail should only be placed when the roadside conditions pose a greater threat than the guardrail itself.

A guard rail is more restrictive than a hand rail as the former provides both support and the protective limitation of a boundary.

Guard rails in buildings are of numerous types, and are required by building codes in many circumstances. A walkway or footpath along a wall works as a guard against vehicles striking or rubbing a building. Guard rails serve both architectural and environmental functions.

On roads with sumps and causeways which get flooded over in seasonal storms require guide rails or posts to indicate the width of the motor able or safe passage width. This rails or vertical posts are height marked so that depth of the flooding water can be seen.

Environmental guard rails are placed along hiking trails, where adjacent terrain is often steep and un-travelable, along trails at scenic overlooks, and also at many elevated destinations of trails.

Guardrails are also included beneath the high sides of heavy vehicles such as lorries. This is in order to prevent smaller vehicles (e.g. cars) from passing between the lorry's front and rear wheels during a collision, and being crushed subsequently by the lorry's rear wheels.

3.1.7 HAND RAILS

3.1.8 COMPONENTS OF RAILINGS AND PARAPETS

Keywords: topmost component / guide rail / psychological support / decorative function / wall hand rail gripping element / inclined or slippery floor / high winds and storms / top hand rail / guiding / extra widths and higher height for supporting the elbow / sectional shape / Standards for hand rail design / lateral stability / joins pieces / noncontinuous / continuous / over-the-post and besides the post / post-to-post and newel-to-newel / discourage the usage / wider surfaces / bar stools' foot rests.

A hand rail is the topmost component of barricade systems like parapet or railing. Hand rails, without the barricade system, are provided in hotel lobbies, corridors, passages. Since no height related or other hazards are operative in such areas, the hand rail functions as guide rail. A hand rail on its own is less protective as a barricade but provides psychological support (assurance) for the hand and body. In this sense it has only a decorative function.

A wall hand rail is used as gripping element, for travel along inclined or a slippery floor. Wall hand rails are required in toilets to change the posture. Hand rails are also provided on ships, sail boats and railway engines for holding in high winds and storms. Hand rails are heated or cooled by water circulation depending on the external conditions. Top hand rails are used in buses and metro trains for commuters to stand. Top hand rails also have hangers for grabbing. Hand rails are also used for guiding visually impaired persons in horizontal movement. A hand rail is the uppermost section of a barricade and so it is used for standing against it, for resting hands or spreading elbows or for gripping. Hand rails are provided with extra widths and higher height for supporting the elbow. For hand support and gripping appropriate sectional shape is required for the hand rail.

Standards for hand rail design are:

A handrail is defined as either a circular cross section with an outside diameter of 32 mm minimum and 50 mm maximum, or a non-circular cross section with a perimeter dimension of 100 mm minimum and 160 mm maximum, and a cross section dimension of 57 mm maximum. For a handrail with a perimeter dimension greater than 160 mm, a graspable finger recess area is to be provided on both sides of the profile. Handrails are located at a height between 860 mm and 960 mm. In areas where children use the facility, a second set of handrails at a maximum height of 710 mm (as measured from the ramp surface or stair nosing to the top of the gripping surface) is necessary. Sufficient vertical clearance between primary and secondary handrails should be minimum 230 mm to prevent entrapment of children. The distance between the wall and handrail is very important. Common requirements are between 38 and 57 mm.

A handrail on one side of a stairway is always necessary, (even where both sides are walls) and on both sides, if the stairway is more than 1000 mm wide. All stairways, balconies and certain other areas above ground level which are likely to be used for other than just maintenance, must also have a balustrade or guard. With a wide balustrade the actual or the effective width of a stair, balcony or passage is reduced. The clear unobstructed width between a wall face and the internal face of a balustrade or between two internal faces of handrails is considered as an allowable passage.

A handrail serves many other functions, it often provides a lateral stability to the barricade and joins pieces of barricade into a functional whole. Hand rails used for supporting the body may be designed to be noncontinuous, but hand rails used for horizontal movement such as in stairs, ramps, escalators, walkways etc. must be continuous. Continuous handrails are called: over-the-post and besides the post, and noncontinuous handrails are called post-to-post and newel-to-newel.

Positions or building elements that are likely to be used as a hand rail are treated to prevent such a purpose. Spikes, sharp knife edge section, sloped top face, coating with non drying (green or ever-wet) paints etc. are some of the means used to discourage the usage. However wider surfaces are provided to support planters and cut off the view of areas immediately close-below. Some handrails also have foot rails that are similar to Bar stools' foot rests.

Keywords: PANELLED PARAPETS / PERFORATED PARAPETS / EMBATTLED PARAPETS / POST AND RAIL PARAPETS / Stupa at Sanchi / American colonists / Indian Railways / MACHICOLATION / floor openings / CRENELS / merlons / EMBRASURE / BATTLEMENT / NEWEL / hollow newel construction / picket / structural supports / half newel / decorative newel drop / tandem caps / quarter-turn caps / BANISTER / VOLUTE / turnout / GOOSENECK / ROSETTE / half newel / EASING / starting easing / over easing / CORE RAIL / BALUSTER / balustrade / guards or spindles / second baluster / window balustrade / quattrocento balustrades / BASE-RAIL OR SHOE-RAIL / FILLET / fillet.

PANELLED PARAPETS: Panelled parapets are made of panels fixed at the top and bottom or as in-fill element between newels and banisters. The panels are ornamented by a carving, relief engraving or are pierced.

PERFORATED PARAPETS: Perforated parapets are latticed structures to restrict view and allow the breeze to pass through. It is also a technique of reducing the dead weight if the parapet over cantilevered structures.

EMBATTLED PARAPETS: Embattled parapets were part of battlements on fort walls with provision of apertures for viewing and throwing objects over the invaders. The same pattern was adopted as a roof parapet decoration of large villas.

POST AND RAIL PARAPETS: These are created with wood or bamboos. In India Stupa at Sanchi has circumscribing stone parapets emulating the wood work. American colonists used local wood to demarcate their lands and for creating cattle yards. Indian Railways use their old wooden sleepers and steel rails for creating such barricades.

MACHICOLATION: A parapet over a projection like brackets, with floor openings through which molten lead, pitch, oil or stones could be poured over the enemy.

CRENELS: Crenels or crenelles are alternating low portions in a parapet of a wall or battlement. The high portions are called merlons. Battlements have crenels to look out and merlons to throw arrows.

EMBRASURE: An opening between two merlons in a parapet (battlement).

BATTLEMENT: The battlement was an early development in military architecture. It was used in Chaldea, Egypt, prehistoric Greece, and Roman fortifications. During the European middle ages the battlements saw greatest development. The crenels became narrower and were splayed on outer sides for wider view. The merlons were rounded or flat at the top. The medieval battlement was often bracketed out from the face of the wall, machicolations, with holes in the floor drop objects over invaders.

NEWEL: A newel was the central post of a spiral or circular stairway, and if such a stairway has no central post, it is said to be of hollow-newel construction. A newel is a large picket or post that supports a handrail of a stair at the starting point or its landing. Newels are also used to support handrails in balconies, etc. Newels are structural supports, and so are anchored very well to the floors. A half-newel is used where a railing ends at the wall. For open landings, a newel may extend below the landing for a decorative newel drop. Newels projecting above the handrails are covered with tandem caps. At corners, there are quarter-turn caps. For post-to-post systems, the newels generally project above the handrails.

BANISTER: The term banister means the vertical mid supports and the handrail, or just either of it.

VOLUTE: A volute is the end of a handrail that is shaped like a spiral in a horizontal plane. A turnout is a quarter-turn rounded spiral at the end of a handrail.

GOOSENECK: The section between sloped handrail of the lower flight, and another sloped handrail of the upper flight of a stair.

ROSETTE: Where the handrail ends in the wall, and if a half-newel is not used, the hand rail is trimmed by a rosette.

EASING: Hand rails that are mounted directly onto a wall with brackets. At the bottom of a stair if such a railing flares to a horizontal railing, the horizontal portion is called the starting easing. At the top of a stair, the horizontal portion of the railing is called over easing.

CORE RAIL: Wood handrails often have a metal core to provide extra strength and stiffness, especially when the rail has to curve against the grain of the wood. The term for such reinforcing metal core is the core rail.

BALUSTER: A baluster is a moulded shaft, square or circular, traditionally in stone or wood, sometimes in metal, and now in plastics, supporting the coping of a parapet or the handrail of a staircase, an assemblage of them being known as a balustrade. Balusters are vertical mid pickets or members that hold the handrail. Sometimes these are made on turning lathes so-called guards or spindles. A nominal tread width, often require two balusters. The second baluster in such cases is closer to the riser and is taller than the first. The extra height of the second baluster is achieved by spacing at the middle, the decorative elements in the baluster. This allows the bottom decorative elements to be aligned with the tread, and the top elements are aligned with the railing angle. However, this means the first and second balusters are not interchangeable and must be manufactured separately. However balusters without decorative elements or with flutes or spirals' pattern can be interchanged.

Building codes also require that opening within balusters be of a size such that a 4" (100 mm) sphere cannot pass. There are three exceptions according to the 2003 International Building Code Section 1012.3, which allow openings to not exceed 8" or 21" depending on occupancy groups or special areas.

The word Baluster = balaustra = pomegranate flower, from its resemblance to the post. French = balustre, Italian =balaustro, Latin =balaustium, Greek= balaustion.

The earliest examples of balusters are from bas reliefs on Assyrian palaces, where these are shown as window balustrades and had Ionic capitals. Though Greeks0 or the Romans have not used balusters. Balusters have been extensively used in 15^thC balconies of palaces at Venice and Verona. These quattrocento balustrades were descendants of unknown Gothic precedents. Giuliano da Sangallo is credited with using it consistently on the terrace at the Medici villa at Poggio a Caiano (1480 AD).Two types of balusters were used: one favoured by Michelangelo -symmetrical in the profile: inverted one bulbous vase shape over another, separating them with a cushion like torus or a concave ring. The other was a simple vase shape. The style of a baluster is often a method of dating the antique furniture or architectural details. For example, the distinctive twist designs of balusters in oak furniture are a characteristic mark of early 17^th C period of the Charles I in England. The modern term baluster shaft is also applied to the shaft dividing a window in Saxon architecture. In the south transept of the abbey at St Albans, England have some of these shafts, and are presumed to have been taken from the old Saxon church. Norman bases and capitals have been added, together with plain, cylindrical Norman shafts.

BASE-RAIL OR SHOE-RAIL: For systems where the baluster does not start at the tread, they go to a base rail. This allows for identical balusters, avoiding the second baluster problem.

FILLET: A fillet is a decorative filler piece on the floor between balusters on a balcony railing. Fillets also become panels or inserts between balusters. Often panels are edge to edge joined to form a larger surface. Modern stairs have such in-fill panel members of wood, veneer, plywood, metal, plastic sheets and glass panes. A glazed or glass fillet must be of glass blocks, toughened glass or laminated safety glass, but annealed wire glass must not be used.

3.1.9 MATERIALS FOR BARRICADES

Keywords: stone and brick masonry / wooden casks of wine / concrete / Metal / plastics and composites / ropes wires, woven tapes and plastic tapes / barricades for public gatherings / cycle stand barricades / non rupturing plastic bags / nets.

Barricades are constructed out of a variety of materials depending upon their projected use, the degree of stability and permanence required:

Stone and brick masonry structures were once very common, wood barricades were first created by placing wooden casks of wine. Concrete is preferred choice for barriers in out door public spaces due to their capacity to withstand high impact, climatic conditions and stability. Metal barricades of coated mild steel and stainless steel in cast forms and geometric fabrications of drawn sections (including pipes and structural) and sheet metal formations, are widely used because of their light weight, ease of installation and ease of replacement. Barricades of plastics and composites have the advantage of being very lightweight, non hurting on impact, transportable, and high quality finishes including colour, night reflectivity -fluorescence. Plastic barricades are used in sporting events, fairs, amusement parks and festivals. Ropes, wires, woven tapes and plastic tapes are also used to create a visual boundary or symbolic barricades. Light beams, air curtains, water jets are some of the modern day innovations.

Barricades are effective through their shape, as much as they are through the materials of construction, and the terrain. RCC castings of variety of shapes and sizes are used as barricades.

Barricades for public gatherings have to be transportable and stable against heavy pushing by crowds. This are often called cycle stand barricades, due to the similarity of stable structure. Non rupturing plastic bags filled with water are used as barricades. Nets are stretched against building under construction to prevent accidents due to fall.

4.0 OPENING SYSTEMS

4.0.3 Expression of Openings

CHAPTER 4.0 INDEX

4.0.1 Nature of Openings

4.0.2 Types of Openings

4.0.1 NATURE OF OPENINGS

Keywords: NATURE OF OPENINGS / continuous entities / openings / junction / barrier system / domain defining elements / subordinated or minor systems / Japanese Gate Torii / eaves / Sanchi Stupa Gate / bands of eaves / toran / rounded arch / pointed arch / eaves is the essence of opening / the sides also mark an opening / metaphysical intervening element / connection / relationship / linkage / trade gateway / eaves and sides / formal opening system / marks a point of exchange with other domains / landmark a domain / power of domain / focus / links / nodes / gateways / linked openings / RELEVANCE OF OPENINGS / SCALE OF OPENINGS / finite size / small opening / large opening / multiple openings / significance of a small opening / contrasting scale / re-scaling / a large window / lites / ganged or multiple doors / wider but controlled opening / openings are spaced out / openings are concentrated or grouped / image projection / large opening means / smaller and fewer openings / large window vs small window / LEVEL OF OPENINGS / negotiable for egress / transit-able in emergency / french window / trapdoor or hatch door / barn door / warehouse gantry girder / high sill / low or zero sill / upper floor windows / THIRD DIMENSION OF OPENINGS / dual character / third facet / depth of the junction / threshold / real or notional / interim space or time / DESIGNING OPENINGS / basic design considerations / key issues for openings in buildings / devices / nature of relationships between spatial domains.

NATURE OF OPENINGS: Barriers are continuous entities, but can be experienced only through the openings within them, and at the junction formed by the end of one barrier and start of another barrier.

Doors, windows, gates, gateways, etc. are openings within a barrier system. These occur within domain defining elements such as: walls, fencings, fort walls, enclosures, partitions, dividers. Such opening systems are subordinated or minor systems as these must occur within a barrier system.

Openings often occur without the inevitable mothering barrier system. Japanese Gate Torii is placed alone anywhere in 'wilderness', in the middle of sea. According to the Japanese mythology, the essence of gate comes into being through the eaves. Torii is a metaphoric gate, formed by head bands, the 'eaves'. The eaves need physical side supports, which are placed as minor elements of the Torii gate structure. The Sanchi Stupa Gate also has three emphatic horizontal bands of eaves, but placed over singular supports. The Toran, buntings, streamers, banners, all are forms of the eaves, and so constitute a gate. The head structure or lintel of an opening system is the place to mark gate deities and signs. The round arch can be considered as a relief to the ponderous horizontal lintel or the eaves. The pointed arch of the Gothic era relieves the opening more.

If the eaves are the essence of an opening, conversely, the sides, also mark an opening. Two posts alone, without any eaves, a head structure or a shutter can create an opening or gate. Set of parallel elements also define an opening. The twin elements are perceptually or conceptually linked by a metaphysical intervening element, that manifest a connection, a relationship or linkage. Petronas Towers, World Trade Centre twin towers, Brazil, electric transmission towers or pylons create gate like effect. Valleys between mountains provide a negotiable zone like a pass, the trough, gorge, etc. which are called gateways. Afghan valleys are considered the gateway to India. Suez Canal is considered a trade gateway to Europe. Silk Route opens a window to China.

The eaves and sides, both on their own, and all together create openings. In any formal opening system both are present. When one is absent or minor the openings tend to be notional.

An opening marks a point of exchange with other domains. Openings or such notional formations are placed to landmark a domain. Commemorative archways, Gateways, plaques, obelisks, pillars, moats, etc. not only denote the power of a domain, but also its focus.

Bridges, pathways, avenues etc. are links joining two points. Such links regulate the exchange occurring through them, so are considered gates. The ports, wharfs, moorings, runways of airports, plug-sockets, are nodes of connectivity and exchange. The nodes are gates. Computer nodes, the Gateways (a device or system that intervenes to provide an exchange) are linked openings.

RELEVANCE OF OPENINGS: Opening systems are also ineffective in transparent, obstructed or frequently interrupted (broken - discontinuous) barriers. A room with a lattice wall all around or a glass cabin has no need for a window. An open pavilion has no need for any door.

SCALE OF OPENINGS: An opening has finite size, however, the barrier system within which it manifests could be infinite in size. An opening can never be larger or equal to the barrier system within which it resides. An opening, occurring in a finite barrier system could be relatively small or large, but openings occurring in very large or infinite barriers can be judged to be large or small in terms of the user.

A Small opening makes a barrier system very evident, whereas a large opening or multiple openings make barriers less effective. Significance of a small opening is due to the contrasting scale against the barrier system within which it occurs. The exchange occurring across a small opening is very intense, compared to a large gateway. Small openings due to their smaller scale allow a controlled scale of exchange. However, a large opening often requires re-scaling through various appendages such as: segregation channels for up - down, and fast -slow traffic, compaction through funnelling, filtration for selective processing acceleration and de-acceleration mechanisms. A large window is divided into smaller units -lites, each of which can have a varied configuration. Entrance foyers of skyscrapers, lounges of Airports and Railway stations, have ganged or multiple doors to serve the demand for a wider but controlled opening. However, air hangers, garages, barns and warehouses require wide doors to meet the functional carriage width, but are inserted with small openings for other uses. Openings are spaced out to take advantage of the location and orientation, and diffuse the exchange over a larger zone. Openings are concentrated or grouped together, to few locations to reduce the wastage of distributed operations.

Openings are scaled in terms of the image projection. A large opening means: capacity to build better, greater control over security, desire for extravagance or grandeur, need to be perceptible from distance. Smaller and fewer openings mean: conservative building technology, problems of safety and security, prudence and need to be less visible.

A Large window illuminates the interiors brightly, creating a fearless but public (non-private) space. Bright spaces are warm, a desirable quality in some climates. A Small window mean a sturdy and stable structure, an intimate (private) space, safety, security and cool interior or a 'cold' space. A wall, the barrier system mothering the opening traditionally has been massive, but more insulating for radiation, so fewer openings disrupt a wall less.

LEVEL OF OPENINGS: Openings are essentially of two types: negotiable for egress or transit-able in an emergency. In both cases, the degree of conveyance may have been intentionally made difficult or easier. A French window is a door for conveyance, and a trapdoor or a hatch door is a window for all purposes. A door could occur at a negotiable level but a barn door for fodder, is placed at first floor level. A warehouse gantry girder could extend out of an upper level door like opening to lift up goods and bring it in. Windows have many grades, of 'high to low' sill levels, as referenced from interiors or exteriors. A high sill from interior space cuts off the view to the outside as in medieval cathedrals. A low sill or zero sill window 'opens' a space as in case of traditional Japanese houses. The upper floor windows of a glass curtain high rise building, clerestory windows and skylights offer a static view, lacking in dynamism.

THIRD DIMENSION OF OPENINGS: All Opening systems have dual character: an inside and an outside one. But very often a third facet is recognised as the depth of the junction (cross section of the opening). Here the significant elements are: the thickness (or the duration of transiting through) of the barrier system, and the configuration of the opening system. The third facet or the dimension of the opening systems is the threshold. A threshold has two distinct worlds on either of the sides, one or both of which could be real or notional. A threshold could also be factual or abstract depending on the real or notional worlds across it. The threshold areas are resting zones, zone for transition, point of decision making, celebration, welcome or separation. The third facet however manifests from what happen in the interim space or time. Changes occur to things that pass through, such as filtration, elimination, mixing, alignment etc. Some of these changes are passive, but many use energy. A window airconditioner, air cooler, exhaust fans, enforces a change. Depth of the door or windows regulates the pattern of illumination and field of view. (For more on thresholds : see 4.1 Openings systems : Doors )

DESIGNING OPENINGS: Basic design considerations for an opening system are: width, height, depth, form (shape, configurations) and position (in the surroundings, angles, orientation). Key issues for openings in buildings are: the massing of openings, the relative size and position in reference to other openings, the contrast it creates against the surface of the barrier system, its height position in reference to eye level, adjoining terrains, ergonomic parameters, etc.

The openings in buildings are placed for the pattern, compositions, for scaling and proportioning, endowing graphical character, for reflecting styles, cultural ethos, religion and such other affinities and identities.

Openings are devices for allowing or restricting the sunlight, air, sounds, privacy and for framing the view of the outside. As a device openings have inbuilt systems to modify the elements transiting through it, such as air, moisture, dust particles, ion charge etc.

An opening in a barrier system primarily connects two distinct worlds, but their own presence assumes many different guises. An opening becomes a medium of investing the nature of relationship between spatial domains.

4.0.2 TYPES OF OPENINGS

Keywords: CLASSES OF OPENINGS / touch the floor / higher sil level / gates and gateways / micro size openings / single function systems / fixed glazing / picture window / shop front windows / space dividers as partitions / computer gateways and ports / hub / protocol, converters and translators / universal architectural system / standard range of options / strict exterior architectural regimen / users / ELEMENTS OF OPENINGS / surrounds / parallel to the ground / perpendicular / head formations / foot entities , side members / fixed openings / hung shutter system / sliding shutter system / architectural aperture / pivots / architectural elements / hinges / sliding channels / wooden frames / Georgian sash windows / aluminium / integrated into the structural fabric.

CLASSES OF OPENINGS: There are two classes of openings in terms of their basic functions: Openings that touch the floor on one or both sides to facilitate floor level movement goods, people and animals; and Openings placed at higher sill level -away from the nominal floor level, and chiefly used for seeking illumination, view and ventilation. At other level gates and gateways besides serving the basic functions of door are used for grandiose. Micro size openings such as cracks or crevices of joints provide minor ventilation needs. Openings are designed as single function systems such as terrace level wind catchers, pip holes, delivery slots, etc.

Openings of fixed glazing serve the function of picture window framing a scenery or shop front windows to display items. Fixed openings also become space dividers as partitions or cover element like a curtain wall. Computer gateways and ports (air, sea, land) serve as a hub for transit, termination and re-connection. At this point one can have choice how, where, when a connection could be made. To provide such choices, the hubs are endowed with protocols, convertors or translators.

As opening is a very universal architectural system. Openings are often mass produced with standard range of options. The openings follow a very strict exterior architectural regimen without consideration of the interior use related needs. For the above two reasons openings of same size, shape and design are used on all orientations, floor levels, neighbourhood conditions and geographic locations. Users wish to mark the openings' system with individual personality, cultural ethos, beliefs, affinities etc. These occur as appendages, add-ons or treatments.

ELEMENTS OF OPENINGS: A openings is formed by its surrounds. Surrounds are participating elements or just notional or casual elements that form the opening. The participating surrounds are either parallel to the ground defying the gravity or perpendicular following the gravity. Eaves, lintels, arches are head formations, ledges; floors and thresholds are foot entities; and jambs, 'surrounds' stiles etc. constitute the side members.

In case of fixed openings all sides are of equal importance, except the bottom one which may carry the load to the gravity. All sides 'hold' the glazing or panelling and provide sealing overlap. However, in case of hung shutter system, one side is used for fixing but in sliding shutter systems either the horizontal or vertical pair houses the channel for movement.

Primitive opening systems have no surround system, the shutter operates in the architectural aperture. But evolved systems the shutter is housed in a frame which in turn is fixed in the structural gap. The surround initially was a an overlap to seal the edges and restrict the shutter opening in one direction only. The shutters, if any were hung through pivots inserted in architectural elements. However, the pivots were difficult to insert, repair or replace, making way for development of hinges and to a small extent sliding channels. The other end of hinges could not be fixed to architectural element like masonry wall. Wooden frames became the unavoidable component of the opening systems. The Georgian sash windows used the sliding channel to avoid the problems associated with hinges. During industrial revolution era steel began to replace wood, and by mid 20^th C Aluminium became the favourite material for opening design. The frame, which was unavoidable component of the openings began to be integrated into the structure system in the form of curtain wall. The opening system and its surrounds all were well integrated into the structural fabric of the building.

4.0.3 EXPRESSION OF OPENINGS

Keywords: EXPRESSION OF OPENING / descriptions, metaphorical expressions and as metaphysical entities / architectural, functional and visual interests / metaphorically / transition from one state of existence to another / metaphysically a triad: an inside, outside and as in-between / of being on one or the other side / being into neither of the two / third reality is the threshold / opening is like dream or thought / OPENINGS FRAME A VIEW / surreal / staging qualities / art, architecture and performing arts settings / foreshortening / C. Riley Auge / J. R. R. Tolkien treatments of doorways, gates, windows, and natural thresholds / constructs / physical boundaries / psychological transition points / point of transgression.

EXPRESSION OF OPENING: In literature openings occur as descriptions, metaphorical expressions and as metaphysical entities. As description, the opening systems occur as entities with architectural, functional and visual interests. Metaphorically an opening is a change. Doors, gates, windows, and other openings express the transition from one state of existence to another. Likewise passageways, bridges, ducts, also serve the function of transition. An opening is a line where the change occurs and the bridges lead a path to or away from such a line. The point of transition is a mark up, a demarcation. Metaphysically the opening constitutes a triad: an inside, outside and as in-between. The construct is a 3-way experience, of being on one or the other side and the state, or of being into neither of the two. The third reality is the threshold, the zone of indecision for some. The paired reality of inside and outside, or existing on one side vs. the other side creates a threshold or an edge. To stand upon the threshold allow time and space for contemplation before committing to circumstances, because the action once undertaken may not be undone. An opening is a relief from the enclosure or very constricting situation. It is a way to fulfill the expected, and a venture for the unexpected. The opening is like a dream or thought, so thin and efferent that one often does not realize if it is real or ethereal.

OPENINGS FRAME A VIEW: The framed view is available so far one is little away on either of the sides, but same frame gets dissolved when one reaches the threshold. The frame losses its arresting or picturesque quality when viewed in a wider context that is a very wide opening encountered very closely. An opening without any apparent framing seems surreal, as much as an opening that is without its adjacent wall or barricade. Both these staging qualities are used in art, architecture and performing arts settings. The framing provides a scale reference, but the third dimension of depth, remains ambiguous due to the foreshortening.

A change manifests on passing through an opening physically, through the depiction or psychical referencing. Architectural entities are three-dimensional constructs and so provide a time and space intervention. The inside or the womb is the origin, so human endeavours continue to revert there. The connecting thread or unbiblical chord continues to retract one to the inside, the womb.

'Often crossing a threshold, real or implied, moves us between safety of the known and anxiety of the unknown. Thus, working on literal and symbolic levels simultaneously, doors and other passageways can provide, both, the physical reality of protection and represent the psychological idea of safety. Additionally, as 3-dimensional constructions, openings allow not only the dualistic reality of inside and outside, but also the possibility to exist within--being neither in nor out. Once one crosses the threshold, there is no going back to what was'.

'Likewise, the psychological threshold provides an inner space for struggling with indecision, fear, and courage before passing into the unknown. The resulting experience changes forever (for good or ill) whoever crosses the threshold'. -'Crossing the Threshold: Doors and Other Passageways in Tolkien's Words and Images By C. Riley Auge`

J. R. R. Tolkien used doors, gates, and other passageways extensively and deliberately throughout both his literary and artistic works to explore and express these very ideas. In fact, many of his descriptions and treatments of doorways, gates, windows, and natural thresholds were worked and reworked numerous times in sketches and paintings before finalizing them within his written texts. Even in his landscape sketches, the focal point is almost always a doorway or other opening. Regardless of medium, the importance Tolkien placed upon these constructs, whether as physical boundaries or as psychological transition points (or both), is overwhelming when one closely examines collections of his artwork, The Hobbit, The Lord of the Rings, and The Silmarillion.

A barrier separates one from what is beyond. It provides a zone where one has survived and will continue to do so eternally. The safe environment perpetuates the identity of the habitant and 'its perception of the macrocosm unquestioned'. The edge of the barrier is the demarcation which when transgressed a new perspective is available. The point of transgression is the door or opening. Openings within the barriers like doors are the frames within which context the change is referenced. 'The Sun god arrives through the Eastern gate and the past is always bounded by the door like the fake door of the Egyptian tombs.' The fake door exists in spite of the knowledge that the dead will never return and the door will remain unused.

(For more refer to 4.1.9.2 Door Myths and Legends).

4.1 OPENING SYSTEMS : DOORS

4.1.1.1 Historical perspective : Doors

CHAPTER 4.1 INDEX

4.1.0 Doors : general

4.1.1.2 Historical perspective : Doors -Types

4.1.1.3 Historical perspective : Doors -Periods

4.1.2.1 Components of Doors

4.1.2.2 Materials and Technologies

4.1.2.3 Hardware

4.1.2.3.1 Basic Hardware

4.1.2.3.2 Secondary Hardware

4.1.2.3.3 Appendages and Attachments

4.1.2.4 Door Mechanisms

4.1.3.1 Door Styles

4.1.3.2 Commercial Categories of Doors

4.1.3.3 Varieties of Doors

4.1.3.4 Other types of Doors

4.1.3.5 Door like Utilities

4.1.4.1 Door like Presences

4.1.4.2 Real and Pseudo Doors

4.1.5.1 Door Sizes and Proportions

4.1.5.2 Doors Functional Sizes

4.1.6.1 Door Opening's Structures

4.1.6.2 Door Openings in Thick and Thin Walls

4.1.7.1 Doors and Vastu Shastra

4.1.8.0 Functions of Doors

4.1.8.1 Illumination

4.1.8.2 Ventilation

4.1.8.3 Passage and Control

4.1.8.4 Safety and Security

4.1.8.5 Insulation

4.1.8.6 View through

4.1.8.7 Other Issues

4.1.9.1 Emerging Technologies

4.1.9.2 Door Myths and Legends

4.1.0 DOORS: GENERAL

4.1.1.1 HISTORICAL PERSPECTIVE: DOORS

Keywords: opening system / controllable opening / substantive barrier system / poor barrier system / poor door system / a finite size and specific functionality / regulators / Dwar / threshold / kiwad / door as a metaphor / symbolic endowments / forms and situations / allegorical connections / Sun / East / life, joy, brightness / West / false door / door of entrance / birth / door of exit / death.

A door is an opening system in a barrier system. The door as an opening system allows the exchange between the inside and outside, but it is a controllable opening. The need for an opening is very acute in strong barriers. A door comes into being if only a substantive barrier system exists. A poor barrier system, one that is transparent, translucent, broken, or uneven will have equally poor door system. An open pavilion cannot have an effective door system and a glass house or a latticed green house need not have an opaque door.

A door is effective if it is smaller in scale then the mothering barrier system. It can never be larger than the barrier system within which it resides. A door could be almost as large as the barrier system, but when it equals to the size of a barrier system, it loses the identity of a door. A door cannot exist without (or in spite of) a barrier system.

A door has a finite size and specific functionality. Doors serve a basic function of an entrance and exit, and are also regulators of privacy, security, environment, pollution, illumination, noise and fire. Such regulations are done by design, materials of construction, placement, and also by use of variety of fittings and hardware.

Sanskrit word for door is Dwar, which means 'through which', 'from', `by'. In Indian mythology the essence of a door is the threshold, here inside and outside, both manifest their differences. In Japan the door is an intervening spatial element -'torii' formed by the eaves, the head. Kiwad the hindi-urdu word nominally used for shutter of a door, is kim + wad = territory bounding or a movable barrier.

A door as a metaphor denotes entry, exit, change or transition, a switch, a control, identification, a nomination and intervening element between an enclosure and open or the free cosmos. Doors have symbolic endowments such as ownership, right of way, a new beginning, a portent of change, exit, departure or death. On the other hand certain forms and situations have allegorical connections with doors. Encounters with a different domain are through a door, or conversely a door or its representation marks the focal point of a domain or the section of its edge -the entrance or exit.

Ancient openings were associated with the Sun. The Sun entered from the East and passed out from the West. The East was associated with life, joy and brightness, and the West with darkness, gloom and death. Intaglios Babylonian seals show Sun god passing through a double valved gate of the East, and beginning to climb the mountain of the sky. The Veda says 'the dawn shone with brilliance and opened for us the doors that are high and wide with their frames'. Even where four sides of a building have openings, it is the East door that is the great door or the gate of sunrise. The great Eastern door of the sun temple at Baalbek, 'city of the sun,' was 21' wide, and 40' high. Tombs in Egypt, Persia and Lycia have on West side a false door that was indicated like a real door. It is low and narrow, framed and decorated like the door of an ordinary house. Door of entrance marks the birth or new beginning and the door of exit marks the death or end of the world. Person with a door has the right of occupation and residence.

4.1.1.2 HISTORICAL PERSPECTIVE: DOORS - TYPES

Keywords: fire / social privacy / covering materials / skewed entry positions / monolithic panel / stiles / rails / shitomi / controlled barrier / pivots inserted into lintels and floor pieces / door frame / concealing it or integrating the door frame.

A door has been the most important element after fire for instilling a sense of security against intruders, wild animals and elements of weather. In cold climates keeping the warmth inside, in deserts the sand storms out, and in tropics protection from rainwater is mainly achieved by a door system. Social privacy is also a key factor in design of a door system.

Just as the hearth was the focus of the family, the door denotes a domain, the home. The first doors were plain gaps with additional facility of cover. A variety of covering materials like, hide, fabrics, woven matings, rubble heaps, sticks, wood logs and planks, metal casts, paper, grass and leaves, and stone slabs were used. These were dumped, heaped, hung or placed strategically. Stripes of hides, vines, ropes, animal guts, sticks, etc., were also used to support the cover materials. Skewed entry positions, such as: cliff faces, entwined passages, narrow or low height(crawling) passageways (like igloos of Eskimos), fall-down (pit houses of China) or climb-up (tree houses), etc., have been used to strengthen the functions of doors. From the period of 'non built' habitations (cave, open air, etc.) to early Harappan, Egyptian and Mesopotamia architecture, the 'door' was a gap that served the purpose of entry, exit and illumination. The earliest record of a door shutter is of a painting in an Egyptian tomb where it is shown to be a monolithic panel of wood. In reality such monolithic panels were technologically not feasible, so Vitruvius writes about doors built with stiles (scapi) and rails (impages), and the spaces enclosed were filled with panels (tympana).

Harappa's main streets were straight walled with no openings, and all door-like openings were placed in the small side-lanes, passages or court yards. House rooms had entry gaps from such passages and court yards. The 'doorway' or gaps were covered with hides, fabrics and woven mats for privacy. The word 'shitomi' (Japanese) for the door literally means 'a small woven mat' recalling the hanging curtain forms of doors in ancient buildings.

The concept of a door as a controlled barrier with a shutter is only 7000 to 8000 years old. Doors of rigid and permanent materials first appeared with monumental architecture or public buildings. Doors for important chambers were made of wood or stone. All ancient doors of wood or stone were hung by pivots inserted into lintels and floor pieces of hard stones such as basalt, dolerites or granite. In later periods the wood pivots were sheathed in cast bronze.

Early doors had no frames, as these were hung by pivots inserted into the building element. When pivots began to be replaced by hinges, as the efficient hardware, door frames were required for fixing the hinge end. The door now had a doorframe a distinctive element from the masonry surrounds. The door shutters were rarely monolithic, but composed of stiles and insert panels. The framed door, and its panelled shutter, both made the system easy to replace system. In 20^th C once again better masonry or wall making techniques have eliminated the need for a door frame, by concealing it or integrating the door frame.

4.1.1.3 HISTORICAL PERSPECTIVE: DOORS - PERIODS

Keywords: PRIMITIVE DOOR COVERINGS / mat / shutter / WOOD DOORS / Pompeian wooden doors / Chinese wooden door / traditional Indian house doors / Indian palaces and fort doors / STONE DOORS / stone pivots / BRONZE DOORS / cast-bronze grilled doors / cast panels / IRON DOORS / nailing / rivetting / nut-bolting / iron hinges.

PRIMITIVE DOOR COVERINGS: Door coverings were made of reeds, straw, cane bamboos, and stalks as mat, often stiffened at the edge to form a shutter. Such door as cover rolled up or pushed aside, and as shutters were hung through leather, fabric ropes or vine straps. The mat or the shutter was secured in similar fashion. Such doors were mostly used in domestic architecture. For public buildings a formal and stronger door was required.

WOOD DOORS: The most preferred material for making doors, in all geographic locations, in ancient times, was timber. Archaeological and literary evidence indicates its prevalence in Egypt and Mesopotamia. Pompeian wooden doors were made of stiles and rails with in-fill planks or panels, and were equipped with locks and hinges. The Chinese wooden door usually consisted of two panels, the lower one solid and the upper one a wooden lattice backed with paper. The traditional Indian house doors were made of carved shutter frames, but with wood planks forming a backing rather than a panel insert. Indian palaces and forts' doors were similar in construction.

According to a Chinese legend, a tomb located near the town of Sian and belonging to the first emperor of the Ch'in dynasty (221-206 BC) had a door that could not be cut with iron swords, because the door magnetically attracted the iron. Gates of a palace were also made of magnetic stone so warriors wearing iron armour were attracted and could not move.

King Solomon's temple doors were in olive wood, and besides olive wood, elm, cedar, oak and Cyprus were also used. These doors were carved, and overlaid with gold. The doors mentioned in Homer would appear to have been cased in silver or brass. Besides Olive wood, elm, cedar, oak and cypress were used. This Roman type of door was adopted in Islamic countries. In China the wooden door usually consisted of two panels, the lower one solid and the upper one a wooden lattice backed with paper. The traditional Japanese shoji was a wood-framed, paper-covered sliding panel.

STONE DOORS: Stone doors were used for tombs and such other sparingly to be opened buildings. The stone doors were heavy and like many other door systems of the time had stone pivots. In later periods stone doors with cast bronze pivots were also used. Stone doors do not accept add-on materials easily. Adding a bronze pivot was extremely difficult. Bronze, wood and steel were easy to include in a composition.

Stone doors have been found at Kuffeir near Bostra in Syria. Burckhardt found stone doors, 9 to 10 ft. high, as the entrance doors of the town. In Etruria many stone doors are referred to by Dennis. In Hauran in Syria, where timber is scarce, the doors were made in stone, and one measuring 5 ft. 4 in. by 2 ft. 7 in. is in the British Museum; the band on the meeting stile shows that it was one of the leaves of a double door.

BRONZE DOORS: Greek temples and Roman buildings had solid doors or cast-bronze grilled doors. Later bronze doors began to be made across Europe and parts of Asia, but by that time the art had died out in Rome. Cast bronze doors, as a tradition continued in Europe till middle ages. Later cast panels with patterns in relief made from a combination bronze, cast steel, and wood were used for assembling larger size doors.

The doors or gates at Balawat 895-825 BC. consisted of two leaves (each about 8 ft. 4 in. wide and 27 ft. high) were encased with bronze bands or strips, 10 in. high, and its tenons were sheathed with bronze. It seems the wood doors were about 3 in. thick, but the hanging stile was more than 14 inches in diameter. In the Hauran in Syria, where timber is scarce, the doors were made in stone, and one measuring 5 ft. 4 in. by 2 ft. 7 in. is in the British Museum; the band on the meeting stile shows that it was one of the leaves of a double door. At Kuffeir near Bostra in Syria, Burckhardt found stone doors, 9 to 10 ft. high, being the entrance doors of the town. In Etruria many stone doors are referred to by Dennis.

IRON DOORS: Iron began to substitute bronze as a tool and weapon material from about 1000 BC, and this must have been the period by which its use as door making material must have occurred. Bronze was more fusible (easy to melt and cast into shapes), harder than pure iron and far more resistant to corrosion. But Iron was more abundantly available. Bronze doors could form a lasting and protective layer of patina (rust) over the surface. Iron had problems of rusting. However, in many regions like Spain, China, etc., Iron Doors, lattices etc. were cast. Medieval churches throughout Europe were using wooden doors fitted with massive iron hinges and bands, to protect shrines and treasures. These doors were further embellished by slivering, gilding and later ceramic enamelling. Iron doors used nailing, rivetting and to a minor extent nut bolting as the joining technique. Forged joining of iron pieces came much later.

Keywords: EARLY EGYPTIAN / lower and upper portions of the tall opening / GREEK DOORS / unifores / bifores or geminae / valvae / fixed and often open-able cast bronze grills / EARLY ROMAN DOORS / semi circular arched doorway / solid bronze double shutters / cast bronze panels / curtains / paginae / BYZANTINE PERIOD DOORS / Hagia Sophia's cathedral / ROMANESQUE PERIOD / masonry vaulting / arched doorways / panelled squarish shutters / GOTHIC PERIOD / France and Germany / Italian doors / cast bronze doors / insert panels / Byzantine niello work / Lorenzo Ghiberti's doors / MEDIEVAL PERIOD / Lorenzo Ghiberti's Gates of Paradise / RENAISSANCE PERIOD / 'bolection' or projecting mouldings / INDUSTRIAL REVOLUTION PERIOD / iron structural sections / developments in glass manufacturing / new door systems / mass produced / door as integrated with the shell / POST INDUSTRIAL REVOLUTION PERIOD / National Standards and ISO / coordination of specifications / NEW AGE TECHNOLOGIES AND NEW DOORS / doors for automobiles / door frames / folded sheet sections / air curtains / invisible intelligent barrier systems.

EARLY EGYPTIAN: Early Egyptian temple doorways were tall (and so seemingly narrow) gaps stretching to the roof beam bottom. The lower and upper portions of the tall opening had distinctly different purposes. The upper part was left open to allow horizontal sun light to illuminate the altar in the early morning or evening. Seasonally moon light was also used for the same purpose. 'From the upper portion of the cleavage, the powers or the spirits entered with the light, and the lower portion was the entry point for the mortals'. Closing the entire opening with a single shutter was not necessary and technologically feasible. The lower gap up to the functional height however was closed for security and privacy.

GREEK DOORS: The ancient Greek and Roman doors were unifores -single doors, bifores or geminae -double doors, or valvae -folding doors. The leaves of the folding doors were hinged, and folded back one over the other. The doors were tall, almost reaching about two-thirds the height of the lofty naos, and when open allowed ample light to illuminate the statue in the naos. The doors were of wood and cast bronze, often panelled with a lattice. The portals of Greek temples were fitted with fixed and often open-able cast-bronze grills. So doors even when closed, the grilles in the door panels admitted sufficient light for the ordinary purposes. The doors were placed behind a colonnade forming the East front face and often a secondary colonnade of the pro-naos.

EARLY ROMAN DOORS: Early Roman doors were like the Greek doors, but with flat and a semi circular-arched doorway. The shutters were comparatively smaller in size but retained the vertical rectangular proportion. The Roman doors had solid bronze double shutters, supported by pivots fitted into sockets in the threshold and lintel. An early example of large cast bronze doors is of the 7.3 metres wide double shutter for the Roman Pantheon. The earliest large examples are the 24-foot (7.3-metre) double doors of the Roman Pantheon. The Romans perfected the technique of cast bronze panels for fabricating very large shutters. Panelled shutters were much lighter in the fabricated form, and so easy to transport, install and operate.

Doors of the ancient Temple of Divus Romulus are of two leaves each with two panels, and are framed in bronze; these were converted and reused in the Christian Church of SS Cosma and Damiano. The doors of the Pantheon are similar in design, with narrow horizontal panels in addition, at the top, bottom and middle. Two other bronze doors of the Roman period are in the Lateran Basilica. The doors of the church of the Nativity at Bethlehem (6^thC.) are covered with plates of bronze, cut out in patterns: those of St Sophia at Constantinople, of the 8^thand 9^thC, are wrought in bronze, and the west doors of the cathedral of Aix-la-Chapelle (9^th C), of similar type were probably brought from Constantinople, as also some of those in St Mark's, Venice.

Rooms of roman houses were separated from the entrance lobbies, porches and other rooms merely by curtains and only occasionally by wood shutters. The doors were made of cypress, oak, deal, box-tree, olive, or elm. For the bolts and pivots hardwoods and cast bronze were used. The wood was aged, and left in the press for years to prevent warping. Doors were panelled rather than made of boards to prevent warping of the wood, the doors were not constructed of boards but were of paginae -panels. The doors of the upper class were veneered and adorned with bronze, ivory, and other ornaments. Ancient roman doors had pivots of hardwood and sometimes of cast bronze.

'The main entry into apartment houses typically took the shape of two wooden leaves that swivelled in pivots fixed into the doorsill and lintel blocks and opened inwards. Other doorways, for example those of the tavernae (shops) were secured every night by means of vertical wooden shutters that set into the travertine doorsill and lintel blocks, although at night and perhaps during midday break access might be made through a small entrance located inside the larger door.'

BYZANTINE PERIOD DOORS: The Roman panelled design and fabrication technique was continued through the Byzantine and Romanesque period. The bronze cast doors were used in the Hagia Sophia's cathedral (838 C., Constantinople), St. Marks Venice, and the cathedral of Aix-la-Chapelle (9^thC.). The doors of the church of the Nativity at Bethlehem (6^thC.) are covered with plates of bronze, cutouts in patterns.

The art of casting doors was preserved in the Eastern Empire, the most notable example being double door (838 AD) of the Hagia Sophia's cathedral in Constantinople (now Istanbul). In the 11th century bronze castings from Constantinople were imported into southern Italy. Bronze doors were introduced into northern Europe, notably in Germany, when Charlemagne installed a Byzantine pair (804 AD) for the cathedral at Aachen. The first bronze doors to be cast in one piece in northern Europe were made for the Cathedral of Hildesheim (1015 AD). They were designed with a series of panels in relief, establishing a sculptural tradition of historical narrative that distinguishes Romanesque and, later, bronze doors.

ROMANESQUE PERIOD: After 950 AD, well planned, grand scale buildings with excellent construction methods like masonry vaulting marked the Romanesque style. The Italian Romanesque architecture had large arched doorways. The straight and often angularly cut sides of the arched doorways were filled-in with columns, pilasters, flutes and other carvings. Actual doors were of much smaller size than the arched doorways. The Roman panelled design and mounting technique continued in Byzantine and Romanesque architecture. The door shutters still retained the squarish shape as panels were cast elsewhere. The panelled squarish shutters were fitted on the inside face of the arched gaps to avoid the mismatch of shapes. The door gap often had multilayered 'traceried over patterns'. Gradually the shutters also began to be shaped matching the arched doorway gaps, requiring the reshaping of the top few panels of the door shutters.

'The greatest works in the Romanesque style date from 1075 to 1125, after this period the style entered a florid baroque phase that lasted a generation and then was revivified as Gothic. A new type of ribbed groin-vaulted unit bay, using pointed arches to distribute thrust and improve the shape of the geometric surfaces produced vaulting that was light, strong, open, versatile, and applicable everywhere -a Gothic vaulting. A whole new aesthetic, with a new decorative system, the Gothic, was evolved as early as 1145.'

GOTHIC PERIOD: Gothic doors were of functional size, both of single and double leaves as well as dual doors. In the Romanesque period, the double shutter doors in the opening portal were separated by a column and the span was headed by a flat lintel, and than once again by a circular or pointed arch. In the Gothic period the spanning of opening was replaced by a pointed arch, giving a narrower look to the opening. The narrower look was further accentuated by the ribbed jamb and arch sides. In France and Germany, the main doorways were on the west face. The doorways were large, deeply recessed, intricately carved, and often with architectural elements such as columns, entablature, pediment and niches. Sculptural features such as statues of saints were placed in the arches in serried rows (e.g. Strasbourg and Rheims Cathedrals). Compared to this, the Italian doors were simpler, but doorways were elaborately treated.

In Italy, Germany and other areas of N. Europe cast bronze doors with an insert panels were used in many public buildings. The panels had designs, monograms and other ornaments in relief, frequently damascened (Ref: see notes on Surface Finishes) in silver and gold, and enriched with bosses and scrolls. From 12^th C onwards few churches in Italy had bronze doors inlaid with Byzantine niello work made by Byzantine crafts-persons. Lorenzo Ghiberti's doors for the Baptistery in Florence (1403-52) marked the beginning of a golden age of bronze casting in Florence and it lasted through the Renaissance and the Baroque era. Italian doors of the Renaissance period were simpler, with scale given by increasing the number of panels, as compared to France and Germany where doors had few or single panel but elaborately carved.

MEDIAEVAL PERIOD: The mediaeval period offers a wide variety of buildings with equally varied door styles, simply because many examples have survived or their records are available. A large variety of door head arches, such as flat, circular, 2,3, and 4 centred. The upper section of the doorway was flatter (of less depth), but its treatment was always elaborate. Wood was the chief door construction material. Iron hinges and spikes etc. were used. Woods of different varieties and metal sheets (bronze, copper, etc.) with plating and gilding were used. Typical Western medieval door for domestic architecture was of vertical planks backed with horizontals or diagonal bracing. It was strengthened with long iron hinges and studded with nails. In domestic architecture, interior double doors appeared in Italy in the 15th century and then in the rest of Europe and the American colonies. The craft of bronze casting, which was neglected till 12^thC., became now a thriving industry. Lorenzo Ghiberti's Gates of Paradise -Porta del Paradiso (1425) is the high point of this craft in Florence, it lasted through the Renaissance and right down to the Baroque era.

RENAISSANCE PERIOD: One of the masterpieces of Renaissance art -the bronze doors for the Baptistery of the Florence cathedral, which consist of 28 panels illustrating New Testament scenes of the life of Christ. Bronze doors inlaid with niello work were earlier produced mainly in Byzantine area (during 11^thand 12^thC.), now began to be produced everywhere in Europe.

In England in the 17th century the door panels were raised with 'bolection' or projecting mouldings, sometimes richly carved. In the 18^thC. the mouldings on the stiles and rails were carved with the egg and tongue ornament. Doors were also made of wood veneers and wood inlay.

The earliest Renaissance doors in France are those of the cathedral of St Sauveur at Aix (1503 AD.), the lower panels have 3 ft high figures in Gothic niches, and the upper panels have 2 ft niches canopies over them, all carved in cedar. The south door of Beauvais cathedral is in some respects the finest in France, the upper panels are carved in high relief with figure subjects and canopies over them. The doors of the church at Gisors (1575 AD.) are carved with figures in niches subdivided by classic pilasters superimposed. In St Maclou at Rouen are three magnificently carved doors, those by Jean Goujon have figures in niches on each side, and others in a group of great beauty in the centre. The other doors, probably about forty to fifty years later, are enriched with bas-relief, landscapes, figures and elaborate interlaced borders.

INDUSTRIAL REVOLUTION PERIOD: The industrial revolution period saw the use of new techniques of creating metal components. Steam powered machines were capable of handling heavy loads of forging, rolling, shaping and die-casting. Iron structural sections began to change the industrial buildings and public utilities. The openings in industrial buildings, railway stations were large and new door systems were developed. The developments in glass manufacturing methods also encouraged the large openings. New door systems such as: rolling shutters, multiple folding shutter doors, collapsible gates, goods elevators' sliding upward doors, warehouse doors, etc. were fabricated of rolled or drawn iron. These doors were functional and without decoration or styling appendages. New doors required radically different hardware such as hinges and locking devices, and surface finishes. Colonies for new Industrial workers were developing in every urban centre, and required low-cost doors. Metal doors, timber flush doors and other alternative systems began to be mass produced. Railway cars, trams, buses and other automobiles required openings systems of different sizes, shapes and very often door as integrated with the shell (a structural component of the body). Industrial valves, oceanic vessels (ships, sail boats, etc.), chemical reaction vessels, processing chambers, steam boilers and other systems changed the age-old concepts about opening systems and provided new design insights. Massive demand from hotels, resorts, hospitals, army (barracks and other buildings), public housing schemes, commercial buildings, etc. supported development of standardized, mass produced, trimmed door systems that were not only easy to maintain but replaceable.

POST INDUSTRIAL REVOLUTION PERIOD: This is a period marked by the end of world war II. The old styles and building techniques gave way to new methods as Japan and Europe began to rebuild their war-torn economies. New developments in Materials Technologies, specifically plastics and other petroleum products began to offer new alternatives. Metal manufacturing now free of war preparations had large spare capacities of production offered better and diverse structural shapes and sizes. Coating, alloying, galvanizing, metalizing techniques offered steel and other metals with different options. National Standards and ISO helped develop a basis for world wide coordination of specifications. Several countries of the world achieved independence from colonial bondage. This created a huge market for the industrially developed countries.

NEW AGE TECHNOLOGIES AND NEW DOORS: New age doors include, both architectural and non architectural entities. Doors for automobiles were most radical in design, not only their size, shape and form were different but new materials were also being experimented. Composites of carbon, fibre glass, etc. were tried out here. Aircraft hangers, home garages, submarine vessels, pharmaceutical and other bio plants, food processing areas, hospital's surgical areas, climate-controlled industrial plants (diodes and other electronic circuits), etc., provided new opportunities to reinvent the door. Laminated composites, surface hardened and alloyed materials, co-extruded plastics, foamed or air-entrained materials, stainless steel and aluminium sheet formations, wood waste products, powder coatings and other solvent-less systems, new varieties of glass and clear plastics, all have changed not only what a door was but how it could be constructed differently.

One of the major component to see a drastic change was the Door Frame. Traditional wood jamb + head frames have been nearly replaced by folded sheet sections (of mild steel, stainless steel, aluminum), drawn sections (mild steel, aluminium, bronze, other alloys and plastics), and formed units of (layered and particle composites of cellulosic materials, paper, plastics, cement concrete). Besides replacing a timber jamb with other materials, attempts began to have no jamb doors. Hinges and other door shutter fixing arrangements were sought to be replaced with floor pivots and sliding tracks. Glass doors without a stile or any other member supported on a floor pivot is an example of this. Frequently opened and closed gaps such as in public buildings (railway stations, airports, malls, office complex foyers, restaurants, industrial plants) have air-curtains (air cascading over the gap and thus forming a breach-able barrier) instead of traditional door frames. In areas where a door was required as a security check barrier, these nodes are replaced with almost invisible intelligent barrier systems that recognise, register and control the access.

4.1.2.1 COMPONENTS OF DOORS

Keywords: shutter or leaf / frame / hardware / wall opening / barricade / door portal / doorway / sides / head / eaves / Hisashi / Torii / DOOR SIDES / DOOR FRAMES / closer or tighter shutting / JAMB / casings / DOOR SURROUNDS / CASINGS / sides of the gap /types of casings / door stop butt / double shutter set / multi shutter system / termination points / architraves / extra wide casings / air lock / PILASTER / anta ANCONES CONSOLE / Todla / FILLET / wall treatments / REVEAL / SPLAYED / DOOR PORTALS / splayed / Buland Darwaza / Tympanum / LITES / TRANSOM / horizontal bar / TRANSOM LITE / FAN LIGHT / classical revival and colonial revival / CIRCULAR LIGHT / rose windows / SIDE LITE / DOOR HEAD / PEDIMENT / Georgian and Greek Revival architecture / broken pediment / EMBRASURE / inward splaying / THRESHOLD / doorsill, or saddle / Shankhavati / TRACERY / plate type / bar type / SHUTTER OR LEAF OF A DOOR / Multi planked wood shutters / stiles / rails / wood joinery / spikes or nails / multiple panels / cast or hammered metal sheets' cladding / cast bronze panels / cast or engraved designs / hinges / shelf supported pivots / STILE / hanging stile / latch stile / panel doors / stile and rail doors / MULLIONS / side-lite / RAILS / rows of panels / kick rail / lock rail / cross rails / PLANKS / slats / BATTENS / slats / braces / iron bars / PANELS / flat / rebated / raised design / SHEATHING / metal sheet or plate / cladding / BEADING / peg / tree-nail / architrave / HOOD / quarter sphere / awnings / MOULDING / ARCHITRAVE / COMPONENTS OF FLUSH DOOR SHUTTERS / FRAME OR EDGES / CORE MATERIAL / composite / monolithic / HOLLOW-CORE / LOCK-BLOCK: / concealed stile / SOLID-CORE / SKIN / embossed / moulded / architraves.

A door as a building element is made essentially of a shutter or leaf. The shutter sometimes requires an intermediating support structure or frame. The shutter and the frame are joined by hardware. The door system is placed in a wall opening, barricade, door portal or doorway.

The door portals have sides and a head, both of which are structurally formed and decoratively treated in many different ways. Structurally the sides are the edges of the gap in the wall, but are reinforced with better materials and construction techniques. The sides are configured to receive the door leaf or the frame. The sides are also shaped to form a frame. The sides are decoratively treated to add to the scale (size) and increase the perceptive importance of the door portal. The treatments on the sides visually 'frame' the door portal, making it a 'stand alone' element. The head is placed both as a structural element and a framing element. As a structural element it supports the overhead section and transfers the load to the side or base. The head is often a component of the roofing system, the eaves.

According to Japanese mythology a door portal is formed by the Hisashi (usually means eaves), whose character has the meaning 'a space to see'. So a door occurs when a horizontal element like the eaves is formed. The horizontal element needs to be supported off the ground, so has sides. The gate Torii (Japanese) is an epitome of this. Torii can virtually occur anywhere in the space, and provide a metaphoric entrance. Torii frames a view or focuses presence.

DOOR-SIDES: The door-sides are distinctively of interior or exterior nature. Door sides are architectural or elements of its framing, but often it is often difficult to distinguish the purpose served by them. Door-side elements are also called door surrounds and are in the form of: casings, pilasters or half or demi-columns, flutes, niches, abutments, architraves, lites (side openings).

DOOR FRAMES: Frames are required primarily to hang a shutter, Frames for doors are used when the surrounding structural elements are incapable of receiving a hinge or such fixing mechanism. In very cold or rainy seasons, frames help closer or tighter shutting. Frames are made from wood, stone, cast or rolled metal sheets, Cement concrete, cement composites, extruded plastics, etc.

JAMB: The vertical support on either side of a door, window or other openings. A jamb is the vertical side member of a door frame. Jambs of extended width to cover the entire depth of the doorway are casings.

DOOR SURROUND: A surround is a decorative entity around a doorway. The term is also used for decorative elements around other openings such as windows and fireplaces.

CASINGS: Door frames have to be of functional size (width and depth) to economise the use of wood. Door gaps are often too deep and a frame cannot cover the entire width. The sides of the gap are covered by a Casing. Casing is a widened frame, or additional panelling that is placed on the remaining sides. The casing usually is placed on the interior face of the door frame, but for interior doors it can occur on any face. There are many types of casings: 1 a casing covers the entire gap and the door frame is mounted over it or is formed by placing a thin architrave that creates a door stop butt; 2 the casing is formed between two sets of frames, which marks the edge; 3 a casing or two sets of it are placed over the remaining portion, not occupied by the frame. Casings are single panel constructions, multi division panels, or in the form of stripes or flutes.

Deep door portals are used for accommodating a set of doors, with an interim space. In case of double shutter set (a set of shutters such 'solid + glazed', 'glazed + louvred', 'glazed + mosquitos nett' ) the doors are hung on the inside and outside edges. In a multi shutter system the casings are hollowed out to accommodate additional sliding shutters.

Casings become termination points for the skirting, wainscotting, dado or wall panelling system. The chief tools for such termination or integration of two elements are architraves.

Extra wide casings are created by having deeper door portals. Deep portals create a zone between the two shutters, to dampen the noise, provide insulation, create an air lock. To avoid deep casings the sides are architecturally or panelling wise chamferred or stepped (serrated as in Gothic doors).

PILASTER: A pilaster (anta in Greek and Egyptian architecture) is half a pillar that is attached to the side walls and projects to provide added support or is for ornamental decoration. Like a column, a pilaster often has a capital and a base. The depth of a pilaster is about one-sixth of its breadth, from a wall.

ANCONES CONSOLE: A bracket that is on either sides of a doorway to support a cornice or projected section of the lintel. A Todla (Gujarat, India) is often used for placing an oil lamp.

FILLET: A small band to separate the door frame or door casing from the adjoining wall panelling, dado or other wall treatments.

REVEAL: A small band or strip at a right angle to the side face of the opening (on the main face of the wall) used to seal the edge of frame or casing or border the opening gap.

SPLAYED: When the reveal is chamferred, or the corner edge of the masonry wall of the opening is diagonally cut, it is called splayed. Windows like openings have been splayed for ages. Door openings are splayed on sides and at head. The splay could be very wide to allow better distribution of illumination or have a wider view. Splay could be both on the interior and exterior faces.

DOOR PORTALS: Historically doors have been placed on the inner edge of the door portal, and front edges have been splayed to accentuate the sides (e.g. Fatehpur Sikri entrance to the main mosque complex is Buland Darwaza within which the actual door is much smaller). Similarly in Gothic architecture door portals are elaborate and serrated but an actual door is always much smaller. Fluting or serration is continued from both sides to over the door head portion (arched or flat lintels). In Mughal architecture additionally balconies and windows were placed in door portals. The angular portion above the door the Tympanum has been surface treated with carvings or fine lattices, and later as transom.

LITES: Lites or lights are the additional openings that occur over or on the side of a door. The lites are intended to illuminate the entrance foyer or vestibule. Lights were used as a characteristic style element for houses.

TRANSOM: The term refers to a fixed horizontal bar of wood or stone that is placed over a door to separate an opening or window above.

TRANSOM LITE: Flat arched, or square and flat headed lintels have an opening shutter (called a 'ventilator') often hinged to the horizontal crossbar or a transom (transom-lite). A transom lite is a window or fixed glazed panels positioned directly above a door or window, and shaped according to the archway (a segmental, semicircular etc.).

FANLIGHT: The lites in semi circular or other archways are shaped, or the lattice work within it is in the form of a fan (fanlights). It is a semicircular window above a door, often with distinctive radial shape. Fanlight doors were accompanied by sidelights. Fanlights illuminated an entry hall or vestibules. In the mid-1700's the design of a fanlight gave a sense of an individuality to the facades of urban row houses. A fanlight is a key identifying feature of Federal style architecture. Fanlights were also found in Classical Revival and Colonial Revival houses.

CIRCULAR LIGHTS: These were left as round openings with delicately carved tracery patterns. These circular openings later in Gothic period became Rose windows. Rose windows were first filled with translucent marbles or small pieces of glass, and later with stained (coloured) glass. Circular lights with circular, segmental or elliptical archways were mounted on entire width comprising of the door and its sidelights. This was a common feature in Federal and Georgian style architecture.

SIDE-LITE: Sidelights are side openings on one or both sides of a door. These were popular in USA after the American Revolution.

DOOR-HEAD: A door head is the upper section of a door that is shaped flat, segmental or as a semi circular archway. Door head, as a term often includes the head of the opening, its treatments and appendages. The door-head as a structural component is a lintel, corbelled arches of various forms (semi circular, segmental, pointed, two points, a pointed trefoil, an ogee, shouldered, etc.), as a decorative system, it is a pediment or gable (triangular, cut triangular, circular, cut circular, etc.), flutes, and as a functional element has transoms, tympanums, fan light, rose windows, etc.

PEDIMENT: A low-pitched triangular gables over a doorway or other openings, often seen in Georgian and Greek Revival architecture. In a version known as a broken pediment, the peak of the triangle is interrupted, often with an ornamental curve and/or a decorative element in the centre. Pediments also occur as head decorations over the chair back, wall clocks and buildings' fronts.

EMBRASURE: The inward splaying of openings such as doors and windows for wider distribution of illumination.

THRESHOLD: Thresholds have an origin since the days of pivot. Early doors were very heavy. Pivots for such doors were made with a metal casing, and placed in a hard wood or stone base. The thresholds, due to wear of the pivots, required frequent replacements. The threshold (a log of wood or other materials) was also used as the support base to hold the jambs, and maintain distance between them.

A threshold also separates two different types of floorings. The threshold serves as a barrier against crawling insects, storm and cold draughts. It is sometimes referred to as a doorsill, or saddle. A threshold is also used to insert a vertical cross bar or a stopper bar to secure the door. Most Indian temples have a high threshold called Shankhavati. Jain temples have doorway thresholds containing a set of Kumbha (urn).

TRACERY: Ornamental curved patterns in windows, doors and other openings often made of wood, stone or cast iron. Traceries are, plate type when cut out of a stone plate, or bar type with geometric patterns formed by narrower bands. Tracery was a typical element of Gothic Revival and Collegiate Gothic style architecture.

SHUTTER OR LEAF OF A DOOR: These were once made of monolithic material such as a single piece of stone or wood, but the limited size of the materials and heavy weight not only restricted the actual size of opening, but the control over its opening-closing mechanism. Multi planked wood shutters require a vertical member as stiles and horizontal rails, and both need to be held together through wood joinery and spikes or nails. Later during Greek and Roman period panelled door construction further reduced the weight of door and allowed construction of larger sized shutters. For large doors multiple panels were used. Large panels of single pieces of wood were not feasible, and panels of multiple planks were always weak. This weakness was removed with use of cast or hammered metal sheets' cladding of bronze and copper over wood panels. In later Roman period and thereafter in Byzantine cast bronze panels (inserted in wood or metal frame work) with cast or engraved designs began to be used. These panels were produced at places far away from their use.

Door Shutters or leaves had inherent size limitation. As the door shutter construction became refined, weight was reduced, and door opening-closing became easier. The primitive doors were held by stacking, tying at the edge by ropes or leather straps. Later pivots were formed as an integral member of the shutter material. These pivot nodes were inserted into hard stone holes at floor and ceiling levels. Problems with pivot mechanisms were many: pivot nodes wore out fast -lowering and often tilting of the shutter, pivots broke frequently making shutter useless, and replacement of a worn or broken pivot required lot of structural changes. Pivots of cast bronze were a better option, but required special joining with wood and more so with stone shutters.

Sometimes during middle ages hinges began to replace the floor pivots. The first hinges were actually shelf-supported pivots. These were formed of wrought iron or bronze. Hinges were easy to fit or replace (in the first case without structural delays, and in later case without structural changes). Incase of pivots the bottom one carried the load whereas the top pivot was more of a holding element. But in case of hinges, all of them shared the carriage of loads.

Shutters are composed of many different materials and techniques: Stone sheets, metal plates, wood, glass, plastics, textiles, woven materials, leaves, leather, water and air jets, ultra sound.

STILE: Stiles are full height right and left vertical edges of a shutter. The hinges are mounted to the fixed side -known as the hanging stile, and the handle, lock, bolt, and/or latch, are mounted on the swinging side -known as the latch stile. Panel doors -doors built with frame and panel construction, also called stile and rail doors.

MULLIONS: Vertical members that run between two rails, and split the door into two or more columns of panels. A mullion is also a vertical member that divides a door and its side-lite.

MUNTINS: Thinner or minor members that divide the door into smaller panels.

RAILS: Horizontal members (similar to stiles) at the top, bottom and optionally in the middle of a door. Rails join the vertical edge members -the stiles. Rails also divide the door into two or more rows of panels. The top and bottom rails are named for their positions. The bottom rail is known as kick rail. A middle rail at the height of the bolt is known as the lock rail, other middle rails are commonly known as cross rails.

PLANKS: Vertical boards or slats that extend the full height of the door, and are placed side by side filling up the door's width.

BATTENS: Battens are smaller slats that extend horizontally across the door to which the planks are affixed. The battens hold the planks together. Sometimes, a brace, a long diagonal slat, or two are used to prevent the door from skewing (dropping down on free edge-corner). On some doors, especially antique ones, the battens are replaced with iron bars that are often built into the hinges as extensions of the door-side plates.

PANELS: Panels are large, wide boards used to fill up the space between the stiles, rails, and mullions. The panels typically have a tongue -a projecting element on one edge, and a groove at the other edge. Panels may be flat, rebated or of raised designs.

SHEATHING: A cover usually of metal sheet or plate applied over a door surface to protect it from moisture, impact denting, scratching, etc. Bottom section of Door shutters often have sheaths of metal, plastic or fibre sheets. Sheathing is also called cladding.

BEADING: A woodworking method used to join two pieces of wood. A mortise (cavity, hole, notch or slot) is cut into one piece of wood. The tenon is created by shaping the end of the second piece of wood so that it can slide into the mortise. After fitting the tenon into the mortise, the joint is made secure by drilling a hole through both the mortise and tenon, and driving a wooden peg, also called a tree-nail, into the hole. Beading is also a small architrave that holds the glazing pane or panel to stile or rail.

HOOD: A covering above a door or window that provides shelter as well as adds a decorative element to the doorway. Hoods are made with wood or metal frames and covered by pieces of slate, roofing tiles, metal sheaths, fibre cement sheets, canvas fibre glass sheets and fabrics, plastics' sheets etc. One of the most used hoods during the last century was a quarter sphere over a semi circular archway of door or window. Modern hoods are manual or automatically collapsible or retractable mechanisms. An Indian bazar shop hood (for many centuries preceding the British Raj and till independence) was formed of canvas like heavy fabric stretched with bamboo poles. Hoods are also called awnings.

MOULDING: In England in the 17th century the door panels were raised with bolection or richly carved projecting mouldings. In the 18th century the mouldings were created on the stiles and rails with the egg and tongue carved ornamentation.

ARCHITRAVE: An architrave is a border that surrounds a door frame or door way. Often it covers the junction of a door frame and masonry wall, casing, panelling, etc. It is often a part of the moulding.

COMPONENTS OF FLUSH DOOR SHUTTERS:

FRAME OR EDGES: Edges on a flush door provide integrity to the structure and allow fixing of hinges, latches, etc. The edges are concealed behind a skin with only its side ends seen. Edges allow a door to be sized (by planning) for the opening.

CORE MATERIAL: Material that forms the core or body of the flush door. It fills up the space, but provides rigidity, reduce the druminess, enhances the insulation. The core material is a composite and sometimes a geometric composition but edged with a monolithic material.

HOLLOW-CORE: A hollow core construction has core formed of units arranged with space between them. Wood stripes, lattices, hollowed, honeycombed, corrugated, nodulated, or expanded forms of materials are used. Hollow-core flush doors are lightweight and have greater insulation capacity. Hollow core doors are used as interior doors.

LOCK-BLOCK: A lock-block consists of a wide edge or concealed stile for full height or for part of the door to facilitate insertion of mortice lock system.

SOLID-CORE: Solid-core doors have entire core area filled with pieces of wood or a panel of wood particles. Low-density particle boards or foams are also used to completely fill the space within the door. Solid-core flush doors (especially foam-core ones) are commonly used as exterior doors because they provide more insulation and strength.

SKIN: The front and back faces of the flush door are covered with a thin layer of materials such as wood veneer, plywood, sheet metal, fibreglass, or vinyl or polyester film. Multi layer skin materials such as veneers and plywoods are layered with the grain alternating direction between layers to prevent warping. The skin of a flush door is sometimes embossed moulded with patterns (in the case of metal, fibreglass, or vinyl). Additional mouldings and architraves are added (to wood) to give the appearance of a panel door. Fibreglass and metal-faced doors are coated to achieve stained wood looks.

4.1.2.2 MATERIALS AND TECHNOLOGIES

Keywords: Nippur / Balawat / hanging stile / door frame / shutter / metal doors / embellishments and treatments / enamelling / malleable rolled sheets / cast door panels / tinning and galvanizing / oil painting / exotic woods / flush panel door / wood and wood-waste composites / door portals / glazed doors /clean -see through glass / French doors / folding and sliding doors / Shoji / canopy door / rolling door garages doors / modern doors / flexible shutters / vault doors / core-fill of mineral slabs.

The first doors were shutters of stone, wood, grass or reeds, leaves, hides or skins, woven mats and fabrics. The shutters, in order to close the opening, were made to swing, fold, collapse, slide or roll up. Ancient doors were primarily hung by pivots, formed as a protrusion of the door material at the top and bottom as the hanging edge of the stile. The pivot rotated in sockets in the lintel and sill or thresholds in the floor. The pivots and the sockets, both of them were later encased with harder material such as granite, basalt, hard woods, bronze, iron, etc.

Stone pivots, found at Nippur dating from 2000 BC., were in dolerites stone. The tenons of the gates at Balawat (now in the British Museum) were sheathed with bronze. These doors or gates were hung in two leaves, each about 8 ft.4 in. wide and 27 ft. high; they were encased with bronze bands or strips, 10 in. high, covered with repousse decoration of figures, etc. The wood doors would seem to have been about 3 in. thick, but the hanging stile was more than 14 inches diameters. Other sheaths of various sizes in bronze have been found, which proves this to be a common method to protect the wood pivots.

Floor pivoted doors were difficult to move or replace. Later pivots (hinged pivots) made of cast metals were wall-mounted instead of the floor and lintel. Wall pivots developed into hinges, when these were fixed to the surrounding frames instead of the masonry walls. The door frame became almost as inevitable an element as the shutter, for any opening system.

Metal doors of bronze, copper and later iron were used for public buildings. Metal doors were cast as panels and assembled into a larger size. Metal cast panels were cast with basic patterns, and later enriched by embossing, recessing, chasing or engraving. Bronze predominantly had patina (oxide - rust) as the finish. Metal surfaces were also plated, gilded or inlaid with Gold and Silver. Such precious metal embellishments and treatments were often plundered by the invaders. Metal panels were also suitable for enamelling (ceramic forming) but this technique was not exploited till 16^thC (similar ceramic enamelled panels were also used for ceilings). During the industrial revolution period malleable rolled sheets of mild steel, brass, copper alloys, replaced the heavy weight cast door panels. The sheet formed panels, however, continued to be finished with metal inlays, chasing, engraving and enamelling techniques. Tinning and galvanizing, were emergent technologies for protecting the metal sheets. Oil painting of metal doors began from 18^th C. onwards.

The external doors of the mosques in Cairo were cased with sheets of bronze or iron, cut out in decorative patterns, and incised or inlaid with bosses in relief. The internal doors were in wood framed and interlaced with Coptic designs of the square and diamond.

For internal doors and for domestic buildings wood has remained the most favoured material. Wood doors were lighter, receive wall pivots and with surrounding frames, regular hinges. Exotic woods (varieties in terms of colour, grain pattern, texture) were used to create contrasts between stiles and panels. Wooden panels were easy to finish and decorate. Lighter hinges with long arms (flanges) supported the members of the door frame. Such typical medieval doors were made of vertical planks and backed with horizontals or diagonal bracing, and the hinges were studded with nails or bolts. In domestic architecture, interior double doors appeared in Italy in the 15^thC. and then in the rest of Europe and the American colonies. The panelled effect was further simplified until, in the 20^thC., a single, hollow-core, flush panel door became common.

Wood is replaceable so it is an ideal material but forests cannot be regenerated fast enough to meet its heavy demand. Wood and wood-waste composites both are now sought to be replaced with alternative materials and technologies.

The size of a door shutter has always been prudent. Stone and metal cast doors were very heavy to install and operate. Metal panelled doors were easier to assemble, but were still heavy and difficult to maintain. The timber as a natural resource had size and supply limitations. Composite doors with elemental panels of rolled sheets were lighter, and with hinges were easy to install, repair, operate and decorate. Doors' shutters have gradually become smaller and functional, but door portals have continued to be of grand size. Large door portals with functional sized door shutters have been common in buildings during middle ages and renaissance periods.

Historically doors have been of opaque shutters, with occasional small inset lattice openings, or few panels as lattice (e.g. Greek temples). Scattered examples of door panels of thin marbles or such translucent stones to brighten the interiors are found. To control the transparency curtains were used over door gaps or entire shutters of metal lattices were used. Glazed doors first appeared as window casements extended to the floor during the 17^thC. Early glazed doors were composed of very small glass panes cut out of blown bulbs. The quality was unclear or muddy. But it provided illumination inside. It was after the glass bed-casting and grinding (levelling and polishing processes) became better, a clean -see through glass was available. The glass panes replaced the wood panels.

French doors (double glazed) were incorporated into English and American architecture in the late 17^thand 18^thC. At about this time, the French developed the mirrored door. During the 19^th C., industrial production of complex hardware allowed folding and sliding doors as inspired by the Japanese shoji, the canopy door (pivoting at the top of the frame), the rolling door (of a tambour like construction), and garages doors opening to the top.

After wold war I, production of automobile, air-crafts and sea faring vessels helped developments of new types of specialized modern doors. These included 3D or spatial frame shutters, large shutters for air craft hangers and industrial plants, gates for dams, canals and dykes. Flexible shutters of stripes of polymer sheets are used in warehouses. Vault doors for: banks, high security storage areas (museums), bombing shelters are designed from alloy steel and metal composites and usually have a core-fill of mineral slabs, glass wool etc. for insulation, fire and radiation protection.

4.1.2.3 HARDWARE

4.1.2.3.1 Baic Hardware

Keywords: three categories of hardware / Basic Hardware / Secondary Hardware / Appendages or Attachments.

Doors have Three categories of hardware: 1 BASIC HARDWARE attaches a shutter directly or through a frame to an opening or doorway, 2 SECONDARY HARDWARE provides control on the movement of a door, and at third level the hardware is 3 APPENDAGES OR ATTACHMENTS that endow various types of functionality.

Sub-Index for 4.1.2.3 HARDWARE

4.1.2.3.2 Secondary Hardware

4.1.2.3.3 Appendages and Attachments

4.1.2.3.1 BASIC HARDWARE

(Click here to go to Chapter 4.1.2.3 sub-Index)

Keywords: STRAPS / sparks of erosion / PIVOTS / end pivots / edge pivots -mid pivots / two-way swinging pivoted doors / pivot hinges / double acting floor hinges / hydraulic floor pivots / EARLY HINGES / wall-hung pivots / long armed hinges / flanged Hinges / MODERN HINGES / BUTT OR MORTISE HINGES / shangles / component / bearing / knuckles / hinge pin / pull out stress / push in stress / neutral stress / downward gravity stress / mouldings / casings / FLUSH HINGE / KNUCKLE HINGES / flush butt hinges / knuckle /PARLIAMENT OR BUTTERFLY HINGES / dovetail hinges / jewellery boxes / deep-set door frames / STRAP HINGE / wider flange / LIVING HINGE / thin flexible hinge / BACK FLAP HINGE / PIANO OR CONTINUOUS HINGES / INVISIBLE HINGES / CONCEALED HINGES / spring loaded / self-closing features / dampening system / H HINGES / HL hinges / BARREL HINGE / Lift-off butt hinges / LOOSE PIN HINGES OR BALL TIPPED HINGES / STOPPED HINGE / butt hinge / DOUBLE ACTION HINGE / middle flange / edge flanges / DOUBLE ACTION SPRING HINGES / UNEQUAL FLANGE HINGE / greater length of flange / reduced width of the flange / FRICTION STAYS / French door / ASKEW OR VERTICALLY MISALIGNED PIVOTS OR HINGES / Hydraulic or spring door-closer / CLASSIFICATION OF HINGES / FULL MORTISE HINGE / mortised / HALF MORTISE HINGE / FULL SURFACE HINGE / HALF SURFACE HINGE / STRUCTURAL HINGES / conditional movement / hinge like conditions / GATE HINGES / Building access hinges / FURNITURE OR CABINET HINGES / concealed hinges / butter fly hinges / piano hinges / butler tray and ambulance stretcher hinge / Drop Leaf Table Hinges / MICRO HINGES / ball-mortise / cylinder-pin system / FLOATING HINGES / two parallel axes of rotation / flatbed scanners.

Basic hardware for doors consists of shutter hanging mechanisms.

STRAPS: The first door shutter holders were straps of leather, ropes, vines, and threads, fabrics or synthetic materials' (plastics and composites) are used as flexible hinges. Straps are still used in some conditions where metal friction is likely to cause sparks of erosion (petroleum solvent plants and cordite plants), but are made from new technology materials such as woven Fibre glass, Teflon, Cavalar, and carbon fibre composites.

PIVOTS: Doors with heavier materials such as stone, cast bronze and wood required pivots. Pivots were initially formed out of the shutter material itself, but later these were lined with metal sheaths. With better technologies of joining, the pivots were formed from cast bronze or iron steel and then attached to the shutters. By the time iron hinges began to be used, the door shutters had become lighter. Pivots allow the door to open inside, and a projection of the portal frame sealed the edges. Pivots are fixed at the corner of the door edge, and also on outside or inside the edge. Doors with outside the edge pivots -end pivots are expected to open to the inside, but can as well swing in both directions. Doors with inside the edge pivots -mid pivots open in both directions (e.g. Aluminium framed glass doors). For two-way swinging pivoted doors a door frame is an obstacle, and as a result such doors do not seal the gap completely. For pivoted doors no frames are necessary. Pivots are also called pivot hinges or double-acting floor hinges because opening movement is allowed in both directions as similar to hydraulic floor pivots used for glass doors in modern buildings.

EARLY HINGES: Early hinges were really wall-hung pivots, but the pin was hung off the side wall, and the girth or ring was fixed to the shutter. The ring had a long band which was fixed with nails to the stiles or rails. The early long armed hinges have become an expression of a medieval door. Flanged Hinges formed of steel, bronze and brass alloys are being used since middle ages.

MODERN HINGES: These are available of brass, bronze, mild steel, stainless steel, ABS and polypropylene plastics, carbon composites, etc. Most of the commercial hinges are made of several components (such as flanges, flange edge liners, pin, pin cylinder liners, coil springs, hydraulic cylinders, etc.), and these are again composed of many different materials.

BUTT OR MORTISE HINGES: These are also known as shangles in old Tudorian English (the large hinges on doors). Hinge like systems are employed in many types structures and movable bridges. In biology many body joints function as hinges. Butt or mortise hinges are made of hard wearing and stiff materials. Today hinges have a shaft or pin over which two flanges move. The pin is made of stainless steel, carbon steel, nylon and Teflon, some of these do not require any lubrication.

A hinge is component that attaches one edge of a door to the frame, while allowing the other edge to swing from it. A hinge can also be an arrangement. A type of bearing that connects two solid objects, and allowing a limited angle of rotation between them. Two objects connected by an ideal hinge rotate relative to each other about a fixed axis of rotation (the geometrical axis of the hinge). Hinges consist of a pair of plates, each with a set of open cylindrical rings (the knuckles) formed out of, or attached to them. The knuckles of the two plates are offset from each other and mesh together. A hinge pin is then placed through the two sets of knuckles to form a single unit.

One door usually requires minimum two, or more hinges. Nominally three bands (horizontal members of a panelled door) have three hinges, of which the top hinge is in 'pull out stress', the bottom hinge is in 'push in stress' due to the cantilever action of the shutter. The middle hinge is in 'neutral stress' state, but all three hinges have downward gravity stress. Butt or mortise Hinges are inset -mortised into the door stile and frame. The hinge is fixed with its pin section (cylinder) remaining out of the door face, to allow 180 of opening, i.e. the shutters can rest on the side of the door opening. However, sometimes mouldings over shutters, frames or casings interfere in the resting of the shutter, for such conditions hinges of larger width are used or fixed with greater outward projection of the pin section.

FLUSH HINGE: These hinges are surface-mounted and do not require a recess to be cut. They are not as strong as butt hinges but can be used for lightweight doors and small box construction.

KNUCKLE HINGES: These are flush butt hinges, fixed over the face of the door and its frame, and so not mortised. The pin cylinder or the knuckle is designed to be visible.

PARLIAMENT OR BUTTERFLY HINGES: These were known as Dovetail hinges and were used for cabinets from the 17th century onwards until the 18th century. The size and form of these hinges vary depending on the use, material and manufacturer. Very small ones are used for jewellery boxes or caskets and large ones used in public buildings. For deep-set door frames Parliament hinges are used to park a deep-set shutter along the corridor -at an opening angle of 180.

STRAP HINGE: A strap hinge has a small height but a wider flange that accommodates two or three screws in a row on each flange.

LIVING HINGE: A living hinge is a thin strip moulded into a plastic part to create a line along which the part can bend. If properly designed and made, its closing and opening capacity lasts for more than a million cycles without failure. It is a thin flexible hinge with flexure bearing. It is formed during injection moulding process for plastics or a composite of it. Such hinges are used on lunch boxes and shampoo or hair oil bottles, and are formed of deformable plastics such as polyethylene, PVC, polypropylene, etc.

BACK FLAP HINGE: Back flap hinge is exactly the opposite version of the strap hinge. It has a squarish flange (height and width are nearly equal) Both are used in furniture items.

PIANO OR CONTINUOUS HINGES: These hinges are long enough to cover the entire length of the shutter, so support the shutter well against warping. Very thin sections of shutter boards (non panelled, without frames) require such hinges. These are used in cupboards, pianos, baueras, and desk top shutters.

INVISIBLE HINGES: These are used for joining two shutters. These are fully mortised as centred on the door shutter's face. Door shutters seem like units of wall panelling as hinges are completely invisible.

CONCEALED HINGES: These are not seen outside a closed shutter and mainly used for furniture doors. These are often spring loaded with self-closing features and with or without a dampening system (slowing down the closing speed during the last few degrees). They are made of 2 parts: One part is the hinge cup and the arm; the other part is the mounting plate. These normally come in two sizes, 25 mm and 36 mm. The hinge is adjustable once fitted to correct the door alignment and planner straightness. These hinges are designed for use with chipboard and MDF.

H HINGES: These are shaped like an H, and used on the flush mounted doors. Small H hinges (75 to 100 mm) are used for cabinets and larger hinges (150 to 175 mm) are used for passage doors or closet doors. Large HL Hinges were common for passage doors, room doors and closet doors in the 17th, 18th and even 19th centuries. On taller doors H hinges were occasionally used in the middle along with the HL hinges at top and bottom.

BARREL HINGE: These Liftoff butt hinges have two components. The bottom section has a cylinder like projection over which a top hollow ring or cylinder is set. The shutter can be lifted off its position for servicing, cleaning etc. These are used in some kitchen cabinets.

LOOSE PIN HINGES OR BALL TIPPED HINGES: These serve the same purpose as the liftoff butt hinges. A removable pin holds two halves of the hinge knuckles together.

STOPPED HINGE: This is like any butt hinge but a square cut projection on a cylinder side of one flange restricts the opening of the shutter to 90 only.

DOUBLE ACTION HINGE: These have three flanges. The middle flange has hinged flanges on either side. The edge flanges are mortised into the side of the shutter, but the middle flange remains off the sides. The assembly leaves a space between the door shutter and its frame or other shutter. The hinge allows the shutter to open in both directions. Such hinges are used in saloon and bar doors.

DOUBLE ACTION SPRING HINGES: These are used on half height saloon doors. The hinge allows the shutter to open in both directions, but being a spring loaded mechanism, the closing action is automatic. In another version of such a hinge, it is fixed to the frame, and the other flange in the form of an arm has a roller at the edge. The shutter is often provided with a plate or channel for the roller arm to slide.

UNEQUAL FLANGE HINGES: These have unequal flanges in terms of width. A thin shutter has thin flange compared to wider flange for the frame side. Unequal hinges also have a greater length of flanges to compensate the reduced width of the flange.

FRICTION STAYS: Friction stays are fitted at top and bottom edges of the surface, and used on French door like systems. Such hinges allow a door to stay-put in its position in spite of the heavy winds, and so prove an ideal fixture on windy faces such as sea shores, mountain valleys etc. The hinge requires framing at least at the top and bottom, making it better suited for windows. It has a sliding channel within which a component fixed to the bottom of the shutter, for converting the rotational movement of opening into a linear thrust, through a collapsible triangular arrangement.

ASKEW OR VERTICALLY MISALIGNED PIVOTS OR HINGES: Fort doors had askew or vertically misaligned pivots or hinges, so in case of an emergency the door would be released from its catch to close fast, and automatically, but this also requires greater man power to open it and a stronger stay to keep it open. Similar systems are employed in modern hospitals, class rooms, garden, and toilets doors, where closed doors are preferred. Hydraulic or spring door-closer do the same function. In refrigerators a magnetic gasket pulls and keeps the door shut. Refrigerators often have doors locking hinges on both sides, allowing a door to be opened on left or right side. Salon and government offices have flap or mid door shutters, with a double flange hinge that can open it both-ways, and also has a spring-coil to bring the shutter to the closed position.

CLASSIFICATION OF HINGES:

FULL MORTISE HINGE: A full mortise hinge has one leaf mortised into the door edge, and the other leaf mortised into the door jamb. This is the most commonly used hinge configuration. Hinge sizes are specified with height first and open width second.

HALF MORTISE HINGE: This configuration is used for door jambs that do not allow mortising, e.g. a channel iron frame. One hinge leaf is fixed to the door edge, and other leaf is applied to the surface of the door frame.

FULL SURFACE HINGE: In this configuration, one hinge leaf is applied to the surface of the door, and the other leaf is applied to the surface of the door frame.

HALF SURFACE HINGE: In this configuration, one hinge leaf is applied to the surface of the door, and the other leaf is mortised into the door jamb.

STRUCTURAL HINGES include arrangements that link, two or more components of a structure but allow conditional movement but do not allow them to come apart or separate out in specific situations. The hinged condition also allows transfer of loads, stresses and transmission of energy. Such hinge like conditions occur in bridges, cranes, vehicles, dams, canal and dyke structures.

GATE HINGES are also called Building access hinges, and include heavy duty hinges for fort gates, estate gates, hanger shutter hinges.

FURNITURE OR CABINET HINGES: These include Concealed hinges with spring loading, controlled closures; butter fly hinges, piano hinges, etc. A butler tray and ambulance stretcher hinge (fold up the legs flat to 90E). Card Table Hinges are mortised into the edge and allow the top (shutter of card tables' cavity) to fold onto itself. Drop Leaf Table Hinges are mounted under the surface of a table with leaves that drop down.

MICRO HINGES: Micro hinges are very small in size and used for jewellery boxes, wall clocks, travel suitcases, attach, bag, micro equipment and machinery cabinets. Many such hinges use ball-mortise arrangement rather than cylinder-pin system.

FLOATING HINGES: It is a hinge that, while able to behave as a normal hinge, enables one of the objects to move away from the other, hence 'float'. Actually the hinge allows for two parallel axes of rotation, one for each object joined by the hinge, and each axis can be moved relative to the position of the other. Floating hinges are used in flatbed scanners designed to scan thick objects such as books. A sheet of paper is placed on the glass, and the cover is lowered over it. The scanner glass and the paper come together very close. If a thick book is placed on the glass, an ordinary hinge would leave the cover at an angle to the glass. A floating hinge raises the hinged edge of the cover to the level of the book, so that the cover remains parallel to the glass, but raised above it. Floating hinges are also used in two-plate electric cooking grills, as they allow for even heating of both sides of a thick piece of food without crushing it. Floating hinges are used for air craft doors, Suzuki (Maruti) delivery vans, etc.

4.1.2.3.2 SECONDARY HARDWARE

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Keywords: mechanics of opening and closing / PADLOCK CHAINS / chain / PARALLEL LOCKING RINGS / hooked rings / LATCH / ALDROP or HOLDROP / shaft / closing handle resting over cleat / BOLT OR NIGHT LATCH -TADI / LATCH-BOLT / DEADBOLT / HASP / chapras / SLAM LATCH / THUMB LATCH, NORFOLK LATCH or SUFFOLK LATCH / LOCKS / wedges or knots / wooden locks and keys / lock puzzles / pin locks / pin tumbler lock / mechanical / electro-mechanical / electronic / keys / levers / 2-lever lock / 6 to 9 lever lock / PADLOCKS / locking ring / LEVER LOCKS / MORTICE LOCK / cylinder locks / locking device / closing device / night or safety locks / lock body / lock trim / strike plate / keyed cylinder / mortise lock / bored cylindrical lock / CYLINDER LOCK / ALMIRAH LOCKS / DEADBOLT or DEADLOCK / spring-bolt locks / vertical deadbolt / COMBINATION LOCK / MULTIPLE-DIAL LOCKS / ELECTRONIC COMBINATION LOCKS / COMBINATION LOCKS ON DOORS / ELECTRICAL AND ELECTRONIC LOCKS / KEY SYSTEMS / INDIVIDUALLY KEYED SYSTEM (KD) / KEYED ALIKE (KA) / MASTER KEYED (MK) / single master-key / GRAND MASTER KEYED (GMK) / COMMON ENTRANCE SUITE / MAISON KEYING (CES) / individual key / COMPUTERISED OR CENTRALLY CONTROLLED SYSTEM / detection devices / electronic card / bio-metrics.

Secondary hardware provides specific characteristics to the door system in terms of control over mechanics of opening and closing. These include: stays, stoppers, locking mechanisms, pivot or hinge fixing -rivets and bolts, studs, nuts, housings, handles, doorstops or catch, door-closer, safety chains, peep holes, view glasses, ventilators, knockers, etc.

PADLOCK CHAINS: One of the simplest locking mechanisms is a chain. Chains are cast of brass, bronze or wrought iron and occasionally braided metal wire or fibre ropes. The chained loops formed of round or oblong rings, with a locking ring at one end, and a fixing hook at the other end, forms a primary locking device. The locking ring is placed over or besides a similar locking ring at the threshold, lintels or on side stiles. A padlock is hung from the junction of locking rings. Similar systems are used for locking bicycles.

PARALLEL LOCKING RINGS: The door and the frame, or two adjoining shutters have hooked rings, which when brought together to a parallel plane or in adjoining horizontal position, allow a padlock to pass through. Often a ring and a chain with multiple loops are used.

LATCH: A latch is a mechanical fastener that holds a shutter against the frame. A latch is functional through friction, a holding notch or a catch. Ball catch type of latch has a small sphere (ball-bearing) mounted on a coil spring. Strap latches have a retractable plastic or notch that is engaged in a slot.

ALDROP (HOLDROP): It is a latch in the form of a metal shaft with a closing handle resting over a cleat through which a padlock is set. The metal shaft, is round, square, flat or oblong in section. The shaft slides through cleats or a set of three ring brackets but its end enters into the jamb to fasten the shutter door.

BOLT OR NIGHT LATCH (TADI): Bolt is a straight sliding shaft with two / three cleats. The shaft has no closing handle (as in aldrop) but instead a notch or a small projecting holder is provided. Some latch shafts have a small aperture in the shaft to insert a padlock to prevent its sliding movement.

LATCH-BOLT: A bolt has an angled (chamferred) surface which acts as a ramp to push the bolt in while the door is being closed. With a latch-bolt, a door can be closed without having to operate the handle. A handle, however, is required to pull back the latch-bolt for opening the shutter.

DEADBOLT: Deadbolts usually extend deeper into the frame and are not retractable from outside except with a key. From inside the deadbolt can be retracted by either a latch or key. The bolt is often not angle cut or chamferred, so that no one from outside can open the bolt by stiff card like credit card. Deadbolts are fixed as add-on system over the inside face of the door. Such a fixing can be undone with a hard kick over the shutter or use a crowbar to break-in. For security purposes deadbolts are often concealed within the shutter body to prevent forceful breaking in. Deadbolts also have additional safety chain, which allows a door to be opened a little to receive a postal-currier delivery or talk to a visitor.

FLUSH BOLT: It is a sliding bolt housed in channel or pipe with projecting a holder pin mounted on a surface or concealed by mortising into the edge of a door or astragal that typically engages into the jamb head and sill to secure the door.

HASP: A hasp or Chapras in India, is a thin narrow plate hinged to a fixing flange. The plate, at its end has an elongated aperture which sits over a padlock placing ring. Hasps are used in small furniture items such as jewellery boxes, wall clocks, drawers, and interior doors.

SLAM LATCH: It uses a spring and is activated by the shutting or slamming of a door. Like all latches, a slam latch is a mechanism to hold a door closed. Slam latch derives its name from its ability to slam the doors and drawers shut without damaging the latch. A slam latch is rugged and ideal for industrial, agricultural and construction applications.

THUMB LATCH, NORFOLK LATCH OR SUFFOLK LATCH: These are stoppers used in vertical or horizontal position. The shaft is moved by thumb. These are often very thin, so can be fixed on the side of a stile of the first of two door systems, on sliding doors, etc.

LOCKS: A device that prevents access by those without a key or combination to open it. A lock nominally is a self-sufficient entity housed in a small chamber that houses its mechanism.

The first locks were perhaps wedges or knots (such as: a thief knot, Gordian knot) on fibre ropes. Wooden locks and keys were in use as early as 4,000 years ago in Egypt. The first known lock was strung on a rope hanging out of a hole in a door and a cylinder of wood with a hole drilled through its axis was its key. The key was inserted into the hole for a correct distance, the rope was pulled to extract the key cylinder and simultaneously pulling the bolt closed. Lock-puzzles were once used to obscure the locking mechanism or even provide a non-functioning lock for the thief to waste time on.

Early improvements in pin locks included increasing the number of pins to increase security, and changing the orientation of the pins to allow the key to provide the unlocking force instead of a rope, thus, establishing the principles of the modern pin tumbler lock.

Locks were mostly mechanical, but later electro-mechanical, and now electronic locks are available. The locks are operated by turning some form levers: through a removable key or such element, dialling in a combination which of activates opportunities, or commands directly or via electro-mechanical (magnetic or other cards). All locks are not intended to prevent unauthorised access. Some are used to control the accidental opening or closing of a door system.

Keys have ground slots and often shaped side channels, which in combination give it a nearly unique capacity. The keys are known by the ground or cut slots, which actuate components called levers. A two-lever lock is used for simple interior doors (no high security risk), whereas a 6 to 9 lever lock is used for outdoor entrances. Keys also have variety of conical projections and depressions all created through a computer programme, which by their position, diameter and depth or height provide a unique capacity. Such keys are virtually impossible to duplicate. Locks are fitted on the exterior and interior face of shutters.

PADLOCKS: Padlocks are portable locks, with their own body and foldable or a separable locking ring. Padlocks can be used over another ring or shackle, or with a chain to tie up separate objects. Inexpensive padlocks are susceptible to direct mechanical attacks which can release the shackle without the use of a key or a combination. Padlocks can be used almost over any type of opening, or with a chain on any vehicle wheel. Padlocks are used to tie up the wrapped around ropes on goods bundles or packages.

LEVER LOCKS: Levers are flat set of grooved or edge shaped devices which can be rotated or pushed by a matching key to operate or activate a mechanism. Insurance companies, police department and other security agencies desire at least a 5-lever lock for external doors of home security system. British Standard (BS 3621:2004) is the one recommended for insurance purposes. A new BS 3621 calls for a bolt throw of 20 mm rather than the 14 mm of the old British Standard.

MORTICE LOCK: (also Mortise in American English) A mortice lock is concealed into a cavity (mortice) in the stile or thickness of the door shutter (unlike a padlock which remains free). A square section pin projects out on one or both the faces to receive the operative handles. Older mortice lock had a large box, but new generation mortise locks are cylinder locks fitted from the front and back, and the locking devices as one, twin or multiple cylinders with projective that come out on the side of the door. The locking device is operated through a key, and an additional bolt -a closing device through a set of handles. The locking device is square ended but the closing device is tapered on one face for self closing but opening through handle movement. Night or safety locks have an extra slider which stops the lock being operative with key from outside.

A mortice lock unit consists of -a lock body (the part installed inside the mortise cutout in the door), the lock trim (such as doorknobs, levers, handle sets and pulls), and a strike plate or a box keep, which lines the hole in the frame into which the bolt fits and the keyed cylinder which operate the locking /unlocking function of the lock body.

Installation of a mortise lock weakens the structure of the typical timber door, but it is stronger and more versatile than a bored cylindrical lock, both in external trim, and functionality. For ornate doors, and for replacement of older locks, mortice locks are preferred, but for functional reasons cylinder locks are used.

CYLINDER LOCK: In these locks the locking mechanism and bolting are two separate systems. The components are standard so virtually any sub component, but importantly the cylinder and the keys are replaceable. Such locks are also available as sets which can be opened by their individual keys and also by a master or common key. Standard cylinder systems include key-in-knob-set cylinders, rim (also known as night-latch) cylinders. There are also many standards (Euro-profile or DIN standard, British oval profile and Swiss-profile) and company specific-patented cross-sectional profiles for lock cylinders, varying in lengths.

Cylinder locks are small in size and diameter, and are fitted from front and back side of a door shutter, rather than from the edge of a door stile (as in case of mortice lock), so are easier to fit and replace.

ALMIRAH LOCKS: These are found on commercial Mild Steel sheets (CRCA) cupboards. These are housed in a box fixed on the inside face of a shutter. The closing device has three components, a locking lever that is moved through a handle, and accompanying it is two vertical locking bars that move upward and downward. Such devices are also concealed on a street side of main doors of buildings for security purposes.

DEADBOLT OR DEADLOCK: It is a special kind of locking mechanism that provides more security than an ordinary key-operated lock. Unlike most spring-bolt locks, in which the bolt is held in place only by the pressure of a spring and can easily be retracted, a deadbolt lock cannot be opened except by rotating the lock cylinder. A variant of the standard deadbolt is the vertical deadbolt, which generally rests on top of a door. 'Vertical deadbolts resist jimmying (in which an intruder inserts a pry bar between the door and the frame and tries to pry the bolt out of the jamb)'.

COMBINATION LOCK: It is operated by setting a sequence of numbers or symbols, instead of key in a nominal lock. The sequence is entered by a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed numerals which directly interact with the locking mechanism, or through an electronic or mechanical keypad. A combination lock requires a correct permutation and not merely the correct combination of digits.

'The first known combination lock was invented in 1206 by the Arab scholar, inventor and mechanical engineer al-Jazari. He documented the device in his book al-Ilm Wal-Amal al-Nafi Fi Sina'at al-Hiyal (The Book of Knowledge of Ingenious Mechanical Devices). Muhammad al-Astrulabi (ca 1200) also made combination locks, two of which are kept in Copenhagen and Boston Museums. Gerolamo Cardano later described a combination lock in the 16th century. In 1852 a German man by the name of Joseph Loch was said to have invented the modern combination Lock for Tiffany's Jewellers in New York City. However the rights to his invention were stolen from his business associate who thereby attained all credit of the discovery'.

MULTIPLE-DIAL LOCKS: One of the simplest types of combination lock, as seen in low-security bicycle locks, in briefcases and baggage, etc. uses several rotating discs with notches cut into them. The lock is secured by a pin with several teeth on it which hook into the rotating discs. When the notches in the discs align with the teeth on the pin, the lock can be opened.

ELECTRONIC COMBINATION LOCKS: These are better then their mechanical counterparts. Such locks are used on safes and drawers. Electronic locks work with power-assisted mechanisms.

COMBINATION LOCKS ON DOORS: Combination locks for doors require one to enter a numeric sequence (pre fixed or dynamic-variable with every use) or a punched, slotted, magnetically or electronically charged key cards to facilitate entry. These locks are often designed for entry by a class of people (e.g. common door entry for members of an apartment), and for conditional access (e.g. in a hotel room the lock becomes unopenable after a guest checks out).

ELECTRICAL AND ELECTRONIC LOCKS: These work with an electric current. Plain-electric locks had magnetic lever system working on the correct voltage or sometimes an electrically controlled-switched lever. Many electric locks are connected to a central access control system of the plant or building complex.

KEY SYSTEMS

Keys have variety of configurations such as: a diameter, the length, shape of the shaft (flat, cylinder, tapered, etc.), and size and shape of slots or cuts, grooves, etc. Modern keys have conical projections and depressions created through a computer programme, which due to their position, diameter and depth or height, are impossible to duplicate.

INDIVIDUALLY KEYED SYSTEM (KD): Here each cylinder lock can be opened by its individual key.

KEYED ALIKE (KA): Many cylinder locks have one key, such as all drawers of a cabinet or many rooms of a mansion, guest rooms on a floor or of a wing. It is also ideally suited to residential applications such as same ley for front and back doors.

MASTER KEYED (MK): A master-keyed system involves each lock having its own individual key which will not operate any other lock in the system, but all locks can be still be operated by a single master-key. This is useful for the concierge or floor in charge of a hotel lobby to access all rooms.

GRAND MASTER KEYED (GMK): This is an extensive version of the master-keyed system where each lock has its own individual key and all the locks are operated by one grand master-key.

COMMON ENTRANCE SUITE / MAISON KEYING (CES) This system is widely used for main entrance door of apartment block, office block and hotels. Each apartment has its own individual key which will not open the doors to any other apartments, but can open the common entrance door and other common service areas.

COMPUTERISED OR CENTRALLY CONTROLLED SYSTEM: It controls the access to all doors. It may also include the detection devices to register the presence (active, resting and sleeping) of a guest or occupant of a room; the status of the rent paid and misuse of various gadgetry or services, etc. The key system in the form of an electronic card or bio-metrics can be reset. The guest or visitors need not surrender the access card at the lobby counter while going out or even on checking out (as the entrance door and many other points in hotel trace and note the movements).

4.1.2.3.3 ATTACHMENTS AND ADORNMENTS FOR DOORS

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Keywords: add-on and integrated systems / fuzzy logic / additional or sub doors / very large doors / small auxiliary doors / DOOR STOPS / dampen the noise / absorb the impact damage / shutter opening beyond certain limit / self closing / askew hinge or pivot alignment / primitive door stops / cotton and fodder stock rooms / self closing doors / door strikes / buffers / door catch / fork pin / a magnet / foot door stop / ESCUTCHEON / STRIKE / SAFETY CHAIN OR DOOR CHAIN / PEEPHOLES, VIEWERS / magnifying glass / one way mirror / fisheye lens / STRIKERS OR KNOCKERS / right of asylum / LETTER SLITS OR MAIL SLOTS / mail receptacle / mailbox / THRESHOLDS / Indian mythology / shankhavati / threshold devices / HANDLES / door handle serves purposes / hand operated / TYPES OF HANDLES / hinged and pivoted doors / horizontal and radial movement / horizontal pull or push / pulled and pushed / NATURE OF DOOR SHUTTER OPENING-CLOSING / DOORKNOB / spherical objects / crystal glass blobs / DOOR HANDLE / horizontal or vertical lever / C shaped static type / Hospital doors handles / Restaurant pantry doors / concealed / fold down / CRASH BAR / crash or panic bar / FASTENERS / CROSSBAR / bolt / reinforce the shutter / prevent break-in by force / GLAZING / putty or mastic compound / transparent to translucent material.

Attachments and adornments endow additional functions and meanings to a door. Modern doors have many add-on and integrated systems, ranging from simple tools, devices to intricate gadgets and complex equipments. These are manual, automatic (mechanical, electrical and electronic), or synergetic, and are programmed with fuzzy logic. Such systems control: opening size, duration, frequency, speed, location, selection, etc. and ergonomically facilitate the working of a door system.

Doors are fitted with additional or sub doors to regulate the traffic and environmental exchange. Very large doors are required for occasional heavy traffic, prestige and for architectural effect, but such doors are difficult to manage in terms of frequent opening or closing. Small auxiliary doors are included within the shutter or besides the main door, for specific functions. Non functional or decorative elements are added to doors as expression, for confirmation to a faith or belief, for solace and other reasons. (For more refer to: chapter 4.3 Opening Systems : Treatments).

DOOR STOPS: A door stop is used with door shutters to dampen the noise and absorb the impact damage to shutter itself, its frame, nearby wall or furniture. Door stops prevent shutters opening beyond certain limit and thereby protect the hanging mechanisms such as hinges. Doorstops also prevent self closing of the shutter due to askew hinge or pivot alignment or wind pressure.

Primitive-door stops were in the form of wedges of wood or metal inserted under the shutter. A door was held open by simply placing a heavy object such as a brick or stone placed in the path of the door. Historically, lead bricks, when available, were popular. In traditional Indian houses of yester years a small piece of wood hinged to the door jambs was placed as a door stop, to prevent a shutter closing due to the winds. Doors were tied to the side walls by ropes or leather straps, which were cut with a sharp blade (in an emergency) to allow a door to close on its own. Cotton and fodder stock rooms have self closing doors, held open by a thin rope, which on catching flame would close the door and prevent spread of the fire.

Doorstop hinges with a rising butt designed to close a door automatically came in use about 1775. Doorstops were made of metals like wrought iron, brass until about 1850. A handle or some other means of lifting the stop easily were incorporated in the design. Doorstops in earthenware and a few in glass were also made. Many took the form of figures of famous persons, such as Napoleon, Shakespeare, Wellington, Gladstone, and Disraeli. Animal forms were also popular.

Modern doorstops include: door strikes of rubber like material or a spring loaded buffer that absorbs the impact and noise of door striking a wall. Such door strikes also have a door catch in the form of a spring metal fork pin or a magnet to hold the shutter. Doorstops are fitted either on the shutter, wall or on the floor. A foot door stop is fitted at the bottom of a stile and has a rubber vacuum buffer, which can be released or pushed with a foot toe.

ESCUTCHEON: it is a decorative base surrounding an eye piece, keyhole or lock cylinder. Escutcheons are mainly decorative, they provide a setting so that an eye piece or the keyholes are easily located. Escutcheons prevent the eye piece or lock cylinder from rotating and prevent damage to the peripheral area.

STRIKE: A plate with a hole in the middle made to receive a bolt. If the strike is for a latch-bolt, it typically also includes a small ramped or mitred area to help the bolt move inward while the door is being closed (also known as a strike-plate).

SAFETY CHAIN OR DOOR CHAIN: Safety chains are used to restrict the opening of a shutter, just enough to see the visitor's face or exchange small articles. Safety chains are often lock-able so an outsider cannot open it. The chain is made of hardened metal which cannot be cut easily by a splicing instrument.

PEEPHOLES, VIEWERS: A peephole is a small opening (or glass windows) placed in a door at eye level to allow people to see who is outside the door without opening it. A simple peephole is an aperture with a metal rim, often with a small grill and a shutter on the inside face. Some have a magnifying glass or one way mirror. Glass peepholes are often fitted with a fisheye lens to allow a wider view of the field from inside with little to no visibility from outside. Micro camera systems are fitted within such devices and connected to viewing screen and intercom system.

STRIKERS OR KNOCKERS: A knocker is a functional entity but often used as an ornamental item on the door. Under medieval English common law, this instrument supposedly afforded the right of asylum to anybody who knocked the door of a church. Bells and chimes operated by rope are also used with doors as calling device.

LETTER SLITS OR MAIL SLOTS: A letter slit is a mail receptacle covered with a swinging flap door and a base plate for its fixing in a door or wall. The slot has limited opening, to allow mail to be delivered and sometimes return the receipt note. The flap door is spring-loaded or relies on gravity to remain shut when not in use. It also restricts straight view of the interior. Many mail slots also have a secondary flap, on the inside to offer further protection from the elements, or have a box or baskets on inside to catch the inserted articles. Mail slots are typically horizontal, but on a small width door this could be vertical. A mail slot is an alternative to the mailbox.

ASTRAGAL: A vertical member attached to the less used or inactive door, of a double door system at the meet point of the lock stiles. It helps seal the junction.

THRESHOLDS: Thresholds are not very evident in modern day door systems, but still have a functional necessity. Doors on windy porches, dusty passages, storm (rain) exposed fronts require a threshold. Thresholds were once a necessary component of door system to fix the bottom pivots and keep apart the lower ends of jambs. Such thresholds were of stone and wood. According to Indian mythology a threshold stops bad effects coming into the interiors. Jain temple thresholds are called Shankhavati due to inclusion of a conch like form in it.

Thresholds often have a small central hole to receive the vertical bolting shaft of door closing mechanism. Modern door mechanisms incorporate a ventilation and air curtain like devices as thresholds. Modern thresholds also have sensors to register the weight of things passing over it. All sensing devices associated with openings are called threshold devices, even if these do not occur at floor level. Gurudwaras and temples have feet wash-pits as thresholds. In pharmaceutical plant an extended threshold mechanism can have water jets to wash of feet or dust the shoes, and dry them out with hot air. Thresholds are used for edge fixing of carpet near door gaps.

HANDLES: Doors require handles in certain conditions. Doors' handles assist mainly opening-closing of the door, but in some instances trigger locking and unlocking mechanisms. A door handle serves purposes like: a grip for closing and opening of the shutter, reduce the wear, staining of the surface of shutter, and spread of infection, through frequent touching. Doors' handles are nominally hand operated but could be elbow, shoulder, knee or feet operated. Automatic doors do not require handles. Less used door may not have a set of handles but instead a key to the lock system may provide a grip.

TYPES OF HANDLES: Handles have many forms. Handles are horizontal or vertical and occasionally inclined. Handles have a grab bar, knob or a niche. Handles are fixed or rotating knobs, bulbs and bars, fixed, folding or shift-able bars, pins with rings, 'L' shaped sections and 'J' type or butterfly hooks. Sliding shutters often have a small slit engraved in the shutter surface for gripping. Aldrops, latches, hasps, tadis, and even padlocks are used as handles. Other forms of handles include buttons, knotted ends of a rope, chains, holes, grab-able edges or projections.

Handles for hinged and pivoted doors require horizontal and radial movement for closing, handles for sliding shutters need horizontal pull or push whereas rolling shutter handles are pulled and pushed in vertical plane. Glass shutters rest on a push-back mechanisms that with a push throw open the glass shutter slightly. Mortice locks, hospital door handles, etc. have locking-unlocking system integrated into the handle.

NATURE OF DOOR SHUTTER OPENING-CLOSING:

Push-in from outside to open inward

Push-out from inside to open outward

A handle is nominally not required, but for preventing staining or wearing of the door shutter surface.

Pull-in from outside to close

Pull-in from inside to close

A handle is required to get a grip on the shutter. Though, one can hold the shutter from the side of the edge but may injure own-self near the jamb.

DOORKNOB: First door knobs were perhaps rope knots that were used for pulling a shutter close and lock it. Doorknobs either are spherical objects fixed over a base plate or attached to an axle that rotated to release the bolt. Door knobs often have an inset push-button or key hole to activate the locking mechanism. Door knobs with human, dwarfs, demonic, animal heads cast in brass, copper and steel, are still popular. Doorknobs also have crystal glass blobs and shaped precious stones. Door knobs require heavy gripping and so are less preferred by infirm people.

DOOR HANDLE: A door handle is a horizontal or vertical lever, attached to rotating pin at one end, which with 30 movement retracts the latch bolt. Doors handles are also C shaped static type, fixed by a set of screw pins from the back side or a plate from a front side. Doors handles are often very long, stretching from shutters' edge to edge, such as in plate glass doors. Hospital doors' handles move up and down to open-close the latch bolt. Restaurant pantry doors have no handles, because waiters push the two-way opening shutter by shoulder. Automatic doors require no handles as the sensor opens and shuts the door. Handles over sliding doors are either concealed or fold down to level of shutters' surface.

CRASH BAR: A crash bar is a mechanism that unlatches a door for an emergency exit. In some countries this is a mandatary requirement for all doors recognised as emergency exit points. It is called crash or panic bar, because when someone pushes against it, the door gets opened. Such bars are normally placed on the interior face of the door.

FASTENERS: A door fastener is a long armed hook device with a pin joint at one end and a ring for insertion at the other end. Fasteners are fixed at top or the middle of the shutter to prevent a door or windows' shutter from closing automatically or due to wind.

CROSSBAR: It is sometimes called a bolt. It is simple plank, bar or beam of wood or metal inserted on the back side of a door to reinforce the shutter and prevent break-ins by force. The insertion is either in the cavities on jamb sides or through special cleats fixed on jambs. Often the bar is pin jointed at one end to keep it from misplacement or theft. On double doors, the bar extends over both shutters.

CROSS BUCK: Horizontal bars are bolted across the vertical planks and used in place of the rails to strengthen the door shutter.

GLAZING: Glazing refers to the panes of glass set into windows, doors and other openings. It can also refer to the putty or mastic compound used to seal the glass. Glazing today refers to any transparent to translucent material used as a panel within an opening or a shutter in it. Glazing is also a process that provides a glossy surface through a coating or through rubbing and polishing an existing surface.

4.1.2.4 DOOR MECHANISMS

Keywords: DOOR MECHANISMS / rotated / hung / opening downward / moat doors / leaf opening upward / pulley based mechanical leverages / pocket doors / counter weights / sloped guide-ways / modern garages / old style warehouse elevators / collapsible or folding type / folded assembly slides / push-shut / doors of public spaces / fire and emergency exit doors / ACTIVE DOOR / dual shutters / secondary or less active or inactive door / MANUAL DOORS / mechanism and configuration / counter balancing and coiled spring / MECHANICAL DOORS -SEMI AUTOMATIC DOORS / wide door / mechanical automatisation / AUTOMATIC DOORS / control and security system / Sensor powered doors / Switch operated doors / Pressure detection doors / Delay mechanism synchronous doors / DOOR SWINGS / left hand LH / right hand RH / left hand reverse LHR / right hand reverse RHR / dual opening doors / bidirectional-mixed traffic / circular swinging doors / sliding or pushing doors / CONSTRUCTION OF DOORS / reinforced by mid bulging / doors of fragile materials / side impact thrust / auto opening and closing system / foot operated handles / automatic opening-closing sensors / buffer or banging plates / SCALE OF DOORS / very wide doors / barricades to channelize / multiple door system / tall doors / tall opening like effects / architectural door portals / functional door / large doors / additional lateral framing / dams and canal gates / 3D entities / extra lateral stability / DOOR MOVEMENT / holder or retainer / load bearing unit / self pivots / hinges / wood door frames / masonry surrounds / space to open shutter / sliding doors / demountable shutters / crossbars / shutters sliding in guides / Stacking of shutters / sliding and folding stack / DOOR HEADS / double shutters / gothic twin doors / Ganged or multiple doors / side lites.

DOOR MECHANISMS: Modern doors have many shapes, sizes and configurations. Traditional doors rotated on pivots or were hung by hinges from sides. Shutter opening downward from top, used gravity for fast closing in emergencies, but fall required a pit for parking and it hindered the surface movement, so was rarely used. Top hung doors or moat doors of medieval English castles opened to form a bridge over the pit. Door leaf opening upward is an action against gravity, and so it is difficult to handle, unless the lift is assisted by pulley based mechanical leverages. Sideways moving of shutters or pocket doors are aided by counter weights or sloped guide-ways. Such mechanisms are still used in cotton godowns doors where a fire could burn a fabric ring holding the door against sliding to a shut position, automatically. Utility delivery vehicles have doors sliding sideways. Modern garages have automatic doors with leaf opening upward and sliding parallel to the roof underside. Old style warehouse elevators have, part of the door sliding up and the other half sliding downward. Industrial units where large size goods and equipments are frequently transferred, door shutters are of collapsible or folding type. The folding action is either in horizontal or vertical directions. In case of very heavy vertical folds, the folded assembly slides while being supported and guided.

Doors nominally open on inside or the side that is controlled or protected by the owner. It is easier to push-shut a door and keep it shut against an intruder forcing against it. However, doors of public spaces such as stadia, cinema, etc. must open out towards a street or open space. Fire and emergency exit doors must also open out.

ACTIVE DOOR: When a door has dual shutters, the first shutter to enter or leave the house, nominally the right side one, is called an active door. These shutters have the locking device and the key hole. The other shutter is called secondary or less active or an inactive door. The secondary shutter is opened when the flush bolt (stopper) is released.

MANUAL DOORS: Manual doors are operated by a person, and in few cases by a trained pet. Manual doors have mechanism and configuration that are within the anthropometric capacity of the user. A heavy door shutter, but with well lubricated and balanced movement system can be operated by a child or infirm adult. Systems that have shutters (inclined or upward), opening against gravity, are difficult to handle. These categories include shutters sliding upward, hatch doors, etc. However, such shutters are made easier to operate by counter balancing and coiled spring mechanisms.

MECHANICAL DOORS -SEMI AUTOMATIC DOORS: Such doors have an assisting mechanism that helps make their opening, closing, locking and unlocking, easier. A wide door requires less pull, but the reach to the shutter due to a larger radius of opening makes it difficult, especially for a wheel chaired, infirm, or a person with crutches or walking sticks. Lever armed handles, double shutters in place of one, askew fixing of hinges for towards gravity auto closing or opening, double hinges, auto (hydraulic) door closer, floor springs, etc. are some of the common methods of mechanical automatisation.

AUTOMATIC DOORS: Automatic doors are single or dual shutters and often operate as multi door system. Such doors usually operate as a sub system of a larger control and security system of the building.

Sensors powered doors activated by some photo-voltaic or infra red sensors that detect the presence of a person or an object, coming into its path, open the door and keep it open for prefixed duration, opening width, and scans the path again.

Switch operated doors are manually operated such as when a person pushes a button to open the door or certain conditions such as the identity checks have been confirmed.

Pressure detection doors operate when: the pressure increases or decreases beyond prescribed levels, by temperature or moisture level settings of the room and by the weight of the person or object through a floor mounted weighing scale.

Delay mechanism synchronous doors do not allow the paired door to open out till the other door has closed properly and an adequate seal is achieved, and other intermediate operations have been completed. Intermediate operations include scanning, cleaning, pressure equalization, disinfection, etc.

DOOR SWINGS: Door swings or Handing, are always specified as from the outside, i.e. outside to inside or public to private.

Left Hand LH: If the hinges are on the left and the door opens in, it's a lefthand door. You push the door with your left hand.

Right-hand RH: If the hinges are on the right and the door opens in, it's a right-hand door. You push the door with your right hand.

Left-hand Reverse LHR: If the hinges are on the left and the door opens out, it's a left-hand reverse door. You pull the door with your left hand.

Right-hand Reverse RHR: If the hinges are on the right and the door opens out, it's a right-hand reverse door. You pull the door with your right hand.

Dual opening doors: Doors for bidirectional-mixed traffic like, a restaurant's pantry, laboratories, etc. need to open both ways, and here the pivot that provides ideal mechanism for dual opening. Salon and flap doors also open both ways.

Circular swinging doors: Revolving doors for office entrance foyers, railway stations and other public places are circular swinging doors, though here movement is restricted to clock or counter-clock wise.

Sliding or pushing doors: Sliding doors have left and right sideways movements. In counter balanced and automatic doors a slight push opens both the shutters simultaneously.

CONSTRUCTION OF DOORS: Sliding panels of doors need to be stiff and could be reinforced by mid bulging or assisted by guide channel or rail, at top or bottom, or both. Fire prone areas have doors of fragile materials, (easily to break in an emergency such as, ordinary -non toughened glass, no fixed grills, thin body shutter leaves) which in case of an emergency can be broken. Car and other vehicle doors are designed to absorb the side impact thrust through provision of extra depth and reinforcement.

Certain doors need to be opened without touching them, as both the hands are occupied (kitchen-pantry service) or hands are likely to get contaminated (operation theatres), such doors have an auto opening-closing system or have a foot operated handles. Similarly doors with high degree of wheelchair commuters, heavy and long trolleys (hospital patients, industrial plants) require automatic opening-closing sensors. Warehouse doors have touch sensitive buffers or banging plates that help the door to open out and away from the direction of pressure or push.

SCALE OF DOOR: Historically very wide doors have been a necessity, for functional as well as for splendour. Wide openings are provided for ceremonies, processions, etc. but wide doors are incapable of regulating the traffic. Such openings have either barricades to channelize the traffic, or multiple door system is used.

Tall doors were less of a functional necessity but a compulsion in monumental structures with royal or public patronage. For very tall doors, the construction of strong shutter and relevant opening control mechanism has been the greatest deterrent. Tall opening like effects are created with architectural door portals, where the functional door is very much smaller.

Large doors require lateral stiffening, as the usual thin shutter leaf construction is insufficient against buckling forces, wind, blasts, and often sonic boom pressures. Aircraft hangers' and spaceships' assembly workshops (Apollo, Columbia, USA) have very large doors with additional lateral framing. Similarly dams and canal gates have to resist not only the pressure of retained water but dynamic pressures of waves and eddy currents. Such doors are designed as a 3D entities. Stadia and such public spaces where people are likely to push the gates, extra lateral stability is required.

DOOR MOVEMENT: Doors have shutters, and the variety of ways these are fixed show the nature of functions that can be served and the level of technology available. In the pivot system, the upper unit is a holder or retainer one and the bottom one is the load-bearing unit. Pivots are still considered ideal for very heavy shutters. Replacing an old style pivot on a shutter was difficult, often requiring reconstruction of the door frame and surrounding structures. Over the years, for lighter panelled doors, shelf-pivots were used. The shelf-pivots became hinges, but later more hinges were used to keep a thin shutter straight. It was possible to fix metal hinges to wood and cast metal door shutters, but to fix the other end of the hinge to a stone or masonry wall was difficult. Wood door frames replaced the masonry surrounds.

For side-hung shutters, a space to open the shutter is required on inside or outside. This is not available in small rooms, narrow passages and also where the immediate terrain is upward-downward-sloping or stepped. For such situations sliding doors or doors with demountable shutters are preferred. Side hung shutters with latches or backside closing crossbars cannot resist an intruder pushing in, for such situations shutters sliding in guides (rails or channels) at sides, top or bottom are ideal. Stacking of shutters by using multiple channels or guide rails allow larger opening. Where multiple tracks are not, feasible shutters are joined together like the bellows of an accordion to form a sliding and folding stack. Folding or collapsible doors were first used in cabinets and cupboards. For a folding or collapsing shutter stack the first or primary shutter is supported on pivot and other shutters are hinged to them.

DOOR HEADS: Doorway width was restricted by the spanning lintel or the arch, but width of the door shutter depended on the materials and technology used for shutter construction and mechanisms of movements such as a pivot, hinges, slider guides, etc. Large doorways require equally large shutters. Double shutters remained a common choice for wide openings. Gothic twin doors had an intermediate support elements. Ganged or multiple doors became popular due to the size restrictions imposed by the glass panes. In verandahs and public places such multiple doors provide the localised choice of controlled opening. Doorways' gaps are also narrowed by placing side lites or side windows. Small shutters were inset within large shutters (such as fort doors). A door within a door is also provided for pets, delivery of milk and postal articles.

The gates at Balawat (now in the British Museum) were of two leaves, each about 8 ft.4 in. wide and 27 ft. high; they were encased with bronze bands or strips, 10 in. high, covered with repousse decoration of figures, etc. The wood doors would seem to have been about 3 in. thick, but the hanging stile was more than 14 inches diameters. Other sheaths of various sizes in bronze have been found, which proves this to have been the universal method adopted to protect the wood pivots. In the Hauran in Syria, where timber is scarce the doors were made in stone, and one measuring 5 ft. 4 in. by 2 ft. 7 in. is in the British Museum; the band on the meeting stile shows that it was one of the leaves of a double door.

4.1.3.1 DOOR STYLES

4.1.3.2 COMMERCIAL CATEGORIES OF DOORS

Keywords: GOTHIC REVIVAL STYLE / Revival Style Architecture in America / Collegiate Gothic / CLASSICAL DOOR / Federal, Georgian, Classical Revival and Greek Revival / MEDIEVAL DOOR / horizontal and diagonal braces / RUSTIC DOORS / rough hewn / INDIAN SHOP (MARKET - BAZAR) SHUTTERS / lock bar or rail bar / INDIAN SHOP (MARKET - BAZAR) SHUTTERS / GEORGIAN STYLE / crown or pediment / pilasters / ADAM or FEDERAL STYLE / fanlights / MOAT DOORS.

GOTHIC REVIVAL STYLE: Gothic style of high middle ages used in cathedrals in Western Europe was used as Revival Style Architecture in America in the 19^thC. It was widely used for churches and universities, where it was called Collegiate Gothic. Gothic Revival buildings often feature a panelled front door set into an arch, partially glazed with Gothic motifs, tracery or a simple rectangular or diamond-shaped pattern.

CLASSICAL DOOR: A general term referring to a door constructed according to the architectural style based on classical Roman or Greek forms. Examples of classical door styles include Federal, Georgian, Classical Revival and Greek Revival.

MEDIEVAL DOORS: European medieval wood doors typically consisted of vertical planks backed with horizontal and diagonal braces. These were strengthened with long flanged iron hinges and stud nails.

RUSTIC DOORS: Rustic doors are similar to medieval in construction but the wood is unfinished or rough hewn (or saw cut) and fixed as the panels but without the framing.

INDIAN SHOP (MARKET - BAZAR) SHUTTERS: These shutters are formed of loose wood planks that are inserted in the top and bottom grooves within a wooden door frame, stone or other masonry. The planks are held together by a lock bar or lock rail of wood or steel.

GEORGIAN STYLE: A style of architecture that took its name from the Kings of England and it was prevalent in the American colonies from 1700 AD until about 1780. Georgian houses usually displayed a strict symmetry with a panelled door as a centerpiece. Typically the door was capped by an elaborate crown or pediment, and often bordered by pilasters (flattened columns) on each side. The style lost favour after the American Revolution, when the Federal and Classical Revival styles gained more widespread use.

ADAM OR FEDERAL STYLE: A style named for British architect Robert Adam, who introduced the use of fanlights, semicircular windows integrated over the door section, to accentuate the doorways of London townhouses.

Adam or Federal style (It is also style of architecture) that was popular in post-colonial North America from 1780 to 1820. Both the Federal style and the Classical Revival style came into favour following the American Revolution, symbolizing the new republic and replacing the earlier Georgian style and its association with England. It is characterized by elegance and lightness compared with the Georgian style.

MOAT DOORS: Moat doors of the forts opened out on the bottom horizontal pivots or hinges. Such doors dropped down into a pit space or formed a bridge over the moat. The moat door had an advantage that it could be opened out swiftly with least effort, but closing was difficult. Doors also were pushed up by use of counter weights for clear width opening. Closing of such doors was aided by gravity and so was effortless. Modern cars are often fitted with doors opening up.

Keywords: LEDGED AND BATTENED / early and rustic versions / plank-style door / boards or battens / ledges / LEDGED, BATTENED AND BRACED / struts or braces / free-end from dropping / LEDGED, BATTENED AND FRAMED / mounted frame / superfluous entity / surrounding element for insertion / pol houses of Ahmedabad / LEDGED, BATTENED, FRAMED AND BRACED / Collegiate Gothic and Gothic revival style doors / PANEL FRAMED OR PANELLED / forts and Indian traditional houses / multi sectional panel doors / traditional wood panel doors / six panel door / cross / Bible / cross and Bible door / panel fixing battens / Lorenzo Ghiberti / PANEL DOORS / stile and rail doors / FLUSH DOORS / laminate or wood veneer / plastic and fibre sheet skin / embossed and printed designs / metal sheet skins / inset ventilators / view windows / postal article delivery slots / pet doors / SOLID CORE FLUSH DOORS / rigid foams / CAVITY CORE FLUSH DOORS / hollow core doors / NON WOOD FLUSH DOORS / MOULDED DOORS / cast or pressed in moulds / architrave borders.

STANDARD DOOR DESIGN NOMENCLATURE / SDI 106-99 / FLUSH DOOR (F) / FULL FLUSH DOOR / SEAMLESS DOOR / STILE AND RAIL OR STILE AND PANEL DOOR / EMBOSSED DOOR (E) / TEXTURED DOOR (T) / HALF GLASS DOORS (G) / FULL GLASS DOORS (FG) / NARROW LITE DOOR (N) / VISION LITE DOOR (V) / LOUVRED DOOR (L / LL) / FULL LOUVRED DOOR (FL) / GLASS-LOUVRED DOOR VL / GL / DUTCH DOORS (D) COMMERCIAL TERMS FOR WINDOWS / OPENINGS WITHIN A DOOR. / 1G / 1G3/ 1G6 / G3 / F/ FL / FV / FVL / FNV / FNLV / FNVL / FV4 / F#V / L1/ L2.

Doors are of many types depending on their materials, methods of construction, opening mechanisms, decorations and finishes, purposes, and cultural settings. Similar doors have unique names depending on the purposes served in various geographic locations.

LEDGED AND BATTENED: Early and rustic versions have two or three thick boards placed side by side without joining, but kept together by nailing the top and bottom ledges. Plank-style door, or unframed doors as found in early American Colonial architecture in New England have several narrow vertical boards or battens that are secured by two or more horizontal ledges, on one or both faces. Decorative hinges, bands, straps and nailheads are used for keeping the battens together and also for ornamentation. The narrow battens reduce the chances of bending-warping. Battens are joined together by rebate, tongue and groove, ploughed and tongue method.

LEDGED, BATTENED AND BRACED: These ledged and battened doors are additionally tied by one or two inclined struts or braces, placed upwards from the hanging edge or bottom free-end, to prevent the bottom free-end from dropping.

LEDGED, BATTENED AND FRAMED: These are similar to ledged and battened doors, but are further held by a mounted frame. The frame is a superfluous entity and not a surrounding element for insertion. Pol houses of Ahmedabad have such doors but with a hollow frame mounted over the boards in place of the ledges. The frame does not participate in fitting of hinges or pivots and mortice lock, etc. However, the absence of braces causes dropping of doors towards the free bottom end.

LEDGED, BATTENED FRAMED AND BRACED: These are ledged and battened doors, but are also braced and frames mounted. The presence of bracing prevents the dropping of the free bottom edge, a necessary precaution in wide doors. The braces are part of the framing system and free of the battens, or alternatively the braces are nailed to battens. A sophisticated form of the basic plank-style construction, frame-and-plank doors are often seen in Collegiate Gothic and Gothic Revival style doors in universities and churches.

PANEL FRAMED OR PANELLED: One of the oldest methods of creating a panel door was to fix boards on the back (inner) face of a frame. The frame was mounted over the boards with nails, rivets, spikes and in recent times with screws or nut-bolts. Ropes, wires and resins have also been used for fixing. Forts and Indian traditional houses have such doors. Greeks and Romans used similar multi-sectional panel door construction. Greeks, however introduced lattices in the upper sections and Romans covered the panel gaps with cast metal units. Romans also began to insert panels of wood, cast bronze, copper, wrought iron, marble, abater, granite, etc., instead of mounting boards on back face. In modern period panels of plywood, particle and pulp boards, fibre composites, glass, glass wool, polyester fibres, plastics (acrylic, PVC, polycarbonate, vinyl, polypropylene), stainless-steel, Aluminium and their composite sheets, etc. are used. Extruded plastic sections are also used to form panel sheets.

Traditional wood panel doors are of single, two panels (top+bottom), and have up to eight panels. A panel doors is referred to by the number of panels it contains. Panels are invariably thin and often hollow or of expanded materials and so reduce the overall bulk of the door. In a six-panel door, the top four panels are proportioned to delineate a cross and the lower two panels represent the open Bible. Such doors were popular in colonial America and so often called a Colonial door, or Christian door, or cross-and-Bible door.

Panels are inserted while assembling the frame, or could have rebates to receive the panels which are then closed by battens. Panel fixing battens are elaborately designed as mouldings. Panels are also cast moulded or rebated to create designs or patterns. One of the best panel door ever created was by Lorenzo Ghiberti for the Baptistery in Florence (1403-52).

PANEL DOORS: Panel doors are also called stile and rail doors, are built with frame and panel construction. The door could have one or several panels of Glass, wood, wood composite, metal plate or sheet, plastic or polymer composite or fabric and woven mats. Panel doors were used by Greeks.

FLUSH DOORS: Flush doors have a completely flat surface on both sides. A flush door has a core formed of strips of wood glued together, surrounded by wood edges, and covered with 3 to 4 mm plywood sheets or veneers on both faces. Commercial are glued urea formaldehyde resins, and water resistant varieties are bonded with phenol formaldehyde or other compounds. Flush doors can be pre-ordered to have a laminate or a wood veneer on one or both faces. Plastic and fibre sheet skins with embossed and printed designs are also available for flush doors. Hospital and some industrial plants have flush doors with metal sheet skins. Flush doors for commercial spaces have inset ventilators, view windows, postal article delivery slots, pet doors, etc. in various functional positions.

SOLID CORE FLUSH DOORS: Solid flush doors have a core formed of tightly spaced strips of wood, compressed wood fibre or particle boards or PU, polystyrene, polythene and other rigid foams.

CAVITY CORE FLUSH DOORS: These are also called hollow core doors. Between two comparatively stiff skin layers a cavity is left-out or filled-in with spacers or distancing elements. The cavity is often filled in with honeycombed particle boards or solid foams to reduce the druminess.

NON WOOD FLUSH DOORS: Modern versions of flush doors are made from synthetic materials. Plastic and metal sheets, plain and design embossed, form the skin and the decorative face, whereas the core is filled with solid forms and expanded materials such as polyurethane (PU Foam), expanded styrene (Thermocole), cement + particle boards, paper pulp boards, mineral wool, glass fibres, corrugated paper boards, etc. These materials provide sound and heat insulation, while providing a body that prevents denting.

MOULDED DOORS: Moulded doors are created by many different techniques. Composite materials such as particles, wood waste or wood pulp, etc. as the 'filler' with their matrix or binding compounds are cast or pressed in moulds. Alternatively after board forming the surface is engraved by a router machine. In both the techniques the surface is provided a coating system or affixed with a laminate or film. Moulded doors are also created by use of thinner panels then rails and stiles to create a setback, offset or set-in type of panel door. Such doors are further 'moulded' by mounting architrave borders at the junction of panels and stiles or rails.

STANDARD DOOR DESIGN NOMENCLATURE: by Steel Door Institute USA: as per SDI 106-99.

FLUSH DOOR (F) The term 'flush' describes a plain surface door without lites or louvres.

FULL FLUSH DOOR: Features no visible seams on the face, though full height vertical seams are visible on sides of door edges.

SEAMLESS DOOR: Features no visible seams on the face or on the vertical sides of door edges.

STILE AND RAIL OR STILE AND PANEL DOOR: Stile and rail are either mitred or butted. Mitred joints are welded and ground smooth so that no mitre joints are visible on the face. Butted joint seams remain visible. The panels are interlocked with stiles and rails and they may be flush or recessed with perimeter surfaces.

EMBOSSED DOOR (E): Full flush or seamless door featuring door faces fabricated or embossed steel.

TEXTURED DOOR (T): Full flush or seamless door featuring door faces fabricated of various patterns of textured steel, i.e. leather or wood grain. Textured Embossed Door (TE): Full flush or seamless door featuring door faces fabricated of various patterns of textured embossed steel.

HALF GLASS DOORS (G): The size and location from the finished floor to the glazed opening will vary as per requirements. Multiple lite patterns are created by inserted muntins. Doors with or one or more glazing panels will have bottom of at least one panel a maximum of 43" from the finished floor.

FULL GLASS DOORS (FG): A maximum 7" rail and stile occur at the top and at the vertical edges. An 8" minimum rail occurs at the bottom. The bottom rail shall be minimum 10" measured vertically from the floor.

NARROW LITE DOOR (N): The glass cutout occurs near the lock stile. The width of the lite shall be minimum 3" and height varying between 10" and 60".

VISION LITE DOOR (V): A lite of 10" x 10" on the vertical centre line of the door. The horizontal centre line can vary between 10" and 60".

LOUVRED DOOR (L / LL): A louver is an opening with a series of slats or blades to allow passage of air.

FULL LOUVRED DOOR (FL): The rail size as specified for full a glass door applies here.

GLASS-LOUVRED DOOR VL / GL:

DUTCH DOORS (D): It is a door divided in two sections, the upper opens first, or both open out independently.

COMMERCIAL TERMS FOR WINDOWS / OPENINGS WITHIN A DOOR.

1G: One / single glass panel, and shutter frame.

1G3: One / single glass panel divided by 2 horizontal thin muntins into 3 sections, and shutter frame.

1G6: One / single glass panel divided by 2 horizontal muntins and 1 vertical member into 3 x 2=6 sections, and shutter frame.

G3: A shutter frame divided by two horizontal members into three glass panes.

F: Full flush door

FL: Full flush door with Louvre opening (usually at the bottom as used for public toilets).

FV: Full flush door with view window (usually at top / eye level as used for offices and hospitals).

FVL: A combination of FL and FV.

FNV: Full flush door with a narrow / slit view window (usually at top but on free edge of door as used for hospitals).

FNLV: Same as FNV but narrow / slit window is longer, almost for full height.

FNVL: A combination of FNV and FL.

FNV2: Full flush door with two narrow / slit view windows (usually at top).

FV4: Full flush door with four view windows.

F#V: Full flush door with four view windows, where # specifies the shape of vision window, such as: O=oblong or oval/ R=round/ D=diamond/ C=cross/ etc.

L1: Full lovers within a shutter frame.

L2: Louvers in 2 sections within a shutter frame.

4.1.3.3 VARIETIES OF DOORS

Keywords: FRENCH DOORS OR WINDOWS / low sill windows or doors with a small threshold / louvered shutters / DUTCH DOORS / stable doors / two divisions / TRAP DOORS / loft doors / SALOON OR PARLOUR DOORS / café doors / bat-wings doors / one way or two way hinges / fixed or adjustable louvers / NURSERY DOORS / SCREEN OR FLY MESH DOOR / REVOLVING DOOR / counter clockwise / clock wise / speed retarder / LEAFED OR WINGED REVOLVING DOORS / two, three and four leaf cental pivot revolving doors / separated the commuters / American revolving doors / automatic sliding shutters / hydraulic door closing with double shutters / dual winged doors / BUTTERFLY DOORS / two winged / two separate channels / push door / TURNSTILE DOORS / symbolic presentation of a barricade / PLATFORM SCREEN AND PLATFORM EDGE DOORS / SLIDING DOORS / top hung system / bottom supported system / Roman times / stacked door system / bypass door system / POCKET DOORS / BYPASS DOORS / FOLDING AND SLIDING DOORS / closing-in-edges / opening-out-edges / as space dividers / BIFOLD DOORS / ACCORDION DOORS / sliding pivot mechanism / Kashmir style room divider / COLLAPSIBLE GATES / single or double sided / portable type / folding panels / piano hinges / CANOPY OR GARAGE DOOR / up and over doors / remote control / canopy door / ROLLING SHUTTERS / quick shutting of the door / timer chain / TAMBOUR DOOR / AMA-DO SHUTTERS / exterior shutters / to-bukuro / SHOJI DOORS / wood-framed sliding panel / Shoji paper / washi paper / FUSUMA / sliding door system / RANMA / REED DOORS / FOLDING DOORS / LOUVER DOORS / Louvred Panelled doors / small width horizontal slats / PET DOOR / dogie door / GARDEN, KITCHEN DOOR / French door.

FRENCH DOORS OR WINDOWS: French Doors are garden side verandah doors. French doors are also known as low sill windows or doors with a small threshold. Such doors may not have a sill or threshold, but often have a drop in the floor (step down) immediately on the outer face. French doors with double shutters (solid panelled shutters and glazed shutters) were used in English and American architecture in the 17th and 18th C. French doors with louvered shutters have been used in the Southern states of United States. The shutter is a framed construction with multiple panes, all or some which have single or double layered glass. Doors may have decorative grilles embedded between the glass panes, or superimposed on the top of the single glass pane. The doors are placed in a designed gap or doorways, such as flat or segmental arch, and as such may have a matching head design.

DUTCH DOORS: Dutch doors or stable doors have two divisions, the upper part remains open for light, view and feeding the horses, and the lower part mostly remains closed to prevent pets and children venturing out, and rodents and animals coming in. Dutch doors are used in shops, stables, barns, tax offices, and ticket booths. The door style was introduced by Dutch colonists who settled in the Hudson River Valley in the early 1600's.

TRAP DOOR: A trapdoor is oriented horizontally on a floor, and often accessed by a ladder, or has a ladder falling out of it. Trap doors or loft doors are used in lofts, for access to services embedded in ceilings and cellars. Some doors also incorporate a collapsible ladder. Boats and ships have a deck trap door that seals the lower chamber in case of a sea storm.

SALOON OR PARLOUR DOORS: Saloon, Parlour or Café Doors were standard features in American 'West' bars, Barber shops, Banks, Butcher's shop, Government offices, Hospitals, etc. In India, these are extensively used in Government offices, hospitals, clinics, bungalows, and guest houses. These are both single and double shutter systems. The shutters cover the mid or the lower section of the opening. Saloon doors that only extend from knee-level to chest-level are known as bat-wings doors. The lightweight swinging shutters have a one way or two way hinges that allow its opening in and out. The Mediterranean and mid East have a version with fixed or adjustable louvres or cloth curtains within the shutter frame.

NURSERY DOORS: Nursery Doors are low level shutters fixed in addition to the main shutter. These provide floor level privacy and keep infants in. The shutters are hinged to side jams or loose boards (panels) are inserted inside grooves. These are often with lattices.

SCREEN OR FLY MESH DOOR: This was an inevitable feature of Dak bungalows in British and Dutch colonies, including the USA. The shutter usually opened out and within its frame a fine mosquito net or wires woven net (to prevent sparrows, squirrels and rats entering the premises) was placed. The fly mesh shutter reduces the amount of light and intensity of wind entering into a room.

REVOLVING DOOR: A revolving door has a top-bottom pivot in the middle of door shutter that forms a shaft. The revolving door's shutter is allowed to move in one direction. Between the point of access and the point of an exit a user walks a circular path between two moving panels. In right-hand drive countries, revolving doors typically revolve counterclockwise, allowing people to enter and exit only on the right side of the door. In left-hand drive countries, revolving doors should revolve clockwise but not always. The user pushes one panel to open the door. With a large diameter of opening the segmental space may accommodate multiple users, trolleys and luggage racks. The glass panes in the doors allow people to see and anticipate each other while walking through. Manual revolving doors rotate with push bars causing all wings to rotate. Revolving doors typically have a speed retarder to prevent people from spinning the doors too fast.

This door design is used primarily to maintain an air seal from the outside face, but minimizing the leakage of the climate controlled air from the interiors. This type of door is also often seen as a mark of prestige and glamour for a building.

LEAFED OR WINGED REVOLVING DOORS: During 19^th and 20^th C, innovation like the two, three and four leaf cental pivot revolving doors were used to keep the warmth in hotel lobbies, foyers and large shops. It also separated the commuters going in or out. Early revolving doors' patents do not mention the term Revolving door but 'a Door without draft of air', 'a door to exclude the noises of the street', A 'Storm-Door Structure that is noiseless', and one that 'effectually prevents the entrance of wind, snow, rain or dust'.

American revolving doors are now collapsible (as per law, so it becomes a double partition collapsing at 180°) or have to be flanked by a hinged door. The revolving doors occupy too much space and so are now being replaced by automatic sliding shutters or by hydraulic door closing with double shutters arrangement. Sliding door systems, work on photovoltaic sensors, lasers, or pressure devices. To emulate the locking out of draughts, noise etc. dual winged doors separated by a small corridor are used.

BUTTERFLY DOOR: A butterfly door is a two winged' revolving door. It consists of a double-wide panel with its rotation axle in the centre, effectively creating two separate channels when the door is open. Butterfly doors are made to rotate open in one direction and rotate closed in the opposite direction. The door is not equipped with handles, so it is a push door. Such doors are popular in public transit subway stations, as it has a large capacity when the door is open. The door shutters in subways are heavy to resist the impact of air currents created by the movement of trains.

TURNSTILE DOORS: Turnstile doors are similar to winged doors but are half or of lesser height and sometimes in the form of a thin bar. These are used in subways and other rapid transit facilities to prevent people from avoiding a fare or a symbolic presentation of a barricade. These doors open out automatically triggered by the presence of a ticket or a credit card. The door or the barricading bar is lifted up or down, folded sideways or retracts into the panel. Modern Metro stations have such doors at the edge of the train platform placed to match the door position of the railway carriage, and open out only when the train stops and open its door.

PLATFORM SCREEN AND PLATFORM EDGE DOORS: Singapore was the first metro system to introduce such doors. These are now widely used on railway stations. Platform screen doors are total barriers between the station floor and its ceiling, whereas platform edge doors do not seal the gap completely.

These doors help: Improve climate control within the station such as disturbed by the high speed trains, in terms of heating, ventilation, and air conditioning. It isolates the tunnel from the platform, prevents accidents and suicide attempts. It reduces unauthorised access to the tracks and tunnels. It eliminates the need for motormen or conductors for train door operations.

SLIDING DOORS: Sliding doors are top hung or bottom supported or both. Top hung system have a wheel system that carries the weight, and bottom guides (continuous or intermittent) to prevent sideways displacement of the shutter. Bottom supported system have floor level wheels and to guide it may have a floor level channel or rail track. In both systems wheels for carrying the load move in vertical rotation, but extra horizontal wheels are also incorporated for guiding the movement. Modern systems are made of drawn metal sections, and have complex support, movement and guidance systems.

Sliding doors have been in use since perhaps Roman times. Channels carved in stone have been found at Pompeii. Sliding doors are preferred in many situations as these do not disturb the space. Sliding doors are of many different types. Simplest sliding doors have one shutter, moving over a wall, panelling, side-lite or into a cavity (pocket doors). Functional slide doors have dual shutters moving in opposite directions. In a stacked door system the shutter (each on a separate track), slide to form a stack on one or both ends. Wardrobes use sliding+hinged doors combination. In 4 door system two end shutters are side hinged and middle two doors slide behind or over the hinged doors. Such a system is called bypass door system.

POCKET DOORS: Pocket doors are sliding doors that slide away from the opening, into a specific parking area concealed by a panel or partition, or into an open cavity like a niche within a wall. It is similar to sliding or stack doors' system, but by hiding the stack of shutters it provides a neat opening.

BYPASS DOOR: Bypass doors have two or more sliding shutters that move past each other. The shutters are commonly used for closets and shop or showroom cabinets. The shutters overlap slightly to seal the gap.

FOLDING AND SLIDING DOORS: Nominal sliding doors do not provide 100% open gap. This is corrected with an integrated folding and sliding mechanism. The system, has two or more shutters side hinged in one set, like folds of an accordion. The shutters' closing-in-edges have top and bottom hinges with the axial pin forming the pivot. The shutters' opening-out-edges have simple hinges. The pivot-end hinges are mounted in a 'fee wheel' set, or is a ball gliding in a channel. The end shutters are often hung the side frame through a set of ordinary hinges. Such doors are used for closets and as space dividers in auditoria, indoor sports facility, banquet rooms.

BIFOLD DOORS: Bifold doors are paired doors that are hinged together to fold onto one another. The end shutters are hung with hinges and also have a top-bottom sliding pivot as part of the bottom hinge. These are often mounted on a track that hangs from the head. It is a popular configuration for wardrobes and cupboards. It is also used for patios, internal doors' partitions such as between dining and drawing room. These doors, when open, occupy very little room space. The doors have a tendency to sag and have a weak lateral strength, so are not ideal for external use. Internal doors are intentionally made to be very lightweight.

ACCORDION DOORS: This are multi fold doors, almost like tambour doors but with vertical slats or shutters. The slats have a backing of canvas or flexible plastic. The shutters, have flexible metal (spring steel), plastic (Teflon) straps or regular hinges. The end, top and bottom hinges often form a sliding pivot mechanism. The door system is often designed to negotiate curvature or form angular or polygonal shape. Kashmir style room dividers are an example of accordion system.

COLLAPSIBLE GATES: Collapsible gates are formed of several vertical members which are joined together by small length members forming a scissors like pin joint. The top and bottom ends of the vertical members are housed in a sliding channel with or without wheels. The vertical members can be pulled to open out to a lattice form or pushed together to collapse into very small width. Collapsible gates are single or double sided and portable type. The portable types are used as a folding barricade. Collapsible gates are mounted with an accordion like folding panels and piano hinges to form an opaque shutter. Collapsible gates were once used in elevators, public passages, etc., but are now not allowed in elevators.

CANOPY OR GARAGE DOOR: Canopy, garage or up & over doors, came out of necessity to have a clean width for parking an automobile in a garage. This door moves up and takes a horizontal position very close to the ceiling line, allowing full width of opening and without the shutter occupying any floor space. Most such doors are automated, so can be opened or closed through a remote control. The door is called canopy Door because when this is mid pivoted for counter balancing, a section of it remains outside forming a shed against weather or sun.

ROLLING SHUTTERS: Rolling shutters became popular to cover up large openings of industrial buildings, warehouses and wide glass fronted shops. These are fabricated with horizontal or slats that are loosely inserted into one another to form a movable joint or hinge. All such slats are held in side channels, and roll up into a cylinder at the top. The slats are fold-shaped or have concave curvature to add to its lateral stiffness. The rolling up into a drum form tightens a winding coil spring which helps in quick shutting of the door. Very small sized rolling-up shutters are used on TV cabinets, wardrobes, cupboards, showcases, dumbwaiter or service elevators. These do not have coil springs. Very wide and very tall, that is heavy shutters are opened and closed through a winding 'timer chain' with sprockets.

TAMBOUR DOOR: It is made of narrow horizontal slats that are joined together by rope or strap at the middle or ends, or by a continuous backing of flexible material like canvass or leather. These doors either roll up or down, or sideways along the tracks or channels. These are typically used in TV cabinets, jewellery boxes, small bureaus, and cabinets.

AMA-DO SHUTTERS: These are exterior shutters in traditional Japanese homes, The shutters are placed on the outer face of the traditional Japanese house to provide a protective cover to Fusuma and shoji doors at night and during bad weather. The shutters when closed make an interior space dark and block ventilation. So some ama-do, in old traditional houses, have small sliding panels that can be opened for ventilation.

The shutters, when open, are stored in special box to-bukuro or an architectural space. The shutter closet is placed just outside of the opening to be closed and the groove in which the shutters are to run. The groove for shutter movement is just one shutter wide. Shutters often have mortises -hozoana, on the edge of one side and tenons -hozo, on the adjoining side, or have a mortise and tenon (tongue and groove) -sanehagi, for a close fit. The shutters are secured by special wooden bolts -otoshizaru that drops down into the sills, or by vertical wooden bolts -agezaru pushed into holes in the lintel -kamoi. A sliding horizontal wooden catch holds the agezaru in place. The last ama-do secures all other ama-do shutters.

First ama-do appeared around the latter part of the 16^th C. They are found on temple buildings -jiin, some shrine buildings -jinja, vernacular dwellings -minka and mansions -yashiki. Theatres built in the Edo period (1615-1867) had ama-do positioned on the upper story behind the audience's gallery -sajiki. They were closed in order to darken the interior during a performance.

SHOJI DOORS: The traditional Japanese Shoji is a wood-framed sliding panel, covered with a thin paper, pasted over the wood grid. The lower section of Shoji is sometimes treated as a wood panel. The wood is normally left unfinished. Shoji doors come in sets of four and are usually six feet high. The traditional function of shoji was to divide the interior space from exterior space. In more modern homes they are also used to partition areas where house-slippers are worn from, tatami rooms where house-slippers are not worn.

The Fusuma and Shoji both slide on wooden rails at the top -kamoi (literally -duck's place), and bottom rail -shikii. The sliding doors do not have wheels, traditionally the grooves were waxed, but modern versions have a vinyl self lubricating strip.

Shoji sliding doors actually come from China. In China, the shoji were only used as partition in interior areas. Lightweight sliding door system inspired by the Japanese arrived in Europe and USA during 1850.

Some call Shoji paper as rice paper, but it is made from washi paper, which is produced from pulp of a kozo tree. By changing the fibre direction and thickness, the transparency, the washi paper scatters light evenly and softly and is also used as lamp shade.

FUSUMA: Fusuma is a Japanese partitioning system. It is a sliding door system covered with a thick opaque paper or cloth on a wood lattice like a grid. Traditional doorways were 90 wide and about 170 tall, but today 190 height is common. These vertical rectangular panels slide, side-stacked or removed to make a larger room or redefine traditional tatami rooms. The Fusuma doors, even though made of fragile material like paper, are easy to replace. It has the function of protecting against cold and conditioning humidity. It also makes a room decorative.

A Fusuma is made by a wooden frame. The frame is covered with paper in the front and back, and then a piece of decorative paper or a cloth is affixed over it. Finally the Fusuma is finished by placing another wooden frame around the perimeter of the door. Fusuma partition doors are often painted with beautiful natural scenery on one or both sides, as a single continuous picture extending across several panels. They typically have a black lacquer border and a round finger catch. Today Fusuma feature plain rice paper or have industrially printed graphics of fans, autumn leaves, cherry blossoms, trees, or geometric graphics.

RANMA: Ranma or transoms are carved on both sides, and used between Shoji and the ceiling to provide air circulation and light. Ranma come in a variety of sizes. These are placed over the shoji, on a wall, with lights behind them as decorations.

REED DOORS: These are sliding doors made of reeds. They can be used as room dividers, wall accents and more. They are used in the summer instead of shoji.

FOLDING DOORS: Folding doors have an even number of sections, generally 2 to 4, folding in pairs. The doors can open from either side for one pair, or fold off both sides for two pairs.

LOUVER DOORS: A Louvre Door has fixed or movable wooden fins called slats or louvers, which allow air movement, restrict the solar incidence, reduce the glare inside by distributing the harsh light from outside, control the vision and provide privacy. Such doors are ideal for high moisture areas like sea coast regions and are widely used in Mediterranean regions. Such doors occur as an external or internal appendage to a glass or fully opaque wood shutter door. The louvre doors are comparatively light weight and weak, so are used as wardrobes shutters and in drying rooms. Louvred Panelled doors can have small width horizontal slats with one edge overlapping the other at a slight inclination to the main face, creating an impression of closed louvres.

PET DOOR: A pet door, also called a cattie or dogie door, a small opening within a door to allow the pet to enter and exit without the main door being opened. It may be simply covered by a rubber flap or it may be an actual door hinged on the top that the pet can push through. Pet doors may be mounted in a sliding glass door as a new (permanent or temporary) panel. Pet doors may be unidirectional, only allowing pets to exit. Pet doors may be electronic, allowing pets with a special electronic tag to enter.

GARDEN, KITCHEN DOOR: A garden door is any door that opens to a garden or backyard. Its size is designed to allow service equipment and large objects. It is often like a double shutter French door.

4.1.3.4 OTHER TYPES OF DOORS

Keywords: COTTAGE DOORS / RUSTIC DOOR / CUSTOM DOOR / CASTLES AND FORT DOORS / lateral stiffness / HATCH DOOR / WICKET DOOR / MOAT DOORS / PORTCULLIS or DROP DOWN DOORS / GOODS ELEVATORS DOORS / PORT GODOWNS' OR WAREHOUSE DOORS / COTTON GODOWNS' DOORS / flexible shutters / BARN DOOR / CARRIAGE DOORS / AIRCRAFT HANGER DOORS / Suez and Panama canals' gates or 'locks' / DAMS AND CANAL DOORS / SHOWER DOORS / FIRE PLACE DOORS / RAILWAY CROSSINGS GATES / AIR CURTAINS / invisible and material less barrier / cascade an air flow / sonar cascade / FLAP DOOR / lap joint / BUBBLE DOORS / BLIND DOOR / disguised functional door / fake or make-believe door / partitioning system / FALSE DOOR / mihrab / FAKE DOORS / fake door and painted windows / speakeasy joints / SECRET DOORS / Bab Al-Sirr / Door of treason / RESTAURANT PANTRY DOORS / FURNITURE AND CABINET DOORS / work or writing surface / removable shutters / fold-out shutter / hand rest / hingeless shutters / STRONG ROOM OR VAULT DOORS / in-fill of mineral blocks / Armour doors.

COTTAGE DOORS: A rustic door design used in homes, garden walls or other locations, based on an architectural style typically found in rural cottages. A cottage door can include many different style elements, including frame-and-plank construction, and the Dutch door style.

RUSTIC DOOR: A general term used to describe a simple door typical of those constructed by early American settlers or often found in rural homes and buildings. Plank-style doors, Dutch doors and Cottage doors are examples of rustic door styles.

CUSTOM DOOR: A door that does not fall into a standard category or period of architectural style, but designed specifically for a client or site. It may include many different styles. All historical doors are custom designed because every door is unique.

CASTLES AND FORT DOORS: Fort doors are called gates due to their large size. The doors are large for functional reasons, such as: passage of horse, camel or elephant riders, chariots and defence equipment, for ceremonial parades, passage of processions and for prestige reasons such as awe, power, grandeur, etc. Castle or fort doors due to their large size require lateral stiffness (provided by larger width or thickness of the shutter leaf, metal-bands of bronze or iron, large sized hinges or pivot rings). Large and heavy gate doors cannot be operated manually and require opening and closing mechanisms (provided by counter weights, inclined hinges, chain pulley blocks). The doors often have a small passage or service door within the main door, view windows for peeping out, and delivery gap for small items. The doors have cross bars on the back face to add to stiffness and provide resistence to forced entry. Gates have spikes to prevent anyone forcibly pushing the shutters in.

HATCH DOOR: It is a door opening placed in a floor or ceiling, in homes for accessing the terrace, lofts or underfloor sections; in boats for under the deck zones; and in aircraft both under and over the floor compartments. The floor and the roof or ceiling hatch doors are opened by lifting out as a free lid or hinged shutter, or by pushing in as plug-lid or hinged leaf. The hatch doors rise up the floor with a marked perimeter or are levelled with the finished floor. The hatch doors often have an attached ladder. Hatch doors are designed as less frequently used opening system. A small hole between two rooms, with a cover is also called a hatch, as for example between chambers in submarines and sub units of space ships. Automobiles also have a ceiling level opening.

WICKET DOOR: A wicket door is part of a gate system to allow only human being while barring cattle and vehicles like cycles, etc. It is nominally hinged or pivot hung door but placed in a segment of a circle barricade to restrict the space of movement.

MOAT DOORS: Moat doors are castle or fort doors that open out on the bottom hinges to form a bridge over the moat or pit. Though this seems a romantic as a concept, it is doubtful if it can span a large distance or carry the weight of the traffic over it.

PORTCULLIS or DROP DOWN DOORS: (Fr. porte=a gate, coulisse=a groove). This consists of a panel or a lattice of wood or iron that can drop down along a channel to close an opening in case of an emergency like invasion, fire or flood. The weight of the door moving downward is assisted by gravity for instant closing, but to lift it back for opening requires pull through pulleys or counter weights.

GOODS ELEVATORS DOORS: These often have a lower half falling down and a linked counter weight mechanism that lifts the upper half upward, while closing the upper half provides the counter force to lift the lower half upward. This arrangement provides an edge to edge opening width.

PORT GODOWNS' OR WAREHOUSE DOORS: During the industrial revolution period godown were erected on lake or sea fronts and had to face storms. To keep the size of opening just bare minimum the height allowed a bent down 'coolie' with a heavy back load. These doors often had additional upper shutters to allow a porter carrying a taller head load.

COTTON GODOWNS' DOORS: Cotton godowns' Doors (and such fire hazardous materials' warehouses) have doors with a combustible string tie, which on burning allowed the hung counter weight to fall and let the door shutter to slide down over rail (towards gravity) automatically, and seal the premises to prevent the spread of fire. Warehouses now also have flexible shutters of striped material that allow both way movement of cargo laden vehicles.

BARN DOOR: Barn doors are wide enough to move in and out the farm goods and equipment including tractors, trolleys, etc. Barn doors often have another door at upper level for accessing the loft level floor stocking the fodder. Barn doors have a braced shutter frame with mounted panels of plywood, wire lattice, plain metal or corrugated galvanised iron sheets.

CARRIAGE DOORS: A door for horse-drawn and automobile carriages. It was a small lower section door with upper section as a framed hollow, or left open, hinged to a side and opened out. The style was used in saloons, parlours and items of furniture. It carried the emblem of family or company.

AIRCRAFT HANGER DOORS: These are very large and being heavy move on wheels and rails. Space craft assembly workshop doors are perhaps the largest sized doors ever used. The movement is helped by counter weights or electric motors that provide sideways pull. Suez and Panama canals' gates or 'locks' regulate the water level.

DAMS AND CANAL DOORS: Dams' doors open out easily due to the force of gushing waters but require high power to shut off. Canal and dam gates take on substantial side thrust of retained water and so have heavy lateral bracing and wide seams. Dutch have devised dams, canals and dyke flood control systems, whose key element is the complex door system. These are sometimes automatic but otherwise triggered by the water level and movement of currents. Suez and such other canals have doors that become a wall to store the water to lift the sea faring vessels.

SHOWER DOORS: Shower cubicles or cabins have doors such as: bypass or sliding door, swinging door, or a combination of both -the bifold doors. The doors are fixed over the shower stall curb or over the bath-tub edge. A major problem is of cleaning and draining the tracks within which the doors move. So shower doors preferably must not have a bottom track to providing free access for the wheel chaired and other infirms. A swinging door is preferable but must open out and that takes up a lot of space for opening. Circular bath tubs, like with Jacuzzi facilities require bifold or multi fold doors. These are able to negotiate curvatures or angles.

FIRE PLACE DOORS: Fireplace doors are of two types: Glass and very fine a metal lattice. Fireplace glass doors retain the heat and so increase the energy efficiency of the fire place. Metal lattice doors become warm and help re-radiate the heat into the room. In both the cases, the sparks are eroded minimizing the risk of fire.

RAILWAY CROSSINGS GATES: Railway crossings have barricade gates consisting mainly of a horizontal bar counter balanced by weights. The bar is pulled down by release of the locking lever and pulled up by chain pulleys.

AIR CURTAINS: Air curtains form an invisible and material less barrier, which can be breached, so function like a door. Operation theatres, food and pharmaceutical plants have air curtain fans to cascade an air flow over the openings. Similarly a sonar cascade in electronic plants removes dust from goods and people entering a clean space.

FLAP DOOR: Flap doors are very common in tents, mosquito net tents, isolation-tents in hospitals, It consists of a flap that overlaps all sides of the opening to form a lap joint. Flaps are made of same material as the tent, or of cotton, canvass, woven polypropylene or fibre glass or such other fabric like materials. To seal the edges other than by overlapping, strapping, velcro, fly chains, etc. are also used.

BUBBLE DOORS: Bubble doors are formed out of glass, metal, or plastic. The shape is a segment of a bubble, or any other rounded bulge, the sectional edge of which matches the shape of the opening. The 'bubble' is hinged to top or side. Bulged shape is capable of taking large pressure, so such doors with or without a reinforcing frame and gasket systems are used in pressure chambers, marine vessels like the sub marine, etc. and for entry out in sky lights, industrial roofs, domes, etc.

BLIND DOOR: A blind door is not visible, as it is designed to blend with the adjacent wall finish. It has no visible trim or operable components. It is a disguised functional door, but not a fake or make-believe door like early Egyptian buildings. Such doors are used in offices and study rooms (to hide secret exits, toilets, etc.) Blind doors are also used to merge the doors, windows and fixed panes openings as one partitioning system. Modern day uses include merging cupboard shutters with other shutters such as toilet, dressing, closet, etc.

FALSE DOORS: A false door is not a real door but a representation of a door in 2D form such as painting or 3D form like an engraved motif or a bas relief. In ancient Egyptian architecture, in a tomb it represented a gate to the afterlife. The door was engraved on Alabaster, stone or wood or painted over the wall of the burial chamber. The door was placed on the Western face, as the side from which the Sun god and the departed soul go over to the other world. (For more ref to 4.1.9.2 Door Myths and Legends). Such a feature may have influenced the mihrab in a mosque as a passage to the god.

FAKE DOORS: Fake doors are make-believe entities that are not doors but made to look like a door, or actual doors hidden by other elements. Make-believe doors were devised to create a balanced interior scape or house front. Fake doors were also used in cabinets to create secret chambers.

The facade at Leinster Gardens, West Kensington, was put up to hide an open air gap created over an underground track in 1868. Between Paddington and Bayswater open-air sections were created by knocking off two houses, to relieve pressure and keep the tunnels free from smoke. When residents complained about noise and nuisance, a five feet thick concrete wall was built fitted with fake door and painted windows, to fill in the gap and hide the blast of fumes caused by trains passing underneath.

Real doors between two adjacent suites, doors to toilets, store rooms, vaults, etc. are often concealed behind library cabinets or panelling. Hidden doors were used in speakeasy joints during liqueur prohibition in USA. -an illicit liquor shop or drinking club. In New York City, in 1928, just prior to Prohibition, Jack Kriendler and Charlie Berns purchased a former bordello and converted it into a bar and restaurant called the '21-Club'. In 1930, they hired architect Frank Buchanan to design a secret door to hide the liquor supply in the cellar, as the place was converted to a speakeasy. To conceal the hidden door from Federal prohibition agents, Buchanan designed the door so that it would appear to be a solid cement wall. The door, which weighed two-and-one-half tons, was supported by massive precision hinges and faced with a cement slab. The secret door could be opened only by inserting a 18" length of wire through one of several cracks in the cement.

SECRET DOORS: Traditional Arabic houses, sometimes have a secret door, Bab Al-Sirr, as an emergency exit. It was camouflaged by cabinet, bookcases or hidden with a window sill. The name comes from one of the six gates cut through an ancient wall in Aden (Yemen), which was opened only in the event of a state security emergency. In modern-day Spain, the Arab fortress of Benquerencia has a Bab al-Sirr known as the Door of Treason.

RESTAURANT PANTRY DOORS: These occur as a set of doors, both of which can move inside or outside, and a mechanism rests the door in closed position. The double door channelizes the in and out traffic, though a mid member is not required between the door shutters. The doors have striking plates at a hand-held tray level and also at feet level, or an automatic mechanism for closing-opening in the required direction.

FURNITURE AND CABINET DOORS: Furniture pieces like cabinets, wardrobes, clocks, etc. require light weight shutters. Bureaus have a door shutter that forms the work or writing surface (like a table top). Kitchen cabinets have upward opening shutters so that work is not hindered by the shutter opening out. Kitchens also have removable shutters for easy cleaning. Computer keyboard drawers have a foldout shutter that becomes the hand rest. Radio (large sized valve sets of the past) cabinets had shutter sliding in the top part above the radio set. Similarly early TV models had pliable shutter sliding to the sides. Clocks had hingeless shutters that were held by mechanical catches.

STRONG ROOM OR VAULT DOORS: Strong rooms where the valuables like precious metals, jewels, cash, documents, art pieces, heirlooms, etc., are stored, require doors that can defy armed robbers, fire and natural calamities. Such doors have combination locks and attached alarms. The doors are made of un-cuttable and non-fusible steels or alloys. The thickness and constructions are such that these are able to resist blasts. To insulate the doors against heat and other radiations, the doors have in-fill of mineral blocks. Strong or Armour doors of hardened steel are also provided in some industrial plants, boilers, kilns and 'bombing' shelters.

Most 19th and 20th Century gallows featured a trapdoor, usually with two flaps. The victim was placed at the join. The edge of a trapdoor farthest from the hinge accelerates faster than gravity, so that the victim does not hit the flaps but falls freely.

4.1.3.5 DOORS LIKE UTILITIES

Keywords: CAR DOORS / SUICIDE DOORS / trailing edge / rear hinged doors / CONVENTIONAL CAR DOORS / front edge fixed doors / CANOPY DOORS / aircraft canopy / BUTTERFLY DOORS / GULL-WING DOORS / seagull's wings / SCISSOR DOORS / beetle-wing doors / jackknife doors / switchblade doors / Lambo doors / SCISSOR-CONVENTIONAL HYBRID DOOR / VLS DOORS / SLIDING DOORS / POCKET DOORS / VERTICAL DOORS.

CAR DOORS: Automobiles have had many varieties of doors, some bizarre in shape, size and styles. Some new features, if not entire doors have inspired many radical opening systems, others have been obscured. Car doors had radically different design approaches because these were produced in sophisticated production facilities, often for one or few clients and in many cases were not even required to be even modestly functional.

SUICIDE DOORS: Horse and other carriages had doors opening outward, and the style was continued in early the automobiles, till first half of the 20^thC. The car doors were hinged on the edge closer to the rear of the vehicle, known as the trailing edge -rear hinged. Rear hinged doors made it easier to enter the vehicle and occupy the seat.

Rear hinged or suicide doors were supposedly very thrilling in the gangster's era of the 1930's because it was easier to shove somebody out of the car with the wind holding the door open. The suicide doors, however at a practical level posed danger of the door falling open or getting unattached in a moving car.

Some modern cars have 'suicide doors', but for the back seats only, and that too overlapped by front edge fixed, front doors. The back door thus cannot be operated unless the front door is opened first.

CONVENTIONAL CAR DOORS: Conventional current day cars have front edge fixed doors. In a moving car, the wind pressure pushes the door shut.

CANOPY DOORS: Normal car doors open out of the car's wheelbase and so can obstruct the road or pavement when opened. This is not an issue with canopies as Canopy doors lift-up to open vertically and stay on the top of a car to provide access for passengers. It is similar to an aircraft canopy. There are many varieties such as the articulated canopy, a bubble canopy, a cockpit canopy, etc.

BUTTERFLY DOORS: Butterfly doors move up and outward making it easier for entry-exit at the expense of saving space. Butterfly doors have been used in top sports car racers.

GULL-WING DOOR: These car doors are hinged to the roof rather than the side. When opened out the doors evoke the image of a seagull's wings. The door opening requires very little street space. In an accident, if a car rolls over, the exit is difficult. The gull-wing doors were designed for housewives owning a Volvo concept car, because lifting the shopping bags or putting down children into the car was easy. Gull-wing doors have a leakage problem in the monsoon and during car washing.

SCISSOR DOORS: Scissor doors rotate vertically at a fixed hinge near the end of the windshield. The doors open out upwards, but stay within the car's wheelbase. They are also known as beetle-wing doors, jackknife doors, switchblade doors, and Lambo doors (Lamborghini).

SCISSOR-CONVENTIONAL HYBRID DOOR: Some scissor doors are also designed so they can open vertically, and horizontally like a conventional car door. The double facility allows the door to be opened in whichever style is best suited to the situation. It is a very complex mechanism.

VLS DOORS: VLS doors have a scissor door configuration. The biggest difference is that they are designed to initially open slightly outward before opening upward to allow the top edge of the door to clear the door frame and A-pillar. Although butterfly doors also move upwards and outwards, VLS doors are not butterfly doors, this is because VLS doors move outwards to a very small degree compared to the angle of butterfly doors. VLS doors also can rotate to 130 degrees.

SLIDING DOORS: A sliding door opens by sliding (usually horizontally), for which the door is either mounted on or suspended from a track. These aren't usually used in small vehicles, but generally more common for minibuses and busses to provide a large entrance or exit for passengers without obstructing the pavement. They are often used on the side of commercial vans as well, as this allows a large opening for equipment to be loaded and unloaded without obstructing access. Drivers or passengers with limited mobility are provided with sliding doors. Their own bulk and the large holes in the body frame require extra strengthening.

POCKET DOORS: A pocket door is a sliding door that slides along its length and disappears, when open, into a compartment in the adjacent wall, or as in terms of vehicles, into the car's bodywork. Pocket doors are often used in architecture, but rarely in vehicles. (Kaiser 1953)

VERTICAL DOORS: A vertical door is a type of sliding door that slides vertically, usually on a rail or track. They slide into a compartment within the car's body and so are also technically pocket doors but they aren't classified as such because they don't slide along their length into an adjacent compartment. The Lincoln Mark VIII concept car's doors slide into the frame underbody and disappear from view.

4.1.4.1 DOOR LIKE PRESENCES

Keywords: PRESSURE COOKER SHUTTERS / pressure doors or plug doors / PLUG DOORS / passenger aircraft / CHEMICAL REACTION VESSELS SHUTTERS / non-plug doors / locking devices / holding vices / nut-bolts / NON-PLUG DOORS / hinges or pivots / free lid / butter fly valves / ball valves / FLY DOORS OR CAMERA SHUTTERS / AUTOMATIC OPENINGS /

PRESSURE COOKER SHUTTERS: These are pressure doors or plug doors. As the pressure inside increases the shutter leaf presses itself harder on the seams. The bulge (convex) shape of the lid has increased area adding to the efficiency of sealing. A well-designed plug door relies only on the strength of the wall around (seams) it and the material the door itself is made from.

PLUG DOORS: Plug door like situations occur on high altitude flying passenger aircraft. Due to the higher air pressure within the aircraft cabin than that of the surrounding atmosphere, the door seals itself closed as the aircraft climbs and the pressure differential increases. This prevents the opening of a plug door on board a pressurized aircraft. However, at lower altitudes or on landing the decompression, allows a door to be opened. Rapid Transit Series buses feature front and rear plug doors. Plug doors are used only on the outer hatch doors on the Space Shuttle and International Space Station as well as on the hatch between the Orbital Module and Descent Module on the Russian Soyuz spacecraft.

CHEMICAL REACTION VESSELS SHUTTERS: These are non-plug doors and rely on the locking devices such as holding vices or nut-bolts to resist the pressure.

NON-PLUG DOORS: Such shutters are not accompanied by traditional 'shutter hanging' mechanisms such as hinges or pivots. The shutter is like a free lid, though often casually tied to the base. A paint tin lid is a common example of a non plug door, relying on the wedge shape of the seam edge. Canvas sheets in artists' frames are held by clamps.

VALVES: Valves have a closing diaphragm or a plunger to seal an opening and thereby curtail the flow. Butter fly valves have a central pivoting diaphragm similar to wings of a butter fly. Ball valves have a ball which gets displaced by the pressure of liquid or gas but shuts the opening by falling down due to gravity, and thereby prevent any reverse direction flow.

FLY DOORS OR CAMERA SHUTTERS: Camera shutters have multiple flaps, which are hinged close to the outer edge, and the inner edges are overlapped. The flaps open and close very quickly by a rotating mechanism that actuates the outer edge section. The inner edges form a polygon or nearly a circle, thus giving a smooth edge to the picture being shot.

AUTOMATIC OPENINGS: These are of many opening systems that serve functions of a door. Such systems are add-on systems to traditional doors or are independent controllers of openings.

Mechanical systems have a coiled spring which winds or unwinds while closing and opening a door and the stored kinetic energy is used for the reverse operation. Mechanical systems also use gravity drawn counter weights to either open or close the shutter, but for reverse action other resources are required.

Automatic systems are electric powered to open and close. Both mechanical and electric powered automatic systems could have sensors to activate the closing and opening. Smoke detectors sense a fire but also close the doors to prevent spread of a fire. Hotels create swipe cards for their guests and staff. A guest's card remains operative so far as credit hold well. Staff cards allow access to the rooms for servicing when the room is not occupied. The sensor continuously transmits the use of card and its schedule or duration of use to the central computer. In addition automatic doors are fitted with safety sensors which control the speed of opening and closing. Heron of Alexandria created the first automatic door in the 1^st C AD.

4.1.4.2 REAL AND PSEUDO DOORS

4.1.5.1 DOORS : SIZES AND PROPORTIONS

Keywords: OPENINGS / sides / head / size, shape, position and duration of the openings / gap in mountains / ships passage / deep openings / GATEWAYS / node / 'Gateways' in communication field / symbolic / landmarks / a gate that leads one nowhere else / DOORWAY OR DOOR PORTAL / architectural corrective / pylons / colonnades / Torii gate / Sanchi stupa gateway / DOOR / opening / doorway / door / shutter / controllable opening system / real, unreal, present or absent / physical door / abstract adornments or attachments / deceptive character / nonphysical door / unreal or metaphoric / virtual doors / invisible doors / make-believe doors / frames or markers / notional or representational doors / shutter like configuration / painted doors / real-functional size / debased scale / pseudo doors / prehensions for a door / make-believe doors / entrance or boundary of an ethereal world / metaphoric doors / signs and symbols / allegories / variations in barriers / passageway / mythological associations / door symbolism / metaphors / breach-able points or weak spots / electrical circuit diagrams / pipe layout drawings / communication field / 'gateway' / closed doors / open doors / door forms / Real door within a Real door / Real door within a Pseudo door / pseudo door / real or functional door / Pseudo doors within a Real door / stepped or recessed flutes / microcosm.

OPENINGS: A gap, crack or a cut in a barrier is an opening. Openings have two omnipresent sides and sometimes a head or top cover. The sides and the head make openings a finite entity. Openings have two faces, and between them some imbalance always exists. Transitions flourish between two sides for an equilibrium to occur. At the opening things may be allowed, accelerated, delayed or stopped. The size, shape, position and duration of the openings impose restrictions and cause changes over the transition.

Openings can also be defined as structures that facilitate the efficient transfer. An opening is also a possibility where a change is likely or can be better managed. A valley is a gap in mountains and so convenient for crossing over. A seaway is deep dredged channel for ships passage. A runway is an efficient place for an aircraft to land. A bridge is best way to get across a difficult terrain. A pipe, duct, cable or a bridges are deep openings.

GATEWAYS: A Gateway marks the node, start point or potential for a transit. Such points are marked, enhanced or endowed with translation or conversion capacities, as called 'Gateways' in communication field. A gateway could also be symbolic, where in spite of the transition, no change may be experienced. The gateways like: Arc de triumph (Paris), Char Minar (Hyderabad), etc. are landmarks in the form of a gate, -a gate that leads one nowhere else. Japanese gate Torii has no lead. Gateway of India (Bombay) does not denote the physical entrance-exit points of India.

DOORWAY or DOOR PORTAL: Openings are of finite size and their potential is realized with a doorway and door. A doorway or door portal, is an architectural corrective to enhance a gateway, functionally, physically and symbolically. Egyptian temples have massive pylons or massive sloping towers fronted by obelisks, to define the doorway. Greeks and Romans have used colonnades as doorways. The serrated portals of Gothic cathedrals add to the size of the door. Bulund Darwaza of Fatehpur Sikri is a large gateway over a small door. The Torii gate and the Sanchi stupa gateway has three lines of eaves as a heading.

DOOR: The opening, the doorway or the portal, the door and the shutter, together constitute a door opening system. A door with a shutter is controllable opening system. The opening, doorway, door and shutter, could all, one or few of them be real, unreal, present or absent.

A physical door essentially requires a real gap and a real shutter. The shutters open, close, or take up many intermediate positions. Shutters have specific configuration, materials, size and scale. Physical doors, however, can have abstract adornments or attachments that give a deceptive character to the door and belie their reality.

A nonphysical door may not have: an opening to transit, a doorway to distinctively mark the opening, or an operative door system to make it functional. A nonphysical door could be unreal or metaphoric.

A virtual door does not reveal itself physically, but otherwise it is functionally as effective. Modern industrial plants, estates and institutional campuses have 'open' gaps or invisible doors with control systems that activate a 'shutter' (a control system) when required. To indicate the position and presence of such monitoring devices, few make-believe doors like frames or markers, are placed. Metal detectors' door frames at airports and public spaces, colour coded markings on the floors, are examples of these.

Notional or representational doors: Over the years, in our minds, a shutter has become so strongly associated as the door that its presence or even notional indication suffices for the opening to be evident. 'A shutter like configurations over a barrier satisfies our expectation that there is a way out or in.' The notional or representational doors, such as the painted doors on Egyptian tomb walls do not take one anywhere, but do satisfy the spiritual needs as an entryway to the other world. Such doors, drawn or carved are of real-functional size as well as of debased scale.

A pseudo door exists with inadequate or no opening system. The door has no real gap for transit, no perceptible doorway, or there is inadequate shutter system. The prehensions for a door are at many levels including: functional, perception, size and scale. Such doors also exist without any apparent barrier system.

Make-believe doors are created to denote an entrance or boundary of an ethereal world. Stage side-wings become exit-entry points. An actor, to enact a departure from the realm, at a certain point on the stage, ceases to act or shows the backside of the body. Door frames standing in a wide terrain or the gate structure such as the Japanese Torii standing in wide stretch of water is an entrance.

Metaphoric doors: Metaphoric doors manifest through signs and symbols. Such doors may not have a functional size, scale and other physical characteristics or functional utility of a nominal door.

The allegories used are:

variations in barriers (representing an overlap or a gap or aperture),

a scaled or functionally sized gap,

a passageway (indicating a pathway to or from somewhere),

signs, symbols and graphics to mark linearity (a lead to some place),

frames (to enclose a view and other sensual perceptions),

miniatures

mythological associations with doors or openings such as: Janus -Roman, Re -Egyptian, Ganesha and Kshetrapal-the keeper of the estate -Indian, two brothers, Shen Tu and Yu Lei -guardians of the passageway -Chinese.

Various forms of these are used individually and in combinations, to enhance the essence of a door.

Door symbolism: A symbolic door is a representation of the nominal door or its important components or essential qualities. Door symbols are abstracted as well as scaled versions. Metaphors are also used to present physical characteristics, crucial functions, essential qualities and historical associations of the doors. Doors denote a break and so the symbolic presentations are used to indicate the breach-able points or weak spots. In electrical circuit diagrams and pipe layout drawings the door symbols are used to denote a break, open position, or a switch. In communication field a door stands for connectivity with the world so a 'gateway' is where traffic converges and redistributes.

A door is a point where change from the known world of inside versus the unknown world of outside is experienced clearly. Closed doors isolate an exuberant interior and open doors permit incursion of wild exteriors. Doors are accordingly shown to be open or closed. 'Heaven is always door-less and shown with its interiors, whereas hell is more represented as an entry point or from outside of its doors'. Symbolic doors are more focussed by framing, detailing, scaling, sizing to offset them from the surroundings.

Various types of door forms are combined like:

A Real door within a Real door: Smaller doors are often placed within larger doors, e.g. forts' doors, shutters for pets' entry, flapped gaps for milk and postal articles.

A Real door within a Pseudo door: Fatehpur Sikri Buland Darwaza is a large structure signifying a pseudo door but with a very small real or functional door within it.

Pseudo doors within a Real door: The pattern or image of a door as a miniature is repeated, often each facsimile receding in scale. Gothic cathedrals have door portal with stepped or recessed flutes on sides and in the arch formation suggesting several layers of door frames. Temple doors are often subdivided into smaller panels, each of which is a miniature version of the main door or a sub temple, a microcosm.

Keywords: SIZE / size of a door economics / technology / large door / contextual structures / doors of smaller sizes / fort gates / PROPORTION / vertical rectangular / sliding doors / WIDTH / actual width / width of passage / architectural door surround / wood framed and hinged doors / pivots / social concern / simple sliding doors / automatic sliding doors / revolving doors / folding doors / garage doors / HEIGHT / within the opening / door head / threshold / passage height / low level doors / heat gain or loss / French windows / transom lites / visual correction.

SIZE: Doors are primarily designed for humans, and sometimes exclusively for passage of goods and animals, but more often sized for all purposes. The size of a door is in relation to: the proportion of the inside room space, fore-space, architectural schema, etc. besides the functional needs of transit, transport, exchanges of environmental elements (breeze, heat, energy etc.) vision across (framing), sound leakage and ingress, illumination, participation, privacy, etc.

The economics and the technology are two main conditioners for the size of a door, but never restricting factors. Doors of extra ordinarily large sizes or monumental proportions have been used through ages. A large door denotes unrestricted transit or reception, fearlessness or power, affluence, dominance, etc. The size of a door is referential and so contextual structures are conceived to enhance the size of the door. Doors of smaller sizes than nominally required are used to slow down and thereby control and check the chaotic traffic of entrants. Doors are made smaller, if are insignificant or to be concealed, such as the secret or escape doors. Smaller doors are stronger, but not necessarily easier to open or shut. Smaller openings reduce the nett opening size and so increase the integrity of the load-bearing structure.

The size of a door is also governed by the architectural scheme of the built mass and its relation with the surroundings. Fort gates and other gateways have not only large doors but also have elaborate structures like abutments, ramparts, bulwarks, bastions, bastilles, battlements, belvederes (Chhatri), buttress, campaniles (bell towers). (for more see chapter 4.4 Opening Systems : Gates).

PROPORTIONS: Traditionally doors have had a vertical form. The vertical rectangular form makes the opening taller then its width. It reduces the load on the hanging devices such as hinge or pivot, and so easy to open. The smaller width doors are technologically more efficient to construct and operate. Doors with two shutters divide the door further, and create a narrower version. The widths are decided primarily on functional passage needs, but heights above human head level (or with head loads) are extravagance. Sliding doors have easier handling if are wider then their heights. Proportions of doors relate to the architectural design, and so are the proportion of doors. Most common set of proportions (Width: Height) have been: Two squares 1: 2, or Golden proportion 1:1.61.

Some famous doors are: Treasury of Atreus, Mycenae 9'-0" x 18'-0", Parthenon, Rome 0'-0" x 24'-2", Erechtheion, Athens 8'-0" x 17'-2", S. Martin, Worms 5'-8" x 11'-3", Palazzo Pietro Massimi, Rome, main entrance door 6'-10" x 13'-8",

WIDTH: Width of a door determines the density of traffic and the size of articles that can pass through it. Height of a door is determined by the architectural requirements, but width of a door is in proportion to its height. Actual width or width of passage is less for door openings set with architectural door surrounds, compared to wood framed and hinged doors. Pivots other than at the extreme corner of a shutter restrict the nett opening available.

In modern times, as a social concern, it is essential to provide doors widths suitable for disabled persons, using walking sticks, crutch, a walker, a wheel chair, stretcher or assisted by others. Width of a door for, toilet, elevators, closets, store rooms, change rooms, and such other lone user utilities are considered more critical for such users. Simple sliding doors allow very exact control over the width of opening. Automatic sliding doors such as for elevators and for entrances of public buildings open to width governed by the density and frequency of traffic. Revolving doors have optimum opening size to maintain the air lock and prevent anyone forcing a reverse movement. Folding shutter doors allow incremental width of the opening. Garage doors sliding up were deiced to get a maximum width of opening

HEIGHT: Height of a door is checked for three parameters: the height available within the opening, the height of the door head, and the height of the threshold. The actual passage height of a door is affected by the level of terrain immediately inside and outside the door. Low level doors have been used to reduce the heat gain or loss (e.g. igloos), the storm water (e.g. sea front warehouses in America).

A threshold protects the interior from dust, rain or snow storms, however a taller threshold reduces the door passage height. A high threshold makes a door little less functional for entry-exit, and takes it closer to the identity of a window. French windows are only high threshold doors.

Egyptian temples had very tall openings, the lower section was shuttered and the upper section was a window like opening. Gothic churches had upper section of the door converted into a rose window. Very tall doors, unless required for passages are turned into transom lites. Very tall doors require a visual correction. Romans constructed tall doors with a wider base and narrower top.

4.1.5.2 DOOR : FUNCTIONAL SIZES

Keywords: door design primary factors / ergonomic factors / new opening systems / dimensions for door design / ISO preferences for modular design / architectural entities / multiples of 100 mm /FUNCTIONAL WIDTH / stretchers / fowler beds / FUNCTIONAL HEIGHT / anthropometrics.

For door design primary factors considered are comfortable passage, safety and universal application and usage. Ergonomic factors also determine the location and operations of various utilities such as latches, handles, door stops etc. Physiological factors for door design are: preferences such as left or right handed or footed, counter or clockwise movements, angle of vision, reach of various limbs, kinaesthesis, sensorial aspects, grips, etc. These issues are often taken for granted because doors have been with us for ages. However, to devise new opening systems one may need to have fresh look at such design considerations.

Many national and International standards have specified dimensions for door design. One of the prime dimensioning systems is the ISO preferences for modular design: for architectural entities the modular size is 100 x : which translates into door sizes in multiples of 100 mm.

FUNCTIONAL WIDTH: i.e. Passage width + the side jambs, structural members or other obstructions, are:

700 mm > This width is used for services areas, toilets, etc. provided disabled and aged persons, requiring accompanying help, are not going to use it (by provision of other options). Such a door size will have very small thickness of framing, etc. as the actual opening will barely meet the ergonomics norms> 619 mm for entry (see 8 below).

800 mm > This width is used for services areas, toilets, etc. provided disabled and aged persons, requiring accompanying help, are not going to use it (by provision of other options). Such a door size will allow reasonable thickness for framing, etc. With Aluminium section framing or no framing (pivot or sliding doors) it can be used for office cabins, bedrooms etc.

900 mm > This is a width very commonly used for bedrooms and office cabins (with a hydraulic door closer) public toilets and services areas. It can be used by disabled with wheel chair or stick, and aged persons requiring accompanying help. The door width allows cabinets, almirahs, refrigerators, washing machines and study tables.

1000 mm > This width, is useful for people carrying a bag, as in transport stations and shopping centres. It is also used for main doors (to allow large size furniture) and for offices (with a floor level hydraulic door closer). Hospitals' rooms require such a size for movement of stretchers.

1100/1200 mm > This width is useful for dual traffic (simultaneous entry-exit) as between restaurant kitchen-pantry-dining area. Hospitals' treatment rooms require such a size for movement of fowler beds.

FUNCTIONAL HEIGHT: i.e. Passage height + threshold + door head, structural members or other obstructions like a door closer, are:

1800/1900 mm > This is a barely adequate size for passage (without framing deductions) as some exceptionally tall persons may have to stoop down (even if for fear of striking the head) to enter.

2000 mm > This is a height size that works for Indian ergonomics, but not for people of many other regions. It is a very common height in mass housing schemes.

2100/2200 mm > These are universal height sizes.

2300/2400 mm > These more used for warehouses (with head load entrance) and auto garages.

Anthropometrics: Users of a door have different levels of physique, abilities and abnormalities (disabilities). These are studied and standards are drawn. A higher percentile (95%) is used for height or width, so that maximum number of people use it comfortably and safely. But a public entity, to provide extra ordinary service may opt for the largest size. A lower percentile (5%) is preferred for reach so that most of the shorter height persons are also able to operate the handle, latches, stoppers, etc.

1 Height of Indian Male @ 95 percentile 1751 mm

2 Height of Indian Female @ 95 percentile 1615 mm

3 Height of common Indian (M+F) @ 95 percentile 1741 mm

4 Erect stature of common Indian (M+F) @ 95 percentile 1771 mm

5 Raised hand of common Indian (M+F) @ 95 percentile 2289 mm

6 Width of Indian Male @ 95 percentile 619 mm

7 Width of Indian Female @ 95 percentile 599 mm

8 Width of common Indian (M+F) @ 95 percentile 619 mm

9 Sideway width of Indian Male @ 95 percentile 409 mm

10 Sideway width of Indian Female @ 95 percentile 439 mm

11 Sideway width of common Indian (M+F) @ 95 percentile 419 mm

4.1.6.1 DOOR OPENING'S : STRUCTURES

4.1.6.2 DOOR OPENINGS IN THICK AND THIN WALLS

Keywords: load of upper structure / lintel-beams / corbelled / arch / pointed arch / transom lite / horseshoe shape / rubble or irregularly coursed masonry / door surrounds / wood frames / casings / arched openings for windows / upper parts of door openings / tympanum / Toran / inclined brackets / metaphysical entrance.

Doors openings have to carry the load of upper structure. Square headed doors had lintel-beams of wood or stone beams that spanned 2 to 3.5 mts. For larger spans the openings were corbelled. In spite of corbels the actual door remained square cornered. For very wide openings, masonry in arch forms was used. During the middle ages a variety of arches were used like: semicircular, elliptical, 2/3/4/5 centred, rampant, compound and interlaced and flat. Materials of arch construction were mainly stones and burnt bricks. Roman arched gateways were typically 4 to 7 mts. in the span, though in public buildings concrete arched vaults of very large spans were used. Pointed arches allowed spanning different widths yet remain within the required height. Pointed arched openings were bulged to increase the size of transom lite opening, and the lower or door level (i.e. below the arch spring line) section were narrowed. The resultant horseshoe shape was slightly gravity defiant and looked delicate, as in middle-east architecture.

Door head entities such as lintels, arches, etc. were supported on door surrounds, instead of the rubble or irregularly coursed masonry walls. The door surround was masonry framing against which the pivoted door shutters were abutted. However, Gothic period (and equivalent time in other cultures) saw well layered masonry and introduction of wood frames for fixing hinged doors. Wood door frames were non load bearing elements placed for 'hanging' the door shutter, and so were just minimal in size. Rest of the opening sides were covered with casings (a door side panelling).

The upper sections of the arched openings for windows were filled with traceries or i.e. pierced panels as a continuation of the pattern from lower section. However, in the upper parts of doors openings, a solid panel was inserted like a tympanum. The tympanum panel was a separate piece, usually placed over a lintel. So a Gothic opening had arch spanning the door portal, and an inset lintel spanning the door opening. The dual arrangement for support allowed the gothic door surround to have chamferred corners or have a serrated form.

In Gujarat and other parts of western India a stylized stone archway -Toran is placed. A Toran is a set of inclined brackets that additionally support the centre of the square headed beamed opening, and pass the load to columns. Toran acquired status equal to the threshold as a metaphysical entrance. The presence of a Toran marked the entrance. Decorative Toran of glass beads, glass tubes, embroidered cloth, flowers, leaves, coconuts, etc. are hung even today to signify a door during celebrations on auspicious occasions.

Keywords: load-bearing / non load-bearing / outer, inner edges or anywhere in between / Byzantine openings / Romanesque architecture / deep-set opening / perceived size of the door / door portals / splayed or chamferred / Gothic buildings / flush-set doors / un-buttressed front walls / curtain wall glass buildings / revolving doors / butterfly doors / door level climate control devices.

Openings are set in various types of barriers, i.e. load-bearing and non load-bearing structures. Load bearing barriers or walls have certain depth. The doors are set either on the outer, inner edges or anywhere in between. The depth to which a door is set affects its architectural and functional qualities. Byzantine openings were set on the external face compared with Romanesque architecture where openings were deep-set or on the inner face.

A door placed deep-set or on interior face must open sideways for resting the shutter or outward but within the wall thickness. The deep-set opening gets a natural shading, but allows reduced amount of illumination. A door placed on the outer face offers a side wall for parking of the shutter. The door gets no natural shading and amount of illumination is curtailed.

Door openings set back in thick walls compress the perceived size of the door. To improve upon this aspect either door portals are added as opening's treatments or openings' sides splayed or chamferred. The angled side surface is further carved, fluted with ornate borders or architraves.

Walls of Gothic buildings became thinner due to the arrangement of flying buttresses and use of load bearing columns. The flush-set door allowed better view across and fuller distribution of light. But the same structural advantage was not available in case of un-buttressed front walls. The entrance doors of Gothic churches were deep set in thick walls but with serrated edges.

Modern curtain wall glass buildings have walls and doors of same thickness. The barrier and the opening both provide illumination and view. Boxed revolving doors or butterfly doors provided the functional depth to the opening. Door level climate control devices such as surface heaters, air curtain fans, floor level suctions and other electronic control devices serve the functions earlier offered by thick wall set door openings. (Also refer to Windows in thick and thin walls 4.2.6.2).

4.1.7.1 DOORS AND VASTU SHASTRA

Keywords: Canons and customs for building design / Vastu Shastra / ORIENTATION OF DOOR / Vijay dwar / Kuber dwar / Magar dwar / Yam dwar / back side / Bhunga houses / Chinese traditions / LOCATION OF DOOR / Sinha dwar / orientation and alignment / Utsang pravesh / Purnabahu pravesh -apasavya / turn to the right / Hinbahu pravesh -savya / turn to the left / Pratyakshya or Prushth bhanga pravesh / turn to the backside / Agni purana / centric doors / TOPOGRAPHY OF DOORS / level of threshold / Utarang / DOOR THRESHOLD / door passage / pedhi / MATERIALS FOR DOORS / Suprabheda / ELEMENTS OF DOOR / VASTU SHASTRA DOOR SCALE AND PROPORTIONS / Tala-mana / Angul / Ganya-mana / Hast / Tunga Ganya / Vistara Ganya / IDEAL WIDTH / GODS STATUES AND DOOR HEIGHT / position or siting for various gods / eye level of the statue / PLACEMENT OF A DOOR IN TERMS OF VEDHA / vedha or obstructions / Tal vedha / Kona vedha / Taalu vedha / Kapal or Shish vedha / Tula vedha / Dwar vedha / Metaphorical forms and deities / Dwarpal / Kshetrapal / Yaksha and Gandharva / Ganapati / Bhairav.

Canons and customs for building design have been formulated in many cultures. These inevitably and importantly relate to the door. According to Hindu canons for buildings, Vastu Shastra, a door is conceived to be the most important conditioner of our experiences of the space within and without. Vastu Shastra deals with doors in terms of: orientation, position, location, size, proportion, obstructions, surrounding elements, appendages, metaphorical meanings and mythologies.

ORIENTATION OF THE DOOR: The most preferred orientation is the East -the Vijay Dwar. Second choice is North -the Kuber Dwar. Third preference is West -Magar Dwar. A South-the Yam Dwar is considered unfortunate, and if unavoidable, must be placed off the central axis. Vastu Shastra treats the back side and South side as the same. Bhunga houses of Kutchh, Gujarat, though dominantly have South facing door.

According to the Chinese traditions a South door is preferred orientation for entrance opening. Neolithic-period houses were rectangular with a south-facing door. Zhou period settlements were also organized on a north-south axis. Houses from the Ming dynasty, show a tendency to face south. Houses built today, if space allows, are also built facing south.

LOCATION OF THE DOOR: An entrance door -Sinha Dwar to the house must preferably be on the front side of the estate. It is ideal, if the house door and the estate (compound) doors have the same orientation and alignment -Utsang Pravesh. However, one of the best arrangement for an entrance door and for visual security is to use the Purnabahu Pravesh -apasavya, in this case after entering an estate one has to turn to the right side to enter the house. Hinbahu Pravesh -Savya: In this case, after entering an estate one has to turn to the left to enter the house. Pratyakshya or Prushth bhanga Pravesh is one where after entering an estate one has to turn to the backside to enter the house. Hinbahu Pravesh is considered inappropriate, whereas, the Prushtha-bhang Pravesh is considered inauspicious. According to Agni Purana the door must always be on the centres of four sides, but never in the corners. But most other canons permit centric doors on good sides, i.e. East and North

Chinese courtyard houses have a main door that did not align with the estate entrance. One entered the house after turning a corner.

TOPOGRAPHY OF DOORS: Door threshold level has been given a great deal of importance. The level of a threshold should be higher than, both the front yard or room, and the room being entered into. Top level -door head: Utarang of all doors in one axial sequence, should be equal, but the level of the threshold and floor level of inner rooms should rise. In other words the inner most door (and by implication the innermost room) should be at a higher datum than the entrance room.

Steps (ramp or any such element that changes the level, colour or texture) must not be accommodated within the door-passage or doorway, in close front or back of it (immediately before or after). Steps should be as wide or wider then the door opening.

DOOR THRESHOLD: Dwar-shakha, Umara, Udumbara, Dehlij, Shankhavati: Important considerations for a door design are its size, proportion and the threshold. The essence of an entrance is in its threshold. A threshold marks a point of change. A door in level with the floor has no Maryada (restrain). It provides a definition -a Laxman-Rekha. A threshold is Dehlij, a border line, a slightly raised sill or obstruction at floor level, a moderate barrier which can be 'prevailed over with due consequences'. A threshold is also a neutral zone. A person on the threshold seating or during the process of crossing is unreliable or unsettled, till one crosses either way. The doorway or the door passage in very thick walled structures is called a Pedhi -an alcove like area usually a place of rest or -the place for kotwal, chowkidar or caretaker. Before leaving fort, large estate or a temple precinct one must sit for few moments in the Pedhi to rest and contemplate, but cross the threshold without hesitation and never look backward.

MATERIALS FOR THE DOORS: Suprabheda recommends Gates (of public buildings) must be placed in all the four directions (Chatur Dwar or Chatur Dikshu). Eastern Door must be of Palash wood, Western door of Udumbara wood, Southern door of Aswattha wood and Northern door of Nyagrodha wood.

ELEMENTS OF DOOR: Dwar-shakha (jamb), Kavata (door panels), Dwar-sandhi (door joints), Phalaka (door plank), Kila-bhajana (bolt), Udumbara (threshold), Dwar Gopura (door tower or doorway), Dwar-Koshtha or Pedhi (the chamber within a doorway), Chitra Toran (drawn, for doors of Vaishyas), Patra Toran (made of plant leaves for doors of Sudra of) and Makara Toran (made of vessels for doors of temples and Brahmins).

VASTU SHASTRA DOOR SCALE AND PROPORTIONS: Two measurement scales are relevant for design of Door. Tala-mana (for sculpture) has the Angul (finger) as the basic unit for sculpture and fine-detailed work. Ganya-mana (for building) has the Hast (hand or arm) as the basic unit. Vertical measurements follow Tunga Ganya scale, and Horizontal measurements are derived from Vistara Ganya scale.

IDEAL WIDTH: Width : Height ratios for a door according to Vastu Shastra are: 9 : 16, 2 : 3 or 1 : 2. Door height should be at least 2/3 of the room height. Doors situated on an axis must maintain the axial alignment. The entrance (first) door must be larger in size compared to the next or the following doors. However, door head level must be maintained and the inner floor level should be slightly at an upper datum.

GODS STATUES AND DOOR HEIGHT: In a temple the position or siting for various gods (statues) follows certain regimen. The eye level of the statue is positioned matching the door height. For this, a door gap is divided into eight vertical sections. The top 1/8 section is left free for Gandharva, Rakshash and Yaksha. The remaining lower seven sections have been assigned to various types of gods. Typically Shiv is placed at the bottom section.

PLACEMENT OF A DOOR IN TERMS OF VEDHA: Doors should preferably be of 2 leaves. Vastu Shastra mentions many types of Vedha or obstructions against a door.

Tal Vedha includes elements like uneven land, Kumbha of oil seed crushing plant, neighbours drinking water storage area, etc.

Kona Vedha occurs with uneven angles of plot or house.

Taalu Vedha is caused by beams of uneven heights, a miss-match pattern

Kapal or Shish Vedha is caused by a beam crossing the door path. Stambha Vedha is formed by a column or well or any such obstruction in the axis of a door.

Tula Vedha develops when beams or columns are not aligned with doors' position.

Dwar Vedha occurs with a tree, well or such other elements in front of a door but within twice the height of building, or due to front or back of a temple but without a public street in between. It also occurs due to mismatched axial placement of doors.

Metaphorical forms and deities are assigned to doors. These include a Dwarpal (bearer or keeper of the door) and Kshetrapal (the commanding deity of the Kshetra -field). These are placed as a direct representation like statuettes or symbolically, at the lower level in the door way. Yaksha and Gandharva are placed on the top side corners of the main door. Ganapati is the prime deity to be worshipped in any ceremony, so is placed, at the top centre of an opening and/or below the statue of the main deity. Bhairav is placed on a door side. (For Chinese and other mythological associations ref to: 4.1.9.2 Door myths and legends)

4.1.8.0 FUNCTIONS OF DOORS

Sub-index for chapter 4.1.8.0 FUNCTIONS OF DOORS

Keywords: prime openings / control many things simultaneously / attached layers / detached layers / sequential placement of doors / ganged doors.

Doors are the prime openings in spite of development of other opening systems such as windows, skylights, and curtain wall systems. A door besides serving the function of entry and exit, is a source of illumination and ventilation. Doors as an element of transit regulates the passage so provide safety and security. Doors also control the passage of energy through their body-material and configuration. Doors when open or if latticed or glazed allow vision in or out, and so become important element for visual linkage between spaces.

Doors are required to control many things simultaneously. No single size, location, or type can satisfy all the demands, and so doors are composed of several attached layers (for example cushioned doors for sound proofing) or detached layers (Jali door or curtain over the entrance door). Sequential placements of doors create a step by step filter as in chambers of Shaolin or in pharmaceutical plants. Ganged doors distribute the traffic into small controllable segments (railway platforms, air ports, public building foyers).

Following functions are discussed:

4.1.8.1 Illumination

4.1.8.2 Ventilation

4.1.8.3 Passage and Control

4.1.8.4 Safety and Security

4.1.8.5 Insulation

4.1.8.6 View through

4.1.8.7 Other Issues

4.1.8.1 ILLUMINATION

Keywords: level and direction of illumination / Control of illumination / lattice or glazing / depth of the door / exterior and interior components and fields / orienting the door / siting of activities / EXTERNAL DOOR / Sky Component or SC / Externally Reflected Component or ERC / Internally Reflected Component or IRC / INTERNAL DOOR / 'borrowed' illumination / Internal door like situation / louvres / DOOR ORIENTATION / consistent level of illumination / Eastern entrances / Western entrance doors / taller door / wider door / transom window / rose window / side lites / within the door lattices / solar radiation through a door.

In all climates, geographic locations and cultures, a door is a major, preferred and often the only source of illumination. The degree of shutter being opened or closed provides easiest control over both the level and direction of illumination. Besides this, the shutter in the form of a lattice, glazing, louvres, windowing etc., provides other options for illumination control. The shape and scale of the opening such as tall, wide, large, small, flush or deep set, etc. offer other means of administering the illumination. In tropical houses the door area is the chief activity zone of the house. It allows safety of indoors and illumination of outdoors.

Control of illumination through a door is availed of:

1 by adjusting the size and shape of the gap on opening the shutter,

2 by providing lattice or glazing within the main shutter or by providing additional shutters for such options,

3 by increasing or decreasing the depth of the door and by shaping the sides of the opening (chamfer corners or splaying),

4 by defining the exterior and interior components and fields near the door to adjust the Sky Component -SC and Externally Reflected Component -ERC.

5 by orienting the door and siting of activities.

EXTERNAL DOOR: The external door of an enclosed space is very relevant for illumination and ventilation. The illumination is substantially determined by the Sky Component or SC, which checks the light reflected from the sky directly into a room. Any overhang or side projection reduces the sky component. The other major factor is the Externally Reflected Component or ERC. ERC depends on the quality of the surface (texture), colours, reflectivity of the foreground and other side areas (side walls). The third important factor is the Internally Reflected Component or IRC. It consists of light reflected from the internal surfaces of the room. Adjustment of IRC is very helpful in controlling the glare through the open door (Glare is the high difference of light between the opening and its surrounding surfaces). The depth of the door affects the sky component SC and so the illumination. To enhance the illumination, thick walls around the door opening are burrowed (as in Gothic buildings) by serration, fluting or chamferring, to increase the width.

INTERNAL DOOR: The internal Door is not very useful for illumination, unless the other side of the door (room, passage, etc.) can contribute some reflected illumination. Such 'borrowed' illumination may be sufficient for 'passive' activities or less used areas like stairs, passageways, etc. However, in hot arid climate and coastal areas like the Mediterranean or Kerala, where external brightness is very high, an external door may bring in radiant heat along with light. This is controlled by placing doors in verandahs or with deep awnings. An internal door like a situation is created by many other means. Doors with louvres are widely used in Mediterranean climates to reduce the brightness and glare. Deep-set doors are also created by placing doors on the inner edge of a thick wall (where possible) or by creating deep portals. A deep-set door has a natural protection against inclement weather.

DOOR ORIENTATION: Door orientation has a direct bearing on the level of illumination. In early Egypt the Sun god was revered and the main doors of temples were East facing. The East and West have been prime directions for illumination in many historical buildings, however, with the ascent of the clear storey openings the importance of a door as the chief illumination provider has decreased. North and South doors have high inclination of the sun, so horizontal penetration of illumination is not very deep, but these two sides (depending on the N or S hemisphere) have consistent level of illumination.

Early Church buildings had Eastern entrances to illuminate the altar from front, but an altar with a back glass lit windows (Eastern) proved to be a better alternative, and gradually churches began to have Western entrance doors.

SIZE OF A DOOR: The size of a door has a direct relationship with the level of illumination. A taller door is more effective then a wider door in illuminating deep interiors. Monumental buildings have tall doors not just for architectural grandeur, but the upper section of the door opening provided the deep illumination during a crowded ceremonial function. In Egyptian temples the upper section of the door was supposed to bring in the Sun god with the first rays of rising sun. The tall door was unmanageable for shutter mechanisms and useless as a passage. The upper section was either left without a shutter or latticed to form a 'transom window'. It was more practicable to leave a transom window or a rose window than load a wall over the door lintel.

The illumination through a door is enhanced by providing side lites or sidelight and 'within the door' lattices. Greek buildings had panelled doors that were partly latticed in the upper sections, or had additional latticed shutters. Side lights or side windows decrease the size of the door shutter and reduce the structural span of the lintel, but increase the perceptive width of the opening.

Illumination through a door invariably accompanies radiation. The solar radiation through a door varies depending on the geographical location, orientation, time of the day, shading devices, nature of the foreground and surroundings, etc.

4.1.8.2 VENTILATION

Keywords: ventilation in primal buildings / optimal opening / ventilation needs / air change / outside conditions / high sill level opening systems / smaller opening / leakage zone / entry-exit points / narrow width door opening / optimum opening size / speed of opening or closing / width / synchronized dual door system / air locking system / air curtain fans / revolving doors / louvered opening / adjustable louvered shutters / gasket and joint masking system.

A door is a major and often the only source of ventilation in many buildings, but a door remains open during day time and in good weather only. Ventilation in such primal buildings during rains and storms (rain, snow or dust) and during night hours is achieved by other means, such as by roof level ventilating holes, permeation through thatched roofs or walls, or through loose fitting doors.

For ventilation most building approval agencies specify an optimum opening of 8% of the floor area for a fully enclosed (room with both a roof and walls) space. Micro openings like roof holes, cracks and other crevices, if any, add to ventilation for the enclosed space. Country tiled and thatched roofs, woven mat walls, and upper level holes also provide additional ventilation capacity. An optimal size door, for passage by a human 700 x 2000 = 1.4 sq. mt (15 sq. ft) has sufficient ventilation capacity to serve a room space of 17.5 sq. mt (190 sq. ft), @ 8 % of floor area.

Ventilation needs are greater for rooms:

that use larger volume of oxygen such as occupied by large number human occupants or animals, or being used for intensive physical work such as gymnasiums, workshops, etc.

that generates noxious gases including carbon dioxide such as in food and other chemical processing areas,

that produce large volume of heat such as in kitchens and foundries,

that output moisture such as bathing, washing or ironing areas.

Greater amounts of air-change from an enclosed space dilute the pollutants, foul air and latent heat. Inversely lesser ventilation helps conserve heat. Tall doors add to the ventilation capacity and low doors curtail the air movement, as in case of igloos.

A door as a ventilation system works better in conjunction with another opening, provided outside conditions support it: such as air pressure and temperature difference across the openings and prevalent air movement conditions outside the door. In warm and humid climates a door allows a floor level draught so it is preferred to many other high sill level opening systems like windows, clerestory openings, roof holes, etc. However, such an arrangement could be a disadvantage in many colder regions. In hot-arid climates, a smaller opening is preferred for cutting down the radiation, but not over the advantages that a door nominally offers in-terms of illumination and ventilation, (e.g. Bhunga houses of Kutchh, Gujarat and mud houses of Rajasthan).

A door is also a major leakage zone in many process areas like electronics assembly, pharmaceutical plants and medical operation theatres. For such spaces as a prime effort number of doors or entry-exit points are reduced. Shaped doors reduce air leakage. Warehouses have narrow width door opening in upper section for bearing columns of forklift or gantry girder trolley. Other strategies include doors of optimum opening size (height and width). The speed of door opening or closing is made quicker by automation. Synchronised dual doors' system (only one of the two doors remains open at a time) with a passage in between is very traditional air locking system. Air curtain fans that cascade a flow of air over the door opening, are also used. Revolving doors with 3 or 4 leaves are common features in lobbies of multi storey buildings.

Openings in very heavy wind areas such as mountain slopes or sea coast regions have very fine latticed door shutters to reduce the breeze velocity entering the enclosed area. Water fountains close to the opening, cascading water over the door or over Khus mats mounted on door gap help add moisture to the room.

For toilets, change rooms, storage areas are provided with louvered opening in the lower section of the shutter to provide some air change. Adjustable louvered shutters for doors in galleries are very common in Mediterranean climates.

Ventilation or leakage through a door is curtailed to save on energy of heating. The door openings are provided with complex gasket and joint masking system.

4.1.8.3 PASSAGE AND CONTROL

Keywords: Passage and control / natural control systems / contrived control systems / make-believe control system / PASSAGE THROUGH DOOR / nominal passage / normal posture / extra effort / non routine passage / short duration / depth of passage / straight passage / twisted or askew passages / stepped floors / rotating doors / air seal / dual synchronous doors / intervening passage / environmental integrity / simultaneous entry and exit / a person carrying a child or handbag / for couples / narrower at lower level / wider at upper level / side hung and pivoted door shutters / passenger elevators / warehouse elevators / garage doors / facing body / sideways body / allowable opening / density of traffic / grouped or ganged doors / EGRESS / egress specifications / PLANNING FOR DISABLED / passage width of a corridor / revolving doors / exit doors for fire and other emergencies / security checkpoints / invisible door / difference between a door and window / functional division / distinct identification / environmentally varied / doors and windows are merged / doors and windows are merged.

The size, shape and configuration of the gap, the shutter and other control systems define the nature of passage and controls over it. Passage and control through a door is natural, contrived or make-believe. Natural control systems form due to the size, shape, configuration and setting (context) of the opening. Contrived control systems function as on add-on devices triggered by programmed logic or other decision making processes (e.g. fuzzy logic). Make-believe control system are unreal but their effects genuine or substantial (a 'do not enter' or 'danger beyond' signs may stop many attempts).

PASSAGE THROUGH DOOR: The size of the door, the height and width of the opening acts as a cutoff for entry of over sized things. The nominal passage is one where a person, animal or goods make an entry in the usual position, least effort and routinely. Entry to an Igloos or tent is not in a normal posture. A hatch door requires a little extra effort to transit. Similarly an emergency exit may not be of nominal size as it is intended to be a non routine passage. The unusual posture and the extra effort are usually for very short duration, except in openings where the depth of the passage is stretched.

The configuration of the passage before, through and just beyond the opening (nature of surrounding terrains) affects the nature of passage physically as well as psychologically. A straight passage is easy to negotiate, but twisted or askew passages, sloped or stepped floors, moats, etc. have been used to control the passage through the door. The predictability or clarity of intentions also facilitates passage through the door. The visual scale and architectural treatment of the doorway, portal or the opening, help in organizing, the passage through the door.

Rotating doors allow only one or two persons to pass through while maintaining the air seal. Dual synchronous doors (when one is opened the other remains shut) with intervening passage such as in pharmaceutical and electronic plants help maintain the environmental integrity. In case of elevators, bus and railway carriages doors designed to be wide enough to allow simultaneous entry and exit. And in case of Airport field buses the doors are wider to allow a person carrying a child or hand bag, or often both. Restaurant doors are designed for couples to enter together. Restaurant kitchen doors, if single shutter, open both ways and if double shutters, marked for entry and exit. But the door gaps are wide enough to allow a waiter to pass through with food trays. Automobile doors are narrower at lower level (feet level) but wider at upper level (the seat level). Automobile doors are small in height, because one never passes through it in upright position. Japanese economic hotels have cubical (coffin) rooms with doors like an igloo to allow a person to slide in.

Side hung and pivoted door shutters opening inside or outside occupy space, which cannot be used for other purposes. Typically corridor abutting doors pose such a problem. Doors in such acute conditions are made to slide sideways or upward or downwards. Passenger elevators have doors sliding sideways, whereas warehouse elevators often have doors that slide up and down. Garage doors slide up to provide unhindered drive way.

The passage through a door if adequate, a person passes through 'facing body', but if narrower then one may have to pass through 'sideways body'. The change of body position from facing to sideways to facing is not easy for infirm persons with olde age, carrying goods or children, etc.

The allowable opening is formed by the angle the door opens. At a very small angle of opening the passage becomes askew or zigzag. Sliding doors on the other hand allow a consistent straight passage in all widths of openings. Public buildings have electronic sensors over gates to adjust the opening size to match the density of traffic. Passage through doors is also controlled by placing a series of doors in a row -grouped or ganged doors, such as at airports, railway stations and multi storey buildings' lounges. Such doors have specific width, usually allowing one person to pass through, but since there are many number of doors, lot of people transit through simultaneously.

EGRESS: Egress requirements for Entrance / Exit are governed by the applicable building code based on building use, occupancy load, and door type (swing, sliding or revolving). Egress specifications cover aspects like: minimum door height and width, maximum door shutter width, panic hardware, steps down dimensions to the exterior, requirements for threshold topography, door swing direction, illumination, operating force, signage, etc.

PLANNING FOR DISABLED: Doors' shutters obstruct nominal passage width of a corridor. The door should open inwards, be sliding or fully opening sideways (with a parliament or similar hinges). In crisis all doors should open to their fullest possible opening size. Bye laws require revolving doors to fold flat in the direction of egress, and must have an additional out swinging doors in nearby location. Exit doors for fire and other emergencies must open out to a safer zone or an open area.

Passage through a door though mostly meant for humans, exclusive doors for dogs and such other pets are designed. Passage through doors is curbed by high sill or thresholds. Indian temples have a high threshold to exclude the ominous spirits.

Doors are security checkpoints or often the security check nodes operate like an invisible door. The security node requires certain speed of passage, which are achieved various speed regulating devices. The security nodes have marks, which by themselves denote an allowable opening -a door.

The real difference between a door and window is in terms of transit or entry exit only, so doors are placed for accessible terrain and windows for the non accessible terrain across. Doors could occur across a space that needs a functional division or distinct identification, whereas a window usually occurs across a space required to be environmentally varied.

In modern architectural paradigm doors and windows are merged or created with a uniform vocabulary such as curtain-wall structures, shop fronts, etc. Sometimes corridors, passages, and transit spaces are so designed that they take over many functions of the door system.

4.1.8.4 SAFETY AND SECURITY

Keywords: transit zone / safety measures / security strategies / DOOR SAFETY / openings related hazards / door and shutter related accidents / door mechanisms / hardware / OPENING RELATED HAZARDS / adequate passage width / insufficient width / generous width / fire and disaster emergency exit / blind shutters / DOOR AND SHUTTER RELATED ACCIDENTS / speed of closing-opening / closing of shutters / banging noise and vibrations / very wide shutters / infirm persons / very narrow shutters / glass doors without any framing / DOOR MECHANISMS AND HARDWARE RELATED HAZARDS / pinching or crushing injuries / sharp edges / door catch / buffered door catch / lining with gasket / automatic doors / thresholds, floor drops or risers / colour or texture difference / DOOR SECURITY / intruder / other 'soft' points / high speed winds, rain storms, birds and insects / forcing an entry / fire or accident / caution the users / strength of a door system / security perception of a door / fewer doors / adequate emergency exits / holistic terms / well planned and managed community / community surveillance system / domain or bastion with single entry / integrated security surveillance systems / method of building management.

An opening system is a frequently used and very important transit zone, so must serve the designed functions, any failures on these counts often have hazardous consequences. Safety measures are predefined strategies for managing the hazards. A door is considered a prime and 'soft' target for break-in by an intruder due to its weaker construction then the barrier system within which it is set, and due to its strategic location. Door security strategies help correct such conditions.

DOOR SAFETY: Door safety relates to two major aspects: Openings related hazards and door and shutter-related accidents. The opening related hazards relate to nature of opening such as location, size, configurations, passages way, usage etc. Opening related hazards also arise due because other side of the opening is unfamiliar or less controlled. The door and shutter related accidents concern to door mechanisms and hardware.

OPENING RELATED HAZARDS: Adequate passage width for transit is very important. An insufficient width retards the speed, or even makes it difficult or impossible to transit through. A very generous width fails to enforce the discipline in transit. Instead of a wide door, multiple (ganged) doors are used for entry and for an emergency exit in public buildings. Doors to safety areas like bombing shelters must be carefully small sized for increasing resistance to blast pressures. Door shutters for a fire and disaster emergency exit must open outward to a street or safer zone. Similarly shutters opening into a corridor or passage are hazardous. Blind shutters, one without a view window or aperture can open out over an entrant. Separate openings or channels are required for each category of traffic, such as people, service staff, equipment, animals etc.

DOOR AND SHUTTER RELATED ACCIDENTS: The speed of closing-opening of the door is controlled by the user. However, for automatic closing-opening of doors and for doors aided by situational conditions (closing towards gravity, pushed by forces like a gush of wind, vibrations, etc.) the speed of closing needs to be governed. Closing of shutters with mechanical, hydraulic or other door closing mechanism, if too rapid can injure an entrant, and when too slow it allows environmental leakage. An automatic door closer (kinetic or spring loaded, pneumatic, hydraulic, magnetic) has special mechanisms to retard the speed of closing in the final stages or moments. Similarly sliding doors in elevators and transport vehicles recognise not only any obstruction in the path but also any imminent obstacles. Sliding downward shutters have mechanisms to (drop) shut very softly in the final stage. Very fast closing causes banging noise and vibrations in certain conditions.

Very wide shutters have an opening gap larger then 800 / 900, the mandatary width of passage necessary for infirm persons. Very wide doors are easy to shut as extra length or leverage is available. However, infirm persons cannot move own body, the wheelchair or the crutches to such a wide arc nor reach out to hold the handle at the edge. Very narrow shutters -less the 550, require a person to turn sideways during the passage, an act difficult for infirm people.

Glass doors without any framing are often invisible and pose the risk of unintentional collision. Their presence must be made conspicuous by means of graphics or hardware fixed to the door's surface.

DOOR MECHANISMS AND HARDWARE RELATED HAZARDS: The accessibility regulations relate to use of door systems by persons physical disabilities to use it safely, comfortably, with dignity and as much as possible independently.

Pinching or crushing injuries of the hand occur due to sudden closing of the shutter, more at jamb level then the head and threshold levels. Sharp edges over handles, stoppers, etc. are hazardous. Insufficient space between the door handle and jamb face injures knuckles of the hand. Doors' catches are essential to prevent door closing due to wind and vibrations. Doors create a banging noise on striking a wall while opening and the jamb while closing. In the first case buffered door catch or lining with a gasket can prevent the noise.

'It is essential that children's fingers be protected from being crushed or otherwise injured in the hinge space of a swinging door or gate. There are simple devices available to be attached to the hinge side to ensure that as the door closes, the hand is pushed out of the opening, away from harm'.

Automatic doors require special measures to prevent injuries. Motorized sliding, revolving and rolling doors and security grates require a safety system that on encountering an obstruction reverse the direction of door movement. This prevents injuries from pinching or crushing. Elevators have built in a mechanism that will not permit it move unless doors have been properly closed. New bye-laws do not permit latticed doors for elevators.

Thresholds, floor drops or risers must be surmountable by the disabled person in a wheel chair and with crutches. The optimum limit for threshold height is 12. Just near the door opening any colour or texture difference across a floor, preferably be aligned with the door.

DOOR SECURITY: A door is a prime target for an intruder for two reasons: a door is the entrance to a building, so a break-in here equals to capturing the building; and the door (entrance, back or any other exterior door) is a node where other interior openings (of rooms, stairs etc.) verge, and for the intruder it becomes easier to spread out from here. However, buildings have many other 'soft' points for easier intrusion, like windows, thin walls, weak roofing, etc.

Door security also relates to integrity of the door against entry of high speed winds, rain storms, birds and insects, etc. Security also relates to forcing an entry to save lives. A very strong door virtually unbreakable or impenetrable can pose equally a large problem in case of a disaster. Similarly a toughened glass door is difficult to break during fire or accident.

There is a tendency to caution the users for the security risks and hazards a door system could have, through signs, signage and other forms of alarm systems. But it is always 'better to reduce the risks, do away with the hazards through design than warnings'.

The strength of a door system derives from: its location, size, composition, materials of construction, the support framing and the nature of basic hardware and additional safety appendages.

Security perception of a door varies from one situation to another. A door visible from a street, such as set flush with the wall surface is less a security risk than the one set back in a niche. Doors supported on all sides (e.g. a hatch door) are stronger then supported on one or two sides (e.g. sliding doors). Doors opening both ways are stopped by the hardware and are poorly secured (e.g. pivoted doors). A transparent (or see through) door of ordinary glass is a security risk being a see-through and breakable. An intruder prejudges the entry but also remains fearful that someone can see from the outside. Malls, stores have glass doors to make the interiors visible and so safe. Fewer door makes a building safer but adequate emergency exits must be provided.

Door security is now considered in more holistic terms. A well planned and managed community provides better security then the strongest door system. Electronic and other surveillance systems can eliminate the need for heavy doors.

Community surveillance systems if a community or a building is safe, its units (offices, residences, etc.) may not require strong individual security arrangements. Community security system consists of organising units of a building and sub units within each unit as a domain or bastion with single entry. Several buildings within a community form a precinct, though not bounded by walls but one that can be patrolled circumferentially. Many colonies discourage erection of high compound walls or hedges, so that individual units remain visible by other members. Yet in case of a complete blackout or during riots some form of security is necessary.

Integrated security surveillance systems solve many of the individual security issues. It works on observation of oddities, recording it for post analysis, warnings, activating the multiple precautionary measures (cutting of exists, power cuts, sprinklers, etc.) Such security systems are part of both the door and the opening system, or even spread across a building. An integrated security system is not an appended system but rather designed and compounded with the building's structure and functions as a unified method of building management. The system to be successful requires coordinated working of many different agencies. An individual user cannot hope to install and operate such a system, but must contract out such a service.

4.1.8.5 INSULATION

Keywords: regulating the transmission of energy / Insulation qualities / sound and heat / better insulation capacity then the wall / leakages / SOUND INSULATION / background noise / select range of sound frequencies / sound attenuation / sound privacy / doors with an absorbent surface / surrounding areas / doors with very thin body / mass increasing treatments / transmission of physical vibrations / isolating the door / door rattling / THERMAL FUNCTIONS / Thermal Performance / heat gain or loss / outside-inside temperatures / nature of door operation / fast opening or closing / very slow shutting / swinging shutters / sliding shutters / revolving doors / air curtains / colour, texture and the latent heat capacity / radiate heat immediately / black coloured elements / Thermal Insulation / heat conduction / radiant heat / black coloured frames / Thermal Leakage / conduction / frequently used entrance and exit doors / revolving doors / air curtains / entrance vestibules with separate entry and exit doors / Moisture protection / storm water penetration / condensation resistance / inward-opening doors / storm water sprays / outward-opening doors / air penetration in hurricanes / deep-set doors / threshold / resilient gaskets / thermal packing.

Insulation relates to regulating the transmission of energy, thorough a door frame, shutter section and reflection off the surface. Insulation qualities of a door are checked on main two counts: sound and heat. Doors are normally expected to have slightly better insulation capacity then the wall within which they occur. However, the leakages through crevices, and gaps remaining at the junction with jambs, heads and at the floor level can often be more then the designed superior insulation qualities across the door section.

SOUND INSULATION: The sound transmission can occur in either of the directions (interior to another interior, interior to exterior, or vice versa) depending on the scale difference of sound level. A noisy exterior can disturb a very quiet interior and a noisy interior activity can disturb the neighbours. However, a little interior noise or background noises can balance the sound intrusion from outside and make the situation bearable. If doors are not properly sound proofed, important information can leak out of executive office doors, even at nominal voice level. On the other hand a telephone booth must cut off road noise without a full enclosure. Mobile telephone units rely on select range of sound frequencies for the pick-up and output sound for clarity.

Sound attenuation through doors can be improved by primarily by increasing the mass of the frames and sash, improving the airtightness of the glazing, sash-to-frame and frame-to-perimeter joints, placing sound-absorptive materials at the perimeter of the doors, single or homogenous material structure of the shutter, double shutter arrangement, an extra layer of sound absorbent material on the noisier side (such as cushioning, curtains), and avoiding tapering side walls or ceiling verging over the door. Other means of achieving sound privacy is to place a door away and in indirect position from the sound generating spot, adding extra noise near the door, reduce the reverberation by acoustic treatment around the door and in the interior space.

Doors with an absorbent surface reduce the transmission of sound across the door mass. Conference rooms, private rooms, recording studios have 'cushioned' or absorbent treatment on the door, or are provided with double shutter doors. Glass doors have thin mass, and cannot take additional insulation or 'anti-transmission' treatments. In such a situation, the surrounding areas such as the door portal, niche, the near by floor or ceiling have such treatments.

Doors with very thin body such as made of thin sheets and hung or supported inadequately vibrate due to physical movement and sound. Thin body door shutters can have mass increasing treatments, such as: thicker coating, additional lamination or bracing. Transmission of physical vibrations can be stopped by isolating the door through gasket and shock absorbers. Door rattling can also be stopped by having multiple smaller shutters in place of a large single shutter.

THERMAL FUNCTIONS: Doors have three major issues:

1 Thermal performance

2 Thermal insulation

3 Thermal leakages.

Thermal Performance: This not an exclusive mark. It results from a complex set of factors such as: nature of the surroundings, the layout of the building, the position and orientation of the door, solar inclination, opening protection systems (chhajjas, awnings, weather sheds), air movement near and through the door, nature of door operation (e.g. swinging, sliding, revolving), heat loss-gain during opening-closing operations.

A door's thermal performance is measured in terms of heat gain or loss. The heat gain or loss occurs mainly due to the difference between outside-inside temperatures, which causes air currents. The temperature gradients are steeper in extreme climates, high pressure zones, with specific types of building and where there are counter openings or cross air leakage zones.

Outside air rushes in or interior air escapes out nearly simultaneously, affecting the temperature of the interior space. The heat gain or loss is affected by the nature of door operation. Fast opening or closing shutters disturb the air causing unusual currents, whereas very slow shutting shutters allow transfer of air. Swinging shutters (pivoted or hinged) displace substantial volume of air compared to sliding shutters. Revolving doors encased in an 'air-locking' module however do not displace air mass. Air curtains also act as a barrier between outside and interior space.

The thermal performance of a door is affected by the shutters shape, construction and materials. The colour, texture and the latent heat capacity of the door shutter affect its thermal performance. Industrial rolling shutters are thin body doors and radiate heat immediately on exposure to sun rays and warm outside atmosphere. Heat absorption by black coloured elements is very high and must be avoided.

Thermal Insulation: Doors absorb incident heat and radiate it to the interior (or exterior) if the door frame or shutter is of heat conductive material. Heat conduction is a function of mass of the material and its thickness. Glass shutters are worst performers. Radiant heat can be reflected back or filtered out to an extent by use of coating or polyester film cover. Heat loss-gain occurs from mild steel and aluminum sections of door frames. 'Black coloured frames often conduct more heat to the interior space than the glazing of the door shutter'.

Thermal Leakage: Thermal leakage from openings like doors occurs through conduction across the door elements and the surfaces, and with air movement through the door and through material joints and component junctions. Heat loss-gain from air leakage is the most significant challenge for frequently used entrance and exit doors.

Several strategies to limit air loss and improve thermal performance are used: Revolving doors minimize heating and cooling losses from air movement. A revolving door remains shut most of the time and functions better for interior climate control. Air curtains provide a barrier of fast-moving warm air that limits penetration or leakage of air even while the door is open. Air curtains are frequently used with sliding doors in public spaces such as departmental stores, auditoria, and industrial plants. Entrance vestibules with separate entry and exit doors provide improved energy performance over a single entrance door, mainly by limiting loss of conditioned air during the door operation.

Moisture protection: It is checked for storm water penetration and the condensation resistance. Inward-opening doors resist storm water sprays better than outward-opening doors. The opposite is true for air penetration in hurricanes, because the exterior positive wind pressures compresses the door shutter against the frame. Deep-set doors, such as in alcoves, niches, and under awnings or weather sheds are well sheltered. The water resistance of doors can be improved by providing a taller threshold, but with the danger of hindering smooth passage. Aluminum and plastic extruded sections have fine grooves (unavailable with wood sections) to house resilient gaskets, and so increase the water resistance capacity manifold. In colder climates hollow door frames without adequate thermal packing lead to wintertime condensation. At macro level water resistence is improved by designing drip moulds, sloping and anti splashing sections for ledges, sills and door head bottoms, encasing by moulding and architraves, using mastic compounds over joints and by using non-drying (ever green or perma-soft) putties for glass fixing.

4.1.8.6 VIEW THROUGH

Keywords: connects spaces / double sided entity / ground plane / visual link / open door / Janus / inside to outward / outside to inward / contrast of dark and light / dynamically scales the door size and shape / interior side / exterior side / during daytime / during twilight hours / nightfall / open door / shut door / frames the view / foreground / ground plane / shape of the door / rectangular door / Gothic cathedrals / twin doors / multiple doors / door heads / architectural treatments / the head level of a door / taller door / upper section of a door / transom lite, rose window or tympanum / depth of opening / field of vision / wall facing the main door / pol houses / Muslim houses / turnstile or thin bar as door / Indian temples / eye sight line / free of obstruction / blind shutters / aperture, view windows or lite / peepholes and security holes / latticed door / fixed or rotating louvres / hinged or sliding window shutters / Glass / fuzzy view / white painting of the openings / glazed doors / white glass doors / laced fabric white curtains / see-through doors / Venetian blinds.

A door connects spaces more effectively compared to a window where the high sill level blocks the access and discourages the flow. A door is a double-sided entity for passage and so the floor seems to flow through it both ways. The floor or the ground plane provides a continuous reference and strengthens the visual link between spaces, across an open door. In spite of all the hazards and the security risks, an open door is preferred, as it provides enlarged field and greater choices. An open door is a measure of social, cultural and political efficiency of a community. The temple doors of Janus, the mythological Roman god of gates, were kept open during war times so that he can connect with the people. Janus was always associated with some form of duality, depicted with two faces, like a door, looking in opposite directions.

A door is viewed from inside to outward and outside to inward. In both the cases the contexts of illumination level, background reference and comparative scales (of physical sizes) are different. The door as an opening system also frames the view and imposes its own regimen. It is the contrast of dark and light across the opening that dynamically scales the door size and shape.

From an interior side: An open door gap stands out against the extremely bright exterior. A small bright spot is viewed against a large shaded surface.

From an exterior side: The interior seen through the door gap is dark, and so contrasts, at least during day time, with a large, modulated or textured but highly a visible architectural surface. The door gap is framed by the bright doorway, door portal and the surrounding architectural mass. During twilight hours the illuminated interior is balanced against the fading exterior sunlight. By nightfall the interior stands out sparkling against the dull street.

An open door, during day time, from outside is just a recessed dark niche, but at night the same door opening begins to reveal the depth of the space. A shut door is a surface variation of colour and texture and occasionally architecturally modulated elements, standing on its own strength or merging into the larger entity, the building.

The door as an opening system frames the view by shaping, scaling, sub dividing, and filtering it. The door is seen at eye level, or up / down a level, but always with foreground leading to it and proceeding through it. The ground plane becomes the link for the transition.

The shape of the door openings has very strongly affected the view through it. A rectangular door, H:W = 1:2, has been the most common and proportionate shape for a door. A double shuttered door is symmetrical and is considered a classic entity. Gothic cathedrals have had twin doors with column support between them, but where multiple doors are required, the doors' openings are in odd numbers such as 3 or 5.

Door heads are flat or rounded, pointed or 'bulged' arched. The shape is further moderated by architectural treatment and by other appendages, under the door head and over the sides or jambs. The architectural treatments include splaying the edges by chamferring, serrating, fluting, masking by casing, architraves and beading, adding masonry elements such as pilasters,

The appendages include pediments, eaves, brackets and Toran.

The head level of a door, if taller then the nominal height of usage, allows view of the sky from inside or greater view of interior including its ceiling from outside. Greater height also illuminates deeper section of the interior space. Taller doors were created for proportioning with architectural scheme or width of the door. Upper sections of door opening however were difficult for shutter fixing, so provided with transom lite, rose window or tympanum.

The depth of the opening affects the view through a door. A door (set on outer or inner face) in a deep gap restricts the field of vision. Historically this has corrected by splaying the edges or by increasing the size of the door portal manifold.

In Indian traditional one room houses the wall facing the main door is intensely decorated with utensils, photo-frames and other showpieces, as it receives the best illumination and immediate attention. In pol houses the brightness of the central chowk gets highlighted against the dark interior of the front room or 'khadki'. In Muslim houses the view through the front door is baffled by a woven mat or curtain. Latticed doors have been used as secondary shutters for providing privacy. Greek temples had latticed door matching the architectural regimen of the building. Dutch doors though first conceived for horses' stables, are now used for curtailing view in the lower section. Saloon shutters serve the same purpose for mid section privacy. Metro stations have turnstiles or thin bars as door for unrestricted view of the incoming or departing train.

In Indian temples the statues of gods are sited with their eyes levelled to a particular height zone within the door opening. Typically Shiva is placed low, often below the 'threshold' level, and forms of Vishnu are placed in the upper zone. The eye sight line of the statue is kept free of obstruction through the estate or precinct gate.

Blind shutters, i.e. a door without a view window is a hazard. Doors abutting a passage or corridor require an aperture, view window or lite of at least 75 width but optimally 200 wide, at eye sight level, centred generally between 1200 and 1600 from the floor. Such apertures are useful for observation of interiors and interior activities as in jails, hospitals, offices, etc. Peepholes and security holes are very small aperture hardware fitted either as a 'talk through' an open hole or with a magnifying view glass. These are now being replaced by electronic close circuit observation system (CCTV). Pol houses of Ahmedabad had a lattice in the floor just above the door to checkout the visitors. American colonial doors have side lites on one or both sides of the door.

Latticed Doors were used in Greek temples. Lattices were designed with geometric or floral forms and as a composition of a large single pattern or repeated units. Emphasis on horizontal, vertical, inclined or curvilinear lines was carefully planned. Door shutters with fixed or rotating louvres are used to restrict view. Doors with hinged or sliding window shutters also regulate the view. Partly covered latticed doors (mid, bottom or top sections) are used to selectively restrict the view. Pol houses, to cutoff view of street level movement, have no lattice in the lower section.

The Glass introduced a new quality of transparency and visual connectivity through a door. First glasses were small in size, wavy (non-flat), and muddy or fuzzy due to the deficient methods of casting. To overcome the fuzzy view, the glass pieces were small in size, coloured and contrasted with heavy mullions. But later as glass became clearer, the mullions, so as to dissolve their presence, were made thinner and painted white. Colonial architecture, first in USA and later in Europe (1875 onwards) shows this white painting of the opening's trend clearly.

Glazed doors of stained glass had very thin mullions and muntins patterned to styles or to highlight the structure of the depicted picture. Clear glass of large size and free of manufacturing defects was not available till about the Industrial age. Till than door panes were assembled by combining clear, figured and frosted glass (called 'water-white') pieces and joined with cames -lead lined joints. The white glass doors of shop fronts and verandah were backed with laced fabric white curtains. After world war II large glass panes, toughened and fire finished were used as see-through doors. The glass panes doors were engraved or etched to create patterns. The doors were masked from inside with colourful curtains or horizontal and vertical Venetian blinds. The see-through glass doors showed the interior spaces, especially during dusk and at night. The ceiling, the panellings (inside front) were highly visible elements through such doors, and so were highlighted with illumination fixtures such as spot lights, down lights and chandeliers. Doors with one-way mirror glass, and tinted glasses, coated polyester films are used to control the degree of transparency. Some of the new technologies include LCD glasses, polarized glass and photo-chromatic glasses.

4.1.8.7 OTHER ISSUES

Keywords: DURABILITY AND SERVICE LIFE EXPECTANCY / detachable systems / replaceable elements / intensively used systems / sparingly used / door maintenance / service life worthiness / SUSTAINABILITY / sustainable systems / add-on systems / highly integrated components / separable and individually recyclable / disposable by degrading / naturally regenerating materials / local tools and technology / FIRE VULNERABILITY / allow time for evacuation / conditions for siting a fire door / passive fire protection method / isolate the fire / maintain its integrity / specific properties of fire doors / leaf or shutter of a fire door / frames of fire doors / coatings and treatments / hardware of fire door / general hardware / specific hardware for fire / inset windows / fire rated in hours / wall that separates two buildings / stairwells / corridors / edges of a fire door / intumescent strip / surrounding zone of a fire door / RECOGNITION / planes of sensory perception / use of identical material or surface colour and texture / de-shaped and descaled / methods of doors recognition / accentuating the door gap / passage to the exit.

DURABILITY AND SERVICE LIFE EXPECTANCY: Doors have shorter service life in comparison to structural components that constitute the shell of the building. During the life of a building a door system may need to be replaced several times, so door systems and their sub-components are designed to be detachable systems and are usually conceived as replaceable elements. Doors are intensively used systems in a building and so have higher maintenance requirements and shorter service life. Even doors that are sparingly used also require regular maintenance. Door maintenance covers attending to the wearing of the hardware and degeneration of the constituent materials. The service life worthiness is checked in terms of the functionality, accident proofing and aesthetics.

Intensity of use is measured by cycles of operation. ANSI typically specifies Level C, Standard Duty -250,000 cycles / Level B, Heavy Duty -500,000 cycles / Level A, Extra Heavy Duty -1,000,000 cycles.

SUSTAINABILITY: The concept of sustainability of doors is no different from other building systems and components. A good design practice is a prerequisite to make a door durable (maximum service life). Sustainable systems must have add-on systems -open-ended architecture, rather than highly integrated components. Sub systems of doors such as constituent materials, hardware, finishes, etc. each must be separable and individually recyclable. When materials are not recyclable, they should be disposable by degrading. Doors composed of single or fewer materials and with detachable subsystems make it easier to recycle the constituents. Recycling is less economical if the door systems contain sealants, high temperature ceramic and other coatings and glass fragments. 'Naturally regenerating materials' like timber are ideal choice but timber is not easily replaceable due to the large demand. Sustainability of a building system results from easy repair-ability with local tools and technology.

FIRE VULNERABILITY: A door is one of the few elements that allows escape during emergencies. A fire door contains fire and holds back the smoke to allow time for evacuation of people and goods. The term fire rated means that a door will not combust or burst for certain period of time. Some of the conditions for siting a fire door are: the walls around the fire doors must be more fire-resistant, the door must be away from other combustible elements such as carpets and curtains. Cracks and crevices around the perimeter of the door must be completely sealed with a less combustible material.

A fire door is a passive fire protection method. If the door nominally remains open, at the time of fire or smoke it must get shut through some device.

Doors rated for fire, are not necessarily all incombustible. But a fire door has the rated capacity to isolate the fire so that all people and important goods are evacuated, and maintain its integrity till fire runs out of fuel, air, or is extinguished. Specific properties of fire doors are like: catch fire after some delay, burn slowly, may not collapse all of a sudden, do not generate noxious fumes on burning, or have fire extinguishing treatments to retard spread of fire.

Door systems have three categories of elements: the door leaf, frame and hardware. These are affected differently by fire.

The leaf or shutter of a fire door is made of combination of natural woods, wood byproducts, wood composites, metal plates, glass, laminates, layered composites, etc., with in-fill materials like gypsum (as an endothermic fill), vermiculite-boards, glass wool, polymers foam (styrene).

The frames of fire doors are made of natural wood, treated wood, wood byproducts, wood composites, folded metal sheet sections (mild steel, galvanised mild steel, stainless steel, aluminium, bronze alloys), extruded or rolled sections of metals and polymers, cement concrete, layered composites.

Coatings and treatments substantially alter the fire rating of a door. Nominal coatings include various types of enamel paints, lacquers and polymer polish, these are not fire resistant, but coatings containing wallstonite and silica perform well in retarding the effects of fire. Similar instead of ordinary polymer films or skins, many 'self extinguishing' polymers can be used.

The hardware of fire doors is of two broad categories: general hardware that is for making a door operational and for handling and specific hardware for fire that is for closing the door when there is for or smoke.

Many fire doors have inset windows (view windows, pip holes, lites) so that one to judge if the door can be safely opened. The windows have wire mesh glass, heat-blast resistant Boro-silicate glass or liquid sodium silicate filled in between two panes, and these are also fire rated.

A door set is fire rated in hours, the time taken for it to resist a fire at a given temperature. Fire ratings are 3 hours to 30 minutes. A 3 hour fire door is commonly used in a wall that separates two buildings or two parts of a large building. The wall around the door in this case would be rated higher, for say 4 hours. Stairwells have fire doors of 1.5 hours rating. Corridors have a fire rating of 1 hour or less, and the fire doors in them are required by code to have a fire rating of 30 to 20 minutes (the intent of the later is to restrict spread of smoke). Generally smaller areas can do with a door of lower fire rating. A door of approved fire rating may not provide the due fire resistence because of faulty fitting and due to site conditions.

Edges of a fire door usually need to have fire rated seals which can be composed of: an intumescent strip, which expands when exposed to heat, gaskets of Neoprene weather stripping to prevent the passage of smoke.

Surrounding zones of a fire door must not support the spread of fire. Carpets, wooden or laminated floors running under the door, a large gap under the door allows the fire to travel past the barrier.

RECOGNITION: A door, even though a very distinguishing component of a building requires a recognition on many different planes of sensory perception. An unreal door, such as in Egyptian tombs was provided with extra ordinary emphasis so that no one missed its presence and thereby its importance. But real doors are often concealed or unintentionally shrouded and rendered unrecognizable even in nominal circumstances. Architecturally doors are merged into the base barrier system, the wall. The fusion is achieved through use of identical material or surface colour and texture. The door edges are matched with the members of the wall construction and opening hardware is concealed. The doors are de-shaped and descaled to look anything else but a door. In an emergency for egress, it is not only difficult to locate such an opening, but determine whether it opens inward or outward. There many regulations that make door recognition mandatory by visual and illuminated graphics. There are many methods of doors recognition: by signage over or beside the opening, by accentuating the door gap or portal and by emphasizing the passage to the exit through floor marks, as in air crafts, cruise ships and lobbies of buildings.

4.1.9.1 EMERGING TECHNOLOGIES

Keywords: developments in materials technology / design innovations / improvised doors / radically different types of doors / unusual opening systems / function like a valve / controller of opening / Isolation areas / research laboratories / nano technology plants / very large and light weight structures / doors of membrane or skin / heart valves / sonar zones / water gates / geometric or space structures / membrane or shell structures / industrial doors / flap curtains of non tearing polymer or composite sheets / barrier were to disappear, collapse (shrink) / camera shutter / transparency / flat sheet / cast-able materials / freedom to curve a door's surface / any dynamic shape or size / expanding-contracting shutters or balloon doors / a self seaming door / biological healing / new modes of transfer, transport or travel.

New technologies of doors arrive more frequently due to developments in materials technology, but also occasionally due to design innovations. Improvised doors are offered by building components' manufacturers, and sometimes devised by creative designers. But ideas for radically different types of doors have been adopted from literature like scientific fiction, children's stories of adventures, media such as scientific movies, television serials, and from video games. New doors have been modelled on various gadgets and industrial equipments. Submarines, space capsules, cameras, chemical reaction vessels, dams, dykes, deep sea drilling units etc. need unusual opening systems. Such opening systems may not be recognized as a door, but rather function like a valve or controller of opening.

Such opening systems or devices, however, have inspired many building designers. Isolation areas in research laboratories and nano technology plants require hermetically sealed zones need doors with a positive seal (completely leakproof). Very large and light weight structures, such as domes and roofs require opening for access to external face. Such circular flexible doors of membrane or skin thin materials diverge to edges for closing, but bulge or sink to a concave or convex form due to suction or pressure. Heart valves are implants that beat but function like a door. Air curtain fans and showers create a wall of cascading air and water, but a breach-able door. Similarly sonar zones, in industrial plants remove particulate matter from the things that move in or out are also a door system. Offshore or deep sea marine structures such as oil-gas drilling platform and recovery or collection centres, coastal protection barriers such as dykes have doors for water. The water gates were once devised as very large geometric or space structures but are now built as membrane or shell structures.

Industrial doors are very large and intensively used openings. Normal sliding, folding or swinging shutters take a lot of time to close or open and with every such operation the interior environment gets corrupted. Air curtains are noisy and cold. Flap curtains of non tearing polymer or composite sheets have proved a better option. Ion charged openings and sonar barriers are not very satisfactory in many applications. Some radical solution is required.

A door is perceived to be an opening in a barrier, an open-able component of the barrier system. However, if whole of a barrier were to disappear, collapse (physically shrink) or become nonfunctional for a while, then it can serve the function of an opening. A barrier will have to collapse to its edge or perimeter, away from its centre, almost like the folding leaves of a camera shutter. Here the leaves could be of gaseous or liquid substance, or a field of energy. Games, science fiction and movies explore such radical concepts.

Wood has been the favoured material for door construction. Since Industrial revolution, steel has replaced wood for many types of large doors. Glass doors provided transparency to the nominally opaque door shutter. The door was still a flat sheet, till cast-able materials such as composites, polymers, formed metal sheets, provided a freedom to curve a door's surface. Woven and knitted fabrics, co-extruded polymer sheets, formed composites, allow the door to be flexible to take on any dynamic shape or size. Elastomers have provided materials for expanding-contracting shutters or balloon doors. An opening that can be cut anywhere in the barrier, a self seaming door is a sci-fiction concept emulating the biological healing. The door is a necessity to transit through a barrier, and the barrier if was non physical, then the form of 'door' required in it is also likely to be very different.

A door has traditionally served the purpose of entry and exit to and from a space to another. New modes of transfer, transport or travel (movie Star Wars: Teleporting) may entirely change the shape, size and configuration of the door in future. Perhaps it will be a controller of opening rather than a door.

4.1.9.2 DOOR MYTHS AND LEGENDS

Keywords: Etymologically / objects and expressions / folklore and legends / physically and symbolically / mundane level / symbolic level / spiritual level / bridge head / illusive opportunity or intangible entity / narrow with dangers of falling off it / backtracking to the reality of home / MAKING OF A DOOR / three phenomenal elements Top, Bottom and Sides / Torii / eaves / Laxman Rekha. threshold / tall sides / columns, pylons or obelisks / ENTRY - EXIT / Aagaman / go in or stay out / Nirgaman / get out or stay in / homeward (return) journey / Vedic ritual / an open door / door knob / hinges / locked door / door opening outward / inward opening door / THRESHOLD / Grih-Pravesh / Udumbara / threshold / stumbles over a threshold / untouchable element / Havan kund / carry a bride over the threshold / trip over a threshold / confirming to Vastu / oriented entrance door / right shoulder to the right jamb / right foot first / EAST ENTRANCE / rising sun and the East face entrance / Eastern light / obelisks / masts / furling flags and festoons / eagles and wheels -Chakra / door heads / Dharma-Chakra / pre Gothic period cathedrals / Western entrances / Gate of the East / Gate of the West / FALSE DOORS / false door / west wall / GUARDIANS OF THE DOOR / horse shoe / portals, doors and gates / protectors or guardians / Dwarpal / Kshetrapal /door guardians / martial door gods / literary door gods / verses written on red paper / Buddhist temples / Taoist temples / musical instrument, sword, umbrella or snake / Confucius / JANUS ROMAN GOD OF DOORS / Roman mythology / god of gates, doors, doorways, beginnings and endings / some form of duality / two faces -looking in opposite directions / Janus / Cardea / goddess of thresholds and door-pivots / to open what is shut and to shut what is open / DOORS IN ROMAN HOUSES / doors that opened inward / owner's place in society / JAPANESE DOOR / schools of etiquette / norms for opening a door and coming into a room / reishiki / REVOLVING DOORS / DOOR OPERATORS / trappers / lift operator boys DOORS IN LITERATURE / physical constructs / metaphysical effects / metaphorical forms / J R R Tolkien / door, window, gate, or other passageway / change in a character's physical, metaphysical, or metaphorical state / function of transition / passage point that signals some type of change in a character / idea of 'becoming' / exploration of openings, and especially doors, gates, and windows / being inside with safety / being outside with danger / Revolving door / Amakudari / key to a door / MIHRAB IN MOSQUE / arched doorway / portent of change / supernatural realm / Bizarre and secret entry ways.

Doors are as ancient as the human abode and so have become part of our conscious and subconscious being. Throughout history and across cultures doors, doorways, portals, gates and thresholds have been potent objects and symbols of superstition, rites and rituals, psychological change, transcendental and religious experience. Doors occur metaphorically in our expressions and recur in our dreams.

Etymologically Doors have been known as: dor (middle English), duru (old English) dur (proto-Germanic), dwer-dwor (proto-Indo-European), Gothic (daúr), Danish dør, Tür (German), turi (old High German), dyr (Icelandic), dyrr (old Norse), foris (Latin), thýra (modern Greek, thura (ancient Greek), dar (Persian), and dver (Russian), Kiwad (Urdu= door shutter).

Doors are synonymous with many objects and expressions such as entrance, gate, gateway, passage, portal, access, adit, admission, admittance, ingress and way. Doors are also refereed to in terms of: indoor -inside a built or enclosed space, outdoor -outside in the open, next door -neighbouring property or territory, at the door -outside or inside the door but on the verge of crossing it, waiting for permission or opportunity to leave or enter, by the door -passing by, at one's door -as compliance or submission, for being responsible, door to door -going or made by going to each house in a neighbourhood, out of doors -deposition, thrown out, removed, through the door -through an appropriate channel, to show the door -thrown out, asked to leave, open-door policies -barriers less, closed doors -private, protected, doors of opportunity, door to success -change of position for success, doorways to the future -future reached through breach or opening.

Doors have been part of our folklore and legends, often with diverse meanings. Doors have been dealt in their interior as well as exterior expressions. The interior expressions relate to way of life, virtues, good manners, exemplary behaviour, restraints, and exterior manifests as supernatural, unpredictable, dilemmas. Doors are equated with other building elements like walls, windows etc. to juxtapose the physical character.

I'm talking to the door, but I want the walls to hear me. The ear is only a door. Walls have ears, paper sliding doors have eyes.

When God shuts one door, He opens another. At death's door a man will beg for the fever. The doorstep weeps for forty days whenever a girl is born. Misfortune only comes in when the door is open.

If you want to keep camels, have a large door. A doorstep is the highest of all mountains. The best kind of closed door is the one you can leave unlocked.

Every dog is a great barker at the door of his own house. Earth is like a prison: we all go in through the same door, but we stay in different cells. Insects do not nest in a busy door-hinge.

He who wants to tell the truth will always stand before closed doors. Luck stops at the door and inquires whether prudence is within. He who is outside the door has already a good part of his journey behind him. Many open a door to shut a window. When a door opens not to your knock, consider your reputation.

The door, physically and symbolically, involves a change of state. At mundane level, a door means control over illumination, intrusion, acoustical disturbance, visual engagement, social interference and movement of air and pollution and thermal emission. At symbolic level a door offers hope, new life or fresh beginning, isolation from the familiar, ventures into unknown, initiation into mysteries, fear and expanded communications. At spiritual level it provides an encounter with the supernatural, a communion and unification with the creator. As Christ said, 'I am the door,' and 'no one comes to the Father but through Me.'

A door leads one out of a space to another space and a door perceptible somewhere. The door here is a bridgehead over the connecting passage. The door also takes one out to exploration of an illusive opportunity or intangible entity. The passage, in the first case is narrow with dangers of falling off it, whereas in the second case there are no options except backtracking to the reality of home.

MAKING OF A DOOR: A door comes into being by three phenomenal elements: a Top, Bottom and the Sides. Japanese gate Torii is essentially composed of the eaves, the omnipresent top. A single stroke did not suffice, so two or three strokes emphasize the horizontal at top (as in Sanchi gate). An Indian door is epitomised by the Laxman Rekha. A territorial mark on the ground that defines wether one is included or excluded from the macrocosm. Here the threshold exists in spite there being no door. The Egyptian temple entrance consists of tall sides formed by a pair of columns, pylons or obelisks. The lintel or head is architecturally less significant, just incidental. A formal door requires all three to be present, and concurrently.

ENTRY - EXIT: During Aagaman -while entering one must either go in or stay out. And during Nirgaman -while exiting one must either get out or stay in. A door is a point of uncertainty. Ones action must be very certain, and one must never stay put in the door itself. One must be very cautious on crossing a door threshold, as trouble lurks in both directions. All activities in the door space or frame, such as standing, seating, eating, drinking or doing anything else is a taboo. One must not look backward during entry or exit, or the willpower and physical strength will dissipate. The homeward (return) journey must be accomplished without an intermediate stop or engagements. On Aagaman, before entering the house door, one must purify own self (disinfect) with appropriate Vedic ritual, like bathing, washing the feet or at least sprinkling of holy water over the head. The Nirgaman, if for a journey to an unknown destination or for an uncertain purpose must be conducted with the permission of elders, masters or gurus, and goddess of the family (Kuldevi).

Mystically, an open door represents good fortune, a new opening in life, or a desire to open up the feelings. A revolving door means a monotonous period ahead and a trap door predicts shocking news, a door knob means unexpected good luck, hinges bring family problems. A locked door shows missed opportunities, denial of opportunities, or can represent 'need to close the door over the past'. A door opening outward may show that one needs to be more accessible to others. However, an inward opening door may represent the desire for inner exploration and self-discovery. A front door is a normal entrance and a back door a nominal one. A house with one door is a preferred abode. Evil spirits enter the house from a back door.

THRESHOLD: A Grih-Pravesh, -a ceremony of entering a home, by crossing over a threshold -Udumbara with right foot forward. It is conducted while entering into a new home, when a new member joins the family like a bride, new born baby, groom, a disciple or an apprentice, and when someone returns after some lapse of time such as recovery from an illness, achievement or trip. Grih Pravesh ceremonies have many forms but it is mainly performed at the door. Most common elements are: a Kumbha either filled with rice or water, a cocoanut and Arati.

The threshold is an element that is to be crossed without touching it. If one stumbles over a threshold by accident the entry or exit must be postponed. The western tradition of lifting the bride by the husband over the threshold reflects similar attitude. A threshold is not always considered an untouchable element, people do touch it with their head to pay obeisance to the place or its owner or touch it with right hand to take a few dust particles and place them over the forehead. The dust near the thresholds or doors of temples, prostitutes' houses, and very rich persons' mansions are considered auspicious, and are also used for construction of the Havan kund (ceremonial and sacrificial fire place).

'The tradition to carry a bride over the threshold of the married couple's home is a very old one and followed in many societies of the world. The belief is nearly same everywhere, that a bride must not trip over a threshold. Some believed demons haunted doorways and could cause the bride to trip. Others felt that threshold was ominous of evil, and one must never step on to it, but rather cross over it. But people do touch the threshold in reverence. Some believe that one must open a door at midnight to allow evil spirits to depart, and that the first person to open the door on Christmas morning will have good luck. It's bad luck, some believe, to leave a house by a different door than the one used to enter the house or to eat in front of a door'. Ogden Nash has stated that 'only a door is what a dog is perpetually on the wrong side of', and for some, the dame luck also stays on the wrong side, at least most of the time.

'A woman who had just given birth was forbidden to tread on another family's threshold, for it was believed that the woman would become a threshold cleaner in her next life. In Liaoning province of Northeast China, people still follow the tradition during Dragon Boat Festival (the 5^th day of the 5^th lunar month) of sitting on the threshold of the door to eat an egg before sunset. After finishing the egg, they throw all the shells outside the house. Such an act is believed to clear the house of disease and bad luck in the following year'.

Houses confirming to Vastu have a properly oriented entrance door, so the place for home-entrance ceremony is also well set. In grih pravesh ceremony the home owner enters the house by touching the right shoulder to the right jamb, and by crossing the threshold with right foot first, but without touching it.

EAST ENTRANCE: The rising sun and the East face entrance have a very intimate relationship in many cultures across the world. The spiritual relationship of Eastern light falling on to an East facing deity (sited in the western section of the building) or place of worship is a well-established fact.

It was universal early practice for the great door to be 'the Gate of Sunrise.' This door of enormous size was properly the sole opening to the temple, serving as much for light as to enter by, it was thrown open at dawn. Dr Hayes Ward in the American Journal of Archaeology (Vol. 3), shows some dozen Babylonian seals, with intaglios of the Sun-god passing through the double-valved gate of the East and beginning to climb the mountain of the sky. The gate has two guardian figures.

It was usual to cover the Eastern door with shining metal for it to glow in the morning sun rays. Sunrays were also received on the metal-clad shiny inclined top faces of the tall obelisks, shining metal finials over tall masts and over furling flags and festoons. The Sun is also metaphorically represented by soaring eagles, circular objects like a wheel, red disc or the winged globe. Images of soaring Eagles and wheels (Chakra) were part of door heads. The moving Dharma-Chakra of the Buddhist temples and stupas atop a Stambha -pillar is perhaps reminiscent of this.

Babylon temples had 'gate of glory as brilliant as the sun'. In Syria it was the same; at the temple of Mabog (Hierapolis) the doors were gilded, as also was the entire sanctuary, walls and ceiling. 'Two immense columns, one hundred and eighty feet high, flanked the door, inside which, on the left, was placed the throne of the sun'.

The preference for East for the main door changed when in pre Gothic period cathedrals began to have Western entrances, so that deities could be backlit with stained glass in the morning sunlight.

Egyptian's temples and tombs had two openings: the Gate of the East, and the Gate of the West. Through the former the sun enters in the morning to pass out from the other in the evening, and therefrom pursue its journey way back by the dark path of the under world.

FALSE DOORS: In the tombs of early dynasties a false door was the focus of the offering chamber that was adjacent to the tomb. It was here the family members placed their offerings for the deceased on a slab in front of the door. False doors were most typically placed on the west wall of the offering room. It was a threshold between the world of the living and the dead. It was a point through which the spirit of the deceased could transit. In some instances, there were two false doors affixed to the west wall, with the left one serving the tomb owner while the right door was meant for his wife.

In Egyptian tombs of earlier period, the false doors were indicated like the door of an ordinary house, low, small and narrow but not pierced through. These doors were not copies of real doors, bur rather a combination of an offering niche and a stela with an offering table. The doors were engraved on a single piece of wood, alabaster or stone panel, or drawn on the walls. They often had one, two or even three pairs of jambs leading to a central niche, so arranged to convey the illusion of depth and a series of frames, a foyer, or a passageway. The niche within the false door had carved statues and the side panels had inscriptions naming the deceased along with the titles, and a series of standardized offering formulas. These texts extol the virtues of the deceased and express positive wishes for the afterlife.

GUARDIANS OF THE DOOR: A door as an entrance needs protection so that evil spirits are warded off it, and as an exit point good fortunes or luck does not escape out of it. Doors have protective charms. The most common charm for the door is the horse shoe. Other objects include olive branches, statuettes of gods, angels and saints. (For more refer to Chapter: 4.3 Openings systems: Treatments).

Portals, doors and gates had inevitable protectors or guardians in the form of real or horrible humans, beasts and monsters. These figures 'fawn on all who enter, but rend all who would pass there again (after death)'. The creatures were such as: winged genii in the form of bulls, scorpions, human-headed lions -the sphinx, lions, Dwarpal, Yaksha. Other forms like Christ, Michael, Gabriel, archangels, Ganesha, Hanuman, signs of the zodiac and sculptures of the months. In India, China, Siam, Japan, the gates are protected by Dwarpal, and presence of the Kshetrapal (the guardian of the local territory) was also necessary.

China has many legendry door guardians. The guardians are brave warriors. The pictures of door gods are hung in pairs, facing each other, it is considered bad luck to place the figures back-to-back.

There are two types of door gods: martial door gods and literary door gods. Martial door gods are usually generals depicted in life-size proportions, wearing full battle armour and wielding weapons, loyal men, great fighters. Commonly seen door gods of this type include 'Shen Tu and Yu Lu', 'Qin Qiong and Weichi Gong', 'Zhong Kui', 'Guan U' and 'Guan Sheng'. Whoever the door gods may be, the common denominator of all front gate door gods is their trustworthiness, strength and loyalty, bolstered by a fierce martial countenance and impressive weaponry. In the past, each Chinese household hosted numerous gods, such as the stove god, door gods, the property god, the well-ness god, etc. To keep ghosts and monsters at bay, prints of such door gods were pasted on front doors.

Emperor Tang Taizong (599 : 649 AD) was beset by demons howling outside of his bedroom at night. Qin Shubao and Hu Jingde, two generals volunteered to guard the door to the emperor's chamber. Thereafter there was no more trouble. In honour of the two brothers' bravery the emperor ordered pictures of the two to be drawn and posted on the palace gates. The two came to be associated as the Guardians of Doors or Door Gods. Qin Shubao has a white face, and Hu Jingde either a red or black one. They protect households from the evil forces outside, as well as marking 'spaces safe'.

Shentou and Yulei are other immortals who were ordered by the Jade Emperor to guard peach trees which demons were gnawing at. Shentou and Yulei carry a battle axe and a mace, respectively. Zhong kui is not a door god but a mythical exorcist (ghost catchers) whose image is often displayed as the 'backdoor general'.

'According to an ancient Chinese text, "The Classic of Mountains and Seas" (shanhaijing?), there was a very large peach tree on Dushuo Mountain (dushuoshan?) whose branches formed an archway through which evil spirits could pass between the spirit world and the earth. The Emperor of Heaven (tiandi ?) was concerned that the evil spirits might harm the people on earth and so he assigned two brothers, Shen Tu and Yu Lei, to guard the passageway. If the evil spirits caused any harm, the two brothers were instructed to tie them up and feed them to the tigers which lived at the base of the mountain'.

A tradition gradually developed to engrave their portraits in peach wood which were then hung on gates and doors for protection from evil influences. Images were also painted on the doors, but only few could afford it. Ordinary people placed a light-coloured broom and a black piece of coal outside their doorways to represent Chin and Yu-Chih, respectively. With the advent of wood block printing in the Sung Dynasty, (960-1297) artistic renderings of deities became easily available. It was during this period that door God charms (taofu?) were replaced by auspicious verses written on red paper (spring couplets -chunlian?). The verses are hung above and at the sides of doors and gates. Traditionally prior to the Chinese New Year houses are cleaned and red trimmings are placed on doorways and windows to scare away the monster Nian as it is afraid of the colour red. Red banners featuring words like 'longevity', good luck', 'happiness', etc., are displayed in homes.

Door guardians used for Buddhist temples are different from those at Taoist temples. At Buddhist temples, the most commonly seen door gods are Wei Tuo and Chia Lan, two guardians of the blessed state of enlightenment. The four Buddhist grand lords flank their sides, each holding, either a musical instrument, sword, umbrella or snake. At Taoist temples, such as those dedicated to Matsu, Goddess of the Sea, the most popular characters for painting on the entrances are the Thousand-Mile Eye God and the Wind Ear God. The Chinese temples dedicated to Confucius, are not decorated with door gods, for the Great Sage did not speak of superstition, deities or demons.

Over the years not only many different guardians for doors evolved but many different image versions became available. The door gods protected one from evil influences of demons and endowed luck, wealth, longevity and happiness. Each character is believed to have different powers. For example, images of the infant door god are suitable for the bedrooms of newlyweds, whereas the ox door god is appropriate for cowsheds.

JANUS ROMAN GOD OF DOORS: In Roman mythology, Janus was the god of gates, doors, doorways, beginnings and endings. Janus also represented the sun and the moon. Janus is always associated with some form of duality. Janus is depicted with two faces -looking in opposite directions.

Janus symbolized change and transitions such as: the progression of past to future, of one condition to another, of one vision to another, and of one universe to another. Janus was worshipped at the beginnings of all events like planting and harvesting, births, marriages, etc. He was representative of the middle ground between barbarity and civilization, rural country and urban cities, and youth and adulthood.

Janus once caused a hot spring to erupt to stop the would-be attackers and forced them to flee. In honour of this, the doors to his temples were kept open during war so that he could easily intervene. The doors and gates were to be kept closed during peace, which rarely happened. But in the time of Augustus it was closed, after he had overthrown Marc Antony, and before that, when Marcus Atilius and Titus Manlius were consuls, it was closed for a short time; then war broke out again at once, and it was opened. Of the several places, Janus had a temple at Rome with double doors, which were called the gates of war.

Janus's most apparent remnant in modern culture is his namesake, the month of January. The name Genoa, the Italian city is believed to be derivation of Janus. The Latin word for door, 'ianua,' itself possibly came from the god Janus.

Cardea is the goddess of thresholds and door-pivots (cardo =door-pivot). She protected little children against the attacks of vampire-witches. She is also a goddess of health like Carna. Cardea obtained the office from Janus in exchange for her personal favours. Her powers were 'to open what is shut and to shut what is open'.

DOORS IN ROMAN HOUSES: Roman houses had doors that opened inward. Roman society permitted only rare individuals of high honour to have doors that opened out on to the Street. Plutarch wrote that the Roman people complimented Marcus Valorous, a founder of the Roman Republic, after his triumph with a house built on the Palatine at public expense, but with doors to open outwards as perpetual recognition of his merit as if 'he might be constantly partaking of public honour'. Caesar was given this plus an additional pediment which Livy mentioned as a decree by the senate for honour and distinction.

For the Romans a door represented the character of the household and was an expression of the owner's place in society. The front door was always open to a stranger and community. An open street door showed a willingness to serve the community participate fully in political and social life.

'Pliny the Younger interpreted that an unwillingness to participate with the community was the same as a willingness to engage in a destructive manner against the community. The Roman's inability, to see behind, the closed doors always caused fear and suspicion, an implication that the paterfamilias had something to hide. A place of concealment was a place of potential revolution as can be seen by the conspirator Catiline in 63 BC. Sallust wrote that Catiline gathered his most trusted friends behind closed doors to attempt overthrowing the Republic'.

The formal entrance to a Roman house was set with certain depth from the street. It was a decorative entryway flanked by half columns or pilasters to create a picture-like frame. Strangers and formal guests were impressed by the passage through the fauces and atrium. The family members, neighbours and other regular visitors however, used a simpler side or back doors set flush with the street. 'In Roman culture, the front door was always open to a stranger and community but to understand and be treated equal to the family, one had to approach from other means'. Hillier and Hanson state that the side or backdoor was left ajar for the working class and to encourage neighbours coming in unannounced. Since the back door typically led to the kitchen, an important room to a house, the entrance carries a high level of presence availability.

JAPANESE DOOR: For the Japanese 'the door to happiness opens outward. A door simply imposes itself upon the room when it opens inward. Having the door open inwards has the outside intruding upon the inside'. Feudal schools of etiquette prescribe all kinds of norms for opening a door and coming into a room. Sukisha, well-bred people use the hand, nearest the door to open it a few inches (the length of a forefinger, to be exact) and then switch hands to slide it back the rest of the way. A man is judged by how he opens a door and a woman by how she shuts. This is so because in a room with a group of men, a woman served the food and take a leave. She would be observed closing the door behind her with grace. The balanced and graceful action of folding down one's knees on the floor, moving into a room, keeping at a level equal to others already in the room, were part of larger ceremony. The skills of opening and closing a sliding Japanese doors are part of reishiki, proper form or etiquette.

REVOLVING DOORS: Revolving doors, when began to be used in American buildings, were marketed with a lot of hype, as 'doors that always remain closed'. With a clear Victorian attitude they declared as capable of avoiding the 'noxious effluvia' and 'baleful miasmas'. The doors were supposed to save life, by preventing those deadly lung and throat diseases which are sure to overtake the unfortunate salesman, cashier, or clerk whose duty keeps him near the constantly opening front door.

DOOR OPERATORS: In the early part of Industrial age children hired to work as trappers to operate trap doors in mines and railway yards. They sat in a hole hollowed out for them and held a string which was fastened to the door. When they heard the coal wagons coming, they had to open the door by pulling a string. This job was one of the easiest down the mine but it was very lonely and the place where they sat was usually damp and draughty. This was like lift operator boys who opened-closed the elevator doors, working for long hours, but in fancy places, in late 19^th and early 20^th C.

DOORS IN LITERATURE: Doors in literature are used in their various physical constructs, metaphysical effects and metaphorical forms. J. R. R. Tolkien the author of The Hobbit and The Lord of the Rings refers directly or indirectly to a door, window, gate, or other passageway that leads to a change in a character's physical, metaphysical, or metaphorical state. While not quite as omnipresent in The Silmarillion, the motif is still used extensively throughout the text. The function of transition refers to a passage point that signals some type of change in a character. Barriers are thresholds that represent the dichotomies of safety/danger, us/other, inclusion /exclusion, and control/chaos.

One of the metaphorical meanings of doorways and openings in Tolkien's work conveys the idea of 'becoming'. As one passes through the doorway and enters a new stage of development or experience, having gained the 'key' necessary to move forward, one 'becomes' something more--more capable, more perceptive, more knowledgeable. Although, we often cling to our comfort zone, it is only by venturing outside our experience that we come to know our true selves. In other words, we must cross the thresholds that paradoxically lead us both outward and inward to a deeper understanding of our strengths and weaknesses and recognition of our relationships with the cosmos, just like Tolkien's fish out of water.

Tolkien's exploration of openings, and especially doors, gates, and windows exist not only as a motif within his written works, but is something he contemplated outside Middle Earth through his sketches. It is likely that his attraction to such passageways grew out of his daily surrounds as he lived and worked among centuries old architectural icons. Images of tunnels leading to and from openings appear to represent these complex initiatory ideas within Tolkien's work. Like the 'Before and Afterwards' sketches, tunnels, caves, and mines function as extended thresholds between what came before and what new challenges wait on the other side, and as the inner realm of conflict where obstacles are met and overcome.

Much of Tolkien's dark woodland imagery is also tunnel-like. He juxtaposes the open land with forest. Forests are entrance points and open lands exit points. In most natural environments he inverts that usual association of 'being inside' with safety, and 'being outside' with danger. More often than not entering a forest is depicted as entering into a dark unknown, as is entering water, caves, and barrows. Coming out into the open light of the fields is to have survived the dark dangers of woods, water, and earth with newly gained knowledge and confidence. For Tolkien passageways as barriers are usually artificial constructs like gates, fences, doors, and bridges and much less frequently a natural element like water or forests. Tolkien has used artificial barriers to symbolically represent the artifice of separation between peoples. (For more Refer to 4.0.3 Openings in Literature).

Metaphorically, a Revolving door is an instance of the easy movement of individuals from one position or situation to another, and back again. For example, from government-related jobs to lobbying jobs and vice versa, resulting in a conflict of interest for those chosen to represent the public and/or special privileges and benefits to former government officials and personnel. A similar metaphor in the Japanese language is Amakudari, it refers only to former government employees joining companies they were once supervising. This is also used when describing early release of criminals who often end up back in prison after a short time.

The key to a door, permission to enter a door or a domain is given to a person of faith. It is at the door the alienation begins to manifest. To enter a premise, one needs to be consecrated by a person of authority, which means the visitor agrees to abide by the rules that prevail within.

MIHRAB IN MOSQUE: A mihrab originally was a room for the great prophet to pray in. It was the focus of the wall that was indicative of the direction of Mecca. It later on became a decorative niche in the wall. Mihrabs vary in size, are usually ornately decorated and often designed to give the impression of an arched doorway or a passage to Mecca.

Doors and doorways frequently appear in metaphorical or allegorical situations, literature and the arts, often as a portent of change. Old buildings, castles, haunted houses, lair of villains or mansions of super heroes have secret passages accessed through doors, traps or openings. One enters or exits a building by triggering concealed levers, buttons or even surprising mechanisms. But one enters a supernatural realm, gets transported to another time and space setting, or even gets transformed into a different form by simply crossing a point or invisible threshold. The change is often secretive that is perceptible to few. Bizarre and secret entry ways are used in mythological stories, fiction, television programmes or films, and now video games to denote a change that is out of normal range. In Batman fiction and movies such secret entryways are used. In computer games such points may lead to new complications, new leads or bonuses, termination of the game or could be a false situation. In architecture entry ways are delayed in time and space that is the transition is not simple or immediate.

4.2 OPENING SYSTEMS : WINDOWS

4.2.1.1 Historical perspective : Windows

CHAPTER 4.2 INDEX

4.2.0 Windows : General

4.2.1.2 Historical perspective : Windows : Periods

4.2.1.3 Historical perspective : Windows : Recent

4.2.1.4 Historical perspective : Windows : Types

4.2.1.4.1 Historical perspective : Windows : Types : Roof level windows

4.2.1.4.2 Historical perspective : Windows : Types : Wall windows

4.2.1.4.3 Historical perspective : Windows : Types : Windows projecting out

4.2.1.4.4 Historical perspective : Windows : Types : Floor level windows

4.2.1.4.5 Historical perspective : Windows : Types : Other shaped windows

4.2.2.1 Varieties of Windows

4.2.2.2 Elements of Windows

4.2.2.3 Components of Windows

4.2.3.1 Materials and Technologies

4.2.3.2 Windows Mechanisms and Hardware

4.2.4.1 Other types of Windows

4.2.4.2 Windows like Utilities and Presences

4.2.4.3 Real and Pseudo Windows

4.2.5.1 Window Sizes, Shapes and Proportions

4.2.5.2 Windows Functional Sizes

4.2.5.3 Architecture of Windows

4.2.5.4 Spatial character of Windows

4.2.6.1 Window Opening's Structures

4.2.6.2 Windows Openings in Thick and Thin Walls

4.2.7.1 Customs, Cannons and Vastu Shastra

4.2.8.0 Functions of Windows

4.2.8.1 Illumination

4.2.8.2 Thermal Management : Insulation

4.2.8.3 Ventilation

4.2.8.4 Passage and Control

4.2.8.5 Safety and Security

4.2.8.6 Vision in-out

4.2.8.7 Other Issues

4.2.9.1 Emerging Technologies

4.2.9.2 Windows Myths and Legends

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4.2.0 WINDOWS : GENERAL

4.2.1.1 HISTORICAL PERSPECTIVE : WINDOWS

Keywords: evolved from the door / serve many functions of the door / placed almost anywhere / upper section of the door gap / as extensive as the barrier system / single aperture element / sub-windows / separately and selectively functional / Government rules and regulations / changes in the form, shape, size and configurations / artificial illumination systems / heating, cooling and ventilation systems / security enforcement systems / health, comfort, and productivity / energy conservation movement / thermal efficiency of openings / exterior into the interior / the interior to the exterior / shop fronts.

A window, like the door, is a gap within a barrier system, and so an opening system. Windows have evolved from the door and even today, continue to serve many functions of the door. A window, however, unlike a door, is generally not meant for anyone to pass through, so can be placed almost anywhere including upper sections of walls or roofs. Windows first evolved as a distinctive opening to manage the upper section of the door gap. Apertures in roof and upper parts of walls were devised to let in light and for smoke ventilation in rooms bounded by other interior spaces.

A door is effective, if it is smaller than the mother-barrier system (such as a wall, fencing, etc.), whereas a window can be, as extensive as the barrier system itself, and still be an opening system (e.g. curtain wall system). Yet windows have to be prudent to be effective.

The primitive window was a single aperture element, but today windows are multiple opening system composed of several subwindows, each of which could be separately and selectively functional. Windows control many aspects simultaneously like: Ventilation, Light, Vision in-out, Emergency ingress-egress.

The word Window originates from the Old Norse 'vindauga' (composed of 'vindr= wind' + 'auga=eye', i.e. 'wind eye'). Window as a word first used in 13^th C, referred to an unglazed hole in the roof. The word window replaced the Old English usage 'eagþyrl=eye-hole,' and 'eagduru=eye-door'. Latin word 'fenestra' describes a window with glass.

Primitive windows were just holes which later were covered with animal hide, cloth, or wood. Next came the shutters that could be opened and closed. Over time, windows were built to protect the inhabitants from the elements and transmit light. The Romans were the first to use glass for illumination. In Alexandria 100 AD, cast glass disks and plates, albeit with poor optical properties, began to appear. Paper windows were economical and widely used in ancient China, Korea, Japan, and windows made of panes of flattened animal horn or oiled parchment were used as early as the 14th century in Northern Britain. Mullioned glass windows were the windows of choice among European well-to-do. In England glass became common in the windows of ordinary homes only in the early 17th century whereas Modern-style floor-to-ceiling windows became possible only after the industrial glass making processes were perfected.

Windows have continuously evolved and inturn, have forced many technological advances. Government rules and regulations have at times slowed down the pace of development (such as window tax of England) but only for a while. Changes in the form, shape, size and configurations have occurred with equivalent changes in architectural styling and living standards of the society. Some of the major infinitives for change have come from artificial illumination systems (gas, liquid fuel and electricity), Heating, cooling and ventilation systems, and Security enforcement systems. These have changed our lifestyles and daily schedules, in turn are changing how, where and when we use a window. Windows have been used as relief to confined spaces for experiencing the outdoors or nature. This too is about to change with remote sensing, view capture and environment duplication systems.

Windows have long been used in buildings for day-lighting and ventilation. Many studies have shown that health, comfort, and productivity, etc. are improved with well-ventilated indoor environments and access to natural light. Victorian age saw the advantage of brightly lit interiors. Poor quality of interior environment and life in workers' colonies of industrial age once again made way for better window system. The energy conservation movement during 20^th C has highlighted the need to optimise the thermal efficiency of openings.

There has been a historical struggle to bring the exterior into the interior, like bring in more illumination, superior ventilation, greater visual clarity and so on; however, during the last one and half century shops fronts have reversed this process, it is now how to bring out the interior to the exterior, such as how to show off maximum interior space, better perception of displayed items, greater security, etc. At another level the conflict persists on how to manage the illumination, vision and ventilation all through the same opening system, or perhaps devise a separate but compatible system.

4.2.1.2 HISTORICAL PERSPECTIVE : WINDOWS : PERIODS

Keywords: early Egyptian, Greek Sumerian or Harappan / roof holes / punctures / wall gaps / clerestory / densely populated settlements of Harappa and Rome / Egyptian temples / Mesopotamian architecture / eye in the Roman pantheon / ethereal feel / Viman / Interiors of tropical buildings / cold climates / humid climate / size and shape / Harappan main streets / Aryan and Vedic cultures / Size of a window / width / lintel, beam or arch spanning capacity / depth / wall thickness and span-width / height / Mediterranean climates / inner face of thick walls / North European buildings / outer face of the wall / colder climates / tropical climates / solar insolation / covered / translucent materials / lattice like frame work / grills / low or eye level windows / eye level windows in upper floors / demountable storm panels / multiple manageable shutters.

The concept of a window in a human habitat is comparatively a later phenomenon. The most primitive opening system functionally distinct from a door, was a hole in the roof or aperture in upper part of the wall. Its primary function was to let the smoke escape, and later on it was also recognized as a source of light. Early Egyptian, Greek, Sumerian or Harappan architecture had no window openings. Roof holes were singular and strategically located. The size of a roof hole was structurally and climatically very critical.

Punctures were also made in upper sections of the walls. These wall gaps were simple holes or leftover spaces in the masonry at a roof junction. A sophisticated version of this was the multi layered roofing system with a gap in between, the clerestory. Though, in densely populated settlements of Harappa and Rome, where dwellings and public buildings were complex and double or more storeyed, features like roof holes, wall gaps and clerestories, for light and ventilation were not feasible.

Egyptian temples had a vertical cleavage in the wall, in front of the altar. The lower portion was covered initially by cloth or woven mats and later a shutter to form a Door. However, the upper portion, mainly used for light and ventilation, remained an open gap. In Egyptian temples clerestory openings by split level slabs were added to brighten up the ambulatory space around the main hall. The concept of a window as an opening was also not clear in Mesopotamian architecture, 'the tall doorways normally sufficed to admit light, ventilation was contrived by terra cotta pipes carried through the vaults.'

An aperture in the roof or upper part of a wall such as the 'Eye' in Roman pantheon dome created very dramatic illumination. In many civilizations upper level openings signified the entry point for the super powers, high spirits or gods. Upper level lighting gives an ethereal feel to the space, best described as 'Viman' temple (Ranakpur, Rajasthan) in Indian architecture.

Interiors of tropical buildings remained essentially dark, even with the advent of roof holes and clerestory openings. Darkness or less light in a room meant less gain of heat. Whereas, wind catchers of Pakistan and other arid regions provide for ventilation, but without illumination that is heat gain. A North European cold climate requires more heat gain and hence there was a very rapid adaption of a window. In humid climate, upper level apertures or windows do not provide the required work or body level air movement, so a door like or low level openings are preferred.

Size and shape of openings vary from region to region mainly due to the differences in climates. Harappan main streets were bereft of any openings, doors like openings were placed on courtyard face of the house. Compared to this, later Aryan or Vedic cultures had very distinctive life style of open and semi-covered living, obviating any need for the opening systems.

Size of a window was governed by three factors. Width of the aperture in a wall was, restricted by the lintel, beam or arch spanning capacity. Depth perception of an aperture was related to wall thickness and span-width. Apertures in thick walls seem to be deep and small. Height of a window aperture was never a major structural problem, but was left unexplored for a long time.

In Mediterranean climates where summers are warm, winters mild and sky conditions mostly bright, the windows were placed on the inner face of thick walls. Against this, windows in North European buildings were placed on the outer face of the wall, to trap heat like a green house. For the design of a window, in colder climates, the entry of light and heat while excluding the breeze, and in tropical climates the entry of breeze and light, while excluding the heat gain are the important factors. In tropical areas heat gain is reduced by smaller size of the opening, dispersing the openings, and by means of latticed cover over the opening. Deep verandahs, chhajjas, awnings etc. help to reduce the heat gain by cutting the solar insolation. In colder climates the cold breeze is avoided by the upper level placement of openings, indirect openings and by closing the opening with translucent or transparent material.

Window openings either were open or covered with translucent materials like: leather, parchment, thin marble slabs, plates of alabaster, fabric, woven matings, cast glass, etc. Window units were divided into several sub parts to fit in the small sized and fragile covering materials. The lattice like frame work reduced the span of the lintel and provided security. Where lattice work was not strong and small enough for security additional grills were attached to the adjoining masonry structures. For reasons of security, privacy and street level noise, low or eye level windows, were not favoured, except in very private courtyards. Roman multi-storeyed dwellings had eye level windows in upper floors only.

In cold climates windows were covered with translucent materials, but with a few open sections that were adequate for ventilation needs. In warm climates, windows required more open sections or open-able sections. But in mixed climates windows with open-able sections were required. Doors like inside shutters were used to close a window. For high-level windows these were difficult to operate from inside or outside. Old Japanese houses prone to frequent hurricanes had demountable storm panels. Windows consisting of multiple manageable shutters came in very late.

4.2.1.3 HISTORICAL PERSPECTIVE : WINDOWS : RECENT

Keywords: EARLY INDIAN ARCHITECTURE / Harappa period / woven matt walls thatched roof / mud filled terraces / roof holes / Gupt dynasty / Rath / Hindu temples of stone / Mandala / four cardinal points / circumbulatory or pathway / Parikrama or Pradakshina / windows on sides / backside window / South face opening / open or lattices on sides / BUDDHIST ARCHITECTURE / miniature chaitya / Ajanta chaitya windows / hermitages like Nalanda, Taxshila, Elora / harappan labourer's cell / chaitya motifs / style statement / VASTU SHASTRA OPENINGS / revival of Hinduism / Veda / Vastu shastra / palace complexes / temple complexes / large buildings / courtyards / small dwellings / chowk / interior windows / articulated surrounds / sill ledge / Gavaksh or Gokh / Indian window / installing minor deities / aedicule / microcosm / an abode / ground floor windows / upper floor windows / protection bars / lean out and see sideways / chhajja / ISLAMIC INFLUENCES / Gokh or Gavaksh / niche / balcony or gallery / Northern parts of India / Zarokha / Ghori / verandah / a private domain / public street facing windows / conservative Mughals and Rajputs / low-level seat-out facility / MUGHAL ARCHITECTURE / chhatri, barasati, roof facilities / half or truncated forms / jali or lattice / small clear openings / Hawa Mahal, Jaipur.

BRITISH RAJ PERIOD / Kothi or Bunglow / double window / awning or chhajja / floor level activities / folding type fly mesh shutters / double hung sash windows / verandah door / higher sill level openings / tapered ledge / outside tapered ledge / inside sloped sill / ceiling level ventilating apertures / awning casement shutter / shutter less latticed opening / transom lites / top hung awning casement shutter / coloured pieces of figured glass / Venetian shutters / Chettiar houses of Tamil Nadu / Government offices of Calcutta.

BYZANTINE ARCHITECTURE / puncture like windows / clear surface of the massive walls / bands of marble and glass mosaic / sparsely spaced windows / interior walls / clerestory / ROMANESQUE ARCHITECTURE / colonnades and piers / jambs or sides / a series of receding moulded planes / rounded arch / receding concentric rings / fluted pier / triforium clerestories / wheel shaped window / rose window / Early Medieval period / Romanesque semicircular arched opening / semi circular arches / pointed arches / interior space that was tall and vertical / sloping intrados / inclined sill / surrounded by a border of slender shafts/ GOTHIC ARCHITECTURE / pointed arch / buttress / sub frames of transoms and mullions / tracery / cusps / floral form / late Gothic or Flamboyant style / shafts / flutes / stained glass / mosaic or paintings in oil or stucco / enlargement of the windows / different widths / same floor height / early English Gothic period / lancet windows / Decorated period / circles / flamboyant tracery / Perpendicular style / latticework grid / rational use of building materials / Gothic 'Lantern church' / perpendicular windows / Spain and Italy / Roman style wall with punctured windows / square headed / Spanish architecture of late Gothic era and early Renaissance / composite facade style / TUDOR STYLE / Perpendicular style / Elizabethan architecture / Europe classical revival / Gothic Revival / Tudor style buildings / distinctive features / oriel windows / overhanging windows / Hardwick hall / false windows / lead cames / casement windows / false windows / lead cames / casement windows / RENAISSANCE STYLE / cultural and artistic movement / symmetrical and proportioned / early part of Renaissance France / Post industrial revolution period / chimneys and glazed windows / Elizabethans / glittering expanses of glazing / Greek and Roman antiquity / 'Mannerist phase' of Renaissance / Palladian arch / Germany / Spanish / Italy / rusticated masonry or moulded bands.

BAROQUE ARCHITECTURE / wall surfaces / curved, undulating and highly ornamented / sash windows / English Renaissance / astylar treatment / quarry-faced ashlar / breast-moulding resting on consoles / Mannerist phase / static composition / one perspective of observation / dynamism. / ROCOCO / Baroque style / French style / neoclassicism.

PALLADIAN ARCHITECTURE / Andrea Palladio's / Palladian or Serlian window / PALLADIAN WINDOW / Italian architect Palladio / Palladian motif / Venetian window / Serlian window / Sebastiano Serlio / Philip Johnson / Andrea Palladio / Roman Renaissance style / Le antichità di Roma / Palladianism / I Quattro libri dell'architettura / Inigo Jones / Christopher Wren / Thomas Jefferson / Palladio's architecture / GEORGIAN STYLE / early Georgian architecture / regular style / later phase of Georgian style / Federal style architecture / Colonial Revival / Neo-Georgian / VICTORIAN ARCHITECTURE / REVIVAL OF TUDOR STYLE / Victorian period.

Historically windows have been distinctive architectonic elements with the peculiar style or the era. The style represents the vernacular culture, materials of the region, and technological virtuosity. It also reflects the outside influences, political conditions. An architectural element as style comes into being by being the most pertinent solution at the time and so widely accepted. Styles have flourished as a fashionable element of the rich and famous.

EARLY INDIAN ARCHITECTURE: Residential buildings of the Harappa period were made of rooms or cells around a courtyard. The door was the main opening for the room for entry-exit, light and ventilation, obviating the need for a formal window. This was a common feature in all domestic buildings across cultures of the time. In the Indian subcontinent the built structures were perhaps small in size, as the climate permitted outdoor living during substantial period of the year. In interior spaces the woven matt walls and thatched roofs allowed the smoke to escape, and some light to penetrate. In case of mud filled terraces, roof holes were placed for the same purpose. The formal window arrived, perhaps between 12^th and 8^th BC, as strategic gap in the wall, 'more to connect to the outside then for illumination'. No temples or such other structures of period till the Gupt dynasty have survived. The temples were either mobile structures like Rath or fixed structures, but both made of wood.

The first indication or recognition of an opening other then door comes with the Hindu temples of stone that began to be built from 1^st C AD. These were conceptually based on the Mandala -the square, with four cardinal points. The openings were oriented to the cardinal points. The Garbha Grih, the inner sanctorum had no other openings except the front door, for which East was the favoured direction. However, an inner sanctorum had a peripheral corridor, a circumbulatory or pathway around the deity for Parikrama or Pradakshina. This path was day-lighted by windows on sides, but a backside window was considered equal to a South face opening and so not preferred. The main prayer hall of the temple was columned structure with open or lattices on sides. The lattice allowed the breeze to pass through and reduced the glare. In some instances the latticed gap was covered by deep chhajja projections, completely obviating the need for a window.

BUDDHIST ARCHITECTURE: Stupa and monasteries were mostly executed during 2^nd C BC and 5^th C AD, some 400 to 1000 years after Buddha. These buildings were either non residential or 'Spartan' -cells for a hermitage and have an opening for entrance but have no door or windows. The sculptural remains at Pitalkhora (2nd Century BC to 1^st C BC) include animal motifs, miniature Chaitya windows, elephants and guardians, and Yaksha figures. The Ajanta Chaitya opening carved in stone is very similar to the contemporary Byzantine openings with a lattice like a framework in stone. The rooms in educational campuses and hermitages like Taxshila, Nalanda, Elora, etc. were barely functional and without the luxury of a formal window, almost like a Harappan labourer's cell. Similar Chaitya motifs have been found in sculptures and wall frescoes at many places. The Chaitya as a wooden architectural window or its representations prove it to be a style statement of the age. Lot of literary references to life styles of the rich and the famous of the 4^th and 5^th C AD, are available, but with little description of the dwelling environment or structure. Life style, was perhaps, a 'matter of what artefacts (clothes, ornaments) one possessed or adorned, and not the space one stayed in'.

VASTU SHASTRA OPENINGS: From 5^th C AD onwards a revival of Hinduism, against the politically favoured Buddhism occurred. Temples were now built of more permanent materials like stone. This was a period where temples of both North and South of India show adherence to traditions prescribed in the Mandala concept of Veda and the Vastu Shastra. This period also saw execution of large palace complexes, but mostly in perishable materials. Large temple complexes with fortifications, gates or Gopuram were patronized by Srenis or Mahajans.

Large buildings now had the courtyard and small dwellings had chowk as the focus of all opening systems. The chowk or courtyards were abutted by verandahs, which provided access to rooms or other sub courtyards. Openings into verandahs or interior windows were not only well suited for the climatic demands, but were functional and safe. Interior windows were perhaps latticed and without shutters, though covered by cloth or woven mat. The interior and the exterior windows were distinctly marked, like the door, with a heavy surround. The articulated surrounds increased the apparent size of the opening. On the interior side the deep-set window offered a sill ledge to keep small things like combs, hair oil, adornments and oil lamp for night illumination. Similar sill ledges were also available over the niches in the walls, and were called Gavaksh or Gokh. The Gavaksh as a form was the forerunner of the Indian window. Gavaksh was used for installing minor deities on internal and external walls of the temple. A Gavaksh was treated like an aedicule (a minor shrine) of Greek or Roman architecture, a microcosm, an abode for the minor god.

Ground floor windows had a taller sill compared to upper floor windows. Low sill upper floor windows had protection bars up to safe or half height. The protection bars were mounted on the outer face or even beyond so that one can lean out and see sideways. The window also had a chhajja as a weather shed. The overhanging chhajja was supported by brackets projecting out from the window surrounds.

ISLAMIC INFLUENCES: During 8^th and 11^th C AD the Hindu architecture reached its classical peak. Architectonic elements were well articulated. The Indian Gokh or Gavaksh form of articulated niche or wall storage space, was now more of a window form. The concept of balcony or gallery was exploited as a Zarokha in palatial residences and public buildings across Northern parts of India, perhaps even before the Ghori invasion.

The Zarokha in many ways compensated the need for a verandah. Zarokha provided a private domain, accessible to the particular room, compared with a verandah which provided little in terms of privacy. Public street facing windows were now appended with Zarokhas. The Zarokhas were also covered with a lattice to reduce glare and heat gain. Latticed balconies were readily adopted by the conservative Mughals and Rajputs to provide the privacy for their women folk. Zarokhas had no window like shutters, but rather a door like solid leaves on the inner-face mainly for security. The sill ledge and the parapet of the Zarokha both were of low height, scaling it to a low-level seat-out facility.

MUGHAL ARCHITECTURE: The Zarokha, Gavaksh and such window forms were further refined in not only Mughal-sponsored architecture, but across India in buildings by other faiths and for other purposes. Chhatri, barasati, other roof level facilities, though not window systems, their half or truncated forms were used in the Zarokha. Large openings were appended with half Chhatri form, made up of two delicate columns and a partly pyramidal roof of straight, concave or convex surfaces. Another important element to mature was the Jali or Lattice as a screen filler element between columns. The jalis were made of sand stones, marbles or wood, carved with geometric or floral patterns. Jalis were strongly divided by mullions and transoms. Jalis were punctured with small clear openings such as in Hawa Mahal, Jaipur. Jalis were primarily used to curtail the glare but were also used to cascade the flowing water from fountain channels to moisturize the air. Jalis were used to separate out women's area in residences, mosques and other places of public gathering.

BRITISH RAJ PERIOD: During the British (and Dutch, French. Portugese) colonizations in India building designs were refashioned to suit their perception, attitudes, functional and climatic needs. The Kothi or Bunglow though built through local materials and techniques and conceived for the tropical climate, had elements that satisfied such needs. The designs provided few new solutions for the local conditions so found immediate and wide acceptance among the local gentry. The double window was one such element replacing the Zarokha openings. The double casement window had top and bottom sections each with double leaf shutters. It was similar to a Dutch door. It became a standard feature of many Indian residences and public buildings. The upper section was sufficiently protected by the awning or chhajja, and so could be kept open in all seasons. The lower section was opened in the evenings for the breeze over the floor level activities. It also allowed one to look out while seating on the floor or resting on the bed. The shutters were shelf-pivot hung or sides hinged, mostly opening to outside. Another set of folding type fly mesh shutters, opening on the inside, but within the wall thickness was also provided. This was a period when across the Europe and USA double-hung sash windows were a rage. Yet nowhere in India sash windows have been exploited.

The verandah door was a major and very effective opening for a room like a French door or window. In addition to the solid wood plank door, it had auxiliary shutters with either fixed Venetian slats or a fly mesh.

Store and other minor rooms were provided with higher sill level openings but with a tapered ledge on the outside or inside. The outside tapered ledge allowed clear view of the street below, whereas the inside sloped sill allowed more light. Across Northern India, rooms had ceiling level ventilating apertures, with awning casement shutter or a shutter less latticed opening. Doors and windows also had transom lites, with a top hung awning casement shutter in square headed openings and arched heads fixed panes of coloured pieces of figured glass with radial muntins were used.

Tall windows reaching from floor to ceiling level had to be avoided for reasons of rain and solar gain. However, windows were masked with Venetian shutters -with fixed but open louvers on exterior face such as in Chettiar houses of Tamil Nadu and Government offices of Calcutta, West Bengal, to curtail the glare while allowing the breeze. The intricate wood joinery did not work well with the long and heavy monsoon. Similar Venetians shuttered windows were used in Eastern India, Neighbouring Burma and other countries of SE Asia.

BYZANTINE ARCHITECTURE: Byzantines' architecture followed the Roman tradition, and continued to construct 'puncture like windows' without breaking up the clear surface of the massive walls. Windows though well coordinated in placement were independent of each other. The self sufficiency was provided by the large plain mass between them and also by the strong divisions through heavy mullions and lattice like frame work. Externally the windows were devoid of any decorative attachments. From inside these were harmoniously placed with reference to archways, domes, etc. Internally the windows and other architectural features were all linked by continuous bands of marble and glass mosaic (which was rendered opaque by oxide of tin). The bands made help merge the inter-window surface planes, reducing the compartmental effect of lighting due to sparsely spaced windows. Later, on the exterior-face several architectural features such as the chamferred corners were added to increase the interior illumination, and also to give an illusion of larger size for the window than there actually was. On interior walls, other decorative elements like, the wall paintings, statuettes, carved niche, alcoves, colonnades, etc. replaced the marble and glass mosaic bands. Upper level openings such as the clerestory in the drum of the dome provided high level of reflected lighting to the interior space compared to lesser number of openings in the lower section.

'The problem in the East was to exclude rather than to admit light, and windows were therefore small, so as to make the interior restful and cool. Contrasting with the external glare of the Eastern sun large unbroken wall spaces were available for brilliant mosaic pictures. Windows were also occasionally formed of a thin frame, three ins. thick, of translucent marble, filled in with glass and creamy, golden-hued alabaster, which the brilliant sunshine wrought into colour like stained glass. The Gothic architects of Northern Europe, where large windows were necessary due to dullness of the climate, adopted a translucent scheme of decoration by means of painted glass pictures in the large traceried windows instead of sheathing their walls with mosaics.' History of Architecture, Fletcher.

ROMANESQUE ARCHITECTURE: Romanesque architecture openings like windows were overshadowed by the colonnades and piers, but the areas adjacent to the openings became very articulated. Jambs or sides were formed of a series of receding moulded planes. The rounded arch above was also constructed with receding concentric rings following the lines of the recesses of jambs below. The Romanesque fluted pier first replaced the Greek-Roman column and later the capitals and entablature. Two or three floor high -triforium clerestories were created to lit up the interiors and manage the semicircular openings. Several windows with semicircular heads were sometimes grouped together and enclosed in a larger arch. Windows often head a central support element in the form of a column or a pier. A wheel shaped window placed over the main West door later became the Rose window, as at S. Zeno Maggiore, Verona and in South Italian churches, as at Palermo.

Up to 800 AD., i.e. Early Medieval period, windows were small in proportion to the entire area of the facade. Many different forms of windows began to emerge with local influences and materials enforcing the changes. The window openings were at first filled with mainly wooden boards, and also with thin sheets of marble, alabaster, gypsum, wooden boards with pierced holes filled with coloured glass. Opaque glass, almost like a glass-ceramic mosaic was used. Thin strips of alabaster set in a bronze frame were also used. The size of the window was functionally bare minimum, and the glass surface small, so it provided adequate light but not the heat gain that was required in North European climates. Windows gradually began to fill the Romanesque semicircular arched opening. Internally the structure was framed, and external walls began to carry loads at the base points of arches. Semi circular arches began to be replaced by pointed arches, which though reduced the span of opening, also reduced the thrust on the pier. Closely spaced light piers and pointed arches created an interior space that was tall and vertical.

Up to the 12^th C the windows of the Romanesque churches had small openings, but for additional gain sloping intrados, and inclined sill were used in thick walls. Originally the openings were without decoration but later received a framework that is they were surrounded by a border of slender shafts. The round shafts had small bases and capitals. The intrados were divided at rectangular intervals by setting up of small columns. Windows were clustered under a circular arch. The surface over the windows but within the arch which had remained flat and without ornamentation now was pierced with small circular openings.

GOTHIC ARCHITECTURE: The pointed arch and buttress system made the external wall virtually non-load bearing. Between the piers and buttresses, windows occupied all the space of the wall face, so were broader and longer. Large windows had sub frames of transoms and mullions, to make them stable against wind pressure, and also to support the leaded glass panes. The mullions almost rose to the base point of the pointed arch, and often went up further up and turned into a pattern called tracery. Tracery is formed by merging separate parts of a circle called foils, at points of contact called cusps. Tracery was primarily used to change the linear character of the sub-frames into a floral form. The tracery filled the upper section of pointed arch opening with new patterns, simple in the early periods but very complex and often confused in later periods. During the late Gothic or Flamboyant style the tracery patterns surpassed circles and segments of circles and became wavy like the flames. However, towards the end of the Gothic period greater sobriety of form came into use and tracery began to decline.

The articulation of the tracery was running parallel to the changes in the column's shafts, and flutes on the sides of the windows and intrados (an inner curved surface of the arch). On interior side, the surface of the openings and the shrunk wall were nearly in level, to keep the 'story board' continuity of the stained glass. Stained glass replaced the traditional wall treatments like mosaic or paintings in oil or stucco. In the evolution of Gothic architecture the progressive enlargement of the windows was not intended to infuse more light into the interiors, but rather to provide an ever-increasing area for the stained glass.

By varying the pitch of the pointed arch windows of different widths were fitted within same floor height. On the exterior face, the side walls were often thin, so flutes and shafts became very slender, but on the front or west side entrance face the small capitals over the shafts were discarded, the shafts and the intrados flutes became one, and formed a tapered opening gap.

Buildings in the early English Gothic period have simple lancet windows arranged either singly or in groups. In the next phase, the Decorated period, the windows are much larger and in the tracery of the windows the circles were omitted. Use of patterns with double curvatures developed into flamboyant tracery. In the later period (1350 C), with Perpendicular style, the stonework of the windows forms a kind of latticework grid, such as the cage of stone and glass interior of Gloucester Cathedral. In this period the elaborate tracery is no longer seen, and the lines on both walls and windows are sharper and less flamboyant.

Gothic architecture saw very rational use of building materials. Materials were imported from far off lands at great cost, so were used judiciously. Stone mullions and column shafts were very thin. Marbles were exposed for their grain.

Gothic 'Lantern church' was formed with perpendicular windows rising from floor to vault, but this was not a suitable style for other buildings like palaces, colleges, etc. In Northern parts of Europe larger openings were useful in depicting the stories of The Bible in church, but in other non religious buildings this was not the requirement. Large windows were also not required in sunny parts of Europe like Spain and Italy. This led to revival of Roman style walls with punctured windows. Windows were once again square headed, comparatively small, multi-functional, eye levelled and easy to merge into variety of interior treatments. These windows were abutted with pilasters, half columns and also by offset arcade of full columns. In Spanish architecture of late Gothic era and early Renaissance, the window and its appended decorative elements created a composite facade style.

TUDOR STYLE: The Tudor style (1485- 1603), a local style of architecture developed in England, Wales and Ireland, during a period of peace and prosperity starting from 1485. It was more distinct in domestic buildings then in ecclesiastical buildings. It followed the Perpendicular style and superseded by Elizabethan architecture. Though at the same time elsewhere in Europe classical revival was thriving. Tudor style in later stages overlapped with the first stirring of the Gothic Revival.

Tudor style buildings have the following distinctive features: decorative half-timbering, steeply pitched roof, prominent cross gables, tall and narrow doors and windows, richly patterned brickwork, beginning of small window panes, large chimneys, often topped with decorative chimney pots, projected upper floors and use of oriel windows. On the interior side walls were richly panelled in wood and ceilings had moulded plaster work. Despite the risk of fire the buildings were timber-framed structures.

Tudor houses of the merchants and artisans had shops or workplaces on the ground and living quarters on the upper floors. With prosperity the houses were rebuilt at the same place but by projecting the upper floor over the street. The overhanging windows of the sides of the street almost met resulting in extremely dark streets.

Windows of Tudor houses of the poor were covered by horn or wooden shutters, but rich began to use the expensive glass, after realizing its effect of at Hardwick Hall. Hardwick hall was considered 'more glass than wall'. Windows were stretched on elevation to illuminate two rooms on two different storeys. Large size glass windows made interiors lighter and airier. False windows -glass facades were used to conceal chimneys. Small pieces of glass were joined by lead cames in crisscross or lattice patterns to form a larger pane. Glass pane windows were casement windows, hung by hinges and opened outwards.

RENAISSANCE STYLE: During the period 15^th C to early 17^th C, in various regions of Europe a cultural and artistic movement occurred to revive the values of Greek and Roman cultures, first in France and Italy by people like Dante, Boccaccio and Petrarch. In England the period was marked by Shakespeare and Elizabeth. The initial movement soon spread to art and architecture.

Renaissance architecture was symmetrical and proportioned compared to the asymmetrical and complex Gothic architecture. Irregular profiles of the medieval buildings began to be replaced with 'order' columns, pilasters, square lintels, triangular pediments, semicircular arches, hemispherical domes, niches with sculptures and aedicules (a small shrine), and symmetrically arranged windows and doors. Gothic and Renaissance coexisted for several decades, but in later periods the renaissance followers were staunch adherents and very hostile to other nonbelievers.

In early part of Renaissance some effects of Gothic elements continued to persist. In France, the picturesqueness and preference for Gothic verticality influenced the position of doors and windows, rather than the functional needs. Two windows were placed under a circular arch divided by a shaft. The openings began to have more surrounding ornamentation than within them like the earlier Gothic. The surrounding ornamentation showed the openings more prominently over the facade. Exteriors though truthfully reflected the interior space modules, but very rarely the function. The facade began to be a mask. The make-believe continued till it was despised as vulgar in the Post industrial revolution period.

The development of mathematical or linear perspective changed how paintings were composed. The painting was regarded as a window on the world. Rendering of landscape in paintings with natural and architectural elements became a new fad. Objects like trees, flowers, plants, distant mountains, and cloud-filled skies were carefully depicted in perspective scale, effect of light and eye perception.

Interest in Renaissance features was largely confined to the educated and wealthy elite, but it pervaded to the common man in the form of environmental improvement through chimneys and glazed windows. Houses became lighter and cleaner and had more private space. Elizabethans (early renaissance in England) delighted in glittering expanses of glazing. Within such day-lighted spaces there would be elaborate fireplace surrounds, square panelling, friezes and ceilings decorated in strap-work -patterns imitating interlaced leather straps.

In the second phase of the renaissance more documented evidence, as published works, on Greek and Roman antiquity was available. Many artists, architects and scholars had started visiting Italian towns. 'Towards the middle of the 16^th C such architects as Michelangelo, Baldassare Peruzzi, Giulio Romano, and Giacomo da Vignola began to use the classical Roman elements in ways that did not conform to the rules that governed designs in the early Renaissance. Arches, columns, and entablature came to be used as devices to create dramatic effects through the manipulation of depth and recession, asymmetry, and unexpected proportions and scales. This was the 'Mannerist phase' of Renaissance. Architect Andrea Palladio though not a Mannerist, explored many variations on classical norms. The Palladian arch became popular.

Renaissance affected every region of Europe differently. In Germany the Oriel windows were used projecting both from facades and angles of buildings. In German window composition was repeated to create a strong linear facade. Spanish renaissance arcades had extensive decoration. Windows were flanked by small columns on corbels and framed in richly carved stonework. Ground-floor windows had characteristic Spanish cast iron grilles. In Italy the facade was like a woven fabric, with eaves, sills, pediments, pilaster, columns, doorways, rusticated masonry or moulded bands, etc. Windows were adorned with galleries and balustrades. Buildings were topped with statues, lanterns, domes, drums, accentuating the vertical lines of the window opening. Florentine architect Leon Battista Alberti, used pilasters instead of engaged columns to divide the facade, and set the windows within them.

BAROQUE ARCHITECTURE: Baroque style which emerged in the later part of Renaissance, many conventions were removed. Wall surfaces instead of being linear now began to be curved, undulating and highly ornamented. Window openings were often oval, circular but deeply recessed. Vertically sliding window or sash windows were favoured for the ease of opening and controlled ventilation. Sash windows had rectilinear subdivisions, and filled with better quality see through clear water-white glass. Sash windows' frames were painted white, and placed in brick masonry work as in later English Renaissance. In Baroque buildings a return was often made to the astylar treatment (avoiding the side pillars, pilasters near the opening gap), from the exaggerated details marking the door and window frames. Door and window openings were surrounded by simple quarry-faced ashlar. Though in costly buildings the windows had an ornamental finish, either a breast-moulding resting on consoles or a panel surrounded by a frame or carried by supports. The attic was not common and 'the top windows were often set in a deep frieze or between consoles supporting the main cornice'.

In early Renaissance and later in Mannerist phase, the architectonic elements were balanced as a static composition, from one perspective of observation but it soon gave way to more dynamism. The spaces were articulated to be a series of interconnected experiences. The architectonic elements lost their individual standing.

In Italy, Michelangelo and Palladio inspired a host of artists. In England Inigo Jones with Italian and Sir Christopher Wren under French influence dominated the scene. Windows and other openings became flat-headed instead of arched, to suit the level ceilings of dwelling-rooms. The sash windows in this flat headed openings, placed almost flush with the outer face of the walls, were painted white to form a contrasting colour scheme flanked by green shutters and the red brickwork.

ROCOCO : It developed as a reaction against the heavy Baroque style. It was known for its feminine curves, intricate designs, and flamboyance. It was emphasized by intricate details, very light pastel colours, and lighter style of architecture. Rococo architecture also brought many improvements to buildings: 'sanitation was improved, chimneys were made more efficient and rooms were better organized to offer more privacy'. In the 1730's the movement became widespread in southern Germany and Austria in the churches and palaces. Though it did not do as well in other countries as it did in France, where it became known as the French style In the second half of the 18^th C, Rococo style gave way to neoclassicism.

PALLADIAN ARCHITECTURE: Palladian architecture is a style of architecture popular across Europe in the 17^th and 18^th C, based on Andrea Palladio's interpretation of classical Roman temple style. The chief element of Palladian architecture has the window motif called Palladian or Serlian window, the later name was given for the designer who popularized it.

PALLADIAN WINDOW: A Palladian window is a large window that is divided into three parts. The mid unit is an arched opening and wider, whereas the side units are narrower and flat headed at the springing line of the arch. Named after the Renaissance period Italian architect Palladio, a Palladian window is a classical, well proportioned and symmetrical architectural entity that are used as a window as well as a motif. A Palladian motif is placed as an opening gap in an exterior passage or as part of a colonnade, such as in Basilica Vicenza, Italy. The gap has a central arched opening, supported by columns which are offset from the wall thus creating two smaller width gaps on sides. Palladian motifs were placed as entrance porticos but Palladian windows gradually began to be placed at second story, over the entrance doors as the focus element of the building's facade. This is characteristic of the Federal style, but has also been used on other buildings from Victorian to modern times.

Palladio worked in the Venice region, so the Palladian window is also called a Venetian window. It is also called a Serlian window, because it was mentioned in the writings of architect Sebastiano Serlio. Palladian windows made a comeback during the Post-Modern era. Architect Philip Johnson used it as a doorway (for University of Houston College of Architecture building -1985 and at the Museum of Television and Radio building -1991, New York City; saying said 'I think Palladian windows have a prettier shape. I wasn't trying to make any more important point than that'.

Andrea Palladio: Andrea Palladio, an Italian is regarded as the greatest Renaissance architect of 16^th C (1508-1580). As a youngster he was apprenticed to be a sculptor, and then worked as a bricklayer and stonemason. He later worked in workshops specializing in monuments and decorative sculpture. He was inspired by the ancient Roman architect Vitruvius (46-30 BC). By 1541 he had assimilated the Roman Renaissance style and began to design villas across Italy. During his stay in Rome (1554-1556) Palladio in published Le antichità di Roma The Antiquities of Rome, which for 200 years remained the standard guide book to Rome.

From the 17^th C Palladio's interpretation of this classical architecture was adapted as the style known as Palladianism. Palladio's work is strongly based on the perspective and his elevations reflect the axial emphasis and symmetry. It represents the formal classical temple architecture of the Ancient Greeks and Romans. At the end of 20 years of intensive building, Palladio in 1570 published I Quattro libri dell'architettura (The four books of architecture), a treatise on architecture. This work was a summary of his studies of classical architecture. He used a number of his own designs to exemplify the principles of Roman design. It popularized the classical decorative details including studies of materials, the classical orders, and decorative ornaments. It became the most influential architectural pattern book ever printed. Inigo Jones translated Palladio's books into English, Christopher Wren and later in USA Thomas Jefferson were inspired by Palladio's writings. The influence of Palladio's buildings and publications continued in 18^th C across Europe, USA and many other parts of the world. Palladio is one of the most influential figures in the whole development of Western architecture.

Palladio's architecture: Palladio designed his buildings in terms of not only facade proportions but the plan proportioned as a shape. He believed that parts of a house must correspond to the whole and to each other. Palladio built his projects from bricks plastered with stucco rather then stones clad with marbles like his contemporaries. The ornate capitals were made of terra cottas. The pediments and architraves were made if wood covered with straw lathing and then stucco. He avoided using, the then popular tapestries, to cover the interior walls and instead applied frescos.

GEORGIAN STYLE: In England, Georgian style refers to the architecture and extending from 1714 to 1820. In America, Georgian refers to the architectural style of the English colonies from about 1700 to the American Revolution in the 1770. Baroque style was exclusively used in palaces and churches but Georgian style was used for the upper and middle classes residences.

In England, early Georgian architecture was strongly affected by the well proportioned and designed work of Palladio. This was against the Baroque style which was excessively decorative. In this phase large houses and public buildings were fronted with massive pediments and colonnades inspired by ancient Greek and Roman temples. Simple mathematical ratios were used to determine the height of a window in relation to its width or the shape of a room as a double cube. A regular style implied symmetry and adherence to classical rules. House fronts along a street were identical, designed with Georgian proportions and employing a decorative vocabulary derived from ancient Rome or Greece.

Later phase of Georgian style was more varied. Within a symmetrical exterior, the interiors were styled to Rococo Gothic revival, Chinese, Indian and other exotic effects. Robert Adam to develop the concept of an integrated interior with walls, ceiling, carpet and furniture all designed as a single scheme, borrowed Byzantine, Italian Baroque, Etruscan motifs and from ancient Greece and Rome.

Georgian Architecture also spread to English colonies of the time. In the American colonies, it became known as Federal style architecture. American Georgian houses typically have well-organised facade with 5 multi paned windows on the first floor and a central colonnaded entrance door on the ground floor. Main windows of the house were larger with 9 or 12 panes, and for dormers small 6 paned sash windows were used.

After, about 1840 Georgian conventions were abandoned in favour of various revival styles including Gothic. Multi-pane windows were not placed closely, so never paired. In the United States this style declined in favour after the revolution, due to its association with the colonial regime. However, it once again was back as the Colonial Revival during the first half of the 19^th C. In Britain the revived Georgian style is referred to as Neo-Georgian.

VICTORIAN ARCHITECTURE: The term Victorian architecture can refer to several architectural styles that were predominantly employed during the Victorian era (1837-1901). This type of window was also used in Victorian Architecture skylights and became even more popular in metal construction with the advent of sheet-metal shops during the Victorian era.

REVIVAL OF TUDOR STYLE: Tudor revival occurred in 1800's, and persisted through the mid 20^th C. Tudor and Elizabethan styles enjoyed a revival in the Victorian period. Tudor revival style used timbers and exposed purely in a decorative manner. The homes of Tudor revival style were supposed to evoke medieval cottages, with features such as overhanging upper floors, mullioned and narrow windows and solid wood doors.

4.2.1.4 HISTORICAL PERSPECTIVE : WINDOWS : TYPES

Keywords: INDUSTRIAL REVOLUTION AGE / INDUSTRIAL REVOLUTION AGE / revival styles / cast iron, wrought iron and mild steel / Portland cement / new structural configurations / building facades of steel and glass / deeper / larger footprint / mullions and transoms thinner / columns and beams / standardization of sizes, shapes, materials and hardware / steel rolled sections / new windows' configurations / casement windows / sash windows / old opening styles / planning attitudes / main facade / climatic orientation / functions inside / localization and customization / internal treatments to openings / mass produced / personalization or exclusivity / ready to use components / ARTS & CRAFTS MOVEMENT / Industrial revolution / England / Aesthetic Style / British movement / Grammar of Ornament / Art Nouveau / American Arts & Crafts movement / Mission style / ART NOUVEAU / clutter and eclecticism / natural forms / sinuous curved lines / windows were shaped with curvilinear shapes / masking grill / free flowing asymmetrical forms / glass decoration / Jugendstil / Sezessionstil / Modernista / Stile Liberty / Stile Floreale / FRANK LLOYD WRIGHT / Queen Anne style / Victorian inspiration / Prairie house rectilinear window design / darkened space below the elongated eaves / negotiate corners / box like Victorian architecture / double hand sash window / long casement shutter / medium for stained glass patterns / modernist movements William Morris / Louis H. Sullivan / opalescent picturesque effect / Tiffany / John La Farge / Japanese Shoji screens / wood muntins / colourless frosting / LE CORBUSIER / struggle for illumination / opaque surface / shimmering plane / dull surface of the structure / separate ventilation system / glazing plane directly into the masonry / Ronchamp and Shodhan Villa / ribbon windows / Villa Savoy / brise-soleil / mechanical baffles / masonry and cement concrete brise soleil / daylight was a living light / artificial light / distribution of daylight / interior plane adjacent to the window / right angle wall or ceiling / slit windows / parabolic reflectors / picture windows / apertures or cut-outs in ceilings / MIES VAN DER ROHE / FLW -walls to define the opening / LC -walls adjacent to the opening as a reflective plane / give shape to space / vertical cutouts or vertical connections crime of ornamentation.

INDUSTRIAL REVOLUTION AGE: The period of late 18^th C marked the last phase of Revival styles. The Industrial scene was fast changing, offering new materials and technologies. Cast iron, wrought iron and mild steel were being produced economically and qualitatively. Portland Cement was developed in 1824. First applications of steels and as a composite with cement were using the old techniques of construction. But soon enough new structural configurations were devised to construct new entities like railroads, depots, shopping centres, bridges, warehouses, factories and commercial complexes. During 1850 to 1870 building facades of steel and glass virtually eliminating the walls began to be constructed. The daylight illuminated interiors of glass fronted buildings along with changes in of fuels for home warming, cooking and lighting created new architecture. Buildings could now be deeper and have a larger footprint.

The glazing for Windows was now larger, and thinner mullions and transoms. The conspicuous columns and beams began to recede from the face of the building. The shop fronts began to have full size glass. Windows units for domestic as well as commercial spaces now began to be produced in factories, with standardization of sizes, shapes, materials and hardware setting in. The demand for public housing was for cheap and quick supplies of building elements. Steel rolled sections for doors and windows began to be available. Many new windows' configurations such as the North light or saw tooth truss lighting, domed and sky lights, port holes were devised. Casement windows with friction hinges and sash windows with spring balances replacing the counter weight system, sliding-folding dual mechanisms, began to offer better control over the opening. Many old opening styles were refurnished with better technologies, typically conservatories, jalousie, bay and bow windows were redefined. Window planning attitudes also changed, till now domestic buildings had a main facade receiving a style treatment for openings and all other sides were treated with non-style, less expensive and simpler window solutions. However, in high density urban areas high rise buildings were seen from all sides and required equal treatment. The equal treatment on all sides did not respect the climatic orientation or follow the functions inside. The window was thus required to do many different things depending on its location. Such localization and customization were done by installing new internal treatments to openings.

The transition to new age was not very smooth, there was resistence to do away the time tested styling and skepticism to accept new things. Both the factors were arising due to the fact that craftsmanship was not as refined, quality assurances were not available and at elemental level the entities being mass produced were too common. The personalization or exclusivity was not available. At another level the resistence was coming from builders' and designer's, who found their roles changing with ready to use components.

ARTS & CRAFTS MOVEMENT: The Industrial revolution caused two distinct responses across the Atlantic. At one end in England opponents of industrial revolution felt that such development is separating human beings from their creativity and individualism. In this period, manufactured goods were often poor in design and quality. So craftsmanship was stressed with disregard to its cost or afford-ability. The result was exquisitely made and decorated pieces that could only be acquired only by the very wealthy. English Arts and Crafts style came to be known as Aesthetic Style. It was criticized as the 'work of a few for the few'.

Arts & Crafts movement was supported by William Morris, Charles Voysey and others, who sponsored production of handcrafted metalwork, jewellery, wallpaper, textiles, furniture, books and hand printing. The British movement focussed on the richly detailed gothic style. Their interior walls were either whitewashed or covered in wallpaper depicting medieval themes. Aesthetic ideas were also borrowed from Medieval European, Islamic and Japanese sources. Owen Jones, published a book entitled The Grammar of Ornament, which was to become a source book of historic decorative design elements, largely taken from medieval and Islamic sources. This work in turn inspired the use of such historic sources by other designers.

The movement was able to forcefully reinstate the ideal of design, and succeeded in impressing the industry to hire artists as designers. By 1910 the 20^th C design became essential component of all products. Its ideas spread to other countries and became identified with the growing international interest in design, specifically with Art Nouveau.

Whereas on the other side of Atlantic, the American Arts & Crafts movement was based on the clarity of form and materials' expression through grain pattern, colour and texture. The machines were used for lowering the cost and greater productivity.

The term Mission style was also used to describe Arts and Crafts Furniture and design in the United States. The use of this term reflects the influence of traditional furnishings and interiors from the American Southwest, which had many features in common with the earlier British Arts and Crafts forms. The result was a 'blending of the arts and crafts rectilinear forms with traditional Spanish colonial architecture and furnishings'. Mission Style interiors were often embellished with Native American patterns, or actual Southwestern Native American artifacts such as rugs, pottery, and baskets.

ART NOUVEAU: This style was concurrent with the Arts & Crafts style but was not concerned with the social reform. Instead, it addressed the clutter and eclecticism of mid 19^th C European buildings. Originating in Belgium and France, Art Nouveau designers used natural forms such as the peacock feathers, butterflies, and insects. The sinuous curved lines of grasses, lilies, vines, all arranged in asymmetrical forms were their inspirations. Forms and patterns from the past styles or from other cultures were resisted in design. Though Japanese approach to nature as depicted in their paintings was admired. Windows were shaped with curvilinear shapes and masking grill to de-form their rectangularity. Art Nouveau free flowing asymmetrical forms were used for glass decoration such as frosting, etching, grinding and stained colouring.

Although known as Jugendstil in Germany, Sezessionstil in Austria, Modernista in Spain, and Stile Liberty or Stile Floreale in Italy, Art Nouveau has become the general term applied to a highly varied movement that was European-centred but internationally current at the end of the century. Gaudi's work like that of most Art Nouveau architecture, was gained through bizarre form and ornamentation.

FRANK LLOYD WRIGHT: FLW by 1893 was an independent architect and began window designing in Queen Anne style, but soon enough began to break away from the Victorian inspiration. It was a move to the Prairie house rectilinear window design that set a direction for the next 25 years. Wright had once said "beautiful buildings I could build if only it were unnecessary to cut holes in them." This was exemplified in Prairie house windows. Windows were no longer punctures in the wall or an element of the wall, but rather began to be elements on their own. They created a visual stand, an ornamental factor, a visual interest under the darkened space below the elongated eaves. He began to open up the interior spaces with clear glass doors and windows as in Prairie houses. Wright began to negotiate corners with windows to break the box like Victorian architecture of the age. The interior spaces became one end less flow. He never accepted the then current ("poetry-crushing guillotine") double hand sash window, but used the long casement shutter stretching as a single panel, uninterrupted by any mid bars, from lintel to sill level. According to Wright the long casement shutter 'brought outside in more effectively than the double-hung sash'. The open expanse of the casement shutters, its glass and the light behind became the medium for stained glass patterns. After a European tour that exposed him to the modernist movements of the time, Wright depended on straight parallel lines and repeated use of small squares as pattern.

Wright's glass designs in an earlier phase were influenced by William Morris and Louis H. Sullivan. He, instead of the opalescent picturesque effect offered by commercial glass designers like Tiffany and John La Farge, relied more on clear glass, abstract geometric patterns and discreet colouring to create what he called 'light screens', evoking the Japanese Shoji screens. In the later part of 1920's, Wright also began to use wood muntins along with colourless frosting as tools for patterning. With the Usonian house in the 1940's, window patterns were created by perforating plywood panels and sandwiching plate glass between them. In Johnson wax building, Wright wanted to create an internal building, without any worthwhile exterior view. The glass tubes in Johnson building negotiated curves, which would not have been possible through flat glass panes. It was a highly unique glazing approach, though not efficient in actual working.

LE CORBUSIER: For Corbusier history of a window was a struggle for illumination. He typically wanted, at least in the initial years, openings to bring outside in. This was due to childhood memories of Northern Europe day lighting, inferior quality of glazing and interior spaces that had small windows and required artificial illumination often during the day time. He, as a cubist saw the glazing plane as an opaque surface slightly receding due to its placement and surface quality. Glass was a shimmering plane against the dull surface of the structure. He liked the configuration for illumination to be unbroken, and so preferred a separate ventilation system. For the same reason he did not like framing for the window. He would rather place the glazing plane directly into the masonry. This was continued in many of the later buildings like Ronchamp and Shodhan Villa Ahmedabad.

Corbusier started placing more then adequate openings, like the ribbon windows of Villa Savoy, and invited complaints from the client. The extent openings became more rational in later projects. To cut the excessive glare he began to use an architectural baffle, a brise-soleil, for the first time, in the Algerian offices blocks (1933). Later he experimented with mechanical baffles for an office building in Rio de Janeiro, Brazil, but mainly used masonry and cement concrete brise soleil for buildings at Chandigarh and Ahmedabad.

For him daylight was a living light was continuously variable, whereas the artificial light was static and local. Corbusier experimented with the distribution of daylight by positioning an interior plane adjacent to the window. The planes were first in the form of a right angle wall or ceiling, but later became inclined as well as doubly curved. Slit windows close to flat ceilings were used in many buildings. He began to use the same technique for distributing illumination of electric lights by large parabolic reflectors.

Corbusier placed openings to frame specific land views as picture windows or often just apertures. Ends of the ramps, stairs, passages, were marked by such openings. Such linking of openings was also used with apertures or cutout in ceilings. These occurred with another smaller or larger cut out below or with a water body to reflect it.

MIES VAN DER ROHE: Mies, like his contemporaries FLW and LC also realized the need to open up the interior spaces. Removal of all partitioning elements, walls, was one common strategy adopted by architects of the period. However, FLW used the walls to define the opening, but LC used the walls adjacent to the opening as a reflective plane to modulate the spaces. Mies used the walls as a simple rectilinear and planar form to 'give shape to space, open it, and link it to the landscape'. 'Without plate glass the ability of steel and concrete 'to transform space would be limited, even lost altogether; it would remain only a vague promise'.

The free-flowing interconnection between rooms and the outdoor surroundings occurred only in horizontal plane. Curiously vertical cutouts or vertical connections remained unexplored in Mies architecture. Mies found appeal in the use of, clean lines, pure use of colour, and the extension of space around and beyond interiors as expounded by the Dutch De Stijl group. In particular, the layering of functions in space and the clear articulation of parts as expressed by Gerrit Rietveld appealed to Mies. Mies' design for wall opening included a bronze curtain wall with external H-shaped mullions that were exaggerated in depth beyond what is structurally necessary, touching off criticism by his detractors that Mies had committed Adolf Loos's crime of ornamentation.

Sub Index for chapter 4.2.1.4 Historical perspective : Windows : Types

Keywords: classified in terms locations / roof level / within the wall / project out of the wall / close to the floor / low sill and head level / shaped peculiarly.

Historical examples of windows can be broadly classified in terms of their locations. There can be five such categories: 1. Windows that are placed at roof level or in someway connected to the roof structure, 2. Windows that are vertically placed but are within the wall, 3. Windows that project out of the wall, 4. Windows that part of the floor, placed close to the floor, or have a very low sill and head level, and 5. Windows that shaped peculiarly.

4.2.1.4.1 Roof level windows

4.2.1.4.2 Wall windows

4.2.1.4.3 Windows projecting out

4.2.1.4.4 Floor level windows

4.2.1.4.5 Other shaped windows

4.2.1.4.1 HISTORICAL PERSPECTIVE : ROOF LEVEL WINDOWS

4.2.1.4.2 HISTORICAL PERSPECTIVE : WALL WINDOWS

Keywords: LANTERN WINDOW / clerestory opening / Ely cathedral / Renaissance and Baroque architecture / cupola / Bell tower / Georgian era / roof lanterns / Victorian era / orangeries / conservatories / crystal palace / Industrial revolution / early lantern structures / modern lanterns / CIMBORIO / CUPOLA / belfry, lantern, belvedere / Chhatri / CONSERVATORY / green house / sun room / ORANGERY / conservatory / greenhouse / France Germany and the Netherlands / SUN ROOM / patio room, solarium, conservatory, patio enclosure or Florida Room / CLERESTORY / stained glass windows / shadow-less and nearly consistent level of illumination / roof hole / transparent roofs or clear domes / CLERESTORY WINDOWS / DORMER WINDOWS / attic window / sloping gable roof / roof over a dormer / eaves / parapet / embattlements, crenels, embrasures / wall dormers / true or dummy window / window surrounds / false or blind dormers / chimneys, lanterns / doghouse / barn windows / hay-windows / types of dormer windows / gable dormer / hipped dormer / insert dormer / turret dormer / French segmental dormer / fanlight dormer / eyebrow dormer / shed or lean-to extended shed dormer / all glass contemporary dormer

Different types of windows have been grouped here in terms of their location and listed in time sequence rather then in alphabetical order.

LANTERN WINDOW: A lantern is a timber-framed structure, usually octagonal, polygonal or circular in shape, placed as a crown over a turret or dome of a building to admit light and allow smoke to escape. The lantern's structure was initially filled with wood slats (louvres) but later was covered with glass. It is a form of clerestory opening at roof level. The glass-covered form, due to the internal illumination, was visible at night from a great distance, like a lantern. Later specific beacons and lights were placed here for the same purpose. Although the primary function of a lantern was to admit light to the interior, it became an architectural capping element, with rib and vault form. The central octagon of Ely Cathedral (14^th C) is a lantern. In Renaissance and Baroque architecture, lanterns came to mean a small cupola-like structure, usually with a decorative arcade, mounted on top of a dome. In some Armenian churches it is also used as a bell-tower.

Typical lanterns capped domes are at: Cathedral of Santa Maria del Fiore (the Duomo) in Florence (1436-71), St. Peter's in Rome (1506), St. Paul's Cathedral in London (1689), and the Capitol in Washington, DC.

During the Georgian era (1714-1830), interiors could be dim and dark even on sunny days, and in absence of electric or gaslight candle power was the only source of illumination. Roof lanterns were used to illuminate the stairwell landings and other areas of home. The key element of a lantern, the glass was hand made and very expensive, limiting the use of roof lanterns in the homes of elite. However, in the later part of Victorian Era (1837-1901), glass was made by machines, became more affordable and orangeries and conservatories also became part of buildings. Virtually every urban row house of the late 19^th and early 20^th C used a metal-framed skylight to illuminate the deep-set stairwell.

The Crystal Palace built for the Great Exhibition of 1851 inspired people for greater use of glass in roof structures of buildings, and the Industrial revolution provided the necessary affluence and technology. Roof lanterns were used for illuminating domestic billiard rooms, reception rooms and kitchens, and in public buildings such as hotels, in places of education, town halls and public libraries.

Early lantern structures were delicate and prone to leakage as good quality sealants were not available. The glass was poor insulator and allowed heat to escape or enter. Many lanterns lit interiors were unconformably cold in winter and warm in summer. The ventilation in lantern opening was possible through inconvenient and inefficient opening mechanisms of cranks and levers. Today, however, modern lanterns have double layered glazing, high quality sealants and remote controlled automated opening mechanisms.

CIMBORIO: Spanish term for a lantern or raised structure above a roof to admit light in the interior.

CUPOLA: A cupola is a small dome-like structure, on top of a building. It is used to provide a lookout and also to admit light and air. The word derives from Latin Cupa =cup suggesting a vault like an inverted cup. A cupola is more bodied and is an architectural element crowning a larger roof, tower, spire, turret or dome. Cupolas also feature as a belfry, lantern, or belvedere above a main roof. The Chhatri, seen in Indian architecture, is a cupola but not used for lighting interior spaces.

CONSERVATORY: A conservatory is a glass and metal structure, a greenhouse, for growing tender and exotic plants, for rearing birds and animals, and occasionally as a sun room in a yard, garden, verandah or on top floor as a terrace facility. Conservatories became popular in 19^th C, after the success of glass buildings such as the crystal palace in London. Conservatories were popular for breakfasts and evening tea parties.

ORANGERY: An orangery is similar to a conservatory or greenhouse. It is generally located in the free ground of an estate or building. The name reflects the original use of the building as a place where citrus trees like orange were often wintered in tubs under cover, for surviving through harsh frosts though not expected to flower and fruit.

Orangeries originated from the Renaissance gardens of Italy. An orangery was built in Padua Italy, as early as 1545, and at the Palace of the Louvre Paris in 1617. The orangeries became fashionable once the long war was over in 1648, in France Germany and the Netherlands. Orangeries became part of ordinary residences during 17^th to 19^th C. Developments in glass making have enabled the form of orangeries. Early orangeries had large windows but opaque roofs, glazed roofs was developed in the early 19^th C. Early orangeries, as existed in Great Britain and France in 16^th C, were buildings that could be completely covered by planks and sacking and heated in the cold season by stoves. In Europe, orangeries facing South were constructed with brick or stone columns, with tall windows to receive optimum sunlight in the afternoon, whereas the ones facing the North had solid walls with smaller windows to be able to keep the space warm. Insulation was a major problem that was tackled with straw packing or covering with wooden planks and woven sacks. Additional wooden planks were mounted over the glass to keep the cold out.

SUNROOM: A Sunroom is an attached structure on the side of a house for to enjoy the outdoor while being sheltered from adverse weather conditions such as rain and wind. The structure is often referred to as a patio room, solarium, conservatory, patio enclosure or Florida Room. In the past such a room was a separate entity from the main house, but now it is integral part of the house.

CLERESTORY: An upper level opening in a building formed either by split-level roof slabs or by a series of windows. A clerestory opening rises above adjacent roofs so provides illumination to the core section of the building. Egyptian temples used clerestory opening between two slabs to illuminate and ventilate deep interiors. Roman, Byzantine and Early Christian buildings have clerestory windows at the base of a dome or vault. Clerestory openings well articulated in Romanesque and Gothic periods, but interiors with large stained glass windows did not require clerestory illumination as it disturbed the picturesque effect. Side windows however, reached close to the gothic vault. Clerestory openings made the upper section of the structure physically light weight, and visually 'celestial'. Industrial plants and sports facilities use clerestory openings for shadow less and nearly consistent level of illumination in interior spaces. Clerestory openings were a necessity as roof hole like openings were technologically not feasible and materials for constructing transparent roofs or clear domes were available.

CLERESTORY WINDOW: A vertical window set in a roof structure or high in a wall, used for day lighting.

DORMER WINDOW: A dormer is an attic window located in the sloping gable roof, on the main face of the building. A dormer is an extension of the attic and provides accessible or functional height right to the front edge of the room, which is used for placing a bed or study unit. The roof over a dormer is slopped cross way from the slope of the main roof. The dormer windows are design-matched with the window of a lower floor, creating an impression of a taller window, both from outside as well as inside. Dormers add a visual interest to the nominally plain gable roof surface. In England when fire laws did not permit architectural projections such as eaves, etc., the front wall was extended as a parapet to cover up the roof end. The parapet was articulated with embattlements, crenels, embrasures and dormers. Wall dormers are lower floor windows extended up to roof, parapet top, or even higher, as a true or dummy window, with all features of an highly ornamental window surrounds. False or blind dormers were added to visually balance roof-levelled other appendages, like chimneys, lanterns etc. Dormer openings are also called a doghouse, because the form of the dormer resembles the pet-house. Attic level barn windows shaped like a dormer used for taking in or out hay are called hay-windows.

Types of Dormer windows: A gable dormer has sloped roof on both sides. A hipped dormer has roof sloping on three sides including front. An insert dormer is set back from the sloping edge of the roof so has some sloping roof on its front bottom side. A turret dormer has multi angled hipped roof. A French segmental dormer has lower floor window continuing above by breaking the line of roof eaves. A fanlight dormer and Eyebrow dormer has rounded top window. A shed or lean-to dormer has single slope roof. An extended shed dormer has roof line extending beyond the main roof line. An all glass contemporary dormer has all sides formed of fixed glass or jalousie.

4.2.1.4.3 HISTORICAL PERSPECTIVE : WINDOWS PROJECTING OUT

Keywords: LANCET WINDOWS / acute pointed arch / Lancet period / LUNETTE / OCULUS / oeil-de-boeuf / bull's-eye / oxeye / wheel / roundel windows / Roman Pantheon / cupolas / volutes on ionic column / Baroque period / ornate carving / Gothic windows / modern circular windows / L Khan's Indian Management Institute / OEIL-DE-BOEUF WINDOW / JALOUSIE WINDOWS / adjustable louvers window / awning windows / slating material / ROSE WINDOWS / WHEEL WINDOWS / circular window / Gothic architecture / ocular window or oculus / Roman circular gaps or oculus / richly decorated element /nave West end of the nave and the ends of the transepts / pierced openings / tracery / Romanesque and Gothic / round arch / pointed arch / inscribed in square / STAINED GLASS WINDOWS / long perpendicular Lancet / circular Rose or Wheel / medallion pattern / story board / darker interior space / modern version a back lit lantern / lead cams / surrounding metal frame / mullions, transoms and muntins / painted black / lumps of cast glass / insert in roof slabs and domes / polished glass discs / glow effect / lines and areas / thin-sliced alabaster / translucent white or coloured glass / patterns, persons or scenes / transparency, clarity, shine and patterns / ground, polished or engraved / early Christian / early Romanesque / Romanesque rounded arch / Gothic buttressing system / cloisonne enamels and miniature paintings / stained glass area / story board / single monumental figure / multiple narrative windows / series of medallions / allover decorative patterns, or diapers, on the groundwork adjacent to the figures /scenes ignoring the mullions imitation of frescoes and oil paintings / Cartoons and sample books / yellow stain Cousin's rose / heraldic designs and details / assembly of coloured pieces of glass / interiors of buildings with large stained glass windows / Cristallo / art of applying metal powders / tonal staining / Catholic church / Protestants / extravagant decorative arts / Renaissance period / pictures on glass rather than with glass / stained glass lost its glory / religious, political and aesthetic / Reformation / stained glass windows with religious content / replaced with clear glass / non-religious subject matter / heraldic panels / simpler religious buildings / revived in the 19^th C / Victorian era stained glass windows / front doors / leaded patterns, bevelled edges and multiple layering / John La Farge / Opalescent glass / Louis Comfort Tiffany / Gemmail glass / Jean Crotti.

Different types of windows have been grouped here in terms of their location and listed in time sequence rather then in alphabetical order.

LANCET WINDOW: It is a tall narrow window with acute pointed arch at its top. It appeared first in French early-Gothic period (1140-1200) and later in the English period of Gothic architecture (1200-1275). The feature was so common, that the Gothic and other ecclesiastical architecture of this era are sometimes called 'Lancet Period'. Lancet windows are placed singly or in pairs. Strictly speaking a lancet window should be austere and without tracery, but the form is often subdivided and filled with stained glass in the Gothic-revival period of the 19^th C. The panels of the lancet windows always tell a biblical story and are read from left to right and from bottom to top. Lancet type openings were grouped in twos or threes under an enclosing arch. The remaining space was pierced with small circular openings.

LUNETTE: A Lunette is an arched crescent-shaped or semicircular aperture or decorative element.

OCULUS: Oculus (pl.=oculi) are a small windows that are circular or oval in shape, and is also called: Oeil-de-boeuf, Bull's-eye, Oxeye, Wheel, Roundel windows. Oculus are a Latin term meaning eye. Oculi was completely open, pierced panels or glazed with crude glass -as was available at the time. Oculi is placed on the top of a dome as in Roman Pantheon or on cupolas, on the drums that support the dome, high in the end of a gable roof or within a pediment over an opening system. In architecture, a shape that resembles an eye is called oculus, such as the pair of volutes on Ionic column. In Baroque period many shapes of ocular windows were used. These were oval or of a more complex shape. They were of very simple form, neither traceried nor crossed by mullions, but were often surrounded by ornate carving. The purpose of such windows was not to see the exterior but rather allow subtle light to illuminate the interior spaces. The Baroque oculus were rarely a dominant visual element, either over the facade or on the interior face. Compared to this the great Gothic windows, were very important elements of the facade scheme. Modern circular openings include L Khan's Indian Management Institute, Ahmedabad and Assembly buildings at Dhaka, Bangladesh. Other examples include modernistic circular openings, marine and space ships' hatch windows.

OEIL-DE-BOEUF WINDOW: It is a small circular window resembling a wheel, often with radiating glazing bars similar to spokes of a wheel. In French, oeil-de-boeuf means 'eye of the steer'.

JALOUSIE WINDOWS: A jalousie window is an adjustable louvers window. The earliest reference to Jalousie dates back to around the 16^th C. It is a window composed of overlapping narrow glass, metal, or wooden slats or louvers, operated with a crank handle for adjusting the louver angles. Jalousie louvres are usually narrow, approximately 75 to 150 in width, individually pivoted at the edge. The louvers are operated simultaneously by lever or crank handle that is connected to all by means of a hinge. Jalousie windows with extremely wide louvered panes, e.g. more than 150, which may not be operated simultaneously, are called awning windows. Modern day jalousie has glass, acrylic, other plastic sheets and metal composites sheet as slating material. Jalousie is not security tight opening. Jalousie Windows are impossible to seal, so is not very energy efficient. However, for the same reason these are well suited for verandah areas of tropical buildings.

ROSE WINDOWS: WHEEL WINDOW: The term wheel window is often applied to a circular window divided by simple spokes radiating from a central boss or opening, while the term rose window is reserved for circular windows of more complex design which can be seen to bear similarity to a multi-petalled rose. The term Rose window is often used as a generic term applied to any circular window, but is especially used for those found in churches of the Gothic architecture and is divided into segments by stone mullions and tracery. The name rose window was not used before the 17^th C. A simple circular window without tracery is called an ocular window or oculus.

German art historian Otto von Simson considers the origin of the rose window to the six lobed rosettes and octagon windows which adorned the external wall of the Umayyad palace Khirbat al-Mafjar built in Jordan around 740. The theory suggests that crusaders brought the design of this attractive window to Europe, introducing it to churches.

Circular openings have originated from the Roman circular gaps or oculus. Circular windows and decorative circular recesses are a feature of many Romanesque churches and cathedrals, such as in Santa Maria in Pomposa, Italy, 10^th C. However, it was by the middle of the 12^th C that it became larger in size and a richly decorated element. By the middle of the 13^th C its size had increased to cover the entire width of the nave. Circular windows were placed mainly at the West end of the nave and the ends of the transepts.

Rose windows with pierced openings rather than tracery occurred in period between Romanesque and Gothic. Wheel windows had spokes like radiating lines emanating from its centre, however, in a rose window the straight spokes became rounded at the outer edge and at the centre began from a hollow roundel. Many varied patterns evolved across Europe. Rose windows were initially placed under round arch, but later began to be accommodated within a pointed arch, as was done in the Reims Cathedral 1230. Rose windows have been inscribed in square, with pierced spandrels, as in Notre Dame of Paris, 1257.

STAINED GLASS WINDOW: A stained glass window can have many shapes, from long perpendicular Lancet to circular Rose or Wheel. A stained glass window is like colourful medallion pattern or story board depicting Christian mythology. It depends on daylight to glow, so it is best seen from darker interior space or in its modern version a back lit lantern seen from outside. One of the most important orientations has been the East, forming the glowing backdrop for the altar. It was perhaps this as a reason why church buildings which were earlier mainly entered from the East began to have West as entrance.

A stained glass window consists of panes of 'white' colourful shaped pieces of glass held together by lead cams and a surrounding metal frame. The composed panes of glass were held between the mullions, transoms and muntins. The lead cams and the surrounding metal frame, were painted black and made part of the picture or pattern composition. Where such black lines were not available, these were painted or overlaid with metal strips.

Even before 5^th to 6^th BC, lumps of cast glass, ground and polished to make them translucent, were used as insert in roof slabs and domes. As early as 240 AD, polished glass discs and cut pieces were inserted in wood and stone panels of the openings for the 'glow effect', The pieces were arranged to form the nodes of a pattern, and later were arranged to mark lines and areas. In Early Christian churches of the 4^th and 5^th C openings were filled with ornate patterns of thin-sliced alabaster set into wooden frames, giving a stained-glass like effect. The opening area began to be filled in by a pane composed of pieces of translucent 'white' or coloured glass pieces. The glass pieces were arranged to portray patterns, persons or scenes. For achieving greater transparency, clarity, shine and patterns, the glass pieces were ground, polished or engraved. The glass pieces were tinted or stained, i.e. painted by a transparent colour, usually yellow to alter the colour tinge.

The window openings in early Christian and early Romanesque architecture were small and few in number due to structural reasons. The interior surfaces were treated with wall paintings, and to illuminate it openings were chamferred and sills tapered. Wall paintings gave way to murals in mosaics of ceramic tiles, stones and glass bits because of their dazzle and permanence. But Romanesque rounded arch and Gothic buttressing system provided extensive window openings. The wall murals were replaced by stained glass window. Romanesque stained glass windows used 'stylized vegetal ornament and decorative beading' around the scenes and figures. The predominant colours were red and blue. This style of stained glass seems to have developed from cloisonne enamels and miniature paintings.

Stained glass evolved as an art form to illustrate religious stories to largely illiterate population in the middle ages. It is said Gothic churches had larger openings not to enhance the level of interior illumination but increase the stained glass area as a 'story board'. Early stained-glass windows displayed a single monumental figure, like those depicted in the cathedrals of Augsburg and Canterbury, or like the Virgin and Child known as 'La Belle Verrière' at Chartres. But soon enough multiple narrative windows, consisting of a series of medallions painted with pictorial subjects began to appear. Another significant development was the use of allover decorative patterns, or diapers, on the groundwork adjacent to the figures. By the end of the medieval period background was not just merely a pattern but buildings and landscape were shown with correct perspective Subject was more pictorial and not subservient to the architecture. In large Gothic church windows scenes ignoring the mullions extended over the whole opening. Actions are seen taking place in far depths from the normal pictorial plane. Faces have individuality and show emotion.

The design of a stained glass window can have figurative motifs like gods, angels, saints, or patrons or non-figurative patterns symbolic, armorial, coat-of-arms or geometric art. The topic may be thematic depending on the purpose of the building, figures representing culture, flora, fauna, or landscape.

Stain glass window production was a big business under the sponsorship of the church. Workshops stayed in one place through several generations. Artists began to copy their own and others' art in the form of 'cartoons' on paper. Often same cartoons were reused with small variations. However, careless imitation of frescoes and oil paintings destroyed the essence of the translucent medieval art. Cartoons and sample books were carried to far off places to seek clients.

During early 14^th C silver chloride and silver nitrate, fixed at very low temperature began to be used for yellowish effect ranging from pale lemon, deep orange and browns. The yellow stain was very useful for enhancing borders, canopies and haloes, and for creating a variety of greens. By about 1450 a stain known as Cousin's rose was used to enhance flesh tones. 'In the 1500 s a range of new glass stains in the form ground glass particles called 'enamels' were introduced. Painting on glass with these stains was initially used for small heraldic designs and details. By the 1600 s stained glass was not necessarily an assembly of coloured pieces of glass but a large sheet of glass skilfully painted or overlaid by thin pieces of coloured glass. The marking of territories with heavy metal cams or black paint, the typical character of stained glass continued for some more time. It was technically not required, so became delicate and thinner.

The interiors of buildings with large stained glass windows became over-saturated with colours and topical (narrative) diversions. Gothic churches with the fluted columns and ribs of the vaults added to the already rich interiors. It was during this that Murano workshops in Italy offered a lead crystal glass called Cristallo. Cristallo was water white glass without the slight colour tinge that was omnipresent in all glasses of the time. Technical innovations in the manufacture of stained glass were developing at a very fast pace in the 16^th C. Crafts people had already mastered the art of applying metal powders over glass and fixing it with second burning or heating. Body tones, variations in shades of draperies, dresses and vegetation, etc. which were earlier projected through black coloured highlighting lines, now were done through staining. Tonal staining made the glass darker and made the interiors less brilliant. Cristallo glass offered a lighter background to tone various colours. Interiors began to sober up. The Catholic church had been the patron of stain glass windows, but the new Protestants were opposed to the use of extravagant decorative arts. In the political turmoil the Catholics were also looking for simpler, faster and economic ways of putting up new buildings.

The Renaissance period in northern Europe supported realistic details. In Italy artworks done in Middle Ages style was considered by Renaissance artist as barbaric. Stained Glass windows became simpler, lighter in colour and with meticulously executed details. Diamond cutting edges and thinner glass allowed better illumination for the Italian wall frescos. White glass like Cristallo and its larger size allowed artisans to paint pictures on glass rather than with glass. The stained glass also began to be used in buildings such as Palaces, town halls, and smaller residences.

Stained glass lost its glory for three main reasons: religious, political and aesthetic. The catholic church had been the principal patron of the arts, but the new Protestants were hostile to art and elaborate decoration. The English Parliament ordered all images of the Virgin Mary and the Trinity to be removed from churches. The high cost of replacing stained glass with clear glass finally stopped the destruction. In Brittany, a congregation covered a window with dung and mud and whitewashed over to avoid spending money to replace it. During the Reformation, stained glass windows with religious content were destroyed. These were replaced with clear glass or windows, either stained or enamel painted but with nonreligious subject matter, like heraldic panels. In France the Revolution brought about the neglect or destruction of many windows. Even in the Roman Catholic countries, the counter-reformation measures called for simpler religious buildings.

The craft of Stained Glass windows once again was revived in the 19^th C. Much of the demand was due to the restoration of churches despoiled in reformation period and during the French revolution period. Stained glass produced was imitating the medieval artwork. 19^th C German glass had painted detail rather than outlines dependent on the lead cams. The stained-glass windows of Victorian Era were used as the focal point, for the interior spaces such as the staircases, foyers, closets, bathrooms, the butler's pantry, etc. The size and position within the building indicated social status and wealth. Colourful leaded glass was used as fancy header and in transom and side lites. Front doors also had glass panes with leaded patterns, bevelled edges and multiple layering.

In USA Stained Glass and other decorative glass (such as bevelled edge, leaded, grooved, layered, etc.) was already in use. John La Farge invented Opalescent glass in 1880. Similar glass was also patented by Louis Comfort Tiffany.

Opalescent Glass is a common term for clear, a semi transparent or opaque pressed glass. It has a milky opalescence with cloudy, marbled, etc. textural effects, often accentuated with subtle colour staining. The opalescent effect is created during the repeated heating and cooling of the glass, with chemical additives. The opalescent effect refracts the colours with light falling on it. Similar effect is created along the edge of the glass and by texturing and layering the surface. Today opalescent glass is less favoured due to the toxicity of the chemicals required for it.

Gemmail glass, developed in 1936, by the French artist Jean Crotti, is a type of stained glass where the pieces of glass that are adjacent to each other overlap allowing for a greater subtlety of colour.

For more ref to Stained Glass 4.2.3.1 Materials and Technologies

4.2.1.4.4 HISTORICAL PERSPECTIVE : FLOOR LEVEL WINDOWS

Keywords: ORIEL / polygonal bay window / columns, piers, corbels or brackets / zarokha / mashrabiya / Tudor style / over gateways or entrances / Gothic revival / BAY WINDOWS / bow windows / Victorian architecture / full bay window / half or part bay window / flower box / Victorian and Edwardian period / BOW WINDOWS / curved or polygonal bay window / bow shape / Federal period / compass window / radial bay window / MASHRABIYA / sahn / Iraq and Egypt / Basra / France / moucharabieh / lathe turned wooden sections / smaller lattice openings in the lower section / larger openings in the upper parts / mid part of the mashrabiya / stained glass / shanashil / dakkah / ota or otla / zarokha / SHANASHIL / porch, verandah or gallery.

Different types of windows have been grouped here in terms of their location and listed in time sequence rather then in alphabetical order.

ORIEL: Oriel windows are a form of polygonal bay windows. Oriel windows have a larger perimeter and so allow wider view of the outside. Oriel windows increase the floor space without increasing the footprint (extent) of the building. Oriel windows are usually placed on the upper floors of the building, but siting on ground floors is common. The windows are projected bays, supported off the base-wall by columns, piers, corbels or brackets.

The word oriel is derived from Anglo-Norman oriell and post-classical Latin oriolum, both meaning gallery or porch, perhaps from classical Latin aulaeum, curtain.

Such windows have of many forms: start from the floor level, seat level or mid body level, the head-side of the projected gap terminates at lower, at human head level or reach to the ceiling level. Some oriels are partly or wholly glazed and are known as oriel windows, latticed forms are found in Indian Zarokha and in mid East or Arab architecture as Mashrabiya. In both the cases the lattice reduces the glare and provides privacy. Zarokha is more commonly made of stone work, and Mashrabiya have carved wood latticework and often stained glass.

Oriels developed in the 15^th C, when under the Tudor kings peace prevailed in England, Wales and Ireland. The prosperity of the great landowners, aristocracy and Church supported new constructions. Although Italy was seeing revival of classical architecture, Tudor style was mainly local. Merchants and artisans, generally living over the shop in a narrow and tightly-packed town houses, added space by building storeys. The upper storeys were projected out over the street. This often resulted in extremely dark streets. Timber-framing despite the fire risk, was popular. Oriel windows were also placed over gateways or entrances to manor houses and public buildings. Oriel windows once again became popular during the revivals of Tudor style in the 19^th and early 20^th C, and during Gothic revival (1740).

BAY WINDOWS: A bay window is an exterior projection of room space, forming a bay of square or polygonal shape. The round (segmental) shaped windows are called bow-windows. Bay windows became popular with Victorian architecture (1870's). A typical bay window consists of three windows, the middle unit is parallel to the house and adjoining two units are set at 30 to 45 degree angles. Bay windows are created: to increase the illumination, provide a wider view of the outside and enlarge the interior space. The bay windows are used on sunny sides in colder climates, over sections facing road side, garden and other natural scapes.

There are three basic types of bay windows. In full bay windows the opening stretches from floor to ceiling level to create a nook in a room. In half or part bay window the window starts at seat or nominal sill level and reaches head height level or full ceiling level. In the third version the bay is more of a flower box projecting out. The nook created by full bay window is well illuminated and has better view of outside so it is used as study area, breakfast space, solariums, hobby area, etc. For these purposes the inner ledge of the bay window is used as built-in seat.

The building act of 1707 in London and other towns of England did not allow projections on a road side, to prevent spread of fire along the wall. This was changed in 1894 so that windows were not required to be flush with the exterior wall. During the Victorian and Edwardian period houses began to have bay windows.

BOW WINDOWS: A bow window, is a curved or polygonal bay window. Unlike the bay window, there is no middle window unit, parallel to the room. Instead several small width window units (fixed and shuttered) are joined to form a bow shape. Bow windows first appeared in the 18^th C in England and in the Federal period in the USA. Bow windows are also called compass window and radial bay windows.

MASHRABIYA: Mashrabiya is a projected window on second or higher floor in mainly in urban setting, but rarely in rural areas. Mashrabiya was used in houses and palaces although sometimes in public buildings such as hospitals, inns, schools and government buildings. It is commonly placed on the street side, but occasionally on the internal courtyard 'sahn' side. Mashrabiya windows are presumed to have formed during 12^th C in Baghdad. Iraq and Egypt are two countries where many examples survive. They are more common in Eastern (mashriq) parts of the Arab world then the western (maghrib) parts. Basra is often called the city with Mashrabiya. It was introduced in France from its colonial sources, and called moucharabieh.

Mashrabiyas are enclosed with carved wood latticework, composed of the lathe turned wooden sections, in complex patterns. Smaller lattice openings in the lower section obscure vision from outside and reduce the air draft, whereas larger openings in the upper parts allow better air draft and illumination. Lattice design differs from region to region.

Mid part of the Mashrabiya is provided with sliding or a side-hung shutter for a clear opening. Mashrabiyas are also lined with stained glass to form an enclosed balcony, and an independent space attached to a room. Shanashil is net or wood screen-covered verandah or porch over looking a street or garden. Mashrabiya in farm houses and for out of the town buildings are more open, with reduced amounts of lattice work and without the lining of glass. Egyptian Mashrabiya projects out at a slightly raised level providing for a Dakkah (a Dakkah is a masonry platform attached to the front part of a house, covered with a rug, it is used for informal talk and tea in Arab rural areas, an arrangement similar to Ota or Otla in a traditional Indian house) or in front of the window similar to the Indian Zarokha.

Mashrabiya adds space to rooms on the upper floor without increasing the foot print area of the building, but these have also been used for correcting the shape of upper floor front room.

Mashrabiya allows air from three sides to enter, even if the draught outside was parallel to the house facade, on the other hand it serves the street and in turn the neighbourhood. Mashrabiya also provides shade for the ground floor windows.

The word Mashrabiya has varied origins. Mashrabiya denotes drinking or absorbing. The name perhaps has derived from a wood lattice enclosed shelf located near a window to cool the pots of drinking water. The shelf evolved until it became part of the room with a full enclosure. Mashrabiya also has originated from verb Ashrafa =to overlook, ignore or to observe.

SHANASHIL: Shanashil (shanshool or rushan) is a porch, verandah or gallery like features covered with fine wood lattice work. It is found in old Iraqi houses of Baghdad.

Keywords: EYEBROW WINDOWS / lie-on-your-stomach' windows or slave windows / CHICAGO WINDOW / WIND CATCHERS / wind scoops / badghirs / horizontal slats.

Different types of windows have been grouped here in terms of their location and listed in time sequence rather then in alphabetical order.

EYEBROW WINDOWS: These are low, inward-opening windows with a bottom-hinged sash. Usually attic windows built into the top moulding of the house, and these units sometimes are called 'lie-on-your-stomach' windows or slave windows. Often found in Greek Revival and Italianate houses.

CHICAGO WINDOW: A three-part window consisting of a large fixed central panels flanked by two smaller double-hung sash windows. These windows were often deployed in bays, known as oriel windows, that projected out over the street.

WIND CATCHERS: Wind Catchers used in the Persian Gulf Countries are natural ventilation systems which catch the prevalent breeze from the terraces and bring down to floor level horizontal slats. Earliest Wind Scoops were built about 2,000 years ago in Iran. The wind tower, an evolved version of the wind scoop as a very effective form of air conditioning has been around for about 500 years. With the growth of the pearl trade people migrated to Bahrain and brought with them the wind tower in the 18^th and 19^th C. Wind-towers and badghirs (meaning a wind trap), which consist of horizontal slats in the lower part of the walls for speeding up the flow of air to interior rooms.

4.2.1.4.5 OTHER SHAPED WINDOWS

Keywords: WHEEL WINDOW / LUCARNE / ROUNDEL / circular light / bottom of the blown glass bottle / DIOCLETIAN WINDOW / Andrea Palladio / Robert Adam / thermal window / Beaux Arts movement / BALISTRARIA : ARROW LOOP WINDOW / cross window / opening widened inward / arrow loop or slit / moon crescent / CROSS WINDOW.

Different types of windows have been grouped here in terms of their location and listed in time sequence rather then in alphabetical order.

WHEEL WINDOW: A large circular window in which the tracery radiates from the centre. A variety of the rose windows are found in Gothic and Gothic Revival styles

LUCARNE: A small dormer window in the roof or spire.

ROUNDEL: A small circular panel or a circular disk of stained glass in a leaded window. Roundel windows are often called bull's eye, oculus, oeil-de-boeuf, oxeye or circular light. Roundel openings were perhaps devised to use the less used bottom of the blown glass bottle while making a flattened glass. Some roundels look like the bottom of a bottle, with rings in glass. Roundels are also found in corners of rectangular doors or window frames.

DIOCLETIAN WINDOW: Thermal, or Diocletian windows are large semicircular openings or niches, usually divided into three lights or sections, by two vertical mullions. The middle section is usually wider than the two side lights on either side of it. The original windows with bronze-framed panes of glass were used in the Baths and palace of Diocletian (3^rd C Roman emperor Diocletian at Spalato, Rome). The window form was used again in the 16^th C, especially by Andrea Palladio, and in the late 18^th C by Robert Adam. It was also called a Thermal window due to its past association with the Roman Thermae (baths) during the Classical Revival buildings of the early 1900's. Diocletian windows continued to be used occasionally in large public buildings in the various versions of neoclassical architecture including the Beaux Arts movement (1880-1920).

BALISTRARIA : ARROW LOOP WINDOW: A narrow opening, often in the shape of a cross window in which bow was held horizontally or vertically to throw arrows without any personal danger. The opening widened inward, to give the archer a wider field-view and the cross shape provided facility for aiming up, down and sideways. Such openings were cut in a medieval wall, parapet, or fortification for use by archers but without any frame or shutter. A balistraria is also referred to as an arrow loop or slit.

CROSS WINDOW: A cross shaped window formed by thin vertical and horizontal slits in an otherwise plane wall. During day time the opening glows against the comparatively shaded interior wall, and at night artificial illumination highlights its shape.

4.2.2.1 VARIETIES OF WINDOWS

Keywords:

GROUP A > ROOF LIGHTS / minuscule size to very large gaps / Roof lights, in the 18^th and 19^th C / Victorian era / Roof window or day lighting / flat or sloped opening / flat / structural geometry / shell structure / multi-paned glass structure / roof lantern / glowing lantern / Orangeries /France and Italy / CABOOSE CUPOLA

GROUP B > CASEMENT WINDOWS / sash windows / handle cum locking device / crank or lever / wind stay / friction hinge / espagnolette / solid, opaque panelled or glaze panelled / full open aperture / long armed handle mechanism / offset hinges / cleaning, glazing fixing and painting of the exterior face / insufficient parking space / window treatments / single casement windows / side lites / patent bolts / double casement windows / French window / single, opening on left or right side / double shutters / multiple casement windows / opening on one side / symmetry / HOPPER WINDOW / draw bridge or a coal-pit receptor or hopper / cellar or subterranean opening / HOPPER LITE / HOPPER VENTILATOR / AWNING WINDOW / awning or a weather shed / transom lites / FRENCH WINDOW / French door / FOLDING CASEMENT / confined space / storm shutters / Venetian shutters / fly-mesh shutters.

GROUP C > LOUVERED WINDOWS / shutter elements / elements within the shutter / awning window shutter / appendage / fixed slats / Jalousie windows / louver surfaces / louvered shutters / louver as an appendage / brise soleil / Venetian blinds / Micro width louvers / chimneys / illumination roof lanterns Alvar Aalto / JALOUSIE AWNING WINDOW / jalousie window /BASEMENT WINDOWS.

GROUP D > PIVOT WINDOWS / first mechanism / weather seal / double hung sash windows / hydraulic floor pivots / skylights, ventilators, hoppers and awning windows / jalousie / friction hinge / CENTRE PIVOT WINDOWS / OFF-CENTRE PIVOT WINDOWS / EDGE PIVOT WINDOWS PIVOT WINDOWS / off-pivot / edge or corner pivot / centric pivot / off-centric pivot / Nylon or Teflon / CENTRE-HUNG SASH / TOP HUNG-IN WINDOW / HORIZONTAL WINDOWS WITH PIVOTS / centred pivot / industrial skylights / minute off-centric positioning of the pivot / Jalousie shutters / VERTICAL WINDOWS WITH PIVOTS / ganged by hinged bar / very tall windows / alignment / CORNER PIVOT WINDOWS / fixing or cleaning of the glass and painting / weather sealing.

GROUP E > SASH WINDOWS / casement windows / no shutters projecting out / shutter is bounded by a frame / hanging shutters / mullions / control over air ventilation / leaded-light casement windows / window tax / glazing bars / Georgian period / plate glass / horns / counter weight bar/ sash cord or chain / pulley / spring balances / weight boxes / view through was fuzzy / a strange mix of materials and finishes / white colour sash windows / Victorian architecture / Queen Anne style of white Sash windows / two distinct sections / fixed glazing / sash sliding horizontally / single-hung sash windows / double hung side windows / simplex hinges / Georgian architecture / triple and quadruple hung windows / tripartite or Venetian / fixed louvered shutters / casements in Gothic and Tudor Revivals / casement increased during the Edwardian period / neo-Georgian buildings / GEORGIAN WINDOW / double-hung window / 6 panels per sash / steel casement windows / BARN SASH WINDOW / HORIZONTAL SLIDING SASH WINDOW / Yorkshire sash windows / BOX-HEAD WINDOW / GUILLOTINE WINDOW / double sash window / HANGING SASH / hung sash / COMBINATION WINDOW UNIT / PRIME SASH.

GROUP F > SLIDING WINDOWS / GLIDING WINDOWS / horizontal windows / along the gravity / vertical windows / to or away from the gravity / counter weight or coiled springs / a limited size of opening / vertical sliding channels / horizontal slider channel / interior face / airtight / pushed open by an intruder / exterior sliding channels / Georgian sash windows / shoji / furrows or thin width rail tracks / self lubricating materials / sliding windows channels / accuracy of alignment / wood / extruded mild steel aluminium / plastics / fibre composites / sliding aluminium and plastic sections / channels for shutters / sections forming the shutter / side edge channels / top edge channel / bottom section / side edge sections / top and bottom edge sections / meeting edge sections, handle sections / very large opening system / mullions and transoms / glass fixing beadings / positive negative wind pressures / wind stays / HORIZONTAL SLIDER / VERTICAL SLIDING WINDOW / bus and railway carriages / DROP WINDOW / fire warehouses

GROUP G > SIDE LITES / MARGIN LIGHT / window next to or over a door or window opening / side lites / margin or side lites / Regency / TRANSOM LITES / TRANSOM WINDOW / above a window or door / exterior transom window / interior transom window / fan lite / MULTI-LITE WINDOW / DIVIDED-LITE WINDOW / glazing bars or muntins / emphatic glazing bars / visual defects in glass / FIXED LITE / FIXED SASH / FANLIGHT / TRANSOM FAN LIGHT / CHICAGO WINDOW / sash on either side

GROUP H > PICTURE WINDOWS: FIXED WINDOWS / provide an unimpeded view / framed picture / fixed windows / transom lite, clerestory, skylight or lantern window / frosted glass / shop fronts / shop windows / curtain wall / aquarium glass front / wall mounted LCD screen or TV / VIEW SASH / tinted glass / metalized polyester film / staining by transparent colours / one way view / visual privacy and noninterference / SHOP FRONTS / SHOP WINDOWS / DISPLAY WINDOWS / technological, economics and safety reasons / transparent and so safe / a display system / new arrivals or preparations / architectural identity / type-casting or branding / architectural elements / pilasters and consoles / fascias and cornice / old shops fronts / stall-riser / shop doors / half glass or with heavy bottom rails / floor pivoted / butterfly leaf doors / Automatic sliding doors / continuous protected passage like a colonnade / a bay or bow window / shop door / glare over the main face / daylight / translucent shop sign board / Display windows / public street level / nominal eye level / shops on the upper floors or at cellar level / street front display system / entire interior volume of the shop / interior display units / display units independent of the shop / graphics rather then actual items / exterior shop front display / day light for illumination / interior display units / artificial illumination / quality of glass / Industrial Revolution / size of glass / safety glasses / single owner / departmental stores / shops with residence on upper floor / shopping centres / illumination technology / nature of display windows / wood-frame and divided by heavy muntins / muntins or glazing bars of metal T sections Small pieces of glass / large piece of glass / soften the look / framing only at the edges / glare / canvas awnings / tinted glass and polyester film coated glass / heavy metal sprayed glass / rolling shutters.

GLASS FRONTS / curtain walls / Architectural gaps / Gothic buildings / mullions and transoms / muntins or metallic glazing bars / surrounding frame / beading or a mastic compound / elastomer sealant compounds / ventilating opening system / gasket that expand and contract / manufacturing, transportation and installation issues / horizontal or vertical joints / a seamless front / condensation formation / rainwater penetration / framing intervention / Fireman's knock-out panels / tempered glass / non-removable reflective dot / spider leg holders / CURTAIN WALLS / span multiple floors / positive and negative wind pressures / connections at floors or columns / glass panel in-fill / curtain wall panelling / mullion and transom system / modular system / sight-lines / visual profile / width and depth of the curtain wall frame / internal glazing panelling internal divisions of curtain walls / internal needs of space segmentation / lateral partitions / air and noise leakage and spread of infection / floor junction / matching horizontal member / override such a junction / thermal and visual comfort, privacy, and solar gain control / Sound attenuation / shed away the water / SHADOW BOXING / visual depth / CABINET WINDOW / PANEL WINDOW / CORNER WINDOW / bay window / bow window / shop fronts and glass fronts / SPLAYED WINDOW / COUPLED WINDOW / DOUBLE WINDOWS / auxiliary shutter / DOUBLY GLAZED WINDOWS / air filled or vacuum space / STACKED WINDOWS / awning, hopper, casement / glass fronts / TRIPLE WINDOW / Palladian architecture / colonial revival houses / treble sash windows / BAND - RIBBON WINDOW / LEAD LIGHT / LEAD GLAZING / STAINED GLASS / GLASS BLOCKS / GLASS BRICKS / glow wall / acrylic and polycarbonate / glass block sizes / styles and finishes / after-glow

GROUP I > EMERGENCY EXIT WINDOW / EGRESS WINDOW / large enough / reachable sill / appropriate surroundings / emergency exit windows / International Residential Code (IRC) requirement for egress openings / DOGGIE OR CAT WINDOW / flap window / DELIVERY WINDOWS / double shutters / SERVICE WINDOW / vertical ducts or horizontal passages / FIRE WINDOW / fire-endurance rating / Fire Resistant Ratings FRR / periods in minutes / structural adequacy / integrity / insulation.

GROUP J > SUPER WINDOW / highly insulating window / better than an insulated wall / SMART WINDOW / ALUMINUM-CLAD WINDOW / KNOCKED-DOWN / LABELLED WINDOW / DOUBLE WINDOWS / MULTI GLAZED WINDOWS / loud or low-frequency noise / INSULATING GLASS (IG) WINDOWS / absorbent substance -desiccant.

GROUP K > INDUSTRIAL LITES / clerestory windows skylights / North lights / port holes / roof monitor / atrium / other issues that dominate design / NORTH-LIGHTS / SAWTOOTH ROOF LIGHTS / reflector for the daylight / weave shed roof / continuous top hung steel sash / industrial age / angled glazing / ROOF MONITORS / raised sections / ventilating draught / ATRIUM / Roman origin / pyramid, dome or half cylinder / Louvre museum / multistoried atrium plaza / LIGHT TUBES / glass lined / fibreoptic conduits / intensified light / passive / ventilating ducts / OPERABLE WINDOW

GROUP L > FALSE WINDOWS / masked by walling, panelling, cladding / shadow boxing / revival architecture / flat or bay window / CAMEO WINDOW / true windows / false windows / masking element / colonial revival houses / GARAGE DOOR WINDOWS / DUTCH DOOR - WINDOW / CAFÉ TYPE / QUARREL / LOZENGE / PROJECTED WINDOW / oriel or Mashrabiya window / BLANK WINDOW

Windows are classified in many different ways:

Historical styling (4.2.1.2 Historical perspective : Windows : Periods / 4.2.1.3 Historical perspective : Windows : Recent)

Location based characteristics (4.2.1.4 Historical perspective : Windows : Types )

Windows Technological Types (4.2.2.1 Varieties of Windows )

Nature of opening (4.2.3.2 Windows Mechanisms )

Different Categories of windows have been grouped here in terms of their time relevance and affinities rather then in alphabetical order.

List of major categories of windows discussed in this section:

Group A Roof light, sky light

Group B Casement windows, Hopper windows, Hopper lites, Hopper ventilator, Awnings windows, French window, Folding casement

Group C Louvered Windows, Jalousie awning window, Venetian window, Basement windows

Group D Pivot windows, Centre pivot windows, Off-centre pivot windows, Edge pivot windows pivot windows, Centre-hung sash, Top hung inward window, Horizontal windows with pivots, Vertical windows with pivots, Corner pivot windows

Group E Sash windows, Georgian windows, Barn sash windows, Yorkshire light, Horizontal sliding sash window, Box-head window, Guillotine window, Hanging sash, Combination window unit, Prime sash.

Group F Sliding windows, Gliding windows, Horizontal slider, Vertical sliding window, Drop windows

Group G Side lites, Margin light, Transom lites, Transom window, Multi-lite window, Divided lite window, Fixed lite, Fixed sash, Fanlight, Transom fan light, Chicago window

Group H Picture windows, Fixed windows, View sash, Shop fronts, Shop windows, Display windows, Glass fronts, Curtain walls, Shadow boxing, Cabinet window, Panel window, Corner window, Splayed window, Coupled window, Double windows, Doubly glazed windows, Stacked windows, Triple window, Band or Ribbon window, Lead light, Lead glazing, Stained glass, Glass blocks, Glass bricks

Group I Emergency exit window, Egress window, Doggie or cat window, Delivery window, Service window, Fire window

Group J Super window, Smart window, Aluminum-clad window, Knocked-down, Labelled window, Double windows, Multi glazed windows insulating glass (IG) windows.

Group K Industrial lites, North-lights, Sawtooth roof lights, Roof monitors, Atrium, Light tubes, Operable window

Group L False windows, Cameo window, Garage door windows, Dutch door - window, Café type, Quarrel, Lozenge, Projected window, Blank window

GROUP A

ROOF LIGHT: SKYLIGHT: In its most common usage a roof or skylight describes an entity that sits atop a typically flat roof in order to provide natural light into the room below. Openings in the roof or ceiling generally facing the sky and meant for ventilation and illumination have been used in buildings for ages. Such openings have been of minuscule size to very large gaps, covering the room's entire roof surface. Roof lights, in the 18^th and 19^th C were made of wood frames with gaps covered by wooden slats or louvres and later with glass panes. However, during Victorian Era with metal construction, skylights became very popular. Virtually every urban row house of the late 19^th and early 20^th C relied on a metal-framed skylight to illuminate the enclosed stairwell.

Roof window or day lighting is a flat or sloped opening as part of the roof, used for day lighting. Skylights are flat, shaped by the structural geometry, or formed as a shell structure by bulging.

One very popular version of roof light was the multi-paned glass structure, the roof lantern. Compared to nominal roof or sky light it is meant to be visible as a glowing lantern over the topmost point of a roof, such as tower, dome or peak of the roof. Roof Lanterns have derived from Orangeries. Structures first built in 16^th C in France and Italy.

For Historical roof window openings ref to: 4.2.1.4.1 Roof level windows

CABOOSE CUPOLA: It is type of skylight and a projecting window mostly in rail road carriage. for more ref to 4.2.4.1 Other types of windows

GROUP B

CASEMENT WINDOWS: Casement windows were the most common house windows before the sash windows were devised. The shutters of casement windows are hinged on the side, and open either inward and outward. The shutters, if of small width open with a handle cum locking device, and if of large width require a crank or lever to open. A wind stay, or a friction hinge is necessary to hold the shutter open in windy conditions, and an espagnolette is used for locking. The casement shutters could be solid, opaque panelled or glaze panelled. Glazing panes are fixed to the shutter by beading or putty compound. Casement windows provide a full open aperture compared to double hung or sliding windows.

A casement window is easy to operate with its long armed handle mechanism and so ideal for difficult to reach situations such as places above cabinets or counter tops. Casement windows open out on nominal hinges or offset hinges that open the shutter little away from the side to allow cleaning, glazing fixing and painting of the exterior face. These are critical issues for casement windows that have protection bars or are located on upper floors.

Casement shutters opening inward cause obstruction if there is insufficient parking space for the opened shutter. Inward opening shutters also interfere with window treatments such as curtains, blinds, etc.

Single casement windows are used on side lites besides a door or fixed window. Average width of wooden casement windows is 400 to 500. Larger widths up to 600 are possible with friction hinges. Very tall casement windows require patent bolts at both the top and bottom ends to shut a window or keep it open in heavy winds. Double casement windows are of two types: one where two shutters meet over a mid member, and the other, where the two shutters meet over each other. The later is called a French window, it opens unobstructed in the centre.

The casement shutter could be single, opening on left or right side. Casement windows with double shutters, open out on the left and right sides, or like the pages of a book open in the middle. Multiple casement windows have even numbers of shutters divided into sets of two each, have all shutters opening on one side, or symmetrical arrangement is created by opening half numbers of shutters on either side.

Casement windows typically are hinged at the sides, but if top hinged are called awning windows and if bottom hinged are called hopper windows.

HOPPER WINDOW: A hopper window is a bottom hung casement windows that open similar to a draw bridge or a coal-pit receptor or hopper, typically opening to the outside. Hopper windows are used as cellar or subterranean opening.

HOPPER LIGHT : HOPPER VENTILATOR: Inward-opening shutters hinged at the bottom, usually forming the upper section of a door or window.

AWNING WINDOW: An awning window is a casement window that is hung horizontally, hinged on top, so that it swings outward like an awning or a weather shed. Awnings are transom lites, used in upper sections of doors and windows as a ventilator.

FRENCH WINDOW: A French window is really a type of door with a small threshold. It is also called a French door. Two casement sashes hinged on the sides to open in the middle. The shutters nearly extend to the floor and also serve as a door to a porch, garden, verandah, gallery or terrace. It is double shuttered, has single or multiple panes of glass for the full height of the shutter. It may have a secondary set of solid or louvered shutters opening to the interior side.

FOLDING CASEMENT: Casement windows hinged together so they may fold into a confined space, such as within the wall thickness. Small width shutters also makes it easier to close without stretching out too much. Folding casements are auxiliary shutters, such as storm shutters or Venetian shutters on the outer face or fly-mesh shutters on the inner face.

GROUP C

LOUVERED WINDOWS: Louvers are 'shutter elements' themselves, or elements within the shutter of an opening system like window or door. Louvers are a set of small to large width slats. Louvers are either fixed or movable, (adjustable) in horizontal or vertical position with pivots.

An awning window shutter is like a movable louver, but it is top hung. Louvers are placed within a shutter, or as an appendage over the outside or inside face of the opening system. Louvers provide visual privacy and control passage of air and shed the rain. Louvers also control the amount of direct sun light and the reflected light component by baffling and reflecting it. Louvers are also used in many utilities such as air distribution and sound proofing systems.

Louvers are used as fixed slats in openings to curtail view and reduce the glare, such as in toilet doors, walk-in-wardrobe doors, kitchen cabinets. Mediterranean homes have louvered door and window shutters as secondary doors for the same purpose. Jalousie windows are louvered windows. Modern jalousie versions have clear or frosted glass slats, and are used in tropical houses to cover up the verandah like spaces. Louver surfaces are treated to improve or reduce the reflection of light, solar radiation and for sound attenuation. Louvered shutters are placed both on inside as well as outside faces of the main shutter. Louvers as an appendage are also placed on the exterior face as Brise soleil and on inside as Venetian blinds.

Louvres are blades, slats, laths, slips of glass, wood, or other materials. Louvers are moved synchronously by a hinged lever arm. The angle of opening is often controlled by motorised louvers and light or sun radiation sensors. Micro width louvers are incorporated into narrow space between glass panes.

Louvers of wood perhaps originated in the middle ages to cover chimneys for escape of smoke, and on illumination roof lanterns to keep rain and snow out while allowing air ventilation. Alvar Aalto, Finnish architect has used the fixed and movable louvers in several of his buildings.

VENETIAN WINDOW: It is the same as the Palladian window, or windows with fixed louvered panels for ventilation, as auxiliary shutter.

JALOUSIE AWNING WINDOW: These are multiple top-hinged sashes, operated individually or synchronously, compared to a louvered window such as Jalousie windows. (For full article ref to Jalousie Windows 4.2.1.4.2 Historical perspective : Windows : Types : Wall windows )

BASEMENT WINDOWS: Wood or metal in-swinging sashes that is hinged at either the top or bottom forming an awning or hopper.

GROUP D

PIVOT WINDOWS: Pivots were the first mechanisms for doors and windows. Pivots were technologically easy to devise, but difficult to install and maintain. Early pivots were crudely made entities, but with better metal technologies pivots soon became hinges. Early pivot windows opened inwards. Even to day pivot windows opening fully or partly inward are difficult to seal the weather. Pivots are used in double hung sash windows for opening a sash to clean and maintain its outer face. Pivoted shutters have an advantage that these can be opened inward as well as outward, as in case of hydraulic floor pivots used in glass doors. Pivots are used for skylights, ventilators, hoppers and awning windows. Louvred windows or Jalousie has pivots. A friction hinge is a form of a pivot cum a slider. (For more refer to window mechanisms: pivots).

CENTRE PIVOT WINDOWS: OFF-CENTRE PIVOT WINDOWS: EDGE PIVOT WINDOWS PIVOT WINDOWS: Pivot windows rotate on a pivot that is either in horizontal or vertical position. The pivot is fixed beyond the edge -off-pivot, at the edge -an edge or corner pivot, at the centre -a centric pivot, or anywhere between the centre and edge -an off-centric pivot. A pivoted sash, when opens partly in, it may not provide completely sealed window system. Pivots are bearing systems that allow easy rotation. Older pivots used hardened bronze, gunmetal brass or carbon steel balls, requiring some lubrication, however modern pivots use Nylon or Teflon like plastics for non-wearing-self lubricating qualities. Pivots are used in double hung sash windows for opening a sash to clean and maintain its outer face. Pivots are used for skylights, ventilators, hoppers and awning windows. Louvred windows or Jalousie has pivots.

CENTRE-HUNG SASH: A sash that pivots on pins in the middle of the sash stiles and sides of the window frame to allow access for cleaning from the inside.

TOP HUNG INWARD WINDOW: An awning window pivoted at the top edge and with the bottom swinging-in.

HORIZONTAL WINDOWS WITH PIVOTS: These are generally centred pivots on the side jambs of the window. However, for auto release opening in industrial skylights, the upper section is made slightly larger than lower section by minute off-centric positioning of the pivot. The upper section being larger is heavier, so opens out or inward as soon as the catch that holds the shutter is released. Ganged horizontal pivoted shutters are called Jalousie shutters.

VERTICAL WINDOWS WITH PIVOTS: These windows have pivots on the top and bottom members of the window frame. The pivot could be centric or off-centric, and so the shutter sections opening inward or outward could be, respectively equal or unequal. The vertical shutter, if it extends out too much, it is likely to sway in wind and difficult to stay-put. Vertical pivot shutters are often ganged up by hinged bar or stick that allows their simultaneous operation. Very tall windows cannot have pivots at top-bottom as neat alignment of the set is difficult.

CORNER PIVOT WINDOWS: Corner pivoted windows usually are placed in offset position. These allow the windows with some gap near the side jamb to access the exterior surface for fixing or cleaning of the glass and painting. The offset position allows full weather sealing of the window and the shutter.

GROUP E

SASH WINDOWS: The word sash, derives from the French chassis, which means a frame or a window shutter that holds a glass pane. Technically sash windows refer to the opening system, where the framed glazed panels are opened by sliding vertically, or horizontally, compared with casement windows where shutters are hinged and open sideways. Sash windows, when opened, have no shutters projecting out, so resist rains better and pose lesser fire risk. Sash windows are less susceptible to warping due to moisture as the shutter is bounded by a frame. Sash windows open while remaining within their frames, and so are not as distracting as do the hanging shutters of the casement windows. The casement shutters had to be of small in width. Otherwise, they tended to 'drop'. The small shutter width required many mullions to divide the opening. The wrought-iron hinges and lead cames of the casement windows were dark and heavy, compared to the clean image of the sash window.

A sash window allows control over air ventilation, as it can be opened to a small slit to nearly 50% of the opening. By keeping open both the top and bottom of a sash window by equal amounts (in double hung sash window) allows warm air to leave at top and cool air to enter through the bottom.

The earliest-known use of sash windows was in the later part of the 17^th C. Sash windows with their better proportions and elegance compared to casement windows, soon became the most important visual element in buildings of the 18^th and 19^th C. Sash windows became so popular that people who could afford, replaced the leaded-light casement windows. Many 16^th and 17^th C houses have 'replacement sash windows', However, such changes were affected on the main facade only, less prominent facades and side faces continued with the original casement shutters.

The window tax (during 1696 - 1861, in England) forced people to wall-up unnecessary windows to save tax, and also add fictitious windows for the sake of composing a facade. In spite of the taxation (window tax and a heavy excise duty on glass in 1746) discouragements, this was the period when windows design saw some of the most innovative changes.

Windows were initially positioned flush with the front face of the building, but great fire of London forced authorities, in 1907, to set back all windows by 4" from the outer face of masonry. To further reduce the risk of fire, in 1774, the exposed wood box containing the cord and weight mechanism was required to be concealed in the side masonry.

The first sash windows of 17^th C were glazed with very heavy glass requiring thick oak frames and glazing bars. However, the availability of thinner cylinder glass from 18^th C onwards during Georgian period, sash windows became lighter and elegant. From 1850 onwards, production of plate glass allowed larger panes of glass. Larger and thinner glass panes eliminated the need for glazing bars. The reinforcement offered by the glazing bars was eliminated, and so horns had to be added to strengthen the junction of the meeting rail with the frame. In more expensive work, the glazing bars were made of iron or brass and painted to appear like wood.

To slide open a sash shutter by sliding up or down, its weight is balanced by counterweight concealed within the window frame. The counter weight bar of lead, wrought steel or cast iron is connected to the window by a sash cord or chain running over a pulley at the top of the frame. The wheels were of wood or brass. In later versions spring balances were used. In an earlier version the weight boxes, set flush with the outer wall, seemed very heavy, but in a later version due to fire laws the weight boxes were concealed in side masonry, making the sash window looks much lighter.

The glass used in early sash windows was not very clear, so the view through was fuzzy and as a result the presence of glazing bars, was a 'relief'. As glass technology developed larger panes, free of blurs and blemishes were available requiring thinner or no mid glazing bars.

The earliest sash windows were of natural wood colour, with brass and cast steel hones, joggles, weight covering plates etc. Curved horns, multi-arched heads, intricate mouldings, leaded lights and latticework started to appear in the sashes, which were often grouped into impressive bays and offset with ornate stone-reveals. The shutter and the side box were made from different quality of wood. The sash window was a strange mix of materials and finishes. White painted sash windows provided single finish effect, very well contrasted by the brick masonry. The white colour over glazing bars also reduced their presence against the glass, making the windows look more elegant. The preference for white colour sash windows has continued till today even though materials have changed from wood to plastics, steel and aluminium.

Before 1887 the houses tended to be painted in one colour, usually white, beige or gray. But later people began to paint their houses in lighter and brighter colours. The vibrant colours became a key identifiable feature of Victorian architecture. The latter part of the 19^th C brought a new attitude toward colour, but sash windows continued to be painted in the Queen Anne style of white.

Sash windows originated as an opening system with two distinct sections: the top was of a fixed glazing (divided into smaller lites) and the bottom section had a casement or sliding (vertical) sash. Some exceptional buildings had exterior-wall flushed windows with sash sliding horizontally and parking on the side wall.

The bottom and top sashes (two are not necessarily of the same size) were divided into 3 x 2 = 6, 3 x 3 = 9 or 4 x 2 = 8 glass panes. Each vertical rectangle reflected the proportion of the whole window. The 3 x 2 = 6 glass pane divisions have been accepted as the classical pattern for sash windows.

Windows with one movable sash are called single-hung sash windows, to contrast from double-hung side windows, where both sections open by sliding against one another, or by one shutter opens by sliding and the other opens out or inward with simplex hinges. Simplex hinges allow the shutter to get locked on one side while the other side is freed for opening for escape or easy cleaning of shutters from both sides. Typical double-hung windows of Georgian architecture feature the lower sash in front of the upper sash. The fixed sash at the top allowed it to match the curvilinear arched openings.

Triple and quadruple hung windows are used for tall openings, common in New England churches. Among the numerous types of 18^th C sash windows, the tripartite or Venetian consisted of a central sash with two side lights, one pane wide. The side lights were often fixed, with the sash cord running over their heads from the central sash into the weight boxes.

Double-hung sash windows were covered from outside by fixed louvered shutters for tropical climates. Some double-hung windows have a full window screen that needs to be positioned suitably over the open section. Sash windows were also built to appear as casements in Gothic and Tudor Revivals. These often involved elaborate detailing with moulded mullions and even concealing the boxes for pulleys and weights.

The growth in use of the casement increased during the Edwardian period, and by 1910 many houses were built with timber casements, with sash windows relegated to less important elevation. By 1939, the use of sash windows was confined to neo-Georgian buildings, particularly post offices, banks, public houses and local housing estates.

GEORGIAN WINDOW: A double-hung window. Early in the 18^th C, a classic glazing style Georgian window of 3 x 2 =6 panels per sash matured. This design, six panes over six panes, remained in use even after the advent of larger panes in the 19^th C. Georgian sash window remained very widely used form till the use of steel casement windows as a cheaper and functionally superior option became acceptable.

BARN SASH WINDOW: Placed on the main face of the barn to access the upper or mezzanine level directly for loading or unloading fodder from a truck or tractor. The window shutters are made of wood planks and rails, slide on a metal runner on the outer face of the wall.

YORKSHIRE LIGHT: It is a window with one or more fixed sashes and a horizontally moving sash.

HORIZONTAL SLIDING SASH WINDOW: It has two or more sashes that overlap slightly but slides horizontally within the frame. In UK, these are sometimes called Yorkshire sash windows, presumably because of their traditional use in that area.

BOX-HEAD WINDOW: The sash shutters slide vertically into the wall space above the header.

GUILLOTINE WINDOW: The first double-sash window, with only one movable sash and no counterweights or balancing system. Its peculiar name comes from its tendency to come slamming down. A peg was inserted through a hole in the movable sash and into a corresponding hole in the frame to prevent it falling.

HANGING SASH: It is a sash hung on a cord connected to a counterweight, also called hung sash.

COMBINATION WINDOW UNIT: Window containing a half screen and two glass storm panels. In summer the bottom storm panel is stored in the top frame, exposing the screen panels.

PRIME SASH: In double hung sash window one of the sash, usually the lower one is the operative unit and is called the prime sash.

GROUP F

SLIDING WINDOWS: GLIDING WINDOWS: Sliding is a very ancient method of fixing window shutters. The method was once preferred for it did not require use of metal hardware. For more on windows mechanisms ref to 4.2.3.2 WINDOWS MECHANISMS.

These are of two types: Horizontal or Vertical sliding windows. Horizontal windows slide along the gravity so require only sideways push and pull to operate. Vertical windows slide to or away from the gravity and require assistance for working away from the gravity. The assistance is provided by counter weight or coiled springs. Sliding windows' shutters, unless open out from their nominal opening gap provide a limited size of opening.

The sliding channels are either horizontal or vertical. The bottom section of the horizontal sliding channel carries the load of the shutter, so requires some assisted movement through a smooth gliding edge, wheel and rail, or groove arrangement. The upper section simply holds the shutter in place but may have side friction if the shutter is not stable in vertical position. Vertical sliding channels do not carry the load of the shutter, as the shutter is moved by hanging counterweights or by lifting and pushing.

A horizontal slider channel, was created within masonry or made of wood. It was installed on the interior face of the opening. Shutter fitting was not airtight and could be easily pushed open by an intruder. Exterior sliding channels are often used for installing auxiliary shutters like Venetian and other latticed shutters. The channel and the shutter both are susceptible to weather unless well covered by a weather shed. Georgian sash windows have one or both shutters moving in a vertical channel assisted by counter weights.

Sliding channels for windows were conceptually revived in Europe after the Japanese Shoji screens (Shoji doors 4.1.3.3 Varieties of Doors) became popular in 18^th C. Interior windows as partitioning device in drawing, dining, vestibules, etc. had very light shutters and were installed with sliding channels. Cabinet shutters, showcases, bookcases also had glazed sliding shutters framed in wood or thicker glass moving on sliding tracks.

Sliding channels for windows are in the form furrows or thin width rail tracks. The windows have a flat edge or wheeled to gliders. Some lubrication was required with early channels, but nowadays window and channel sections, both are formed or coated with self lubricating materials or materials with very low resistence like Nylon, Teflon, etc.

Sliding windows channels require very high accuracy of alignment. Wood is affected by moisture movement and cannot provide stable alignment in all seasons. Mild steel, extruded aluminium and plastics and co-extruded fibre composites provide the required accurate alignment and stability. Extruded mild steel sections have heavier wall thickness and rust so have a limited use in very heavy - large sized openings. Aluminium also rusts very fast and has a high rate of electrolysis loss, so must be oxidised and painted by dipping or powder coating. Plastics as a polymer do not rust or require painting, but are susceptible to UV rays and the fire rating is not good. Fibre composites (fibre glass + PVC or resins, etc.) as co-extruded sections are the best of all the available options.

Sliding aluminium and plastic sections are of many types: primarily channels for shutters and sections forming the shutter. Within these there are many variations: Channels are side edge channels, which provide holding space for the shutter, a top edge channel that has a non load-bearing rail, and a bottom section for drainage storm water. Shutter framing sections have two variants: Side edge sections are simpler whereas the top and bottom edge sections, move over the rail channels, and so have arrangements for fixing runners or sliders. In addition, the shutter sections have meeting edge sections, handle sections, etc.

To construct a very large opening system, a framing of a hollow box or T section is used to form mullions and transoms. These sections are with one or double facing grooves to lock the sliding channels or the glass fixing beadings.

Sliding windows with sufficiently strong glass panes are able to resist positive negative wind pressures, so are fairly safe in hurricanes. The size of opening once set remains unchanged and no wind stays are required.

HORIZONTAL SLIDER: A horizontal slider or sliding window has sashes that slide horizontally. There is one sliding channel per one or two shutters in duplex system. The shutter slider shutter must be so shaped for smooth operation that its width is at least half its height. Sliding windows are poor in terms of leakage at edges and meeting junctions. Shutters must have gasket systems at all such locations. Horizontal slider windows are typically more vulnerable to storm water and air leakage then any vertical sliding window.

VERTICAL SLIDING WINDOW: One or more sash that move in a vertical direction. Such windows have one (commonly the bottom one, going up) or both shutters as sliding unit. Some units have one slider shutter, and the other is, both a slider and awning like casements. Vertical sliding windows are common in bus and railway carriages. Georgian sliding windows are the classic examples of vertical sliding windows.

DROP WINDOW: A vertical window in which the sash can descend into a cavity in the wall below the sill. Fire warehouses have such shutters over ventilating openings like exhaust fan apertures, stayed by a thin combustible rope, which on catching fire releases the shutter to close and prevent spread of fire.

GROUP G

SIDE LITES: MARGIN LIGHT: A lite or light is a fixed or open-able, and often a narrow glazed window, next to or over a door or window opening. It provides light and ventilation to the vestibule area, when the main door or window is shut it allows delivery of mail etc. and interacts with the visitors without opening the shutter. Side lites visually widen the effect of the main opening. Side lites are placed in verandah and upper floor balconies. In the early 19^th C, the use of margin or side lites became very popular and, combined with cast-iron balconies, created a style now termed Regency.

TRANSOM LITES: TRANSOM WINDOW: An upper section opening above a window or door. An exterior transom window either is a fixed glass or has a sash that operates as an awning, i.e. top hung. However, an interior transom window is fixed, has a sash that operates with hinges at the sides, top or bottom, or has vertical or horizontal pivots. Modern day transom openings also incorporate a sliding shutter as framed glass or direct glass panes. Transom openings are used for ventilation when the lower side door or windows are closed. Transom openings are attached to the main frame of door or window, called transom lite, but could also be a distinctly separate entity. A transom with circular top may also be known as a fan lite.

MULTI-LITE WINDOW: DIVIDED-LITE WINDOW: A window glazed with small panes of glass separated by wooden or lead glazing bars or muntins, arranged in a decorative pattern often dictated by the architectural style in use. This was a common way of creating a large glass pane due to the historic unavailability of large panes of glass until the beginning of the 20^th C, but is continued as a tradition even today. Smaller pieces of glass joined by emphatic glazing bars overcome the visual defects in glass, which was very common in early glass.

FIXED LITE: FIXED SASH: A window which is non-operative (doesn't open).

FANLIGHT: TRANSOM FAN LIGHT: A half-circle window over a door or window, with radiating bars.

CHICAGO WINDOW: A large fixed sash, flanked by a narrow, often movable, sash on either side. First used by Chicago School architects in the late 19^th and early 20^th C.

GROUP H

PICTURE WINDOWS: FIXED WINDOWS: A picture window is a very large fixed window in a wall or as a part of a larger window set intended to provide an unimpeded view, like a framed picture. Picture windows occur on their own, alone, or as a mid unit in a bay window. A picture window has a very large clear glass pane that is often without any glazing bars, or it is glazed with only few glazing bars, near the edge of the window. Picture windows are also called fixed windows, because these cannot be opened, and serve limited function of view and illumination. However, a fixed window, such as in a transom lite, clerestory, skylight or lantern window whose function is limited to allowing light and not used to view out could have frosted glass. Fixed windows placed on shop fronts to show and protect the displayed items are called shop fronts or shop windows. A wall consisting of windows is called a curtain wall. A curtain wall over its glazed surface and through its framing system takes stresses induced by wind, vibrations, etc. It is a fixed window construction. Aquarium glass front is also a fixed window arrangement. A modern version of a fixed window has a wall mounted LCD screen or TV that shows a live or recorded video. LCD screens can be designed for one side video view, whereas from the other side it remains a see through window.

VIEW SASH: A view sash is used for viewing so has thinner and clear glazing. It has no muntins or glazing bars to distract the view. View sashes of various grades of 'clarity or transparency' are created by use of tinted glass, by mounting glass with metalized polyester film and staining by transparent colours. View sashes have mounted patterns, muntins, lattices or traceries to frame the view, to 'correct' the vision through as in case of early glass of fuzzy or wavy quality. View sashes or fixed windows with 'one way view' are used in interrogation rooms, child care rooms, observation rooms, etc. for visual privacy and noninterference.

SHOP FRONTS: SHOP WINDOWS: DISPLAY WINDOWS: First shop windows were very small sized openings, like a glazed section within a door or window. The glass in the door or window could only be enlarged to the extent of the frame. But the glass used for technological, economics and safety reasons were of smaller units. It just gave a glimpse of the activity inside, and an assurance to female customers that the shop is transparent and so safe. For the vision inside, the shop had to be brightly lit even during the day time. In small localities where the nature of a shop is familiar to everyone in the neighbourhood, display may not be important to attract a customer, but a display system for new arrivals or preparations was necessary.

Shop fronts endowed a unique architectural identity to the shop, and typecasting or branding for the nature of business in the shop. All shop frontages along a street were nearly of the same sizes so each shopkeeper tried to include exclusive features with the shop front. Exclusivity was achieved by architectural elements, configuration of the shop front, colour and other finishes scheme, signage, and above all by window dressing.

Pilasters and Consoles provided a strong edge to the shop front and enhanced it within the building. They also provided a separating feature for the shop front from the adjoining shop fronts. Fascias and Cornice were other elements incorporated with the shop face. A cornice was purely decorative above the fascia or used as cover for the hide retractable blinds, folding awning or roller shutters.

Old shops fronts were raised off the road level and also from the shop interior floor level, by means of a stall-riser. The stall risers provided a base for the display items and protected the shop window from ramming. With single piece glass system the stall risers have been eliminated. Earlier stall risers did not align well with the floor level entry door. Now the shop window glass and the door glass both are frame-less and almost reach the floor.

Early shop doors were half glass or with heavy bottom rails (as a feet knocking unit). The doors had engraved name and logo of the shop. The doors were floor pivoted, so opened both ways. Nowadays the doors have air-cascading fans to keep the interiors protected. However, butterfly leaf doors are rarely used, as shoppers find it difficult to carry purchase parcels through it. Automatic sliding doors provide better passage.

Shop fronts were, once not regulated. So upper floors were extended to protect the shop front area. Such unregulated projections extended to the edge of the footpath, and required support of columns. Over a period entire street had a continuous protected passage like a colonnade, like the designed colonnade in Connaught Place at New Delhi. However, later rules did not permit more than 11 inches of projected cover. The provision was used in shaping the shop window like a bay or bow window.

The display covered the entire frontage of the shop except the two major obstructing elements, the entry door for the shop section, and another door for the residential quarter on the upper floor. The shop door was set back to provide a protected entrance bay. It also allowed the shop front to form a bay shape and increase its perimeter. The bay shape also permitted the view of the interior from an angle when glare over the main face occluded the vision through.

The shop front window was tall enough to cover the entire height up to the beam bottom or the bottom of a projected floor above. It provided ample daylight, necessary for many North European locations. However, in S. Europe and other countries the shop front glass was stopped at door height level, covered by the sloping awning or used for translucent shop sign board.

Early Display windows were on the public street level, customer looking at the displayed items, and in few cases whole or part of the interior, all at the nominal eye level. But shops on the upper floors or at cellar level required a different setup. Street front display system at whatever level, was very important, but took away a lot of floor space. Display system visible from outside as well as inside the shop provide dual efficiency. Such dual faced display systems also allow greater view of the shop interior. Boutiques, parlours and showrooms used the entire interior volume of the shop as a display setup. Interior display units were very useful to showcase precious (jewellery) and easily perishable (food stuffs) items. Display units independent of the shop were also placed on public access routes such as bus depots and railway stations. Large departmental stores required interior display units. The shop fronts of large departmental stores had too many things to display, so graphics rather then actual items were placed.

Exterior shop front display substantially depended on day light for illumination, whereas interior display units were nearly dependent on artificial illumination.

Over the years the store windows have changed mainly for Four reasons:

1 The quality of glass and size, both have improved since Industrial Revolution. Major quality improvements have been for clarity of glass, such as free of colour tinge, specks, bubbles and undulations. The size of glass has increased several times accompanied by strength. Safety glasses such as toughened or laminated glass requires no other protective layer.

2 The store formats have changed from a single owner/ set of commodities or services, to departmental stores, malls' mega marts.

3 Neighbourhoods have changed from a street of a row of shops with residence on upper floors to shopping centres like clustered shops, shopping arcades, multi level shopping centres.

4 The illumination technology has changed. From spot lights, diffused lights, neon tubes, CFL, glow panels to fibre optics and LCDs.

All these have affected the nature of display windows. Earlier the glass panes were set within a wood-frame and divided by heavy muntins, as glass available was of small size and breakable. Heavy mid members obstructed the clear view. Very thin muntins or glazing bars of metal T sections provided uninterrupted look. As larger sizes of glass became available, single unit glass shop windows became common. Small pieces of glass, each reflected light differently so created a very patch look, but the large piece of glass as a single unit had only one angle of reflection. Large pieces of display glass were engraved or ground with borders and corner patterns to 'soften the look'. Large glass front require framing only at the edges, which are often concealed in ceilings, side wall panelling and flooring.

To reduce the glare folding canvas awnings were stretched over nearly covering above the head level section of the opening during sunny days or hours. Tinted glass and polyester film coated glass are used to reduce the solar gain and UV damage to the goods displayed. At places like beauty parlours, barber shop, it is possible to use heavy metal sprayed glass that has nearly one way vision.

Modern security experts desire a see through shop front than an opaque shop closing system. Many towns do not permit rolling shutters over shop fronts.

GLASS FRONTS: Glass fronts are very large fixed single glass or seamless glass panels within an architectural gap such as arched or flat headed masonry aperture or one formed by beams and columns in a framed construction. Glass fronts are designed for stability against vibration, displacement stresses, but not a significant amount of wind loads. Most glass fronts are at lower elevations and do not face heavy wind pressures. However very large glass fronts that cover several floors and column-beam bays, and bear heavy wind-pressures are called curtain walls.

Glass fronts became apparent in Gothic buildings with windows filling up the entire arcaded gap between columns, replacing the wall. However, as the glass available then was small, larger glass panes were composed by combining small pieces of glass with lead cams. The composed glass panes were fixed within a strong grid-work of mullions and transoms. Later in Victorian architecture extensive glass fronts were created in public, domestic buildings and conservatories, by using very large pieces of glass held by muntins or metallic glazing bars within a surrounding frame.

Muntins or glazing bars required beading or a mastic compound to weather seal the joints. Mastic compounds based on bitumen, asphalt, alkyd resins were not longer lasting, requiring frequent redo work. Natural rubber compounds were used more effectively after WW II. However, from 1955 onwards full range of polymeric and elastomer sealant compounds began to be available.

A separate ventilating opening system was required with very large glass fronts. But this issue was solved by centralised climate control systems. In large glass fronts wind or other lateral air pressures caused by echoes, sonic booms, expansion of air etc. are relived by patent gasket that expand and contract under specific conditions.

Glass has limited size due to manufacturing, transportation and installation issues. Very large glass fronts have number of horizontal or vertical joints. The vertical joints could have a framing intervention, but very often glass to glass joints are required to create a seamless front. A vertical joint if not properly sealed by a sealant will allow condensation formation outside an air-conditioned space and rainwater penetration in the monsoon. A framing intervention in glass front panelling invariably has greater depth, so has better lateral stiffness. But a glass to glass joint panelling has no such lateral stiffness, which however is now provided by multi-legged pin holders called spider leg holders, and connecting flying bars if necessary.

'Firemen's knock out panels are required for venting fumes and emergency access from the exterior. These are made from fully tempered glass to allow full fracturing of the panel into small pieces and relatively safe removal from the opening. Knock out panels are identified by a nonremovable reflective dot (typically two inches in diameter) located in the lower corner of the glass and visible from the ground by the fire department'.

CURTAIN WALLS: Curtain wall systems 'differ from glass front systems in that they are designed to span multiple floors, and take into consideration design requirements such as: thermal expansion and contraction, building sway and movements, water penetration, drainage and diversion or deflection, and thermal efficiency for cost-effective heating, cooling, and lighting in the building.'

A curtain wall is a building facade which does not carry any dead load from the building. However, other than its own self weight, it transfers the horizontal incidence of positive and negative wind pressures, seismic forces, maintenance loads and miscellaneous vibrations. A curtain wall is designed to resist air and water infiltration. The loads are transferred to the main building structure through connections at floors or columns of the building. Unitized curtain wall systems accommodate the differential movement between the structure and the thermal movement of the frame at the joints between each wall unit.

First curtain walls had steel members, and later of Aluminium, alloys and plastics. Curtain walls are conceived as glass panel in-fill within a frame or grid. Other materials used for curtain wall panelling include stone, precast cement concrete, metal sheets, composites of various types (plywoods, fibreglass reinforced plastics, paper bitumen sheets, multi layered plastics, etc.), shingles and louvres.

Curtain walls, in terms of their method of fabrication are of two basic types: In a mullion and transom system, the vertical members, often called sticks, are installed first. Alternatively vertical and horizontal members, both are set on the site to form a grid, within which glazing are installed. The vertical or horizontal members, both are visible or concealed or any one of the set is visible. The glass is either fixed from interior or exterior sides. In a modular system, large modules of one or two stories height, complete with mullion and transom members are factory assembled. The unit when installed on site, form a visible or concealed grid. These are also installed from interior or exterior sides. For low rise construction with easy access to the building face, outside glazing fixing is preferred. For high-rise construction interior glazing fixing is favoured, but if swings and cranes are available external fixing can be used.

Sight-lines are defined as the visual profile of the vertical and horizontal members of the curtain wall system. The sight-lines are a function of both the width and depth of the curtain wall frame. Lateral load resistance requirements (wind loads, spans) generally dictate frame depth. Sight-lines may be 'heavier', i.e. revealing or stronger in a look or 'lighter', i.e. concealed or less revealing, slimmer in a look. A curtain wall presents a very different image on the interior face then what is perceived on the exterior face. A curtain wall externally concealing all its support system and showing edge to edge glass panes without any perceptible surrounding frame can have another set of internal glazing panelling to hide the frame structure or for greater insulation.

Internal divisions of curtain walls may not match with internal needs of space segmentation. Some of the lateral partitions must touch the glass face, so require to be very carefully managed for air and noise leakage and spread of infection (as between hospital spaces). Another problem of similar nature occurs at the floor junction. A curtain wall may recognise the bottom or top or both edges, and have a matching horizontal member. Alternatively the curtain wall unit may override such a junction. In both cases appropriate design solution must be planned to prevent air and noise leakage and infection spread.

Glass alone and all over a face cannot satisfy the thermal and visual comfort, privacy, and solar gain control. Modern curtain wall panels are often made with double or triple thicknesses of glass separated by air space for insulation. Sound attenuation capability of curtain walls is improved by placing in-fill material within frame sections and by making construction as airtight as possible. Thickness of glass, cavity provision in dual glass system also improves sound proofing.

The exterior face of the glazing and the framing sections help shed away the water. Yet, water can enter curtain wall system by means of: gravity, kinetic energy, air pressure difference, surface tension, and capillary action. Water resistance is a function of glazing details, frame construction, drainage details, weatherstripping, frame gaskets and sealants.

SHADOW BOXING: This an interior treatment over an opening to create the appearance of depth behind a transparent glass of a fixed window. A glossy, plain or textured surface is placed close (40 to 50 away) to a glass pane on the inside face of an opening system. The interior backdrop of reflective surfaces adds the most visual depth.

CABINET WINDOW: A projecting window for the display of goods, as in a retail store.

PANEL WINDOW: A form of picture window consisting of several sashes or fixed glazing but separated by crossbars or mullions, or both.

CORNER WINDOW: It is the corner arrangement in a bay window or the meeting arrangement in a bow window. Two adjacent glass panes meet edge to edge and form a straight or angular junction. The edge may be sealed in extreme climates by a mastic compound or thin width masking tape. The joined glass relives the nominally opaque corner. Such junctions are commonly used on shop fronts and glass fronts.

SPLAYED WINDOW: A window unit set at an angle in a wall, rather then the nominal at right angle position.

COUPLED WINDOW: Paired windows or two shutters separated by a mullion or multiple sets of paired windows or shutters.

DOUBLE WINDOWS: A window with an auxiliary shutter on the inner or exterior face, such as storm, fly-mesh or Venetian. It is also an insulating window with air space between glass panes.

DOUBLY GLAZED WINDOWS: An insulating window with air filled or vacuum space between glass panes.

STACKED WINDOWS: Combined grouping of awning, hopper, casement, or non-operative windows to form a large-glazed unit, such as for covering stair cases, and large glass fronts.

TRIPLE WINDOW: Generally it refers to any threesome group of windows with square heads, such as found in Palladian architecture and in colonial revival houses. The treble sash windows stretched from floor to ceiling, in tall rooms of 18^th and 19^th C houses of America.

BAND/RIBBON WINDOW: One of a horizontal series of three windows or more, separated only by mullions, that form a horizontal band across the facade of a building Most commonly found in buildings erected after 1900. Le Corbusier has used ribbon windows in his buildings like Villa Savoy. Frank Lloyd Wright used Band windows to highlight horizontality of the elongated eaves roofs.

LEAD LIGHT: LEAD GLAZING: STAINED GLASS: A window with small panes of glass set in grooved rods of cast lead or came. The glass may be clear, coloured, or stained.

GLASS BLOCKS: GLASS BRICKS: Glass blocks are a hollowed block used in building partitions, covering openings in slabs and walls. Glass blocks provide a fixed glazing for feeble illumination in passive areas such as basements, parking, passage, stair landings, shower stalls, attics, etc. Glass block walls though provide dull illumination, are used in extensive areas to create a 'glow wall'. Glass blocks are available in many sizes and thicknesses. Heavier thickness blocks ( more then 75 tk) are used for construction of glass walls or for casting into floor slabs. Lighter sections are used singly. Similar blocks of Acrylic and polycarbonate materials are also available. Commercially the common block size is 200 x 200 x 100. It has rim or edge side chase area to receive the cementing material. The blocks as unitized construction allow curvature formation in slabs and walls. The inner surface of the block is moulded with patterns and that prides a unique surface quality. Coloured glass blocks are also available. Glass block walls are weather resistant and difficult to break-in. Glass blocks are more energy efficient than traditional plate glass fixed windows.

Glass block sizes include: 100 x 200 / 150 x 150 / 150 x 200 / 200 x 200 / 300 x 300. Styles and finishes include: Bevelled edges, Corner blocks, End blocks, Angled blocks, Radius blocks for rounded walls, Double ended block for step down walls, Satin or matt finish, Sandblasted matt finish and Engraved or acid etched finish. New types of Glass blocks include Fibre optics, LEDs and LCDs to provide self illumination. Glass blocks also include fluorescent treatments that provide 'afterglow'.

GROUP I

EMERGENCY EXIT WINDOW / EGRESS WINDOW: A window large enough for exit-entry by people and with easily a reachable sill, so that occupants can escape through the opening in an emergency, such as a fire or disaster. Such openings also require appropriate surroundings for the purpose of escape. In the United States, exact specifications for emergency windows in bedrooms are given in many building codes. Vehicles, such as buses and aircraft, frequently have emergency exit windows as well. Such windows have no protection bars and gazing pane that are easily breakable in an emergency.

There are Four International Residential Code (IRC) requirement for egress openings: The clear opening (without the frame) must be at least 500 wide and 600 high, but subject to total size of app 1.5 sq. mts. The ground on either side must not be more than 1100 deeper from the bottom level of the opening. The window must operate from inside, and open to a yard street or porch.

DOGGIE OR CAT WINDOW: These are placed alone or within a door shutter but very close to floor level so that a pet can negotiate it easily. Most such windows are one-way, i.e. allow free entry or exit. When both-way passage is possible, the window is called a flap window.

DELIVERY WINDOWS: At domestic level delivery windows are used for milk, groceries, newspaper and postal articles. As technology of packaging, nature of commerce and mode of delivery changes, the size, shape, configuration and location, of such openings also has changed. Earlier many houses in Europe had a coal delivery window at cellar level, but now gas and electric heating systems have changed the need. Bottled milk delivered at home is now a rare event, as milk is purchased in tetra pack from a departmental store on weekly basis. Delivery windows were part of the door shutter or as an appended system near the main entrance or kitchen door. The delivery window had two shutters, with some space in between the two for storage of delivered items. The double shutters provided privacy to the house holder and safety of the delivered product.

SERVICE WINDOW: These are the small size openings provided to access the vertical ducts or horizontal passages such as drainage, AC, ventilation and electrical cables ducts. The size is determined whether a person uses it for repair access and inspection or for entry into it. In the later case the sizes are wide enough for egress and sometimes tools, equipments like scaffolding, etc.

FIRE WINDOW: A window with fire-endurance rating specified for the location and use. Fire-resistant Ratings FRR is given to a tested complete window assembly. FRR refers to periods in minutes for specified fire resistence of the window. Structural adequacy refers to the ability to maintain stability and adequate load-bearing capacity. Integrity is the glazings ability to resist the passage of flames and hot gases. Insulation refers to the ability to maintain a temperature on the glass surface not exposed to the fire.

GROUP J

SUPER WINDOW: A popular term for highly insulating window with a heat loss so low that it performs better than an insulated wall in winter, since the sunlight that it admits is greater than its heat loss over a 24 hour period.

SMART WINDOW: A generic term that refers to windows with switchable -chemically active or photo sensitive coatings to control the solar gain. Windows with draperies and blinds offer very limited ability to control the light and nearly mask the view. Whereas, electro-chromatic glazing can darken and lighten gradually, in response to the gradually changing conditions. And even in its most darkened or coloured state it still permits a clear views of the outside.

ALUMINUM-CLAD WINDOW: A window with a wood or wood composite core but covered with an aluminum sheet. The outer sheet may be powder coated or anodised to resist the elements.

KNOCKED-DOWN: Not assembled. Parts for a window frame pre-manufactured for assembly later on a job site.

LABELLED WINDOW: Windows bearing fire-rating labels of Underwriters' Laboratories (UL).

DOUBLE WINDOWS: A double window has two sets of shutters, opening on the inward and outward face or sliding one over the other. The main shutter is either opaque or glazed but the second shutter could have Venetians, lattice, fly-mesh or opaque panel. The dual layering of the shutter, offers multiple optional facilities.

MULTI GLAZED WINDOWS: A doubly glazed window has singular layer of shutters, but the glazing panes are double layered. The layered glazing has a space that is vacuumed, sealed or filled with inert gas like Argon or Krypton. The double glass panes offer four surfaces for various types of treatments. The gap between the panes can be increased for more effective noise insulation, but this reduces the effectiveness of double glazing as a heat insulator. Multi glazed windows have shutters of substantial thickness and weight. Double glazing helps to reduce the medium to high frequency range noise levels. However, double glazing cannot filter out loud or low-frequency noise such as of traffic.

INSULATING GLASS (IG) WINDOWS: An insulated glass window consists of at least two panes of glass held apart by a spacer. The surface of the spacer is metalized and sloped outward or inward to reflect back the radiant heat. The spacer also contains an absorbent substance -a desiccant, which prevents moisture accumulation in the cavity and prevent fogging.

GROUP K

INDUSTRIAL LITES: Industrial lites include fenestrations of many different varieties, such as clerestory windows skylights, North lights, port holes, roof monitors, atriums, etc. These opening systems mainly serve for illumination and ventilation needs. The illumination required is of dull brightness for warehousing areas, to very bright light in fine work areas. However, many other issues that dominate design are: consistency of brightness throughout the day, maximizing the day lighting hours, increasing or eliminating solar radiation depending on the climate zone, distribution, incorporating the ventilation system, safety and security and maintenance.

NORTH-LIGHTS: North-lights are placed on a face away from the equator (North or South respectively in the Northern or Southern hemisphere). Beyond the zone of 23N and 23S, sunlight never enters from North / South sides, which means an opening on this face provides daylight without the solar radiation. North lites are used in all types of buildings, but more so in industrial plants, to take maximum advantage of the day light.

SAWTOOTH ROOF LIGHTS: A sawtooth roof has series of triangular section roof units, where the shortest side, as a vertical or slightly inclined plane form the opening. The other side forms the roofing plane and reflector for the daylight. Sawtooth lights are placed across the width or length of the structure and also at any angle to match the North or local conditions. These systems were once called 'weave-shed roofs'. The availability of continuous top hung steel sashes in the Industrial Age encouraged use of saw tooth openings. An angled glazing causes problems of dust collection, snow loads and leakage.

ROOF MONITORS: Roof monitors are the raised sections of the roofing system used for additional lighting or ventilation. The additional side walls available due to raising of the height are opened up to install ventilating apertures. Roof monitors are placed in the mid section of the large industrial plants to cause a ventilating draught.

ATRIUM: Atriums have a Roman origin. Central areas of large villas had open courtyards to provide illumination. Modern day Atriums have pyramid, dome or half cylinder like structure that is glazed all over. The glazed surface is fixed to preclude leakage, but to stop for green house effect and ventilation, the vertical sides (the collar area over the perimeter) are provided with louvres or open-able shutters. Atria were used over shopping malls to form a Bazar like shopping street. Louvre Museum, Paris has a glass pyramid covering the exhibits. Hotels and resorts create a multistoried atrium plaza by covering up the sides and the roof with a glazing system. As such structures are very large, require additional framing to resist the wind loads. Such atria have automated glazing system to control the brightness and solar radiation.

LIGHT TUBES: Light tubes are ducts that are glass-lined or have embedded fibreoptic conduits. One end is taken to roof surface, where by means of flat, parabolic or concave surface illumination is concentrated, the other end inside an interior space, the intensified light is thrown through a diffusing filter over a reflecting surface such as wall, floor or ceiling. The system is passive but could have electric light to supplement during night hours and dull days. The light tubes can also work as passive ventilating ducts with stack effect.

OPERABLE WINDOW: A window which can be opened for ventilation.

GROUP L

FALSE WINDOWS: A false window is both an interior as well as exterior element. On exterior sides the dummy window is placed to compose a series or symmetry on the elevation. False windows are placed to hide view of suspended ceilings, partitions, beams, etc. An exterior window may not be visible on the interior face as it is masked by walling, panelling, cladding, etc. The false window as an interior element may enlarge the size of an exterior window, or as a new insert creates some configuration. False section is backed with shadow boxing (ref to GROUP H). False windows are commonly not meant for ventilation.

False windows were frequently used in Revival architecture to stretch the flat or bay window to the upper floors, add on a fake dormer, internally stretch a mid level sash window to the floor or ceiling levels, and to generate a proportionate scheme for interior panelling. False windows are also created to confirm to local Planning and Zoning Regulations.

CAMEO WINDOW: Cameo windows are true windows unlike false windows, however, the styling these represent on exterior and interior fronts are different. This is done to confirm the styling of the street front, confirm to regulations for alterations and renovation. A cameo window could be a masking element to provide modern day technological efficiency. An old style window construction may not weather seal the premises or its energy (heat transmission) efficiency is not appropriate, so a new set of window system is placed against the existing system on the exterior or interior front. The cameo windows also help to redefine the shape and size. In colonial revival houses an oval or round window created to match the exterior mouldings and ornaments had a camouflage system on the interior side. Cameo windows were created between two sash windows as panelling system, but housing painting, exhibit or a bookcase.

GARAGE DOOR WINDOWS: These windows are part of the garage doors that open by sliding upwards and horizontal towards the ceiling. The windows are mainly for breaking the large monotonous surface of the door and only occasionally to illuminate and ventilate the interior space.

DUTCH DOOR - WINDOW: A Dutch door has two sections, the lower section when shut, the upper part acts as a window opening. The upper section often has extra latticed shutters for security or glare reduction.

CAFÉ TYPE: A shutter unit that only covers the lower portion of a window.

QUARREL: A diamond- or a square-shaped glass piece set diagonally. A medieval term for small panes of glass set diagonally in Gothic windows.

LOZENGE : A window with glazing bars set diagonally.

PROJECTED WINDOW: Projected windows like Caboose in Automobiles and railway carriages that allow sideway view of the street or estate. However, unlike an Oriel or Mashrabiya window these have smaller width and projected depth, often occurring as a projected niche. (ref to: for more on Caboose)

BLANK WINDOW: See false windows.

4.2.2.2 ELEMENTS OF WINDOWS

Keywords: BRISE SOLEIL / sun baffle / baffles or fins / louvres / depth of the baffle / spacing / arrangement / dampen sound / privacy and physical intrusion / Mashrabiya / Qamariyah / Zarokhas / Sudare / Venetian blinds / create a surface homogeneity / Le Corbusier / brise de soleil / atrium cover / jalis or stone lattice / CHHAJJA / WINDOW LEDGE / WINDOW SILL / WINDOW SEAT / ZAROKHA BAITHAK / FOIL / a basic pattern flower or leaf having 3/4/5 petals or leaflets / tracery / trefoil / quatre-foil / cinquefoil / TRACERY / Bars or rib / relief -blind tracery / hollowed out -pierced tracery / decoration over walls and windows / screens in stone / pierced marble screens / plate tracery of the tympanum / foil work / cusped circles / rayonnant tracery / flamboyant tracery / perpendicular style of Gothic architecture / LATTICE / GRILL / JALI / sticks or rods / bamboo and cane / sheathed in copper sheets / forming and indenting / plate tracery /geometric patterns / floral patterns / British period / square or a lozenge shaped holes / woven wire called gauze or mesh / knitted or entwined wire called chicken mesh / expanded metal / wrought Iron lattices / forged or shaped / chiselled, chased, rivetted, shape forged / plate like tracery / ends, finials and cresting / rivetting and hot forging / WINDOW HEADS / transoms / decorative / lintels or beams / flat, segmental, circular to pointed / plate and pierced tympanum, traceries, lattices / pediment / SPANDREL / spandrel wall / spandrel beam / TYMPANUM / pediment / Romanesque and Gothic periods / PEDIMENTS / heading mass / flattened triangle / horizontal line, and an angular (triangular) or curvilinear top.

BRISE SOLEIL: (Fr =sun shield) A screen to break the sunrays and often cut the sun light entering into a building. A brise-soleil or sun baffles are placed outside the windows or over a building's face to shield a wall or roof from solar radiation. Brise soleil are horizontal, vertical, inclined in both planes or a combination as a 'pigeon box' grid. The baffles or fins are often manually or automatically adjustable in the form of louvres. The efficiency of the system depends on depth of the baffle, spacing and its arrangement in reference to the position of the sun, or source of annoying glare from the reflective glass facade of opposite building, a brightly paved courtyard, beach or water body.

Baffles are also used to dampen the sound such as from busy street, railroad, high speed boating lane or airport. Fine baffles or lattices are used to shield interior spaces for privacy and physical intrusion. Mashrabiya and Qamariyah openings of Arab world, Zarokhas in Indian buildings, Sudare screens of Japanese buildings and modern day Venetian blinds serve the same purpose. Brise-soleil is also used as an outer covering over the facade to conceal not only building's many functional elements but create a surface homogeneity.

Le Corbusier for the first time in 1933 designed an architectural baffle system, brise de soleil, for an Algerian office block. Later he used horizontal gear-operated, adjustable baffles for an office building in Rio de Janeiro, Brazil. Corbusier has used masonry and cement concrete brise soleil in many of the Chandigarh and Ahmedabad buildings. US Embassy in Delhi uses baffles all around its perimeter as atrium cover over a central water pond. Jalis or stone lattice in Mughal and Rajasthan architecture serves the same purpose as Brise-soleil.

CHHAJJA: A chhajja is an Indian shading device over any opening, like doors, windows, Zarokhas or verandah and may cover plain walls for architectural continuity. Chhajjas reduce the sky component from solar radiation and reduce the glare. Mughal Chhajja is in inclined slabs of stone placed over the lintel stone, but super-loaded with some masonry and parapets. Wooden framed Chhajjas with wood planks as covering or flat ceramic roofing tiles are common in Pol houses. At places the wooden and stone Chhajjas are superficially supported by richly carved solid as well as hollowed out brackets. During British raj Chhajjas of galvanised corrugated sheets supported over a wooden frame became a cheap and lightweight option for Bungalows and Government buildings. These chhajjas were hinged at the top end and supported by end hooked steel rods that allowed to shut them in heavy monsoon showers. Chhajjas work like canvas awnings, but are heavier and more durable.

WINDOW LEDGE: An outside horizontal element of a window, a bottom section of the window-related setback in the masonry but which may not be a sill at the base of the window frame. A window ledge also occurs as a projection at the floor level. Window ledges provide a baseline for pilasters, half columns and engaged columns placed on sides of a window opening. Window ledges other than decorative function serve many functional needs, like protection to floor and wall below and support base for servicing. A window ledge is used for placing flower planters but is a nuisance as doves sit here and spoil the lower section of the building with their droppings.

WINDOW SILL: A window sill is placed at the base of a window frame on exterior and interior sides. Similar sills were placed under door openings. Once the sill stone provided base for inserting the base for the pivot, and maintained the width of the frame. Exterior window sills are often inclined and width-wise projects out to drain of rain water. Interior sills are of wood, polished stone tapering such decorative surfaces. Interior sills for low level windows are as window seat.

WINDOW SEAT: A window seat is a sill wide enough or extended to accommodate a seating posture for one or many persons. The sill is at comfortable height (between 250 to 650) or alternatively against a taller sill additional seat is provided. Window seats are provided for good view, adequate illumination and better ventilation conditions.

ZAROKHA BAITHAK: A Zarokha baithak is the raised platform that is the floor or base of Zarokha. The raised Zarokha has two columns and is surrounded on three sides by short height tapering parapets. The projecting platform and the width of the wall together provide sufficient width and depth for two or more people to share the space. The inner most face of Zarokha was masked by a bamboo strip roll curtain. The outer face of the wall aperture within the Zarokha, sometimes had wooden shutters or the street faces of the Zarokha were covered by stone lattice. The Zarokha as an ornamental opening had a centric and dominant position in the room space. The niche of the Zarokha seems like a royal throne.

FOIL: The term is derived from the Latin folium, meaning leaf. Gothic windows were headed by pointed arch, and mullions were continued to form small pointed arched units. The rest of the area was pierced with a circle inscribed with a basic pattern flower or leaf having 3/4/5 petals or leaflets. The carved foil patterns were called tracery or decorative openwork. There are many varieties of such foliated decorations: trefoil, quatre-foil, and cinquefoil -lobed leaves. Arabs also fretted arches with cusps.

TRACERY: Bars or ribs like elements that are used for decoration in relief -blind tracery, or hollowed out -pierced tracery, form. Figuratively, tracery is any intricate line pattern used as decoration over walls and windows. The term is applied to decorative elements of Gothic architecture, and also for screens in stone, wood and metal of European architecture, Mughal buildings in India and Islamic windows of Persia, Turkey, and Egypt, etc.

European tracery originated in Byzantine work, in which pierced marble screens often embedded with small glass blocks were used in openings. During and after the Romanesque period, tympanum (top portion of circular arch opening) was pierced for decorative effect, which ultimately separated as a rose window. In early French and English Gothic buildings, plate tracery of the tympanum was pierced with a single circular pattern inset with a four-lobed pattern, called foil work. Later, the number and complexity of the pattern increased. During 13^th C, large window openings formed under a single arch were divided by stone mullions. The tympanum, instead of being filled-in by plate-pierced tracery, had bar or rib like elements that continued the stone mullions. In France, the bar tracery had cusped circles.

Early tracery had mouldings of only one type, but French Rayonnant tracery used different types of mouldings according to the size of the mullions or ribs. The French developed flamboyant tracery of free and flowing curves producing windows and architectural adornment of extra ordinary lightness and intricacy. During late 14^th C, the Perpendicular style of Gothic architecture, the curvilinear tracery over the straight mullions also became straight enhancing the verticality.

LATTICE: GRILL: JALI: One of the most primitive forms covering an opening for safety was sticks or rods inserted horizontally, vertically or both in the peripheral structure. In China, India and other Asian countries bamboo and cane are in use for ages. Other primitive forms of lattice forms were basket weaves, loose woven rugs, crochet work fabrics, knitted fabrics fastened over an opening. For openings in forts and estate walls stronger material was required for grills. Stone and bronze were the first options. For decorative treatment stone, wood, bronze grills were sheathed in copper sheets, which was then surface treated by forming and indenting. Stone grills were of pierced plate tracery type. Jalis of geometric patterns were first employed in South Indian temples, and later in Mughal architecture in India. Free floral patterns were used extensively in Hindu buildings and occasionally in mosques and mausoleums. During the British period verandah, passages and other open spaces were covered on sides by cross stripes of wood, forming square or a lozenge shaped holes. The verandah like spaces were also covered with jalis of woven wire called gauze or mesh, or knitted or entwined wire called chicken mesh. Jalis expanded metal aluminium or mild steel were used. In all these cases the mild steel was annealed and rusted very quickly.

Wrought Iron lattices began to be used 13 and 14^th C windows opening, especially those of the treasuries of mansions and cathedrals, required high security and were filled with strong interlacing bars of solid iron. The horizontal and vertical members of the lattice were forged or shaped to form an inseparable union. In the course of time when the need for protection lessened, the grills became less massive and opened way for ornamentation. Some time during the 15^th C cold working of the iron allowed steel to be worked like a wood. Iron pieces were chiselled, chased, rivetted, shape forged. Iron plates were also used for plate like tracery elements. Round and square rods and bars were twisted, coiled and beaten into complex foliage forms. Ends, finials and cresting were cast from materials like brass or bronze and mounted over steel roods. Rivetting and hot forging was chief techniques of joint making. However, joints were so skilfully done and concealed that the grill seemed like one cast or formed piece.

WINDOW HEADS: A window is headed by many different types of elements, many of which have a structural role, i.e. supporting the overhead loads, but many others are dividers like transoms, and still others like a Toran, are simply decorative, i.e. shaping, framing and proportioning the opening. Lintels or beams are flat headed elements made of wood, stone steel or cement concrete. Variety of arch forms, such as flat, segmental, circular to pointed are used. Arch is much stronger form in terms of its mass, but creates a void in the upper section that must be filled in. Historically a plate and pierced tympanum, traceries, lattices have been used for the purpose. Upper sections of the windows have been top mounted with a decorative configuration called a pediment. A pediment may skilfully conceal a flat headed or arched structural entity.

SPANDREL: also spelled Spandril, is roughly a triangular area above and on either side of an arch, bounded by a line running horizontally through the apex of the arch, a line rising vertically from the springing of the arch, and the curved extrados, or top of the arch. When two arches adjoin, the entire area between their crowns and springing line is a spandrel. If it is filled in, as is ordinarily the case, the resulting structure is termed a spandrel wall. In medieval architecture it was usually ornamented. In buildings of more than one story the spandrel is the area between the sill of a window and the head of the window below it. In steel or reinforced concrete structures a spandrel beam is a hollowed entity between two floors extending horizontally as a large span from one column to another. The triangular area under stair flight over a ground floor is also a called spandrel.

TYMPANUM: Triangular or a semi circular piece over an opening system, often surrounded by archivolt. It can be said to be an area above a lintel but under the heading arch or the area within a pediment. The area is often decorated with sculpture in the Romanesque and Gothic periods.

PEDIMENTS: A pediment is any decorative mass over an opening, niche or any heading mass, such as over a roof top, parapet, cabinet, chair or other items of furniture. The most basic form of the pediment is a flattened triangle (low rise) emulating a classical Greek or Roman building. Pediments have become very complex in shape and in a depth configuration. Most pediments have a strong base or horizontal line, and an angular (triangular) or curvilinear top, however, both of these have been cut. Pediments contain statuettes, circular openings, oculus windows, medallions, coats of arms, etc.

4.2.2.3 COMPONENTS OF WINDOWS

Keywords: WINDOW FRAME / configured aperture / wall / structural grid / glazing pane / sash system / grills or safety bars / hardware / window treatment systems / high lighted, minimized or concealed / built-in / solid frame type / cased frames / external openings / climate and security / internal openings / casing, linings or panelling / replaceable / shell structure of the glazing material / HORNS / splayed / HAUNCH or HAUNCHION / horns / JAMB / lintel and sill stones / spacer bars / double hung sash windows / cavities for counter weights / reveal / wider jambs / double shuttered windows systems / extended jambs or casings / architrave moulding / casing or panelling / weather stripping / mullions / transoms / muntins / EXTENSION JAMB / jamb lining / jamb extender / HOLLOW JAMBS / SASH / WINDOW SHUTTER FRAME / chassis / four framing members / head and bottom rail / side hung windows / bottom supported windows / pivoted and sliding / mid stiles / mid rails / divider rail / mid column stile / centrally pivoted opening / CASING / architrave / HEAD CASING / MEETING RAIL / double hung sash window / extra horizontal rail / lock or check rail / MEETING STILE / meeting rail / ANGLE BRACE / MULLION / vertical member / structural element / functional and decorative components / side hung casement windows / friction hinge system / side lites / Palladio / foliage / Industrial Revolution period / floral configuration / vertical nature / transoms / Rose windows / radial ribs or dividers / stained glass windows / inner edge of mullion's face / architecturally on exterior face / interior face / muntins or glazing bars materials / mullions without glass panes / curtain wall system / sticks / concealed / vertical elements of panelling and partition system / unitization / BOXED MULLION / MUNTINS / mullions and transoms / sash bars / glazing bars / cames / Tee section / steel casement windows / common patterns created by muntins / 6 x 3 rectangular divisions / lozenges or diamond shapes / lead cams / highlighting lines / CAMES / stained glass windows / TRANSOM / transom bar / beam or bar transom lite / LIGHT / LITE / OPERABLE TRANSOM / ANCONES / Todla / ARCHITRAVE / ASTRAGAL / moulded wood profile / meeting stile seal / RABBET / REBATE / GLAZING / putty or glazing bead / BEAD / putty lining / BEDDING / GLAZING BARS / muntins / GLAZING CHANNEL / GLAZING CLIP / GLAZING GASKET / SADDLE BAR / FACE GLAZING / INTERIOR GLAZING / EXTERIOR GLAZING / BALANCE SPRING / coiled springs / PARTING SLIP / PARTING BEAD parting strip or stop / BOSS / CAP / CAFÉ TYPE / TILT BAR / hinged / pinned or pivoted / REGLET / STORM CLIP / LABEL / LABEL STOP / HEAD FLASHING / DRIP CAP / WASH CUT / sill or ledge / WATER DRIP / WEEP CUT / drip cut / HEADER / flat headed opening / lintel, beam or a flat arch / arches / wood beam

WINDOW FRAME: A window at simplest level is a configured aperture in a wall or within a structural grid. The wall or structural grids by themselves are not efficient in accommodating a regulatory mechanism that is the essence of a window. It requires at least two side members or a four-sided assemblage. A window system may consist of a matrix of four side assemblages. A window frame houses a glazing pane that is single, layered or composed out of pieces of glass, or a sash system employing variety of hanging or sliding systems. The window frame also houses grills or safety bars and many different types of hardware to keep the sash closed, open or in secured position. The frame often accommodates number of window treatment systems within its body space. A curtain wall is an opening system in the form of an exterior wall with a framing that is high lighted, minimized or concealed.

A window frame is called built-in when fixed during or with the masonry and is of solid frame type, but frames for double-hung sash windows are hollowed frames, called cased frames. External openings require heavy duty framing due to climate and security reasons, but Internal openings have lighter requirements and so may be hung-fixed directly to the casing, linings or panelling, without any heavy framing. By keeping a window a separable entity from its holding structure such as a wall etc. it becomes easily replaceable.

Very large glass walls of an atrium, green houses, etc. require lateral stiffness, nominally not available within the opening system. The stiffness is acquired by forming a shell structure of the glazing material or by integrating the opening frame with the structure of the building.

HORNS: These are ears like projections from the horizontal members (at top and bottom) of the window wood frame. The ends are slightly narrowed down -splayed, on all their four sides, for fixing the frame into masonry. A non splayed horn of a surface-fixed frame is seen through the plaster.

HAUNCH or HAUNCHION: Some frames are fixed over the finished masonry (i.e. not during the masonry work), plastered openings or over casing or panelling, in which case horns are not required or a very small horn, called a haunch is used.

JAMB: Vertical members forming sides of a window frame. Jams are held apart by similar bottom and head members. In early periods, rural windows consisted of only jambs inserted into the lintel and sill stones, or were secured by spacer bars of wrought iron or mild steel. Side jambs of double-hung sash windows have cavities for counter weights to move. An exterior portion of the jamb is called a reveal. Wider jambs are required for double shuttered windows systems. Extended jambs or casings are required to cover up the wall width on exterior and interior face of the window. Where the window on interior face is offset by a small depth from the face, the left out space, if small, is covered by an architrave moulding, and if wide, it is covered by a casing or panelling. On the exterior side, if the left out space is small, it is covered by weather stripping -a type of storm water repealing architrave moulding, and if large, is covered by stone cladding. Jambs are also made of stone or carved in stone masonry. In a window framing system, the vertical mid-members are called mullions and horizontal ones are called transoms. Mullions and transom have nearly same sectional size (though could have slightly a different configuration) as jambs, but thinner sections called muntins are also used for subdividing the frame. Stone jambs, mullions and transoms often have an additional inset wooden framing for fixing window sashes (open-able shutters).

EXTENSION JAMB: A board or panelling that is used to increase the depth of the jambs of a window frame to match the width of the wall is also called a jamb lining and jamb extender.

HOLLOW JAMBS: Jambs for double-hung windows have cavities formed through casings for movement of counter balance weights.

SASH: WINDOW SHUTTER FRAME: The word sash has derived from a chassis, meaning a frame to hold a glass pane. Earlier it was set into masonry work forming the jamb, mullions and transom. The sash was hinged, pivoted or placed in a sliding track to form an open-able shutter. The shutter frames were invariably of wood, but during the last 150 years rolled and extruded sections of mild steel, aluminium, and polymers have nearly replaced wood. During last couple of decades, the sash less windows of glass, acrylic and polycarbonate sheets are widely used. A sash has essentially four framing members, but could have more. The head and bottom rail are nearly identical except minor details for handling the storm water.

For a typical side hung windows the top and bottom rails have tongues, and the vertical members, the stiles have grooves. For bottom supported windows such as pivoted and sliding the framing joinery method is other way around, which is the side members', stiles have tongues and bottom members, rails have grooves, and run for full width.

Additional mid stiles and mid rails are used to divide the shutter, for creating a pattern or to provide additional stiffness. For louvred shutters such as Venetians a divider rail is used to create two separately operable units. A set of mid vertical and horizontal members was used to form a cross in religious architecture. In a centrally pivoted opening, the mid column stile runs vertically at the place of a pivot, and additionally has horizontal top and bottom rail to support the glazing.

CASING: A thin band, strip or trim, plain or moulded, planted over the internal and external face of a window frame to cover up the space between the frame and adjoining masonry or the surface finishes like plaster, cladding or panelling. Casings are also called the architrave.

HEAD CASING: Top or an upper member of any element or structure. In windows, it refers to the top of the frame.

MEETING RAIL: In a double-hung sash window two sashes meet and overlap, at this junction an extra horizontal rail is required to keep the shutters away from each other, climatically seal the gap and act as lock or check rail.

MEETING STILE: these are required for horizontally sliding sash system, and in abutting casement windows serving the same purposes as the meeting rail.

ANGLE BRACE: This is a temporary member fixed to a window frame or shutter at opposite corners or two upper corners to maintain the squared position during handling and installation.

MULLION: A mullion is a vertical member that divides a wide opening. A mullion could be a structural element supporting lintel above and adding to the lateral stiffness to the window plane. Otherwise, mullions are functional and decorative components. Mullions provide side support to the glazing panels, or frames that hold the shutter or sash. Mullions as a side member or jamb are necessary for side hung casement windows, but can be avoided in friction hinge system.

A set of mullions around a central glazing pane creates side lites. One of the most famous side lites was created after Palladio. Mullions are straight members, but in gothic architecture the upper sections of the mullions branch out as foliage. Mullions are fluted with one profile through their length, but in post Industrial Revolution period mullions of cast steel with a floral configuration were used. Here mullions' vertical nature was diffused and coalesced with transoms, which are nominally horizontal elements. In Rose windows the radial ribs or dividers have no distinct mullion or transom definition.

Mullions are important elements in stained glass windows. Mullions divide the mythological stories into sections, or a large story board is created by ignoring the intermediate presence of the mullions. This was also achieved by using mullions of very thin sections and by placing the stained glass on the inner edge of mullions' face. This arrangement enhanced the divisions of the window architecturally on exterior face but created a large continuous or smooth plane on the interior face. Mullions of very thin size used to join small pieces of glass into a glazing pane and so with no structural role are called Muntins or glazing bars.

Mullions are made of materials such as wood, stone, steel, aluminium or polymers. Stone and wood mullions without glass panes are placed over openings to create a partially open space and for creating a sense of security, privacy and an architectural pattern.

In case of curtain wall system, a mullion is connected to floors, and transmits stresses during earthquake and other structural movements. Curtain wall mullions are highlighted on the exterior face as sticks or concealed within the window system by additional layer of internal glazing or panelling. Vertical elements of panelling and partition system, if add to the lateral stiffness are also called mullions. Vertical sticks or mullions allow unitization of window and grill system. Window panes with surrounding framing are assembled in a factory and inserted between the mullions on the site. Such a system also allows easy replacement of parts.

BOXED MULLION: These mullions have a hollow space where counter weights of a double-hung sash window are inserted.

MUNTINS: Muntins are thin mid members in glazed windows and screens. Muntins were required, when for technological reasons the glass size was small and not perfectly smooth. Muntins are non structural members and are thinner compared to the mullions and transoms which have a structural role. Muntins are also called sash bars or glazing bars, and if very thin, then cames. Muntins as glazing bars are designed to hold glass panes from both side edges through beading or caulking putty. The common metal glazing bar has a 'Tee' section. Muntins could be horizontal, vertical, slanted or even floral, whereas the mullions are vertical, and transoms are horizontal. Steel casement windows have several muntins to divide the glass so that in case of breakage, only a small section may require replacement. Muntins or glazing bars are made of wood, bronze, drawn sections of mild steel, aluminium, polymers and composites.

Most common patterns created by muntins were 6 x 3 rectangular divisions in Georgian and other double hung sash windows, and lozenges or diamond shapes when placed diagonally. In stained glass window mullions and muntins break the picture into pieces. Lead Cams and later of various alloys were used to join glass. Lead cams were skilfully placed to define colour boundaries, folds of draperies and other marks in the scene as a very thin highlighting line, often coloured in black.

CAMES: Thin stripes of lead, groove edged to join small pieces of glass into a large pane for use in casement and stained glass windows. Cames often followed the lines of the artwork, such draperies, garments, scenery, etc., and were painted black for highlighting. In early 19^th C lead cames were replaced by alloys containing copper and tin. After WW II polymer compounds and elastomers are widely used as cames.

TRANSOM: A transom bar is a member that divides or separates a window, so it is within a window, above a door or another window. In architecture, it is a transverse beam or bar that separates an upper level window from a door or window below it. A transom lite is a window in the upper section of a door or window, but could have independent position anywhere in the upper section of a room. Transom lites are rectangular, fan shaped or circular (oculus or rose windows).

LIGHT: LITE: A smaller window or a pane of glass that is placed on side or top of a door or window. A lite also indicates the number of divisions a glazing pane is composed of. For example classical double-hung windows have two sashes, each of which has 2 rows of 3 units; also, called 6 over 6 lites.

OPERABLE TRANSOM: A glazed sash, usually over a door which may be opened for ventilation.

ANCONES: (Gk.= elbow or hollow) Consoles are on either side of a door or large window frame for supporting a cornice overhead. It is a projection either from the frame itself or from the column or pilaster placed beside the frame of the opening. In Gujarat, India, vernacular houses have a Todla projecting out of the junction of transom and jamb.

ARCHITRAVE: A moulded frame around an opening or gap.

ASTRAGAL: An astragal is moulded wood profile that is placed as a stopper and cover at the meeting place of two shutters. It is also known as a meeting stile seal. It seals the joint against weather, sound leakage, passage of light and smoke in case of a fire. An astragal provides stiffness to the door shutter.

RABBET: A cut or groove along the edge of adjoining stiles of two shutters, so when overlap, a sealed joint is formed that stops penetration of light and protects privacy.

REBATE: A cut along the stile and rail for fixing a wood, glass or panes of other materials. Panes are fixed by glazing putty, wood or metal bead.

GLAZING: Installation of glass or other transparent to translucent panes in a window opening or within a sash. To hold the glazing pane, putty or glazing bead is used preferably on the exterior face.

BEAD: A small section wood or metals strip, often shaped, used to fix glass panes in a window or its sash frames. The beads are mitre cut at corners. A nominal tradition is to keep the face of the bead slightly sunk or projecting from the face of a frame, the stile or rail. Beads are nailed in wood sections, or fixed with machine screws in metal sections. Putty lining is an option for beading. Nowadays beads are laid on caulking compound or sealant to make the edge water and draught proof. Modern curtain walls' glass panes are fixed without any bead, directly by a sealant or into a holding gasket. Beads are also called a glazing bead, glass stop, wood stop or sill bead.

BEDDING: Method of glazing in which a thin layer of putty or glazing compounds is placed in the glass rebate and the glass is pressed into the bed. The glazier then shapes the deposit with a pointing tool and it is covered and finished by putty. A 'green' bedding does not dry out, remains wet, soft and pliable for a very long time. It helps in absorbing vibration in glazing materials.

GLAZING BARS: Glazing bars, often called muntins are used to compose a larger pane out of smaller pieces. Early double hung sash windows had 6 over 6 lites with glazing bars. The glazing bars of wood, and sometimes of metal are used.

For Casement windows, customarily, horizontal glazing bars are continuous from one sash side stile to another, but vertical glazing bars are intermittent. Whereas for vertical sliding sash windows, it is other way around. This is done to prevent the sagging of the glazing pane assembly.

GLAZING CHANNEL: Groove or rebate cut into window frame or sash to receive the glass panes.

GLAZING CLIP: A metal clip for holding glass, temporarily or permanently in a metal frame while putty is applied.

GLAZING GASKET: Special extruded plastic, shaped for attaching window glass to metal or masonry wall opening. It also serves as a cushion against vibration and other loads. A gasket is a good heat and sound inhibitor.

SADDLE BAR: A light steel bar placed horizontally across a window to stiffen leaded glazing.

FACE GLAZING: Common glazing set with putty in a rebated frame.

INTERIOR GLAZING: Glazing panes that are installed from inside of the building structure have the interior glazing bead or putty. The pane joint is likely to be leaky compared to exterior fixed glazing. Interior glazing is used when outside access for fixing is unavailable, such as in tall buildings.

EXTERIOR GLAZING: Most common method of glazing. Typical issues for such fixing are: How to carry the glass to the required location, how to bring the glass from interior space to the exterior when there are safety bars in the openings, how to fix the furthest edges of very large glass, how to fix the last panel of the glass. Exterior glazing has lesser leakage problems, but inspection, replacement and maintenance are difficult.

BALANCE SPRING: Early double hung sash windows had counter weights of cast metal for ease of opening and closing, but these were heavy. In later period coiled springs were used for the same purpose.

PARTING SLIP: A thin wood strip that separates the counter weights in the side box of each jamb of double-hung windows.

PARTING BEAD: Two sashes of the double-hung sash windows are separated by a vertical strip on each jamb, also called parting strip or stop.

BOSS: Carved ends of weather mouldings of doors and windows. Bosses are often carved with heads of angels, flowers, or foliage.

CAP: Decorative moulded projection, or cornice, covering the lintel of a window.

CAFÉ TYPE: A shutter unit that only covers the lower portion of a window like Dutch window or door.

TILT BAR: A vertical bar connected to all louvres, so louvres can be concurrently position adjusted or closed. Tilt bars fixed to the edge of the louvres are hinged whereas when fixed to the small edge, are pinned or pivoted.

REGLET: It is plastic, fibre composite, metal, rubber or wood moulding inserted in a concrete or masonry side wall to create a perfectly sized opening and a uniform housing groove, for a spline-type gasket to receive the window glass.

STORM CLIP: Devices attached to the muntin of a metal sash to stop the pane from moving outwards.

LABEL: A projecting moulding by the sides and over the top of an opening.

LABEL STOP: Ornamental projection on each end of a label, sill, or sill course. Often takes the shape of a gargoyle or other decorative carving.

HEAD FLASHING: Flashing is installed in a wall over a window.

DRIP CAP: Horizontal moulding to divert water from the top casing so water drips beyond and outside the frame.

WASH CUT: Bevelled cut over the edge of sill or ledge to drip out storm water.

WATER DRIP: Moulding sometimes used on exterior surfaces of an in-swinging casement sash to prevent water from being driven over the sill.

WEEP CUT: A groove -drip cut, on the bottom part of the ledge, a horizontal board, sill or any other masonry projection to throw off (drip out) the storm water and thereby prevent to run over the wall or opening below it.

HEADER: A horizontal member that supports the upper section and transfers its loads, so that a safe and stable opening is formed in the masonry structure. A flat headed opening has a lintel, beam or a flat arch as the heading element. Openings are also headed by many different types arches: segmental, circular and pointed.

A lintel and flat arch extend beyond the opening gap just enough to get a bearing surface that is adequate for load transfer and stability, whereas a beam extends up to a junction in a masonry structure or a load-bearing element like a column.

The term header is generally used in reference to a wood beam, whereas a lintel often refers to a stone, steel or cement concrete beam. (For more Ref to Elements of Windows 4.2.2.2).

4.2.3.1 MATERIALS AND TECHNOLOGIES

4.2.3.2 WINDOWS MECHANISMS AND HARDWARE

Keywords: intentional apertures / illumination and ventilation / orientation and seasonal relevance / regulators / multi functional entity / simpler entity / lesser quantity / fewer varieties / prime regulatory mechanism / security / lattice panel / forerunners of the hinge / first-ever locking device / country tile covered roofs / holes / clerestory openings / architectural vocabulary / graphical identification or tags / warm climates / colder regions / glazed open-able shutter / wedges / by tying / control the quantity of illumination, air change, view or the access / permanent lattices / twigs into side masonry wall / masonry surrounds / stone pivots / bronze / stone lintel and threshold / replacement pivot nose / iron pivots / square frame / hung as a shelf with a pin / snug fitting / glazed with translucent materials / glazing materials were composed as panes / compact grains / strength and superior detail execution / transparent, thinner and larger glazing materials traceries / wood / multiple shutters / interior side / exterior side / Palladian motif / repeated use of one type of window size and shape / Georgian double hung sash windows / large sized openings/ gas / electric illumination / large glass windows / shop window front / hot rolled steel sections / forged wrought iron sections / industrial fenestrations / aluminium sections / extruded plastic sections.

GLASS / glass technology / glassed -glazed windows / crudely stretched disk / coloured glass / glass cast disks / Le Corbusier / Notre-dame-du-Haut / flattened bottoms of blown glass vessels / cylinder glass / arcs of concentric circles / wave lines / contamination by metallic compounds / imperfections in manufacturing / small size of the glass / joining small pieces with lead lining / stained glass / buildings in Constantinople / Saxon buildings / internal and external splays / Tudor window / open-able shutter or casement windows / projecting system / single and double hung sash windows / non projecting system / 6 over 6 format / fire finished ground plate glass / cast Plate glass / board glass / rolled sheet glass / music lines / plate glass / sheet glass / floating glass / fire-polish / float glass / figured and cathedral glass / glass colours / safety glass or shatter proof glass / armoured glass / a layered composite system

STAINED GLASS/ inconsistencies of colour and clarity / pre Gothic windows / images of holy figures / story board / colouring a glass for stained glass / POT GLASS / FLASH GLASS / coating or flashing / STAINING / ENAMELS / first Golden Age of Glass / coloured glass windows / pictorial windows staining and painting processes / Christian religious buildings / Muslim palaces / Vidimus / three types of stained glass windows narrative windows / figurative windows / patterned windows / rose windows / post Industrial age stained glass windows / traditional stained glass windows / cartoon / lead cames / special glass paint / waterproof and rattle-proof / mastic compound / postural compositions / three-dimensional perspective / cristallo glass / glass corrosion / glass disease / Art Nouveau / Belle Epoch.

COPPER CAMES / Tiffany / PLIQUE A JOUR / translucent enamels / stained-glass window in miniature / GRISAILLE / bands / monochrome colour painting / GLAZING / GLAZIER / OPALESCENT GLASS / cathedral glass / IRIDESCENCE / CATHEDRAL GLASS / TRANSLUCENT GLASS / LATTICELLI - RETICELLI / flash or layered glass / STREAKY GLASS / WISPY GLASS / TEXTURES / BLACK ENAMEL PAINT / MEDALLION OR NARRATIVE WINDOWS / FIGURE WINDOWS / ROSE WINDOW / PAINTED GLASS / PICTORIAL WINDOWS / ANNEALED GLASS / float glass / TOUGHENED GLASS / tempered glass / TIFFANY / La FARGE / FAVRILE GLASS / STREAMER GLASS / FRACTURE GLASS / FRACTURE-STREAMER GLASS / RIPPLE GLASS / RING MOTTLE GLASS / DRAPERY GLASS / BREAKER-GROZIER PLIERS / SILVER STAIN / CAMES / FLASHED GLASS / FERRAMENTA / LEADED GLASS / LEADED WINDOWS / BEVELLED WINDOW / INSULATING GLASS PANES / SOUND-INSULATING GLASS / TRIPLE GLAZING / DIFFUSING GLASS / FROSTED GLASS / manufactured / post production treated / figured glass / armoured or wired glass / opalescent glass / Groung glass.

STEEL WINDOWS / wrought iron / ferramenta or saddle bars / copies of wood windows / iron windows / hot rolled steel sections / extrusion sections / cold rolled steel sections / CRCA sheets / pre-coated mild steel and stainless steel / extruded sections / industrial steel windows / ALUMINIUM WINDOWS / tarnished on exposure / wears off due to electrolysis / stiffeners at mechanical joints / welded / high thermal conductivity / anodizing, oxidizing / painting / direct contact / stiffeners and hardware / good design / industrial plant / thermal breaks or discontinuities / small hollow units inside / standard sized windows / shape stability / aluminium extrusions / foils / PLASTIC WINDOWS / extrusion / pressure moulding / thermoplastic material / composites / PVC WINDOWS / plasticizing compounds / vinyl or vinyl siding / coefficient of expansion and contraction / uPVC -unplasticized PVC or Rigid PVC / acrylic / FIBREGLASS / layered composite / wood jamb section / fibreglass filler / plastic matrix / extrude COMPOSITE WINDOWS / engraved bronze / glass panes in-fill panels / stone mullions transoms and muntins / galvanic isolations / wood as a core fill / SEALANTS / temporary seal / permanent seals.

First windows were merely intentional apertures in a masonry wall for illumination and ventilation. Window apertures function with nature, so their orientation and seasonal relevance were very important factors of design. To serve so many function the apertures were further conditioned with add-on systems or regulators. Over a period of time the windows became a multi functional entity, but a technologically very complex one. A simpler entity employing lesser quantity and fewer varieties of materials has always been the design goal.

Early dwellings had only one opening, and it was also used for entrance, illumination and ventilation. The prime regulatory mechanism required for such an opening was for security. Grass, sticks, branches, etc. were stacks tied or woven to form a panel, and placed to cover up the opening. The lattice panel was weighed down by heavy stones or tied to a side post. The ties, forerunners of the hinge, were of vines, ropes or hide straps. Another side post was required to hold the closed panel, and this again was done by a rope, the first-ever locking device.

The opening, if tall, its upper section was left open or covered by another fixed lattice panel. The lower and upper section now had distinct functions. The lower section was for entrance and the upper for illumination and ventilation. Upper level openings were favoured for ventilation and ventilation, and were devised in many different ways. Thatched or country tile-covered, roofs had crevices, which were good ventilators, and in solid roofs holes were provided for the same purpose. Later by staggering roof planes clerestory openings were created.

The door and window began to serve distinct functions and accordingly had the size, shape, location and appendages. Materials and technologies for each became sharply focussed. Even today one is serving the others' purpose. The size, shape and technologies though distinctive, the consistency of architectural vocabulary often was intentionally made similar. The unification of the door and window forms is so complete that graphical identification or tags, such as entry-exit, are required.

The nature, size of openings, location and their distribution require attention to complex set of issues. In warm climates windows and doors, both were latticed to allow greater ventilation. Their number and extent were kept small due to problems like storm water, glare, solar radiation gain and privacy. In colder regions, substantial illumination meant greater solar radiation gain, but large window areas with thin thickness were poor in thermal insulation. In absence of viable glazing the openings had to shut opaque or open, forcing its sparse use.

A window with a glazed open-able shutter nearly solved all the issues. The open-able shutter was not a novel entity, and doors already had such leaves, offering many different options in illumination, climate and security control. Doors like leaves were installed in window openings. These shutters were at higher datum or sill level and not meant for access through it.

The window shutter, like the door, was heavier, stiffer, opaque and opened inward on pivots. First window shutters were of solid wood planks or few planks joined together by top and bottom rails. The shutters were held open by wedges placed under them or by tying to the nearby wall. Like the door, window opening size was adjusted to control the quantity of illumination, air change, view or the access. Permanent lattices were created on the outer or inner face by inserting twigs into side masonry walls. The shutter was not a tight fitting and leaky for cold winds and rain storms. Masonry surrounds, small projections over the sides, tops and as a threshold provided a cover for better fit. Pivots required a non wearing nose and a harder base. Stone pivots were heavy and difficult to attach to the wood plank shutter. Bronze was a better option, but in many locations it was difficult to procure it. For pivot base stone lintel and threshold were adequate, but had to be removed to insert a replacement pivot nose. From 6^th C. AD iron pivots were made, these pivots had long arms for attaching them to wood by nailing. Stone surrounds were lined with a 'square' frame of wood mainly to hold the pivot. The pivot instead of being inserted into the sill and header was now hung as a shelf with a pin. With this arrangement it was easier to lift a shutter off its place and no masonry alterations were necessary to repair a shutter. The surrounding frame and the shutter had snug fitting, and both became thinner.

In large buildings of Northern Europe, windows in the lower section had fixed panels and in upper sections had lattices that remained always open. This was done to avoid body-level cold draughts. Domestic buildings such as houses had fixed windows for illumination and doors were used for ventilation. Open-able shutters were rarely used. Fixed openings were glazed with translucent materials like thin alabaster, marble, mica, greased parchment, canvas and paper. Ground pieces of glass were also pierced into wood planks. With the pivot-hinge like shutter opening system, the glazing materials were composed as panes and held within a frame, to form an open-able shutter.

Fixed windows had framing system of stone or wood. Materials with compact grains were used for better strength and superior detail execution. These included marble, granite, hard woods, cast bronze, lead and wrought iron. Finer quality materials reduced the bulk, created a much lighter window allowing more light. As transparent, thinner and larger glazing materials became available, framing members became equally thin and elegant. Elegance was achieved by curvilinear patterns such as traceries of Gothic buildings.

Wood remained favourite material for window making for nearly 2500 years. Wood sizes became thinner and it was used more efficiently. Windows became very intricate in detail, complex in working and well proportioned. From 17^th C onwards, metals which were used as hardware and adornments, now began to be important components of the windows, such as glazing bars. Wood windows were painted. Windows in public buildings and residences of upper class invariably had multiple shutters, and were treated with draperies. On an interior side the window was integrated with the panelling and other cabinet work. On an exterior side window was conceived as a composite architectural entity, such as the Palladian motif. Buildings were designed with repeated use of one type of window size and shape, such as the Georgian double-hung sash windows. The trend of large sized picture openings of Gothic architecture began to manifest differently. Production of large and clear (fault less) glass encouraged very large sized openings. The resultant brilliantly day lit interiors also required brighter, colourful, elegant and well-spruced furniture and furnishings. This trend was also aided to a great extent, first by use of gas and then electric illumination which removed the soot and smoke.

Drawing rooms, entrance vestibules became spaces to be displayed through the new large glass windows, just like goods in a shop window front. The mind set about security of glass began to change.

During the Industrial Revolution period hot rolled steel sections began to replace forged wrought iron sections. These new sections were used in industrial fenestrations like fix glass openings, and saw tooth North light trusses windows, multiple stacked casement windows, skylights, and commercial atria and roof covers. Timber still remained material for windows' construction for the elite. After the WWII aluminium sections, first almost copy versions of rolled steel sections, but later light sections of very thin walls were produced. Aluminium was non rusting, easy to fabricate and required less maintenance. Aluminium sections are now being replaced by extruded plastic sections, co-extruded and formed sections of composite materials. Metal alloys typically copper and bronze with aluminium, and stainless steel may soon replace plastics.

The need for a window has completely changed. Large or deep spaces are artificially illuminated and ventilated. Inside-outside relationship has also changed. Outdoor or indoor audio-visual connectivity is possible through TV screens.

GLASS: Historically development of a window has been moulded by the glass technology. Glassed (glazed) windows have in turn changed not only the Architecture and Interiors of buildings, but life styles and cultural aspirations of people. Glass was the best window covering material man would ever have in the past two millenniums.

Glass manufacturing was known to the Phoenician mariners, but Syrians were the most eminent glass makers of the ancient world. During 1500-1300 BC, after the conquest of Syria, glass manufacturing came to Egypt. The first glass was made by a primitive process of casting, where the melt was poured onto a plate and then drawn with pincers, creating a crudely stretched disk. The size of the disk was small, shape irregular and translucency muddy. Production of coloured glass was not very significant, but usage by Romans was extremely profound. Glass cast disks were placed in punctures in walls and roofs. The sides of the punctures were chamferred to enlarge the dazzling effect similar to what Le Corbusier has done in Notre-dame-du-Haut, Ronchamp, France. Later flattened bottoms of blown glass vessels having better transparency were used. Large size plates of crown glass were made by splicing the bottom part of a blown globe and flattening it. Similarly mid section of a blown glass cylinder was spliced and flattened on a furnace top to produce cylinder glass. Crown glass was characterized by arcs of concentric circles, whereas the cylinder or board glass had wave lines. Crown glass appeared to be of better quality than the cylinder glass. Yet, in both the cases glass never 'water white clear' its tones ranged from purple to green, chiefly due to contamination by metallic compounds and imperfections in manufacturing methods. The size of a glass pane was small. Clarity was obscure, reasonable for illumination, but not for view through.

The small size of the glass was a major problem, but it was overcome by joining small pieces with lead lining into a large glazing pane. The glass joining techniques became so refined that joints were very thin lines and designed as boundaries of colour and texture within a picture. A new medium of creating art work -the stained glass, came into being.

Large buildings in Constantinople were fitted with glass windows. Religious buildings were constructed with nearly unlimited budget, so cost of glass or its transportation distances were never an issue. But ordinary people for their domestic buildings used the easily available and affordable opalescent colourless glass. The opening size of windows remained small. In Britain, solid wooden shutters were never completely replaced by the glazed sash. In Saxon buildings the window shutter rarely exceeded 230 in width, owing to many reasons like: the absence of glass, the necessity for defence, the structural limitations, and weather protection. Internal and external splays were used to increase the flow of natural light. The Tudor window limited by the size of glass available, had small units, divided and supported by mullions and transoms. This style also prevailed during the Elizabethan Period. In the Netherlands small width shutters were useful against driving rain. Open-able shutter or casement windows were projecting system, with shutters hanging out of the plane of the frame and so had structural limitations of size.

Single and double-hung sash windows were non projecting system, with shutters remaining within the frame. Sash windows allowed larger size of glass and greater number of glazing panels within a shutter. But the glass available was not completely flat, of even thickness and 'see through' clear. The sash was divided into equal rectangular units. Many combinations of patterns have evolved but most accepted one has been the 6 over 6 format (per shutter 3 horizontal x 2 rows = 6). It has dominated the architecture for nearly 400 years. The glass used in sash windows was not perfectly clear for vision, but clear enough to show the curtains or the grandeur of interior at night. During the 1900's it became possible to have large show rooms or display windows due to the availability of large sized, reasonably faultless fire finished ground plate glass.

Glass manufacturing saw a quantum jump in terms of capacity and quality. During the 17^th C Crown glass measuring 600 x 400 almost without the curvature was produced. A new technique was developed in France, where the glass was spread out evenly by rollers and subsequently ground and polished. Such cast Plate glass was used for large mirrors and glass coaches for the nobility. Board glass was improved in 1832 when the cylinder was made larger, and allowed to cool before being split by a diamond instead of the iron shear. Board glass, due to its inferior quality and uneven surface was available at lower price and used by the poor people. In 1847 by casting the glass directly on a table, cast plate glass of 3 mm thickness was made. These sheets were dull and opaque but often coloured, fluted or impressed with a pattern. These were suitable for skylights and glass roofs, where clear polished glass was not required.

In Belgium during 1904 production of rolled sheet glass began. The molten stream of glass was 'baited' from a fire clay slot and drawn away in the form of a sheet by means of a series of rollers, and was cut to the required sizes. Glass was mass produced but was of inferior quality with 'music lines' and devitrified glass crystals.

'The problem of drawing chamber and flattening bed was solved by drawing the glass vertically by a flat iron heated bar as 'bait' and bent to a horizontal position. The sheets were cooled by water coolers, allowed to set, then reheated over the bending roll by a gas burner before passing through an annealing lehr. While devitrification was eliminated as the glass was drawn directly from the bath instead of through a slit. The surface of the glass was often spoilt in bending over the roller, the temperature of which had to be closely controlled and the surface carefully prepared in order to prevent damage to the surface of the glass. The surface thus produced generally lacked the brilliance'.

'In yet another process, the sheet was drawn directly from molten glass, but was not bent to the horizontal level. Thus the proper (the original formation) surface of the glass was preserved and devitrification minimized. However, the drawn glass tended to 'waist' or to become narrower in width, and this was overcome by a pair of air-cooled, gripping rollers to hold the edges of the sheet just above the level of the furnace'.

The development of plate glass was prompted by the need for perfectly parallel surfaces (even thickness) which were not readily available from the sheet glass. Since 1688, plate glass had been made by casting. The molten metal was poured on a casting table and rolled out into a sheet. Grinding and polishing was done on a table with glass sheets embedded in plaster of Paris. The table was rotated and water containing an abrasive, usually sand, was fed under runners. Grinding was done by two circular iron- shoed discs. Coarse sand was first applied and finer grades of sand or emery was then used to obtain a perfectly flat, smooth and silky surface, After grinding, the sheet was moved to the polisher to be further polished by felt pads.

An improvisation was achieved in sheet glass casting by rolling the glass to produce a smoother sheet with less waves and wrinkles, Smoother glass helped in reducing the amount of grinding. A continuous grinding machine which ground both sides of the ribbon simultaneously was devised.

In 1952 Pilkington Brothers Limited produced a floating glass by casting a continuous, 2540 wide ribbon of glass over molten metal. Heat was applied from above and below to raise the temperature of the ribbon surfaces to achieve a 'fire-polish'. The float glass was able to give high surface finish, flatness and minimized distortion.

A variety of decorative glasses were developed. Figured and cathedral glass was made by extrusion between two rollers to produce various degrees of transparency and textures. The glass colours were generally obtained by the addition of metallic oxides which dissolved in the glass melt mass giving characteristic tonal colours, blue with cobalt and copper, red with manganese and copper, green with chrome and nickel and yellow with carbon and sulfur.

Safety glass or shatter proof glass was developed by embedding a wired mesh during glass casting. It is often called armoured glass. Glass nowadays has not just remained a single pane but a layered composite system. It is composed by specialized assembly techniques with several layers, of fillers, cladding, coatings, films, a vacuum, etc. Many of these techniques are well-guarded patents.

STAINED GLASS: Till 10^th C interiors had natural light from splayed windows, upper level openings and skylights. The windows either were pierced with traceries or covered with opalescent glass of various hues depending on the quality of raw materials and production technique. The inconsistencies of colour and clarity became little less prominent when a glass pane consisting of smaller pieces joined with lead was used. Such pre Gothic windows illuminated the mosaic and drawn paintings on the load-bearing walls. However, the structural revolution with the pointed arch and flying buttress, almost removed the load-bearing wall surfaces from the interior space and replaced it with extensive window surfaces. It was also an expensive proposition to use so much glass. 'A Cistercian interdict of 1134 restricts the use of white glass, as an overindulgence'. Glass surfaces were treated with images of holy figures, and later found patrons for creating a story board, all in colourful glass mosaic. The interior now had little less brightness, but became very vibrant with colours.

There are four primary ways of colouring a glass for stained glass windows:

POT GLASS: A clear glass with sand, soda and lime and potash is produced and colours in the form of various metal oxides are added to the glass melting pot. Copper oxide produces blue-green, Gold yields ruby or red, Cobalt gives blue, Manganese purple and Iron various shades of green to yellow Impurities in these oxides leads to a very wide variation of colours.

FLASH GLASS: Colouring through pot glass was unpredictable. Colours of the pot glass were too dark, subtle colours and intermediate tones were not possible. Flash glass is made by coating or flashing white glass with thin layers of coloured glass when before cooling. Flash glass is more transparent then pot glass.

STAINING: Pot glass and Flash glass, both had their limitations. Certain body-skin hues were not possible or were rather too heavy or opaque. Early in the 14^th C light colour glass was over painted with a preparation containing silver sulphide or chloride. When re-fired, the silver changed to a yellow colour. Subsequent staining and firings produced a deep orange.

ENAMELS: Enamels are coatings of compounds of ground glass and oxides, which on firing becomes transparent, but imparting colour and some texture. Enamels do not have the brilliance of pot metal glass. However, the quality of clear glass over which the enamels are applied provides the brilliance.

It is believed that coloured glass came from ancient Egypt or further East, to Phoenicia and from there to Greece, Rome, Byzantium, Venice, and eventually to France. First four centuries of the Christian Era may be called the First Golden Age of Glass. The glass-makers of the period knew how to make a translucent glass, and also knew crude glass blowing, painting, and gilding. They knew how to build up layers of glass of different colours and then cut out designs in high relief.

'The writings of the Fathers of the Latin Church, Lactantius 240 -320, Prudentius 348 -405, and St. Jerome 420. mention coloured glass windows in the early Christian basilicas. The 5^th C poet Sidonius Apollinaris has described glazed windows in Lyon. France. Pope Leo III 795-816 is recorded to have provided windows of different coloured glass for St. Paul's basilica at Rome. 8^th C alchemist Jabir-ibn-Hayyan in his Kitab al-Durra al-Maknuna -book of the Hidden Pearl, described 46 recipes for producing coloured glass. 12 more formulas were added by al-Marrakishi in a later edition of the book. Glazed church windows were widespread in pre-Carolingian Europe. It is stated that the windows contained various stories, in the 10^th Church of Saint-Remi at Reims. The fragments of what may be the earliest pictorial window's extant were excavated at Lorsch in Germany. It was possible to reconstruct a head of Christ, which shows some stylistic affinity with Carolingian manuscript paintings and probably dates from the 9^th, 10^th, or 11^th C. The earliest complete pictorial extant of windows are those containing five figures of prophets in the Cathedral of Augsburg in Germany, belonging to the beginning of the 12^th C'.

Coloured glass was made by staining and painting processes. Coloured glass, known as 'metal' was made by adding various metallic oxides during manufacturing. Iron impurities provided a greenish tinge which was a major impediment in production of clear or whiter glass. Natural pot-metal glass was too dark to transmit much light so a thin layer of coloured glass was applied by flashing as a thin layer over a sheet of whiter glass. After panes of glass were cut according to an overall pattern, the pieces were painted with faces, folds of draperies, inscriptions, etc. using black pigment.

Stained Glass windows mainly occurred in Christian religious buildings and in Muslim palaces. In the former case the subject matter of the window was determined to suit the location, a particular theme or the whim of the patron. A small design called a Vidimus was prepared for initial approval. In the later case the art work consisted of only patterns.

There are essentially three types of stained glass windows. Narrative windows have panels which relate a story. Figurative windows have rows of saints or dignitaries. Patterned windows have floral, geometric patterns or abstract figures. In the first two types of windows, scriptural texts, mottoes, names of the patrons, coats of arms, medallions, flora and fauna, natural scenes, celestial bodies, angels etc. were included in the composition. The third type windows include: Rose windows where strong ribs structure and its radial form was not very suitable for depiction of stories, and post Industrial age stained glass windows had non religious patrons and designers of the abstract art era.

For traditional stained glass windows a full sized cartoon over paper, canvas, a white wall or on the floor was drawn. In Medieval times the cartoon was drawn straight onto a whitewashed table, which was then used for cutting the glass, painting it and assembling into panes. The cartoons could be sized to fit into blanks within a full scale rendering of the tracery pattern of the window. This was done to have continuity of scenes and their background across the mullions, transoms and muntins. Exact position of the lead cames that hold the pieces of glass in place was determined to match lines of the scene, colour and texture boundaries. Details of fine features such as faces, hair and hands were over painted onto the inner surface of the glass using a special glass paint which contained finely ground lead or copper filings, ground glass, gum arabic and a medium such as wine, vinegar or urine. The glass pane was made waterproof and rattle-proof by forcing a mastic compound (of linseed oil and whiting powder) between the glass and the cames. The cames were often painted black to create a uniform width line.

In the last phase of the Gothic period the emphasis shifted from religious static scenery and narratives to postural compositions and three-dimensional perspective. The colour scheme became simpler and less vivid. Water white Cristallo glass began to take up greater area.

The invention of Cristallo glass is attributed to Angelo Barovier in 1450. Cristallo is a clear glass, like rock crystal, without the common slight yellow or greenish colour originating from iron oxide impurities. This effect was achieved through small additions of manganese oxide. Often Cristallo has a low lime content which makes it prone to glass corrosion also known as glass disease.

'Art Nouveau or Belle Epoch had Charles Rennie Macintosh, William Morris and Edward Burne-Jones striving for new forms by using curvilinear lines, swirling motifs through stained glass as the medium'. Frank Lloyd Wright created painted, stained and patterned windows for nearly all his buildings. He called such windows 'light screens'.

COPPER CAMES: Lead cames were being used for ages for joining glass. Occasionally other materials such as alloys were tried out. Tiffany, the glass artist and his firm popularized copper cames. Copper alloy was very pliable and could be hammer forged or Tin soldered to form a joint. Very fine quality joint can be created using copper cames, such as for famous Tiffany glass lamp shades.

PLIQUE A JOUR (Fr: open to light). It is technique of producing translucent enamels in open frameworks of cross soldered wire or stripes. The space between the wires or stripes is filled with enamel compound, which after firing form an effect like a stained-glass window in miniature. The technique was used largely for making vessels, jewellery and demitasse spoons in 14^th C.

GRISAILLE: Grisaille is a floral pattern painted on glass with vitrifiable paint (one which is fired after application to fuse into the surface of the glass). The figurative stained glass windows, with vivid colours were distracting. So the Cistercian Order under St. Bernard found a better option, grisaille painting with black or brown outlines over a transparent glass. The grisaille panels allowed more light, diminished the bluish intensity of stained glass interiors and accentuated the contrasting colours. Figures were painted as grisaille and surroundings had stained glass colours. Alternating layers of coloured glass and grisaille were used as bands in the figurative windows. The grisaille was cheaper, simpler and faster in execution, so found greater number of users. It nearly replaced the stained glass in the 17^th and 18^th C.

It also refers to monochrome colour painting in its varied shades, usually black or brown, to represent objects in relief in grey scale. A grisaille may be executed as under-painting for an oil painting (in preparation for glazing layers of colour over it), or as a model for an engraver to work from. Rubens and his school sometimes used monochrome techniques in sketching compositions for engravers.

GLAZING: The art and craft of fixing a glass pane or any other similar transparent material to allow illumination through it in an opening system. Glazing is also any material that permits light through it, and used for such a purpose.

GLAZIER: A person who can cut and fit the glass. Glaziers are expert in fixing glass with lead cames, beading and putty.

OPALESCENT GLASS: It shows milky or pearly iridescence. It reflects as well as refracts light. It is also a generalized term for semi-opaque glass that has a milky appearance. The opalescent glass is cloudy, marbled and sometimes accentuated with subtle colours. Ancient glass was opalescent due to defective manufacturing. It transmitted very little light but glowed bright against outdoor sunlight. It was usually of one colour but had 'a mixture of two or more colours with streaks and swirls'. Later refined manufacturing processes produced glass of substantial clarity, such as the cathedral glass. During 18^th and 19^th C many different processes were devised to create opalescence. The opalescent effect is produced by alternating heating and cooling of the glass and with the addition of chemical additives. It is also created by layering or plating small pieces of glass and fusing them with heat.

IRIDESCENCE: It is the quality of the glass surface that produces a metallic sheen which appears to change colour as the angle of view changes, creating a rainbow effect. It is caused by multiple reflections from multilayered, semi-transparent surfaces in which phase shift and interference of the reflections modulates the incident light, by amplifying or attenuating some frequencies more than others.

CATHEDRAL GLASS: It was devised when glass was opaque with streaks and swirls in it. It was in 10^th C, that a transparent Glass of one consistent colour was produced for the Cathedrals.

TRANSLUCENT GLASS: It has greater capacity to transmit light than an opalescent glass but is not clear enough to see through it.

LATTICELLI: RETICELLI: This is like a flash or layered glass. Vitreous threads of milky white or colour glass are embedded during casting of clear glass to form a lace like a reticulated pattern. It is known as latticelli, or reticelli from the elaborate twisting and interlacing of the threads.

STREAKY GLASS: It is made from stirring together molten glasses of two different colours, generally of opalescent type. The streaks so produced were used for vivid effects.

WISPY GLASS: It is made from stirring together two glasses of different colours but one opalescent and the other cathedral glass. The cathedral glass was made background and the coloured pot glass was the effect imparting colour, such as for the sky or water.

TEXTURES: The surface textures were more commonly added to the clear or cathedral glass, to make them non-clear that is difficult to see through or frosty so that glazing shows its presence by even brightness. Textures were created through flashing, layering, dusting, streaking, rolling and pressing, etc. Manufacturing defects such as ripples, concentric rings were exploited as textures. Some of the textures were directional like straight or wavy lines or included dots and lattices.

BLACK ENAMEL PAINT: Black enamel was made from ground glass plus iron filings. It was used to create the details on the earliest stained glass. It could be applied thick and black, or as a thin grey or grey-brown wash.

MEDALLION OR NARRATIVE WINDOWS: These were placed at a height where congregation could see the mythological stories and figures of it. The glass employed was the pot metal, providing vivid colour, high presence but slightly less brilliance due to higher opacity.

FIGURE WINDOWS: These were placed in higher locations, upper sections of the perpendicular windows. It illustrated the ancestry of Christ such as Adam, Noah, Moses, David, and Solomon.

ROSE WINDOW: see 4.2.1.4.2 Historical Perspective : Wall Windows

PAINTED GLASS: - From the fourteenth century in Italy, translucent oil paint was painted onto stained glass to enrich the range and quality of colours.

PICTORIAL WINDOWS: Pictorial windows depicted a broad-based story across several glazing panes ignoring the window support lines like mullions and transoms.

ANNEALED GLASS: Glass as it is cast contains many stresses within its plane making it very brittle. Annealing is process of reheating the cast or formed glass to its softening point and cooling it slowly. Annealed glass breaks into large, jagged shards that can cause serious injury, and so considered a hazard in many applications such as in sky lights, ceilings, automobiles, doors and low height windows. Float glass is annealed during the process of manufacture. However, most toughened glass is made from float glass that has been specially heat-treated.

TOUGHENED GLASS: Toughened glass is also known as tempered glass. It is a safety glass with increased strength for conditions like pressure (swimming pool apertures for illumination, aquariums, port holes, etc.), thermal resistance (ovens and reaction vessels, foundry windows), safety apertures. It usually shatters in small, square pieces, however it is not used for automobile windshields as the broken pieces could fly and harm the driver and passengers. For car windows a layered or sandwich glass is used so that broken glass' pieces do not separate out. In commercial buildings glass toughening is carried out after all holes, treatments, engravings are complete over a frame less door or fixed glass walls or panelling system. Toughened glass has typically four to six times the strength of annealed glass.

TIFFANY: Tiffany glass is the generic name given to varied types of glass developed and produced by Louis Comfort Tiffany (1848-1933), one of the most famous stained glass artist of the USA. Tiffany was an interior designer, and in 1878 his interest turned towards the creation of stained glass, when he opened his own studio and glass foundry.

"Rich tones are due in part to the use of pot metal full of impurities, and in part to the uneven thickness of the glass, but still more because the glass maker of that day abstained from the use of paint".

La FARGE: John La Farge (1835-1910) was an American painter, known for his murals, watercolours and stained glass decorations. He developed and subsequently manufactured an opalescent glass.

FAVRILE GLASS: It is a glass patented by Tiffany in 1880. The trade name Favrile was derived from the French word, fabrile, meaning handcrafted. It has superficial iridescence. 'This iridescence causes the surface to shimmer, but also causes a degree of opacity'. The iridescence was obtained by mixing different colours of glass together while hot.

According to Tiffany: "Favrile glass is distinguished by brilliant or deeply toned colours, usually iridescent like the wings of certain American butterflies, the necks of pigeons and peacocks, the wing covers of various beetles."

STREAMER GLASS: Streamer glass is a textured glass with a pattern created by glass strings affixed to its surface. Tiffany made use of such textured glass to represent, for example, twigs, branches and grass.

Streamers are prepared from very hot molten glass, gathered at the end of a punty (pontil) and swinging it to form long strands. These strands or streamers are pressed on the molten surface of sheet glass during the rolling process, and become permanently fused.

FRACTURE GLASS: Fracture glass refers to a sheet of glass with a pattern of irregularly shaped, thin glass wafers affixed to its surface. Tiffany made use of such textured glass to represent, for example, foliage seen from a distance.

The irregular glass wafers, called fractures, are prepared from very hot, coloured molten glass, gathered at the end of a blowpipe. A large bubble is forcefully blown until the walls of the bubble rapidly stretch, cool and harden. The resulting glass bubble has paper-thin walls and is immediately shattered into shards. These hand blown shards are pressed on the surface of the molten glass sheet during the rolling process, to which they become permanently fused.

FRACTURE-STREAMER GLASS: Both streamers and fractures are applied to sheet glass during the rolling process. Tiffany made use of such textured glass to represent, for example, twigs, branches and grass, and distant foliage.

RIPPLE GLASS: Ripple glass refers to a sheet of textured glass with marked surface waves. In the manufacture of rippled glass, a roller spinning faster than the forward motion of the glass is used. Tiffany made use of such textured glass to represent, for example, water or leaf veins.

RING MOTTLE GLASS: Ring mottle glass was invented by Tiffany in the early 20^th C. It refers to sheet glass with a pronounced mottle or varied colouring created by localized heat-treatment leading to crystal-growth and opaque effect. It was traditionally used for organic details on leaves and other natural elements.

DRAPERY GLASS: Drapery glass refers to fabric like folds in glass. Drapery glass was used for 3D effect in flowing robes and angel wings and to imitate the natural coarseness of magnolia petals in stained glass windows.

A small diameter hand-held roller, is forcefully manipulated over the sheet of molten glass, to produce heavy ripples, while folding and creasing the entire sheet. The ripples become rigid and permanent as the glass cools.

BREAKER-GROZIER PLIERS: A tool, pliers used by a glazier or the glass cutting-fixing craft's person, to sheer the edge of the glass.

SILVER STAIN: Silver stain was fired onto clear glass to produce a translucent yellow - or any colour between murky brown and deep amber. It was discovered around the beginning of the fourteenth century, apparently in France, and was used sparingly at first, and then very creatively to produce local contrasts on coloured glass.

CAMES: A slender grooved lead bar used to hold together the panes in stained glass or lattice windows. Later, zinc, copper, brass, etc. were substituted for the lead.

FLASHED GLASS: Natural pot-metal glass coloured blue or red was too dark to transmit much light, so the medieval glazier hit on the technique of applying or "flashing" a thin layer of the coloured glass on to a sheet of white glass, thus getting over the problem.

FERRAMENTA: Traditionally, when the glass panes were inserted into the window gaps, iron rods were put across at various points, to support the weight of the window, which was tied to the rods by copper wire. Some very large early Gothic windows are divided into sections by heavy metal frames called Ferramenta. This method of support was also favoured for large, usually painted, windows of the Baroque period.

LEADED GLASS: Glass panes composed of small pieces, which are joined and held together by lead.

LEADED WINDOWS: Same as leaded glass.

BEVELLED WINDOW: Bevelling is process of dressing a glass where the edges bevelled cutting them at an angle, polishing or rounding to create a surface with iridescence. The angled edge works like a prism for the light to refract. A window may be divided into smaller section by cutting V cut grooves on its face or additional smaller pieces with a bevelled edge are fused onto it. Bevelled windows are used to add intermediate presence between outside and inside, or used to admit light while obscuring an uninteresting view.

INSULATING GLASS PANES: Double or triple layered glazing with an enclosed, dehydrated, or hermetically sealed vacuumed or air filled space between the panes. The space widths are 9 to 20. Cavities are often filled with neutral gas. The interior surface of the glass is treated for redirecting and filtering some radiation. The units are factory prepared and cannot be recut on the site. The glass is efficient for sound insulation.

SOUND-INSULATING GLASS (also sound-resistive glass): Double glass fixed on resilient mountings and separated so as to reduce sound transmission.

TRIPLE GLAZING: Three panes of glass with two air spaces between, commonly consisting of an insulating glass with a separate storm sash available in an insulating window in a single frame.

DIFFUSING GLASS: Glass with an irregular surface for scattering light; used for privacy or to reduce the glare.

FROSTED GLASS: Frosted glass is any glass that obscures vision. The glass is manufactured or post production treated for making it translucent. The manufacturing methods include texturising (Figured glass, armoured or wired glass), or adding pigments or other non reacting opaque particles (Opalescent glass). Post production treatments include grinding by rough media (Groung glass), sand blasting, acid etching, affixing polyester films and over printing. Frosting is done to obtain visual privacy while admitting light, to compound decorative patterns over an otherwise plain glass and distribute light evenly and reduce the visual glare.

STEEL WINDOWS: First metal windows were forged from wrought iron by medieval blacksmiths. For many years wrought iron was known material, but not widely used material, and the crafts' persons to handle it were rear. The material had extra ordinary stiffness, but could not be finished well in absence of a paint system. Wrought iron windows (fixed) with leaded lights were used in churches and in simpler domestic buildings. However, cast elements of it were frequently included in the structure of the window, mainly for strength and stiffness. Typically leaded lights were braced with Ferramenta or saddle bars. Later in A Victorian Era double-hung sashes windows had muntins or glazing bars of metals, and channels for sliding the counter weights were lined with metal sections. It was only in the mid 18^th C that new casting and forging methods made metal windows, a viable alternative to timber for the construction of sash windows. The castings were copies of wood windows with same stylised carvings, etc. Iron windows were fireproof, strong, not affected by wet weather, comparatively cheaper and mass producible. 'The first 'fireproof mill', William Strutt's Derby Cotton Mill of 1792 had iron windows'. Iron windows were also used for mental asylum and jails. With beginning of 1800, with the Regency period metal windows became common in homes, 'In 1833, Loudon's Encyclopaedia of Cottage, Farm and Villa Architecture reported, "Windows of cast iron, are very fit for cottages and are now made of different forms and very cheap".'

In 1856, Sir Henry Bessemer pioneered a new production process for hot rolled steel. New standard sections promoted small workshops everywhere that produced steel windows for the rapidly expanding market of domestic, commercial and industrial users.

There are basically two types of steel sections: Hot rolled steel sections are made by hot rolling a billet. The shapes are solid like squares, bars, etc. Extrusion sections are complex than hot rolled sections and form the bulk of shaped sections for doors, windows and trims. Cold rolled steel sections are thin plates and sheets that are formed into various shapes (e.g. zee purlins, door jambs) and including hollow sections (pipes or tubular forms).

Steel windows like sash windows are formed from CRCA sheets (Cold rolled cold annealed) of at least 20 gauge thickness. After forming and corner joining the readied windows are stress relived, and galvanised or treated with typical 5 or 7 step treatments for painting. Nowadays pre-coated mild steel and stainless steel are also used for fabricating such windows.

Steel casement windows are commercially assembled from extruded sections for side jambs, mid member or mullion for meeting, shutter sides, shutter mid members, glazing T bars, etc. The sections are known by their weight per running length, however, windows are specified by their depth (thickness 25 / 30 / 40 and 45) for various conditional uses and opening sizes. Sections are welded (deposition or fused) and ground. Steel windows are typically glazed using glazing tape, glazing wedge, setting blocks, custom pre-fitted glazing beads and a cap bead of sealants. Industrial windows use armoured or wired glass. Industrial steel windows are generally provided with continuous snap-in glazing beads which can be easily removed to replace the broken glass and reinstalled with new glazing materials.

ALUMINIUM WINDOWS: First aluminium windows were of solid sections, but being a costly material, thinner wall thicknesses were required. Extrusion gave superior results, a polished surface with very thin walls. Aluminium had several deficiencies: its surface gets tarnished on exposure, being a noble metal it wears off due to electrolysis, it requires stiffeners at mechanical joints, cannot be welded as easily like steel and has high thermal conductivity.

Tarnishing can be avoided by anodizing, oxidizing or painting the surface. Electrolysis can be prevented by avoiding the direct contact with other conductive metals such as stiffeners and hardware. Stiffeners can be avoided by good design. Aluminium can be welded by Argon welding and for that entire window must be fabricated in an industrial plant. Its thermal conductivity can be managed by inserting thermal breaks or discontinuities between the outer and inner faces of the windows. Ideal isolation can occur with dual window system, next in preference may be the dual or triple glazing unit and lastly the use of solid or soft thermo breaks in the form of resin, foam or rubber lining. Window sections with greater number of small hollow units inside the section of the frame add to the isolation efficiency (thermal, moisture, sound), but may add to the weight.

Fine quality windows can only be produced in plants rather then assembled on a site. Standard sized windows, usually pre-glazed, produced in large numbers can have welded or bent-folded corners instead of the mitred assemblies. Such windows are used in large housing schemes, buses, railway carriage, air crafts and seagoing vessels. The windows' and the shutters' three or all four sides are of made from one continuous member, giving better shape stability and protection against air, moisture and noise leakage.

Aluminium was isolated early in early 19^th C. at the Paris exhibition in 1855 Aluminium bars were exhibited next to the crown jewels. But it was not until 31 years later that an economical way of commercial production was discovered. Aluminium is produced in ingots, extruded shapes, rod, tube, bar, sheet, plate and foil. Steel, like Aluminium offers a wide range of alloys. Aluminium extrusions and foils have emerged as the most widely used materials in all fields.

PLASTIC WINDOWS: The word plastic is used to denote a wide range of semi-synthetic and synthetic materials that soften and become plastic at comparatively low temperature, so that can be shaped by extrusion and pressure moulding. The heated thermoplastic material is forced through dies of which it extrudes as thin-walled hollow sections, complete with rebates, grooves and nibs for beads, weather seals, glazing seals and for fixing hardware. Plastics are mixed with many other plastic monomers and polymers. Plastics also form the matrix phase in composites with variety of fillers, notably glass fibre, other natural and synthetic fibres and minerals.

PVC WINDOWS: PVC as a plastic was invented during 19^th C, but its commercial viability was proved in 1930's. At that time it was a solid material difficult to process or put to any use. After adding plasticizing compounds it became soft and pliable. It is a low-maintenance material and widely used across the world for the extruded doors and windows frames. In USA it is known as vinyl or vinyl siding. PVC is a poor conductor of heat so like steel and Aluminum windows does not require a thermal break. PVC has comparatively large coefficient of expansion and contraction, so requires metal reinforcements. The metal reinforcement besides restricting the movements due to temperature, facilitates better fixing of cross sections at right-angles, hinges and other hardware. uPVC -unplasticized PVC or Rigid PVC is now widely used in the buildings' components. Modifiers such as acrylic are added to improve the impact strength of uPVC.

The environmentalist group Green-peace has been advocating global phase-out of PVC because they claim dioxin is produced as a byproduct of vinyl chloride manufacture and from incineration of waste PVC in domestic garbage. The issues of migration and brittleness of the PVC compound are overcome with the use of modern impact modifiers. Scientific tests by other authorities show that there is no relationship between the PVC content of the waste and dioxin emissions.

Natural colour of the uPVC is off-white and it is UV light resistant. But addition of colours affects the UV resistance. In case of fire PVC does not ignite and burns if the heat source is very close, but does not contribute to the spread of flame.

FIBREGLASS: Fibreglass frames are available in many different forms. One of the oldest methods is to form a layered composite using fibreglass as filler as loose fibres, non woven sheets or woven fabric, and polyester resin as the matrix. Such sections conveniently emulate the shape of a wood jamb section. The sections are joined almost like timber joinery but with metal reinforcement. The advantage is high strength and excellent resistence against moisture and termite. A faster method to form similar section is to mix the fibreglass fillers and plastic matrix, and extrude them. This again nearly copies the old wood jamb section. A third method is to form the filler+matrix mix and extrude a section with very thin walls. Such sections are very similar to aluminium or PVC sections, but in terms of strength, longevity and resistence far superior.

COMPOSITE WINDOWS: First composite windows in the history consisted of woof frame and engraved bronze or glass panes in-fill panels. Low quality woods were clad with metal sheets for protection or for extending their sizes. Gothic windows of stone mullions, transoms and muntins with stained glass panes can also be called composite. Double-hung windows had brass and copper metal glazing bars. First industrial age windows had used wrought iron either as a frame or the shutter, and other element was of wood. Early aluminium windows had poor weather resistance, and for galvanic isolations were fixed in wood frames. Mies Van der Rohe also used bronze clad windows. Wood has been used as core material for sheet formed steel, extruded aluminium and PVC windows. Wood as a core fill in material is now being replaced with PU form, expanded cement concrete, and expanded polystyrene. Combination of Aluminium as outer layer, and Vinyl or Acrylic, as the inner layers are also used.

SEALANTS: Sealing materials are required in fixing the windows into masonry structure, between two adjacent window units, between the window frame and its shutter, between shutters and between the glazing and shutter system. The sealing system could be drying putty, green (non-drying) putty, mastic compounds, heavy bodied adhesives, beading sections of wood, metal or plastics, rubber gaskets, elastomeric compounds, compressible foams, gaskets and bonding chemicals. Some sealing systems create a temporary seal due to mechanical pressure, attraction, temporary adhesion or by positional circumventing. Other seals can be conditionally made and unmade for repair, maintenance, etc. Permanent seals are everlasting and stable. Seals are created by positional circumventing, inserting pre formed gaskets, liners, beads, etc. or by coating, applying or injecting liquid compounds. A sealing system works under stresses of displacement such as vibration, expansion, contraction, torque, etc. It also resists or allows movement of air, moisture, sound and other forms of energy. In many instances a sealing system creates a joint between two similar or dissimilar materials.

Keywords: TYPES OF WINDOWS / nature of operation / hinged windows / side hung / casement / top hung / awnings / bottom hung / hoppers / close hinged / open hinged / offset hinged pivot windows / corner pivot, centric or off centric pivots, and offset pivots / sliding windows / horizontal or vertical channels / louvered system / mounted windows / catch mechanism / pivoted / surround / small spanned / single shuttered / lattices / sill and lintel fixed pivots / shelf supported metal pivots / window frame / rebate in the frame / planks mounted over stiles and rails / framed construction / mortised stiles and rails / inserted panels / solid shutters / translucent sheets and panels / arched gap / shape the fixed lites / transom / mullions / multiple windows / wooden mullions and transoms / stone transom and mullions / a composite entity / framing grid / shape formation / security bars / hinges / offset hinges / hinged casement windows / outer shutters / storm shutters / fixed louvered Venetian shutters / inner shutters / mosquito netting / rustic wooden window shutters / rebated channels / exterior or interior channels / secondary shutters / side lights or transom lights / single and double sash windows / pulleys and counter balancing weights / steel spiral springs / removable system / auxiliary shutters / lifted and stacked elsewhere / window shutter / plank shutter / frame of vertical stiles and horizontal rails / framed shutter / interior shutters opened inward / exterior shutter opened outward.

SLIDING or GUIDING CHANNELS / track or channel floor / micro rails formed over the floor / top of channel forming walls / very smooth, non wearing or self lubricating materials / castor or grooved wheels / bottom channel / drainage section / horizontal guide wheels / locking mechanism / HARDWARE / ASSISTED MOVEMENTS FOR CASEMENT SHUTTERS / pull in arm / handle and wind stay / ASSISTED MOVEMENTS FOR DOUBLE HUNG SHUTTERS / ASSISTED MOVEMENTS FOR ANTI LIGATURE CONDITIONS / anti-ligature hardware / PIVOTS / off-pivot / edge or corner pivot / centric pivot / Jalousie / HINGES / leather strapped / EXTENSION CASEMENT HINGE / offset hinge / ESPAGNOLETTE / locking device / steel almirahs / WINDOW STAYS / pull in arm / friction stay / multiple louvres / vertical sliding windows / safety bars / CASEMENT ADJUSTER / window or casement stay / CASEMENT STAY / wind stay / EGRESS HINGE.

TYPES OF WINDOWS: Windows can be classified by their nature of operation. These mainly are: Hinged, Pivoted, Sliding and Mounted

Hinged windows with side hung units are called casement windows. Top hung units are called awnings, whereas bottom hung are called hoppers. Hanging or fixing of shutters have many variations. Shutters are close hinged (no space between the side member and shutter), open hinged (little space between the side member and shutter), and offset hinged (wide space, large enough for maintenance).

Pivot windows shutters have corner pivots, centric or off centric pivots, and offset pivots.

Sliding windows have horizontal or vertical channels with full length slides or nodes as slides. In sliding systems, multiple units may slide up, down or sideways, Sliding systems could also be a composite one as sliding + folding. Multiple shutters ganged together create a louvered system.

Mounted windows are seasonal or infrequently used additional shutters, such as those used for storm protection, delivery counters, etc. The shutters are loose leaves or panels that are mounted in predefined slots or through some catch mechanism of mechanical, magnetic or electrical nature.

First window shutters were designed like door shutters, pivoted and opened inward. The thick sides in the heavy wall opening accommodated the opened shutter. The construction of the shutter was also like the door of the time, without any frame, but a masonry offset was provided to act as a surround. The shutter when open allowed illumination and ventilation, but when closed, it was opaque like a wall. The window shutter was loose fitting and was leaky at the edges, as the door. Holes or slit gaps were punctured in the shutter panel of wooden planks for view out, minor ventilation and illumination. Windows openings were small spanned and initially single shuttered. Wide shutters were too difficult use. The window shutter was secured with wood planks or a brace on the back face. In tropical countries additional fixed lattices of wood, stone, woven mats and fabrics were used for protection and to subdue the glare, radiant heat and direct solar radiation.

Sill and lintel fixed pivots were clumsy to install and maintain so soon gave way to shelf supported metal pivots on the sides. These were leaner and could be fixed beyond the edge, allowing better closing and easy replacement of the shutter. The other end of the shelf pivot was a long metal arm, fixed to the shutter by nails or spikes. The same arm also helped to keep the shutter planks together replacing the functions of rails. The shelf pivots were first fixed within masonry, but it was more convenient to fix them over a set of wooden posts. The wooden posts soon became full all sided window frames. The shutter instead of resting over the frame now was placed in a rebate in the frame. This arrangement provided a tighter fit.

The shutter instead of simply being planks mounted over stiles and rails began to have framed construction. The mortised stiles and rails and inserted panels, formed the body for the shutter. Some of the window panels were formed of thin marble, alabaster, mica, oiled cloth or paper, parchment and such other translucent materials for illumination. At places the window was divided into two sections, the lower one had solid shutters, but the upper section was covered with translucent sheets and panels formed of crudely cast but polished glass pieces joined with lead cames. The separation of upper and lower sections allowed the use of an arched gap. It was easier to shape the fixed 'lites' in the upper section.

A horizontal mid-member, the transom, divided the window into two to three sections, and stiffened the window frame. Similarly mullions divided the wide gap opening into multiple windows, some of which were shuttered and others had fixed lites. Wooden mullions and transoms had length limitations, beyond 2 mts of length the elements used to get warped. Gothic buildings used stone transoms and mullions, which together with stained glass panels formed a composite entity. Transoms and mullions also formed the framing grid to combine several types of windows. The framing grid allowed shape formation for bay windows, bow windows, oriels, lanterns and sky lights.

The window also had security bars of wood or forged metals, first inserted in side masonry, and later in the wood frame. Security bars provided the required stiffness, making the window frame leaner and elegant. The latticed security bars were patterned in geometric as well as floral designs, often shown through the window glass. Similar patterns were also created on window glass by means muntins, lead cames, glass engraving, frosting etc.

Shelf pivots were soon refined into hinges. Hinges allowed greater width opening, often beyond 3/4 of a circle. Offset hinges (like a parliament hinge) allowed a shutter open over small projections like eaves, architraves, mouldings, etc. or set a window frame slightly inside from the face of the masonry. Hinged shutters began to open outward, an ideal condition for thin section walls which could not 'park' the shutter within its depth. With hinged casement windows it was also possible to have double layers of shutters. The outer shutters were solid 'storm' shutters or fixed louvered Venetian shutters, and the inner shutters were glazed or had mosquito netting.

At rural level the window shutters continued to be simplistic, avoiding use of metal hardware such as pivots and hinges, or complex joinery involving mortises, rebating etc. The rustic wooden window shutters were made to slide in horizontal or vertical rebated channels created in masonry surrounds or wooden window frames. Channels were mounted on interior face of the opening if the local climate was arid. Otherwise, channels were mounted on the exterior face. Exterior or interior channels for fitting secondary shutters are required for storms, mosquito netting, etc. The channels extended on one or both sides depending on the single or double shutter design. The channels in masonry surround or over the wooden frame of the window, were placed touching the face of the window. Such sliding shutters when opened horizontally or vertically, covered the side lights or transom lights, respectively. Single and double sash windows have originated from this technique, but developed into very sophisticated construction with pulleys and counter balancing weights for easy operation. The pulleys and counter weights in sash windows have now been replaced with steel spiral springs.

Window shutters are also designed as removable system. Auxiliary shutters like storm covers or mosquito nets are not required all the time, have shelf pivots or loose pin hinges or catch mechanisms. The loose shutters can be lifted and stacked elsewhere. Sliding grooves also allow a shutter to be removed for cleaning or stacking.

A window shutter was like a door a solid single plank of wood, sometimes stiffened by stiles or rails or both. The plank was pierced for ventilation, illumination and view out. The plank shutter was very heavy and thick. A refined shutter is a square or rectangular frame of vertical stiles and horizontal rails (top, centre and bottom). A framed shutter was very thin and stable against moisture. The shutter frame was filled in pierced panels, fixed or movable Venetians, micro windows and glazing materials including leather, parchment, oiled fabrics and paper and lattices of different materials. The window shutter was mounted overlapping the frame or placed within the frame. Commonly the interior shutters opened inward and exterior shutters opened outward, but not necessarily. The opening of the shutter was regulated to control the illumination, ventilation, privacy and view out. Shutters are made 'open-able' by many different mechanisms. Shutters are hung by hinges or straps on horizontal or vertical sides. Shutters move on pivots fixed at the centre, corner, or as placed outside the plane as offset, on horizontal or vertical sides. Shutters are made to slide or glide in channels or over rails in horizontal or vertical directions.

SLIDING or GUIDING CHANNELS: Windows shutters slide in channels formed of small height walls on either side. The shutters move on the track or channel floor, on micro rails formed over the floor, or over the top of channel forming walls. The movement is assisted by lining the channel floor or track head with a smooth finish, or by use of very smooth, non wearing or self lubricating materials such as glass, Nylon or Teflon. The sliding over track head is also helped by castor or grooved wheels. In horizontal sliding window system only the bottom channel bears weight and is provided with movement mechanisms. The bottom channel collects rain water cascading down the face of the shutter, which is drained by a drainage section. The top channel could be plain groove for holding the shutter. However, for very large shutters horizontal guide wheels are included. Side ends have holding channels that also weatherproof a window. Sliding windows have a locking mechanism set into the hollows of vertical box sections of the shutter or handle cum spring clamp holds the end shutter against the vertical end section.

HARDWARE: Hardware for windows have become sophisticated, micro sized, automatic, remotely regulated and endowed with artificial intelligence. The sizes have become smaller and became a gadget in their own right. For more ref to Hardware for Doors 4.1.2.3.1 BASIC HARDWARE.

ASSISTED MOVEMENTS FOR CASEMENT SHUTTERS: Assisted movements are required where the opening casement is very wide. The shutter when open, its free edge is beyond 450, the nominal reach of the stretched hand. A levered arm is fixed beyond the half way width of the shutter to pull in the shutter for closing. The same pull in arm also serves the purpose of a handle and wind stay. In case of double shutter arrangement, to close the outer shutter without opening the inner shutter, a chord is used in place of the arm.

ASSISTED MOVEMENTS FOR DOUBLE HUNG SHUTTERS: double-hung sash windows have counter weights or coiled balance springs to assist in closing and opening vertically sliding windows.

ASSISTED MOVEMENTS FOR ANTI LIGATURE CONDITIONS: Jails and facilities for mentally retarded persons have anti-ligature hardware, and one of the most important aspect of it is avoidance of any hardware over windows. The closing and shutting of the window is done from outside, through concealed mechanical levers or remote control.

PIVOTS: Pivot windows rotate on a pin in a barrel that is placed either in horizontal or vertical position. The pivot is fixed beyond the edge off-pivot, at the edge -edge or corner pivot, at the centre -centric pivot, or anywhere between the centre and edge -off-centric pivot. A pivoted sash, if it opens partly in, then it may not provide a completely sealed window system. Pivots are bearing systems that allow easy rotation. Older pivots used hardened bronze, gunmetal brass or carbon steel balls, requiring some lubrication, however modern pivots use Nylon or Teflon like plastics for non-wearing and self-lubricating qualities. Pivots are used in double hung sash windows for opening the sash to clean and maintain its outer face. Pivots are used for skylights, ventilators, hoppers and awning windows. Louvred windows or Jalousie has pivots.

HINGES: Primitive-door covers were leather strapped to a side post. The straps allowed movement but kept the cover straight up. The flexibility of the leather and the movement capacity was reestablished by a set of two barrels moving relative to each other around a pin. A shelf pivot, has a pin fixed to a projection over which a barrel with the flange rotates.

EXTENSION CASEMENT HINGE: Hinge for a casement window which provides clearance for cleaning the two sides of the sash from the inside also called offset hinges.

ESPAGNOLETTE: It is a locking device, normally mounted on the frame of a French door or casement window, with a handle or knob, fixed mid or body level. It rotates a round bar with hooks at the ends into sockets at the head and sill of the opening. This type of lock is often used on a semi-trailer truck to fasten the rear doors and on steel almirahs.

WINDOW STAYS: Windows stays are hardware that allows a window shutter to open and remain at a fixed angle. The window shutter maintains the position in spite of positive (pressing in) or negative (suction) pressure of heavy winds. The window stays are long armed to reach beyond half way width of the shutter and are used as the pull in arm for closing the shutter. A sliding window and one that is fixed with a friction stay does not require a stay mechanism. Multiple louvres such as series awnings have a connecting bar to close all shutters simultaneously. The bar is locked to position the shutter open. Vertical sliding windows have counter balance or coiled spring to hold the shutter in a fixed position, yet locking mechanisms are provided so that the shutters, on their own do not move. A locking or controlling device with the stay can restrict the opening size to less than 100 and there by eliminating need for safety bars.

CASEMENT ADJUSTER: A device to hold a casement window in any open position same as window or casement stay.

CASEMENT STAY: A bar for holding a casement window in any of several fixed open positions against wind, so also called a wind stay.

EGRESS HINGE: A hinge utilizing a scissor-type bar at the bottom, allowing the window to open wider than perpendicular to the frame and providing an avenue of escape in case of an emergency.

4.2.4.1 OTHER TYPES OF WINDOWS

4.2.4.2 WINDOWS LIKE UTILITIES AND PRESENCES

Keywords: ANTI-LIGATURE OPENINGS / hamper exit in a crisis / entry for rescue / enforcement for non opening / prevention from closing / grills that prevent escape / hold to hang own-self / shutter opening-closing regulations / breakable materials / detachable components / BANK CASH COUNTERS /cash and document transactions / aperture / different opening or arrangement / two sill levels across its depth / traditional bank counter / sunken hopper / floating and shifting boat / good business atmosphere / open banking / barrier and windowless exchange HOLES, PEEP HOLES / micro size windows / air change, moisture ventilation and drainage / relief apertures / FOOD HATCH IN JAILS / space underneath / exterior sliding shutter / DRIVE-IN FACILITIES WINDOWS / deliver goods and services / sales windows / POSTAL SLITS / horizontal micro windows / CONFESSION WINDOWS / confession booth / grid or lattice covered opening / PROJECTOR ROOM WINDOWS / Projector windows are deep set / spread of fire from either side / CONTROL ROOM WINDOWS / panoramic view / lift cranes / rooms for radiography / caboose window / VEHICLE WINDOWS / animal drawn covered wagons / folded like an accordion / sliding framed window shutters / hinged or pivot openings / Dutch door / steam rail carriages / automobiles / stress relived annealed glass / Stagecoach / post chaise / CAR WINDOWS / windows on sides, front, back / roof / WINDSHIELDS / drag coefficient / aero-screens / foldable front screens / SIDE WINDOWS / micro or mini cars / folding roof cars / tropical safari cars / quarter glass or lites / QUARTER GLASS / quarter lite / valence window / WIND WINGS / vent windows / divert breeze to the interiors / vent pipe or duct / OPERA WINDOW / SUNROOF / MOON-ROOF / BUS AND TRUCK WINDOWS / AIRCRAFT WINDOWS / cockpit windows / cabin windows / vapour-coated / layer of gold or silver / BIOSCOPE KINETOGRAPHIC CINEMA / kinetoscopes / view windows.

ANTI-LIGATURE OPENINGS: Ligature means tying, fastening or binding something, typically a bleeding wound with a bandage or strap. Anti-ligature is quality of a device that prevents someone from doing a hazardous act by tying up the body, such as for suicide. The term is also associated with door hardware or lock that may hamper the exit in a crisis or entry for rescue. Anti ligature systems are used with hardware, gadgets, furniture, furnishings, building components, and elements of opening systems such as doors and windows.

Anti-ligature system for windows include: enforcement for non opening to prevent escape in prisons and preventive rooms, unauthorized transactions for strong rooms, high security zones for choices, isolation in the bio sensitive zones, prevention from closing for discouraging locking-in at old age homes, paediatric facilities, stairs and corridors, kitchens and other fire hazard rooms.

In case of windows this is achieved by grills that prevent escape, by providing only vertical members in grills, mullions, etc. so that no one gets a hold to hang own-self. Window shutter opening-closing regulations are from outside or remote controlled. Glass and other breakable materials and easily detachable components are avoided. Sill levels are designed for appropriate users. Dungeons (cellar-based detention rooms), top floor rooms and rooms with no windows, very small sized windows or very high level windows were preferred for imprisonment.

BANK CASH COUNTERS: Bank cash counters are points of cash and document transactions. The transactions occur across an aperture, but for verbal and visual communication a larger and different opening or arrangement is required. In the first case, an exchange of documents and cash occurs, whereas in the second case two way talk and vision are required. But openings for both types of requirements must prevent exchange of any thing larger, and any forceful intrusion. On customers' side the aperture required is at higher level, for the transaction occurs in standing position, whereas the banking staff on the other side of the counter conducts the business in sitting position, and so requires a lower level for aperture. The duality creates a window with two sill levels across its depth. The traditional bank counter had a single window to exchange everything, cash (paper and coins), cheques, other documents and teller coin. This was also the point to push in a hand or hook for lift off or hold-up. It is now replaced with a sunken hopper, at the bottom of the glass. Alternatively a floating and shifting boat of A4 size paper are used. Audio communication occurs through micro holes in the glass screen or through an electronic talking device. The glass barrier and the aperture within it are considered inappropriate for good business atmosphere, so are being discouraged through greater use of ATM. and by open banking. An open banking is a barrier and windowless exchange occurring across a table of nominal height.

HOLES, PEEP HOLES: These are micro size windows mainly used for viewing an interior or exterior without being observed. Small holes are also used in relieving air pressure of the enclosed space such as cabinets. Small holes are also used for causing micro air change, moisture ventilation and drainage. Compressible cushions and foams, have relief apertures for movement of air.

FOOD HATCH IN JAILS: Food hatch is a window in a door or wall, used to serve food dish and often to observe the interior condition of the cell and its occupant. A hatch in old English meant lower section of the door. During middle ages jail doors had little space underneath to slide in a food plate. Modern jails have small exterior shelf to place the food plate, and an exterior sliding shutter to visually isolate the occupant from the happenings in passage.

DRIVE-IN FACILITIES WINDOWS: Many businesses serve their customer on street or drive sides without leaving their vehicle. Drive in facilities take orders and also deliver goods and services. Sale windows are also used at night time, in high vandal risk areas to sell small items including medicines. The windows usually have double glass shutters of which only one can remain open any time. The interim space becomes the buffer zone. Cash etc. is paid through a sunken hopper that has a very thin aperture. Glass is unbreakable (vandal-proof), but if broken by some means, a security shutter drops in to prevent the intruder and isolate the interior space. Such booths are now unmanned -automated, with video capturing every visitor.

POSTAL SLITS: Postal slits are horizontal micro windows formed in the door or a postal box. The door slit is so designed that in open position it prevents view of the interior. Postal slits are so shaped that it will not allow any retrieval of a delivered object or dropped in items. Postal slits allow articles of predefined size, usually A4 size shorter width and 15 to 20 thickness.

CONFESSION WINDOWS: Confession windows are part of confession booth, used for the confession or Reconciliation The priest and penitent are in separate compartments and speak in whispers to each other through a grid or lattice covered opening. The opening when not in use is often covered by a folding or sliding opaque cover or a curtain. A crucifix is sometimes hung over the opening or is part of the grid or lattice pattern.

PROJECTOR ROOM WINDOWS: In early 1950's a cinema hall was a very happening place. The darkened cinema hall was enlivened by the brightly lit and flickering projection windows. A cinema light beam (visually alive due to atmospheric dust and changing light) connected it to the screen casting a deep flickering beam. The window was small but the image projected out was huge. Projector windows are deep set to prevent spread of fire from either side.

CONTROL ROOM WINDOWS: Auditoriums, Press room in sport stadia, control rooms of industrial plants, cabins of goods handling equipments, sea faring vessels windows, glass panel windows. These are view windows, generally having a fixed glass, often curved or bayed for capturing the panoramic view and so greater perception of events happening out. The fixed glazing is treated to restrict the view inside from outside. It also causes lesser distraction in the hall or outer area due to noise and activities occurring on the inside. Lift cranes have control windows that allow view on all side including top (roof) and bottom (floor). Rooms for radiography (X ray) require windows that curtail radiation transmission across it. A caboose window is continued as a cupola in tourist coaches like buses, omnibus and railway carriages, similarly in cranes side windows are continued to floor level for greater visual perspective.

VEHICLE WINDOWS: Vehicles' windows are with us since the days animal drawn covered wagons. Simplest vehicle windows have a soft cover that can be unrolled or folded like an accordion. Horse drawn carriages had sliding framed window shutters inserted down in the body cavity or over the outer face. Hinged or pivot openings had no place in vehicle windows as the rattle would undo their fixing. The entry door also had a window that worked like a Dutch door, the lower section was a regular hinged door, and the upper section had an accordion fold sliders.

With steam rail carriages and automobiles the travel speeds became faster, wind and chill became unbearable. A new configuration for the window was needed to replace the canvas folded blinds. Glass at that point of time was very brittle, incapable of bearing the jerks of rough roads. From 1680 glass windows were made from stress relived annealed glass and encased in thin brass sheet framing. 'On the front part of the open carriage, a screen of wood or leather called a dashboard was used to intercepts water, mud or snow thrown up by the heels of the horses'.

Stagecoach, a heavy and cumbersome carriage drawn by either four or six horses and its wheels without any form of springs, was introduced in Britain in 1640. Its intercity travel was barely at 4 miles per hour, but over unpaved roads. It carried eight prosperous passengers inside the stagecoach. Lower class seats were available in a large open basket attached to the back. And the privileged travellers sat on the roof with the luggage holding a hand rail to prevent the fall off. Animals drawn vehicles were called: tomtom, victoria, jurigari, tanga, ekka, a stagecoach, a charabanc, omnibus, a gig, a sedan chair, brouette.

'The post chaise is designed for just two passengers seated side by side and facing forwards -with a splendid view of the landscape through large front and side windows. The view is not obscured by a coachman, since the carriage is drawn by four horses with postilions riding on two of them. Driving in such a vehicle with Boswell in 1777, Samuel Johnson declares: 'If I had no duties, and no reference to futurity, I would spend my life in driving briskly in a post chaise with a pretty woman.'

CAR WINDOWS: Car windows have derived from carriage and stage coach windows. Cars have windows on sides, front, back and also on the roof. The windows are fixed panes such as usually on front and back faces, or open-able depending on the style and purpose the vehicle serves. The shape of the window was initially flat plane but later contoured by the wind movement at high speed and also in consonance with the form of the car body. Convertibles have folding top, fixed, folding or retracting front and back glass panes and sliding side windows. Convertible top cars offer an outdoor experience but on the move.

A convertible automobile has a roof that can retract and fold away, converting it from a covered top to an open-air vehicle. Roofs are not detachable as affixed to the body of the vehicle by hinges fold away, either into a recess behind the rear seats or into the boot or trunk of the vehicle. The roof opening and closing operations are either manual or automatic via hydraulic or electrical actuators. Soft tops are made of vinyl, canvas or other textile material while hardtops are made of steel, aluminum, plastic or other rigid materials. Convertible cars are known as rag-tops, drop-tops, spiders, roadsters, cabriolets or simply top-down cars. A soft-top convertible may also be referred to as a cabriolet or cabrio, although a two-seater soft tops often retain the name roadster, referring to their body style. Hardtops are marketed under the terms a coupé cabriolet, coupé convertible or simply retractable hardtop, while two-seaters more commonly use coupé roadsters.

WINDSHIELDS: Front windows of the car, or aircraft, motorcycles, etc., are called a windshield. It is made of laminated safety glass or high-impact acrylic plastic. A windshield protects the driver from the wind, temperature extremes, dehydration due to fast loss of body moisture, flying debris such as dust, insects, and rocks. With special coatings it improves night vision by regulating the glare. On sports and racing motorcycles a windshield aerodynamically improves the drag coefficient but may not shield the rider much. Aircraft windshields have a layer of tin oxide in the glass sandwich which on passing an electric current act as a heating element to prevent icing on the glass. In a similar system car windshields have embedded copper wires for the same purpose. Commercially these are known as Quick-clear or Insta-Clear. Such copper wires often obstruct the signals from satellite or land antennae systems. Small height windshields, less then 200 in height are called aero-screens. Open sports and field vehicles like Jeep, etc. have foldable front screens.

SIDE WINDOWS: Side windows can be fixed panes or raised and lowered by a handle, or powered. In some micro or mini cars, operable side windows are provided only for front seats. Front windows normally slide up in side channels attached to the columns, but the top rim may not be provided for folding roof cars. Glass for the windows has a bottom rim holder, and in case of a tapered shape glass (wider at bottom then at head) the side channels become effective when the glass is nearly up and closed. Tropical safari cars like jeeps have only lattices in window gaps and for rain water protection a folding soft cover is provided under small eaves projection. In two door cars, the side window is abutted by front or back, or both, quarter glass or lites. These are fixed or open-able.

QUARTER GLASS: It is also called Quarter lite or Valence window. The quarter glass may be a side window, pivoted or fixed window, between the front wind shield and the door, within the front door, on each side of the car just before the start edge of rear windshield. Open-able quarter glasses are called wind wings.

WIND WINGS: Wind wings also called vent windows and are pivoted or hinged triangular glass that when fully opened divert the breeze to the interiors. Since 1970 these have been discontinued. Ventilation in some tropical cars is now provided through a vent pipe or duct from a front fender to the leg space near the front seats. For passive ventilation windows also have a small height panel over the glass top side with micro holes, which can be covered with a sliding panel.

OPERA WINDOW: In some automobiles the fixed quarter glass may be set in the corner or 'C-pillar' of the vehicle. The opera windows increase drivers' visibility over the front glass.

SUNROOF: MOON-ROOF: An automobile's sunroof is opaque and slides open to allow sunshine and fresh air into the passenger compartment. It is fixed or operable (venting or sliding) opening in the shell of the roof. Sunroof may be manually operated or driven by a motor, and are available in many shapes, sizes and styles. A moon-roof is of clear glass or plastic that allows view and moonlight inside the automobile.

BUS AND TRUCK WINDOWS: Bus and truck windows are larger in height and wider. The larger size of window glass allows view of the front almost as close as the fender. A wider glass allows close turning by the vehicle. The glass is laminated and toughened, often coated with anti glare finish.

AIRCRAFT WINDOWS: Normal window glass, such as was used in the early days of aircraft manufacturing could not withstand the stresses of high altitude and high speed flying. Aircraft windshields were then made from a thermally reinforced glass, Herculite that was developed back in 1938. Now a modern version Herculite II has glass containing lithium and a post casting treatment with a bath of liquid sodium nitrate. The sodium ions detach the lithium ions from the material and take their place, resulting in compaction of the surface. Special, very thin, polyurethane based coatings are vapour deposited to increase the chemical and mechanical resistance of the material. Cockpit windows are made of multilayered high-impact resistant material. Sheets of laminated glass with inter layers of polyvinyl Butyral (PVB) are bonded by autoclaving. Designed for upfront rain and hailstorms, bird hits, high temperature variation and pressure difference between interior and exterior. However, cabin windows are normally constructed from single-layer acrylic. Windshield glass is heated for protection against misting or icing, by of a matrix of wires or by wafer thin film of metal oxide generally based on indium that is vapour deposited on the inside face of the outer pane. Panes are often vapour-coated with a layer of gold or silver to reflect the solar radiation and protect the cockpit from heating up.

BIOSCOPE: KINETOGRAPHIC CINEMA: It is a cinema projection and viewing facility. First bioscopes showed a series of picture frames painted or printed over a roll of paper and moved with front or backlit illumination. The viewer through a window a hole, sufficient to accommodate one or both the eyes, saw the cinematic or motion effect. Later bioscopes used fil stripes of actual cinema sequences. The number of viewer windows depended on whether the unit was head carried or mobile in cart. The first Kinetoscopes were installed in a public parlour during 1894, in New York.

Keywords: CABOOSE / railway carriage or transport vehicle / cupola / full vision arrangement / bay window / lookout / horse carriages / heavy duty trucks / side view mirrors / automobiles / tourist coaches of buses and railways / side windows combined with roof edge openings / WIND CATCHERS / arid countries / CAMERA SHUTTER / still camera / leaf mechanism or sliding curtain / focal-plane shutters / leaf shutter / diaphragm shutter / central shutter / interchangeable lens cameras / non digital film cameras / shutters for newer digital cameras / movie camera / PROJECTOR SHUTTERS / double or triple bladed rotary disc shutter / SCOPES natural view. but an altered observation often a reconstructed scene formed out of non optical or 'human eye in-observable' data.

CABOOSE: A Caboose is projection in a section of a wall of a railway carriage or transport vehicle. Very often vehicles with such forms are also called Caboose. Caboose projections essentially have side windows allowing views of the sides. Similar arrangement over the roof allowing a view of the entire horizon, are called a cupola. In a full vision arrangement the caboose projection was continued as a cupola. A caboose is very similar to a bay window. In the UK, brake vans usually have a bay window known as a lookout.

Early horse carriages had such projections, but were soon replaced by side mirrors. Heavy duty trucks with a driver's cabin smaller then the wide bodied cargo-holds or containers, have long armed side view mirrors. Automobiles have open-able roof tops, curved glass to provide panoramic view but rarely a caboose arrangement. Tourist coaches of buses and railways have side windows combined with roof edge openings to provide greater perspective of tall buildings on a narrow street.

WIND CATCHERS A wind catcher (Persian =Bâdgir, Arabic =Baarjiil) is a roof level opening connected to a duct leading to downstairs rooms. It is used in many arid countries of mid East regions including Iran, Pakistan, Afghanistan. It is a traditional architectural device used for many centuries to create natural ventilation in buildings. Wind catchers come in many forms, such as the fixed head like unidirectional, bidirectional, and multidirectional or mobile.

A wind catcher is capped with several directional ports at the top (traditionally four). By closing all ports but the one facing away from the incoming wind, air is drawn upwards, or by opening the ports on wind side cool air flows downward. The air movement is aided by the opening size and ambient temperature available in the lower section of the building.

Thick wall construction increases the latent heat storage and delays the heat release. The wind catcher with water body is able to reduce the temperature in lower level spaces in mosques and houses in the middle of the day to frigid temperatures. In Persian architecture wind catchers coupled devices are routinely used as a refrigerating device (yakhchal) and in many traditional water reservoirs (ab anbars) for storing water at near freezing temperatures for months in summer.

CAMERA SHUTTER: In a still camera, a shutter is a control device that allows light to pass for a determined period of time. The light exposes the photographic film or charges a light-sensitive electronic sensor to capture a permanent image. Camera shutters are placed within a lens assembly, behind or in front of a lens. Shutters in front of the lens were used in the early days of photography, whereas shutters behind the lens were used in cameras that offered no lens changeability. A leaf mechanism or sliding curtain is usually used to shut off the beam of light where it is narrowest. The exposure time and the effective aperture opening size of the shutter were originally mechanical devices but are now electronic systems. Camera shutters, in addition incorporate a synchronization system to trigger the flash light.

Focal-plane shutters were made of cloth, metal, or plastic curtains which shield the film from light. Sometimes double shutters are used, as one opens a slit, the other closes in. Focal plane shutters have the advantages of allowing the use of interchangeable lenses without requiring the expense of a separate shutter for each lens. It caused distortion of fast-moving objects. Cameras with larger curtains shake due to the movement of a shutter. A leaf shutter consists of one or more pivoting metal leaves which open out. Shutter speeds as fast as 1/40,000 second is possible. A diaphragm shutter consists of a number of thin blades which slide over each other briefly to form a circular aperture. The larger number of blades forms a polygon-shaped aperture. A central shutter is normally located within the lens assembly where a relatively small opening allows light to cover the entire image. The alternative to a central shutter is a focal-plane shutter.

Interchangeable lens cameras with a central shutter within the lens body require that each lens has a shutter built into it. In practice most cameras with interchangeable lenses use a single focal plane shutter in the camera body for all lenses, while cameras with a fixed lens use a central shutter. Non digital film cameras, with a central shutter and interchangeable lenses often have a secondary shutter or dark slide to cover the film and allow changing lenses in mid-roll without fogging the film. For single-frame photography, either mechanical or mechanical plus electronic methods are used. Shutters for newer digital cameras are a combination of electronic and mechanical devices. Some cameras employ a 100% electronic shutter, created by turning on and off the imaging sensor's signals. Digital cameras that can also take video implement this method for their video modes. A movie camera uses a rotary disc shutter which masks and allows the event to be captured into time divided slots, each of which alone is an image or when viewed in a sequence at a peculiar speed, it creates a continuous image or motion picture.

PROJECTOR SHUTTERS: In movie projectors to cutoff the flicker (for persistence of vision) a double or triple bladed rotary disc shutters admit light two or three times per frame of film.

SCOPES: Scopes are instrumental aids for viewing. It is a windowing device to see things: remotely, in detail or greater perspective, by means of optical magnification, by digital imaging, by image enhancement, by background masking, by filtration, etc. Sometimes what we see through such a device is not a natural view. But an altered observation often a reconstructed scene formed out of a non optical or 'human eye in-observable' data. Typically it is a graphical presentation at some accepted scale. Many scopes have associated tools for manipulating the micro objects, as for example surgical procedures.

4.2.4.3 REAL AND PSEUDO WINDOWS

4.2.5.1 WINDOW SIZES, SHAPES AND PROPORTIONS

Keywords: Real, functional or physical / Metaphysical or spiritual / responses that are predictable and reliable / verticality of perpendicular architecture / dormers / windows shapes / circular and such round shapes / oculi or eye windows / doorways / large architectural recesses / alcoves or niches / window tax / four sided framing system / glass to glass junction or curved glazing / curtain wall / curtain wall grids / mirroring / single surface system / LCD and LED systems / dual surface system / functions are isolated and managed differently / security of a window encourages / pseudo windows like cameras and sensors / MACINTOSH AND MICROSOFT WINDOWS / Interface Manager / Windows / 'file' capable of executing or storing data / tiled / active and latent icons / inward windowing system / exterior architecture / interior world and an exterior cosmos / inner or core functions of a computer system / storage, processing power and programmes / well located and connected house / net-a-physical entity / physical and metaphysical presence.

Windows serve two distinct sets of purposes: Real, functional or physical and Metaphysical or spiritual. But inversely functional purposes are not necessarily served by only physical windows and pseudo windows just are not relevant only metaphysically. A real window exists as an opening for an enclosed space. It relieves the restrictions imposed by the barriers that form the building shell. Moreover, a real window usually has mechanisms that allow whole or parts of it controlled. A real window is a multi functional element and so it is fairly a complex entity. Real windows have been with us ages and so we associate forms, shapes and materials to cause responses that are predictable and reliable. Dutch door and French doors are nearly real windows.

Pseudo windows appeared in early middle ages for mainly two unrelated reasons. First, Windows on the interior front were commonly from floor to the ceiling, but this stretch was no match to the majestic tall windows of religious buildings and public buildings with high ceilings. To create an impression of a tall window or the verticality of perpendicular architecture, ground and upper floor windows were at least on the exterior front, combined. The floor junction zone was masked by a fake window. To stretch the window height further roof level windows or dormers were also included in this. Two, Roof top lanterns, sky lights and were fashionable but always leaking, so were mounted as make-believe entities over the roof.

Windows shapes have been faked. Circular and such round shapes do not allow fitting of shutters, so such windows were usually internally masked with square edged windows. Oculi or eye windows were often exterior surface decorations. Splayed sides make a window seems bigger. Large doorways are inset with doors of mere functional size, similarly, and large architectural recesses have been used to circumscribe small windows. Small deities are housed in alcoves or niches that are pseudo windows. Cabinets adjoining windows on interior fronts are patterned like windows.

Window tax was part of the English architecture and buildings were designed to show off many openings, but many of these were walled up from inside or were simply painted images.

All glazing materials have been mainly stiff flat sheets and curvilinear forms were difficult to make so curved windows were made as polygons. A window has been a four sided framing system, and at places some of these sides need to be removed for providing unhindered view and also for forming larger glazing panels. At a corner the junctions of two frames need to dissolve for panoramic view. Such problems are solved by making glass to glass junctions or curved glazing. Such windows are usually fixed glazing type and the function ventilation has to be arranged by other means. A curtain wall is a pseudo window front and often conceals not only the structural members such as beams, columns and walls, but also mullions and muntins behind it. Glass fronts are also used to cover up bad architectural details of the buildings. Curtain wall grids like skins impose a new patterning system over the facade.

Windows have been used for bringing outside in and showing of the interior spaces. These functions are now not only altered but replaced completely. Glazing surfaces are translucent or transparent but mirroring by high gloss reflectivity provides a new dimension to the window surface. These are now becoming vivid by LCD and LED display system within the glass panes. Touch screen technology endows a new capability. LCD and LED can maintain consistent levels of illumination and provide a desired vista. Windows are single surface system that is one face reveals nearly whatever is happening across its other face. LCD and LED systems can create dual surface system whereby a window on its exterior face can be a hoarding or display facade while still providing clear vision from interior side and also natural illumination.

Windows serve many functions such as vision in-out, ventilation, egresses, security, etc. but to create exclusive form some of these functions are isolated and managed differently. Typically ventilation is often managed through the perimeter apertures or HVAC systems. Glass treated or formed into a layered composite for thermal management.

Windows provide security in many different ways, both in real and metaphysical sense. A person exposes very little of own-self when shielded by a defensive aperture such as in fort walls and roof tops. Security of a window encourages one to do acts which might pose serious consequences (de-fenestration) like dumping unwanted things and people, throwing oil, tar, pitch, stones, spears, etc. over the invaders, confessing sins, peeping into someone's privacy, delivering articles, insanities infamies, etc.

Windows were the main source of overseeing for security in many establishments, but are now being replaced by pseudo windows like cameras and sensors. These devices do it remotely and also record and analyse the happenings.

MACINTOSH AND MICROSOFT WINDOWS: The first independent version of Microsoft Windows, version 1.0, released on 20 November 1985, was originally going to be called Interface Manager but Rowland Hanson, the head of marketing at Microsoft, convinced the company that the name Windows was more appropriate.

It was not completely a new interface to look into what is happening to the data, and some similar features were already tried out by Apple computers. Each section or icon was representing a 'file' capable of executing or storing data. For example, icons or windows were only displayed as tiled on the screen, that is, they could not overlap or overlie one over another, but icons interacted with others in time and space. There were active and latent icons in terms of time reference. Spatially the icons on a screen were more relevant then others that were not seen. The icons were perceived to be windows or peep holes that allowed one to see through it. It was an inward windowing system, like an architectural entity seen from outside. By shifting of the windows (icons) across the screen a new architectural entity was being created. By enlarging the window a lot more detailed view of the interior content was available. But each enlarged icon was a cosmos or a 'building' of its own.

Windows of earlier versions were more of the exterior architecture. The user remained an outsider often almost like alien, with very limited real penetration. The later versions of the windows gradually attempted to turn the system outward, as much as it was inward 'looking'. The computer became a centric entity where there were an interior world and an exterior cosmos, truly like a window which has exterior and interior functions.

Some of the inner or core functions of a computer system have been storage, processing power and programmes. A window on a screen provides connectivity to these but is always limited by the individual capacities. Across the world substantial latent capacities exist in every computer. If all these could be amassed, greater resources can be available. A system where these are available externally can be like comfortable and well located and connected houses, one can reach out of the window for greater efficiency, neighbourly help. Windows as a computer system has become a net-a-physical entity from its physical and metaphysical presence.

Keywords: SIZES / width of the opening / technology of spanning a gap / lintel beams / flat arches / edges and sills were chamferred /arches / header beams / round arches / pointed arch / arched gap / perpendicular architecture / wider than any glazing material then available / pierced panels / transom / springing point of the arch / between the sill and the springing point of the arch / equal height sections / grid or matrix / overcome the presence of such strong delineating elements / glass / restricting but shaping factor / acrylic and polycarbonate sheets.

SHAPES / pointed arch / perpendicular architecture / rectilinear matrix / non load-bearing panel / tympanum / traceried patterns / tool for expressing a wider opening / exterior face the domestic tall window / interior side / cut into distinct several windows / floor to ceiling height windows / punctured gap windows / vertical rectangles in shape / double hung sash windows / revival periods / Greek, Roman and other classical vocabulary / stand-alone element / addition of architectural elements / integrated opening unit / large integrated window / flat headed openings / double hung sash windows / disciplined facade / lites / Mashrabiya / Oriel and bay windows / Lantern / beacons roof eye / oculi / glass domes and hatch windows / wood windows / wrought iron engraved or chased patterns / heat forging and rivetting / saw tooth North light trusses / hot rolled steel sections / standardization of openings' shapes and sizes / shape or size restrictions / Orangeries / atrium / spider leg joints / elimination of framing.

PROPORTIONS / rectilinear / squareness of its corners / Golden section / Palladio / double shutter French (doors) windows / Venetian shutters / horizontally wide windows / Corbusier / Frank Lloyd Wright / Guggenheim museum / Ronchamp / vertical narrow windows / relative term / absolute parameter / human anthropometric data / placed in a thick wall / deep set without splayed extrados / perpendicular architecture of Gothic period / Lancet / towers and turrets / cross.

SIZES: The width of the opening has been a major restrain. It is primarily determined by the technology of spanning a gap. Flat headed openings, first with lintel beams and later with flat arches have spanning limitations. Typical span widths have been 2000 to 3000. For a greater amount of illumination, several windows were placed together forming a matrix. But thick walls reduced the apparent size of the opening. Window side edges and sills were chamferred to receive more light and also perceive a larger opening. Windows were placed.

Arches opened up windows from the narrow confinements of the header beams. Round arches increased the area of the opening. It created an opening that was taller than the span. Round and segmental arches required heavy abutments or a balancing parallel arch to take care of the side thrust. Pointed arch carried the thrust downward and so could be placed over a column. It was now possible to group several small openings under an arched gap. The grouped windows were not separated by interim walls but by thin mullions that provided the lateral stiffness. The tall and narrow windows under a pointed arch and divided by mullions presented a perpendicular architecture.

The narrow window was wider than any glazing material then available. The window space was covered by pierced panels and budget permitting by a pane made of small pieces of glass joined by lead cams. The tall window needed a horizontal brace, the transom.

The transom reduced the vertical size of the window. Transoms were first included at the springing point of the arch, and secondly somewhere between the sill and the springing point of the arch. This arrangement created three nearly equal height sections within a window. A strong grid or matrix was formed in the window face. To overcome the presence of such strong delineating elements, the mullions and transom had greater depth then the width and were fluted. To dissolve mullions and transoms the stained glass scenes or religious stories were carried across several panes.

Glass has been restricting but a shaping factor for windows. The pot glass was too dark or opalescent. Crown and Cylinder glass were small in size and unclear in terms colour and clarity. Glazing panes had to be formed by recombining small pieces with lead cames or with thin muntins or glazing bars. Double-hung sash windows exploited the fuzzy and small size glass by imposing a strong matrix. Large size of the glass and strengthening techniques have been used to create shop fronts and curtain walls. Glass surface treatments and shaping by bending and forming newer glazing options. Acrylic and Polycarbonate sheets offer glazing options that are stronger, lightweight and mouldable to any shape. Synthetic woven fabrics are offering new opportunities for openings' design such as roof lights, glass domes, atrium covers.

SHAPES: The shape of the opening has been mainly square cut. A puncture in thick masonry walls with a flat headed top created a stable structure. It permitted a shutter. But arches created a wider opening but thrusting the sides. The round arch required abutting-walls or similar arches to balance the sideways thrust. A round arch could not be placed in the end bay. It could not be rested on a column unless it is balanced on other side by a similar size arch. Pointed arch relieved the walls of thrusts and could rest on a column. Pointed arch made the opening even narrower, and the mullions strengthened the verticality of the window as in perpendicular architecture. Pointed arch allowed openings of different span widths to be equally taller with same springing line.

The arched openings left a gap in the upper section that was difficult to fill in by regular a rectilinear matrix. The upper sections of the grouped openings under an arch were filled in by a lighter non load-bearing panel, the tympanum. It was lighter due to its thin thickness and was made lighter by piercing with traceried patterns. The mullions of the lower section were continued upwards to form the curvilinear traceries. The curvilinear traceries also became the terminating features for mullions.

The closely spaced mullions supported the opening and stiffening it laterally, but were obstructing the depiction of large scenes. Stained glass scenery were stretched across the mullions, ignoring their presence. These also became a tool for expressing a wider opening. The mullions began to be leaner, now made with compact grain stones like granite, and in later years from wrought iron.

Tall windows were suitable for ecclesiastical buildings, but domestic floor heights were smaller. On the exterior face the domestic tall window stretched for several floors and often into the roof as a dormer. The same window on the interior side was cut into distinct several windows reaching from floor to ceiling. Floor to ceiling height windows created a new language of interior spaces compared to the punctured gap windows.

It was not very difficult to compose a large glazing pane by joining small pieces of glass with lead cames or glazing bars. But where the windows were required to have an open-able section, the shutter has restraining effect on shape and size of the window. A shutter, pivoted or side a hung casement, had to have the hanging edge straight. Wood windows with stile and rail construction had a tendency to deflect, if made too wide. So the wood shutters have remained vertical rectangles in shape. Double casement shutters meeting together, made the opening square in shape.

Vertical sliding windows like double-hung sash windows had shutters that were square or horizontal rectangles. But two such shutters together in a wall gap altered the shape. Classical double-hung windows could not be large, because heavier wood stiles and rails increased the weight of a shutter to be lifted. A very thin section compromised the lateral stiffness. Greater number of glazing bars allowed larger deflection of the shutter.

Horizontal sliding windows, of recent times, have shutters fully supported on channels parallel to the gravity, so need to be more horizontal then vertical. All sliding shutters are square edged and cannot be odd shaped.

The revival periods brought to an end, the gothic architecture shaping the form of the windows. The reliance on Greek, Roman and other classical vocabulary made windows to be a stand-alone element. For this, the size and shape of the windows were perceptively altered with addition of architectural elements like pilasters, half columns, pediments, etc. Palladio did this very skilfully. Exterior window appendages integrated the opening with the facade. A basic integrated opening unit was repeated in same scale, or its versions were used to compose the facade. To make space for such appendages window units were distanced from each other. To creative a cohesive face, the window units had an intervening wall surface treatment such as rusticated and other stone patterns, cornices, running bands or courses. Initially opening compositions were meant for the main face, but later on all sides of the building.

Many other functional shapes for windows have been devised. Functional shapes include small oculus to large rose windows, a slit like a lancet to Corbusier's ribbon windows. Metaphoric cross shaped windows in ecclesiastical buildings to Tee shaped arrow windows in forts.

For multi storeyed buildings large integrated window units with round or pointed arch or one with a pediment could not be easily stacked one over the other. For commercial and palatial buildings flat headed openings were better for stacking. Double-hung sash windows created a very disciplined facade. The size of the window could be increased proportionateley. A taller floor height would have wider windows, as it was composed of almost two squares. Its subdivisions or lites reflected the rectilinear proportion of the whole unit. It had no heavy transoms or mullions. The classical facade composition for a building had five windows on upper floor, and four on a ground floor with the central bay taken by a door. This window became so well accepted that it was popular for nearly 250 years.

Mashrabiya, the projected windows of the Arabic world were designed for sideways view in a narrow street. This purpose was modified in its European adoption. Oriel and bay windows were used to enlarge the room space and receive more light and from many directions. Lantern openings had flooded the interior spaces, and also been the beacons over roof tops. The dramatic lighting effect of the roof eye and oculi openings are now recreated with glass domes and hatch windows.

By 17^th C it was well realized that for wood windows have reached the structural limit and a new material was required. Wrought iron seemed to be a stronger material. It permitted engraved or chased patterns almost like a wood surface but its joining method of heat forging and rivetting was not offering the required rigidity to the window.

Industrial buildings of 19^th C had deep interiors and were day-lighted with may different types of roof lights including saw tooth North light trusses. The fast increasing demand from industrial, commercial buildings and mass housing could only be met through hot rolled steel sections. The large scale production of steel windows also led to standardization of openings' shapes and sizes. Steel windows were well integrated with other steel structures of the time such as roof lights, north lights, skylights and large glass shop fronts.

Availability of large size glass plates also removed the shape or size restrictions for windows. The large size of glazing gave an opportunity to do away with overbearing effect of the support grid or matrix. Orangeries of the past have turned into atrium spaces. Glass walls or curtain walls have glass edge to glass edge adhered joints and spider leg joints, completely eliminating the framing. Elimination of framing and virtual glazed walling are now possible because the function of ventilation is not with the windows. Similarly large size glass in openings is accepted for it is tougher, and unbreakable. New methods of safety and security have also facilitated use of glass.

PROPORTIONS: Windows have been rectilinear in vertical or horizontal formations. The squareness of its corners was eased with circular, segmental and multi point arches. Yet under the arched heading the essential shape has remained rectilinear. The width was restrained by mainly structural reasons, and the height set by the floor. But floors have been negotiated by continuing the opening, often by masking the floor lines. Square is not a very favoured shape for windows, perhaps because the multiple shutters within it make it rectilinear. The favoured proportion of width vs the height is of Golden section. Most proportionate relationship between a door and window opening was evolved by Palladio. And most accepted proportionate window form has been the Colonial double-hung sash window. Yet another classical form is of Double shutter French (doors) windows with Venetian shutters opened out flat on the side wide walls, creating a square shape divided into four vertical rectangles.

Horizontally wide windows were not very uncommon. Clerestory and cellar lights have been horizontal stripes in buildings with beam and flat roof construction. Horizontal windows are placed close to the roof or floor bottom level to distribute illumination, such as in Egyptian and Greek buildings. A series of windows in a raw formation also creates a wide strip effect, if mid support sections are dissolved with appropriate surface treatment or the sides are splayed. Corbusier in his early work used the ribbon windows. Frank Lloyd Wright stretched the window to emphasize exterior horizontality, more so with deep roof projections. Guggenheim's museum has spiral ribbon windows. Corbusier has used horizontal windows to float the Ronchamp roof from the support walls. Saw tooth truss North light windows create long ribbon openings.

A vertical narrow window is a relative term as it connects with the architectural mass of exterior and the interior space. But it is also an absolute parameter in terms of the human anthropometric data. In the first instance, a window seems narrow when placed in a thick wall and is deep set without splayed extrados. And in the second case a window considered narrow if deficient for egress and its sides obstruct the cone of vision. Narrow windows have been very commonly used to emphasize the verticality of form such as in perpendicular architecture of Gothic period. Vertical windows such as the Lancet have been used in small diameter circular architectural forms such as towers and turrets. Narrow windows or slits are placed in an embankment, fortifications, parapets, etc. for shooting arrows and spears. Narrow windows with horizontal ribbon openings are used to form a cross in religious buildings.

4.2.5.2 WINDOWS FUNCTIONAL SIZES

Keywords: different functions / exclusive or limited functions / function and size relationship / other openings such as crevices, gaps, cuts and doors / architectural expression / human use / view window / ventilation window / 6 to 15 % of floor area / emergency exit or rescue / sill level / work posture level for ergonomic profile of the users / hanging as a casement shutter / warping resistance as a sash window / lateral stiffness as a sliding pane / handles on edge / single casement shutter / commercial extruded sections / International Standards Organization, ISO / Modular preference / architectural design / multiples of 100.

Windows serve many different functions: such view out or in, egress, ventilation, illumination, for throwing out and receiving things and filtration. Windows of exclusive or limited functions have been devised with unique and often bizarre shapes. The function and size relationship is often not very distinct as other openings such as crevices, gaps, cuts and doors also serve or even prevent some of the functions of windows. Windows have been conceived to serve architectural functions also. The size, shape, placement and grouping of windows, all create an architectural expression for the building.

For human use, the view window should be wide enough to allow a 60 conical view of the outside. This is possible through a small width aperture in a thin wall and by being close to it, but may not be feasible by standing away or for a deep-set aperture such as in a thick wall. For ventilation window size of 6 to 15 % of floor area is advised (depending on passive areas like store rooms to very active areas like kitchens and exercise rooms), by various building bye-laws. Window egress design is based on size required for emergency exit or rescue of mainly humans but sometimes goods and equipment.

Windows for domestic use require a sill level that an infant cannot jump out, such as provided for barricades, railings and parapets, that is at least 850 high. Windows must provide a clear view and often wind draught and the solar incidence at the work posture level for ergonomic profiles of the users. But as windows are multi functional and serving a wide variety of users its top member or the head must not hinder any of its uses or users. Mid horizontal members, must not obstruct vision in sitting or standing position, that is between 1100 and 1400. Width of a window shutter is dependent on its safe capacity of hanging as a casement shutter, warping resistance as a sash window and lateral stiffness as a sliding pane. The nature and capacity of closing-opening devises also restrain the width of the window shutter. For handles on an edge, the ideal width of a single casement shutter is 450. Sliding windows are preferably designed within 3600 width, as commercial extruded sections are available for this length.

International Standards Organization, ISO has specified Modular preference for architectural design, and so all commercial windows are available in multiples of 100 (less fitment margin).

4.2.5.3 ARCHITECTURE OF WINDOWS

4.2.5.4 SPATIAL CHARACTER OF THE WINDOWS

Keywords: separation of a window from the door / window next to a door / identical and often the superior functionality of the door / placed away from a door / side-lites / fan lights or transom windows / opaque tympanum / rose or oculus opening / wall punctured windows / linear sequence / planner matrix / equalization of head level / very tall window openings / curves of the pointed arch / lean wooden mullions / clearer and colour free glass/ composite entity / very narrow or slit windows / wall termination or structural junction / Lancet windows / small size apertures / acutely specific purpose and location / texture creating or surface modulation unit / surface of the glazing / vivid element / static and opaque face of the building / architectural composition at a facade level / Palladio / composition of openings / opening system for Chandigarh buildings using brise de soleil / single, few or multiple units / linear patterns / balanced patterns / orientation, location, floor level, interior space usage and neighbouring elements / multiple windows.

Windows have originated as a distinct opening from a door. The upper section of the door was perhaps the prime window. The process of separation of a window from the door lasted several centuries. A window next to a door was subjugated by the identical and often the superior functionality of the door. A window had its own distinctive role when placed away from a door. It was Palladio, who successfully joined them together. The side-lites, as the window accompanying the door is called, came in as a simplified form after Palladio's very elaborate composition. Fan lights or Transom windows placed over a door are as old as the arched opening. But in Gothic architecture the upper section of the door was an opaque tympanum and the window was a separate entity, like between two columns or as a rose or oculus opening.

The early wall punctured windows were spaced apart to maintain the integrity of the load-bearing wall, but the windows had to be linked together on interior as well as exterior face for a composite facade. On interior front the chamferring of the intrados helped window gaps seem to be closer. But on exterior face the windows were grouped by extra bands at the sill and lintel level.

Windows are visually related to each other by placing them in a linear sequence, such as at the base of a dome in Hagia Sophia, Constantinople, or as a planner matrix, such as in Venetian palaces. Windows were placed as separate but in repetition of units, or a large window unit was divided by mullions, transoms and traceries. Corbusier has used brise de soleil to create a surface texture.

An arched window does not allow stacking, unless substantial floor heights are available to accommodate the arched section. An arched window is as taller as its width, forcing one to either restrict the size of the opening or increase the floor heights. Head levels of arched windows for different widths of openings are varied. A pointed arch allows equalization of head level for different widths of openings.

Very tall window openings were suitable for religious buildings like church, but openings for domestic buildings these were mostly flat headed. In tall buildings the mullions continued in the arched following the curves of the pointed arch, but in domestic buildings, due to smaller scale of the opening, arched openings were less common. Flat headed openings were small, and so heavy stone mullions were not required, and instead the grid was formed by very lean wooden mullions.

Windows of religious buildings were covered with pot and stained glass, and later with grisaille painting. Domestic buildings had panes of wood and then clearer and colour free glass. In religious buildings open-able sections of the windows had a distinctive position, separated from the fixed glass panes. In domestic buildings the window was a composite entity where the open-able shutter itself was glazed.

Very narrow or slit windows occur as wall termination or structural junction. It presents a darker vertical line during daytime a brighter line when backlit at night time. Lancet windows were used to accentuate the vertical nature of towers.

Small size apertures are used as windows, when appropriate (cost, availability and technology wise) glazing materials are not available, such as for blizzards prone buildings or tropical housing. Small windows are used for limited view, privacy, ventilation and exchange. Acutely specific purpose and location-based windows are small as these serve a very limited purpose such for sleeping on the floor, seat level view, privacy, banking or business transactions, safety against falling off and as a social punishment in jails.

Architecturally windows have been used as texture creating or surface modulation unit. Windows are setback from the masonry surface of the wall so create a play of shadows, and help emphasize the depth or the massiveness of the walls. An open gap allows one to view the interior space which is deeply shadowed or shows up the colour furnishings inside, adding a variation to the usually monotonous facade. The surface of the glazing is very smooth, glossy and reflective of the changing surroundings, makes a very vivid element over the dull, static and opaque face of the building. These aspects are key issues in urban architecture of curtain walls. A window allows one to see the inhabitants of the building making it very 'lively'. Window treatments, on outside or inside, personalises a house, such as seen in row houses or public housing. A small window or a covered window, raises the curiosity about the activity or the occupants inside.

Architectural composition at a facade level involves a balanced setting of walls and openings in proper order. Palladio created a composition of openings. Similarly Corbusier orchestrated the opening system for Chandigarh buildings using brise de soleil. Hawa Mahal Jaipur is a climate solution.

A window occurs as a single, few or multiple units over a facade. As a single unit it creates a focus, but may be dwarfed by the scale of the monotonous masonry surface. To emphasise the window many architectural elements are added over the window face, such as pediments, Chhajjas, side columns, pilasters, cornices, etc. Few windows over the facade form linear patterns by their one to one relationship. Balanced patterns mark a stable architectural entity like historical monuments. Few windows, each different from the other and with unique settings reveal the multi functionality of the architectural entity or could be an architectural composition like Ronchamp. Such amalgamations of windows often have few common elements and some distinguishing features based on orientation, location, floor level, interior space usage and neighbouring elements. Multiple windows are the marks of public spaces. Multiple windows due to their consistency provide a sobriety in chaotic urban setting. Multiple windows of different sizes and forms are grouped under a larger entity like an arch, overhang or brise de soleil (Corbusier in Chandigarh). Multiple windows in regimented form represent industrial mass production and efficiency.

Keywords: surface elements / perceptive form / reverse -mirror image in the glazing surface / single picture frame, simultaneously reveals / membrane / stretch out the sensorial faculties / see, smell, listen and feel the other side / opening out the interior spaces / bringing in the exteriors / opaque glazing of heavily coloured pot glass / glass became thinner, lighter in colour / cristallo glass / cristallo was a dull opalescent surface / better casting, polishing and fire finishing / realities of interior and exterior happenings / see-through element / reshaping its perceptive size, scale and extent / stratification of view / changing a space, intentionally and accidentally / furrowed gaps / shadows as a form creating element / windows like bay, bow, mashrabiya and oriel / zarokhas / Masking / character of the windows / geometric composition / system of subdividing the window / Framing / inevitable joint management system / Transparency / simultaneity of exterior and interior spaces.

Windows are surface elements, but a surface that is penetrable. As a surface element it has a great presence on both exterior and interior sides. A window is fairly a complex entity against the comparatively simplistic wall. Its surface never remains static. Its shutters are shifted to different positions. The contextual conditions like climate, illumination, distance and angle of observation and the purpose of use are continuously varying and in turn reshape the windows' perceptive form. The external changes are reflected as a reverse -a mirror image in the glazing surface, and the interiors are seen through it. A window, on a single picture frame, simultaneously reveals the changes occurring in the interiors as well as exteriors. The dynamism of the window gets enhanced further by the framing, masking and filtration of the perception.

A window is like a membrane, which may not permit one to go through it, but it allows to stretch out the sensorial faculties. We see, smell, listen and feel the other side through the window. The extension to the other side of the window through the sensorial faculties is always short and casual. The frugality experience stimulates us to go across it, albeit by other means. A person on the outside perceives the safety in the interior, and the one in a bounded space sees the variety of experiences available outside. Doors are dilemmas, either go out or remain in, but a window provides no such options.

Windows have been used for opening out the interior spaces or for bringing in the exteriors. The historical window with opaque glazing of heavily coloured pot glass was extremely colourful but static. As the glass became thinner, lighter in colour the changes in outside levels of illumination began to be noticed on the interior face. This was aided by use of water white Cristallo glass. Interiors seemed much more natural, and attuned to the outside changes in light intensity. Till 19^th C windows were vivid elements in an otherwise static exterior or interior surface. From outside the Cristallo was a dull opalescent surface, but clear glass with better casting, polishing and fire finishing began to be iridescent. The glass was recognised as having two distinctly different faces. Iridescent on the outside face due to reflections and a 'water-white' flawlessly clear and non glossy surface on the interior face. Corbusier used the opaque iridescence of the exterior surface to juxtapose the exterior masonry surface. But FLW used the deep shadows to eliminate the exterior iridescence and colour staining to break interior clarity. Mies used the exterior mirror like gloss to reflect the changes occurring in the surroundings simultaneously showing up the interior, and thereby reduce the massiveness of the built-form. Window glass is now often used to mix the realities of interior and exterior happenings on a very large joint-less single plane. The mix creates a very vivid object, like a water body reflecting the sky and the floor concurrently. Metalized opaque glass belies the two-way transparency of a see-through element.

Wall to wall glass openings dissolve one or many sides of a volumetric space, reshaping its perceptive size, scale and extent. The spatial illusion becomes more intriguing when such a large reflective glass surface is used.

We are conditioned to expect certain spatial effects in a space. A narrow space visually gets widened by a glass opening, though functionally remains the same. Skylights and clerestories add 'lightness' to the space. Lights such as roof holes focus the attention. Openings, depending on their location and nature redefine the space configuration. The stratification of view to the outside offers different scale to the space. Significantly bright areas highlight the details, and so are perceived and registered, more effectively then darker zones. A window becomes an element for changing a space, intentionally and accidentally.

Windows are furrowed gaps into an otherwise solid mass. The depth is highlighted due to the dark interior, and shadows cast by strong and directional light. The shadows as a form creating element was very well exploited by L. Kahn in his Asian buildings. The same effect at a micro scale and in repetition creates a lattice used in Indian Architecture. Windows like bay, bow, Mashrabiya and oriel have been used to enlarge interior spaces and also to correct the interior shape of the space. Zarokhas add to the interior space but have also been used to undulate the exteriors.

Masking has been very commonly used to change the character of the windows. Greek and Roman architecture subdued the openings as a secondary and less visible layer. Romanesque windows once again came to the surface, but openings were framed by the semi circular arch. Coordinating several windows was a concern as the height of the rounded arch was defined by the width of the opening. Gothic architecture solved the problems of geometric composition by pointed arch. It also created a system of subdividing the window opening through mullions, transoms and glazing bars. The window opening was masked by traceried patterns. Window masking became an effective tool to overcome the deficiencies of glass, size, clarity and impurities. The deficiencies made the windows subservient entity of the load-bearing structure. Glass houses, orangeries, etc. allowed windows to define a space without the use of a wall. The need for very large and deep sun lit spaces for bus depots, railway stations, markets, and factories redefined the windows spatial nature.

Framing is a property of all openings. Openings have their sides and mid members within the view cone depending on the point of observation. Palladio masked and framed the exterior face of the opening. The double-hung sash windows did the same on both, exterior and interior face. Framing is now used as an inevitable joint management system, and but often made imperceptible. Stratification (window openings' position @ low, mid or higher level with reference to height of the user or the task plane) is an important ergonomic parameter that affects the spatial perception.

Transparency is a quality of the glass, and the most important aspect of the surface of the opening. A window opening in the form of a glass curtain wall or shop front, shows up the space in its exterior surface configuration, and also the spatial depths of its interiors. The simultaneity of the exterior and interior spaces adds to the dilemma of the physical reality vs the virtual reality.

4.2.6.1 WINDOW OPENING'S STRUCTURES

4.2.6.2 WINDOWS OPENINGS IN THICK AND THIN WALLS

Keywords: gap in a planner structure / within linear structural members / planner and linear entities in geometric arrangements / nature and man-made structures / window heading / width of a window / support end conditions / vertical depth / end conditions of window heads / framed structure of beams and columns / some additional features to complete their functional purpose and often for metaphysical identity as a window opening / window cover / circular openings / CAD design tools / mouldable materials / examples of complex shapes of modern opening systems.

Windows have been primarily carved-gaps in a planner structure like a wall or roof slab. Windows were formed within linear structural members such as columns, beams, struts, etc. Opening gaps are also articulated by combining planner and linear entities in geometric arrangements. Openings like features and situations get formed in nature and man-made structures. A manmade window is an intentional opening. It has sides, parallel to the gravity and perpendicular the gravity, and accordingly is structured.

The window heading is the most critical and restrictive structural entity. Width of a window is limited by the load to be carried over the window head. The flat headed monolithic lintels, arch, composite structure like a reinforced concrete beam or the geometrical composition like a truss, all require a specific support end conditions and some vertical depth to be effective. The vertical depth has been a drawback on the upward stretch of the window opening. Window heads have to be at a lower level then the bottom of the floor above. Arched openings in spite of the height, offer a functional gap (for fixing open-able shutters) that is nearly half the size. End conditions of window heads require specific structural arrangement. Arched openings transfer thrust sideways which must be balanced by counter thrust or allowed to be transferred to the wall at an angle. Pointed arch alleviates the problem of thrust transfer. Flat headed beams must be supported over load distribution courses in masonry. Provision of openings lightens the mass of a wall but due to the thrusts in various directions the remaining section of the wall is more heavily fatigued. A framed structure of beams and columns provides an edge to edge opening. Such openings are very large but need to be re-divided into smaller sections by mullions transoms and glazing bars. The mid members support and brace the beam and columns.

Openings are formed as hollowed spaces or cavities in the massing of solids. These are natural stacks so have no structural definition, but may require some additional features to complete their functional purpose and often for metaphysical identity as a window opening. The additional features at functional level include some control mechanisms like shutters, shading devices and safety features. At metaphysical level, the opening is envisioned to be a window-like feature. For this, the opening is shaped and sized to be like a window. Irregularly shaped gaps are divided by mullions and transoms into regular geometrical forms like square, rectangular or circular, by imposition of a grid or matrix. The shapes are sized to receive glazing or shutter, which however may not be actually placed in the position.

One of the most common controlling entity of window's opening is the window shutter or glazing surface. Horizontally pivoted units and vertically sliding have straight sides and vertically hung units and horizontally sliding units have top and bottom as straight units. Circular openings are few and are usually fixed glazing, permanently open or centrally pivoted units.

In the past it was difficult to perceive, an odd-shaped or odd-volumetric shutter over equal complex openings' frames. Modern CAD design tools and mouldable materials offer exact fit frames that fit or cover odd shaped architectural gaps, and shutters for it. Automobile openings, air craft windows, space craft's hatches, openings in bubble tents, etc. are examples of complex shapes of modern opening systems.

4.2.7.1 CUSTOMS, CANNONS AND VASTU SHASTRA

Keywords: third dimension / planner structure of the windows / character of third dimension functional features / architectural expression / inner side faces or intrados / deep extrados / glare / splayed by chamferring / enlarged surface area / sky component / Romanesque and early Gothic architecture / undisturbed interior surface / fire hazards / issues of encroachment of public lands / windows to be within the wall / window tax / framing and masking / architectural add-on elements / middle-zone formed a niche / glass curtain walls / architectural play of depth and shadows / volumetric play of the building mass / surface finishes / visual reflectance and glow / sign board facades / touch screen provides.

Walls are load-bearing entities, and with their thickness provide the third dimension to the nominal planner structure of the windows. The depth of the wall provides its own distinctive character to the window. The character of third dimension is functional as well as architectural. Functional features of a wall include solar shading and climatic protection. Architectural expression of the wall depth modulates the facade and gives a unique flavour to the interior space.

A window is set over the outer or inner face of the wall, or some distance away from both the faces. A window, placed on the outer face, takes away the deep shadows of opening the gap but creates a deep inner side face or intrados. However, windows placed on the inner edge have deep extrados. The deep extrados or intrados make a window seem smaller then it actually is from their respective face. The seemingly smaller window gap has very high brightness. Such windows require counter illumination on the interior side to reduce the glare.

To distribute the light better in the interior space, inner sides -intrados (with a window fixed on the outer edge) and outer sides -extrados (with a window fixed on the inner edge) were splayed by chamferring. Inner vertical sides, window heads and sill, all were sloped to enlarge the surface area. The chamferred side faces due to the enlarged surface area became more visible and distributed light better in the interior. The chamferred sides on the outer face allowed more light by increasing the sky component.

The effects of square and the chamferred sides were well known to the mural artists (working with different mediums such as tempera, mosaic and frescoes painting) who composed the stories, shading, perspective angle, colour's hue and tone of artwork accordingly.

In Romanesque and early Gothic architecture the windows were fixed on inner face creating a plain and undisturbed interior surface. But by the time this was perfected the walls were completely diminished, and windows were as wide as the gap between two columns.

In medieval period, windows began to be projected out of the buildings over the street, creating serious fire hazards and issues of encroachment of public lands. Both of these were corrected through improved fire laws, which forced windows to be within the wall and the Window tax curtailed the number of openings in a building.

Windows in thin walls require framing and masking, but thin depth of side walls do not allow scooping out or niche creation. Architectural add-on elements such as half columns, extrados, porticos, etc., were placed to frame and highlight the opening. The surface of the window itself was strongly stated by articulated divisions and contrasts between glazed and other surfaces, like rusticated masonry. Windows were also placed in inward or sunken bays, the middle-zone formed a niche for painting, fireplace or library cabinet. Building's facade with thin walls was also undulated by outward bay windows, ledges and other projections.

Thick walls have greater insulation capacity, better heat retention capacity, and window gaps have deeper shading against rain and sun. The shutters, when opened can be accommodated within the gap niche. On the other hand thin walls have poor U value, and a shallow window gap provides no shading. Some form of external shading system is required. Such shading systems have been used for creating architectural facade system, as in Chandigarh Secretariat building.

Glass curtain walls are thin body construction, but are translucent without any opacity -solidity of mass. The thin wall construction requires new concepts for openings' systems. In thin wall or glass wall buildings, shading of solar radiation is now sought through the glass technology and the ventilation through separate HVAC system. Thin walls save floor space and so are economic in spite of the compulsory recourse to other compensatory facilities. The nominal architectural play of depth and shadows for 3^rd dimensional visual depth is not available with openings in very thin walls. This is now recreated either by volumetric play of the building mass or by variegated surface finishes. For such surface modulation, beyond the usual colour and texture, now visual reflectance and glow (illumination from within) are being used. The picture-stained windows of the gothic era or the colourful lantern sky lights are becoming vivid with changing graphics. The sign board facades of commercial districts in Tokyo, Hongkong, Shanghai or New York, once a night time entity has come to stay through the day. Such faces are part of the public spaces or street architecture. At another level the touch screen provides the same fare. The mix of the two will become part of architectural and interior face of buildings.

Keywords: local -vernacular flavour / place and its climate / fail-safe window strategy / technologically economic and efficient options / irrespective of the climate / concern for conservation of energy / basic planning factors / SILL LEVEL / low sill high plinth / high sill at whatever plinth level / nature of privacy / PLINTH LEVEL / urban houses / orientations / HEAD LEVEL / ORIENTATION / favoured entry point / oriented to Mecca / Yam / South entrances / North face / less interesting for external architectural modulation / South face / Vastu Shastra, Feng Shui and other cannons / realistic as well as metaphysical planes / window as a subordinate opening / placed on the same axis / Vedha / Feng shui / locating and scheduling objects and activities / location and an axis not just in space but also time / Qi -chi or Chee / basic five elements / avoid the negative and enhance the positive effects / glass and HVAC systems / major technological innovations / conservation of energy and new technologies to view / next triggers of change.

Windows in buildings emerge after years of trials. Many such traditions are universal, being followed across ages and cultures. There are many factors that give a window local -vernacular flavour. Local factors like the climate, materials, crafts, culture, etc. format a window. The place and its climate determine the windows' size, shape, the nature of shutter, transparency, the sill and head level. The human response to these local factors gradually develops into a fail-safe window strategy. Yet, windows do change as technologically economic and efficient options are devised.

Historically the nature of a window was primarily determined by the climate of the place, but with modern HVAC systems, at least for a while windows were conceived to be irrespective of the climate. The concern for conservation of energy resources has once again brought the nature in focus. There is a better respect for some of the basic planning factors like axial placement, size consistency, increment and diminution in sequential placement of windows, the sill and head levels, the depth of the window, the ergonomic relationship between the task plane and openings.

SILL LEVEL: A low sill provides a body level circulation of air, but the same in a high plinth building cuts off the interior from the effects of high surface temperatures of surrounding ground surfaces. A high sill at whatever plinth level protects the user from cold drafts. Sill levels are also determined for the nature of privacy desired. Ground floor rooms over a street side have higher plinths compared with the buildings located within a private estate. Upper floor windows have lower sill levels.

PLINTH LEVEL: Low plinth buildings with low sill gain heat from raised temperatures at ground level and high reflectance of the surrounding ground surfaces. In warm and humid climates (typically tropical sea shore locations), low plinth buildings and low sill windows allow better air movement in the interiors. Heat gain is curtailed by deep and acutely sloping shading devices. However, North European churches and other public buildings have low plinths but high sill level windows to curtail the draught. Urban houses in busy streets have higher plinths to achieve privacy.

Sill and plinth level manipulations work better on some orientations then others. South side (in Northern hemispheres) ground surfaces receive solar radiation nearly throughout the day, whereas East and West receives it only for a part of the day.

HEAD LEVEL: Windows placed away from the door or in different walls may not maintain the common head level, but axially placed windows or windows adjacent to the door follow the same head height regimen. Indian Vastu Shastra prescribes all openings to have the same or lower head level in comparison to the main entrance door.

ORIENTATION: The sun has been the cause of energy and illumination and is revered. East has been the favoured entry point for all major buildings. Important chambers and entities like an altar, statues, thrones etc. are oriented to Eastern opening. The major exceptions have been Roman and Muslim religious buildings, former were oriented to the plaza or marketplace for visual connection and the later have been oriented to Mecca. Indian Vastu Shastra considers East and North as (holy, spiritually richer, auspicious, metaphysically lighter, a source of energy) better sides for any type of opening. Vastu Shastra equates the South face with a back side, and considers it the side of Yam (death), inauspicious for entry or window like opening. For buildings like temples it forbids any opening on South face. Many Neolithic period Chinese houses have South entrances. Mohen-jo Daro, like the Chinese houses had no windows on the street side walls.

Early church buildings had Eastern entrance, but in later periods began to have Western entrance, to place the deity against the East back lit glass. Buildings with East or West entrances are stretched on North-South axis. The long stretch of North-South side windows illuminates the interior space throughout the day. However, in colder climates, nonreligious and multi functional buildings like palaces, bath houses, schools, etc. had very extensive spread, for which windows were favoured on all sides except North. North was cold face even for illumination. In warm climates North and East, are considered favourable for openings.

The North face ( in Northern hemispheres, except between 0 and 23N) receives no direct sunlight. A Northern courtyard (in Northern hemispheres) is shadowed by the building's own mass and receives very little solar radiation. North face is considered a cool or cold side and desired or detested depending on the need for heat gain. North face (in Northern hemispheres) is bereft of shadows, so seems less interesting for external architectural modulation, but the same side viewed from an interior space receives consistent brightness throughout the day. The South face receives direct solar insolation and is comparatively a warmer side throughout the day. But in Southern hemispheres the opposite holds true.

Other then orientation and climatic factors Vastu Shastra, Feng Shui and other cannons deal with placement of openings in buildings at realistic as well as metaphysical planes. Vastu Shastra treats a window as a subordinate opening to the door in the dwelling shell. A window is placed alone, fronting another window of equal or unequal size, or opposite a door but of larger size. Doors and window must be preferably placed on the same axis and with their head levels at the same datum. Window openings on front and sides of a building are allowed, but forbid any opening on the back-face of the building. A window like the door must not be fronted by a column, corners of a wall, part of the opening, tree or any such obstruction or Vedha.

Feng Shui helps in locating and scheduling objects and activities in a space, built or otherwise. The perfect spot is a location and an axis not just in space but also time. Qi -Chi or Chee, is the energy or vital force that relates to the orientation of a structure, its age, and its interaction with the surrounding environment including the local microclimates, the slope of the land, vegetation, and soil quality. Feng Shui is helpful in avoiding, blocking and redirecting the energies.

Feng Shui shows how to mix the basic five elements: wood, fire, water, metal and earth. The five elements may interact to create a balance and a serene state that provide for a prosperous and healthy life. Qi begins to be positive or negative in terms how, where and what form it enters a space.

Feng Shui prescribes what must and must not occur before an opening so as to avoid the negative and enhance the positive effects of Qi, the energy. Typically a water body opposite to an opening helps to absorb the energy. Couches and chairs should always be placed in a way that allows those who sit on them to easily look out of the openings.

Windows, size and form have been strongly influenced by factors like political security, religious beliefs, ethos, styles or fashions, for conformity with local building regulations (Window tax, London's fire prevention laws) and technology available. Courtyard houses, urban street or row houses, suburban houses and apartment blocks, each requires a different set of openings, determined by its architectural extent, street connection, styling and security management systems. Glass and HVAC systems have been two major technological innovations to change the form of the window. Conservation of energy and new technologies to view out could be the next trigger of change.

4.2.8.0 FUNCTIONS OF WINDOWS

SUB INDEX for 4.2.8.0 FUNCTIONS OF WINDOWS

4.2.8.1 Illumination

4.2.8.2 Thermal Management : Insulation

4.2.8.3 Ventilation

4.2.8.4 Passage and Control

4.2.8.5 Safety and Security

4.2.8.6 Vision in-out

4.2.8.7 Other Issues

4.2.8.1 ILLUMINATION

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: ventilation and illumination / associate darkness with coolness and brightness with warmth / Ultraviolet (UV) / Visible / Infrared (IR) / DAY-LIGHTING / natural light / maximize visual comfort and reduce energy use / amount of light / nature of illumination / quality of illumination / three basic sources of day-lighting / direct component / sky component / reflected component / artificial illumination / burning fuels / smoke and soot / degradation of interior spaces and also a health hazard / upper latitudes / hours of working light / buildings in arid zones / compact massing / large size openings for illumination / ENERGY CONSERVATION / clean and non polluting source of illumination / electric illumination / conservation of energy / go-green policy / energy savings / WINDOW LOCATION / window with an interior wall at right angle / window in a wall with interior colour of lighter shade / window in a dark coloured wall / chamferred or splayed sides / inner edges / chamferring of the outer edges / sky component / chamferred sill / windows located high in a wall / depth of daylight penetration / light coloured floors / lumen / glass blocks or glass bricks / MODELLING / windows, skylights, clerestories / natural luminance / direction of light / ever changing nature / contrast in brightness levels / multiple orientations and height levels / light from a single bright source / light from a large diffuse source / light from multiple directions and if in different intensities / very large diffuse source / large top source like roof / REFLECTANCE OF ROOM SURFACES / GLARE / MIXING NATURAL AND ARTIFICIAL ILLUMINATION / change over from day-lighting to night-time illumination / advanced controls / day-light during the twilight zones / changes are occurring very fast / colour diffraction of horizontal sunrays / windows with large sky components / large open horizon / on-off switching controls / adjust the opening of windows and shading devices / turn of electric lights off randomly as well as selectively / stepped and Dimming controls / reflectance controls / GLAZING MATERIALS / as high up as possible / using clerestories and skylights / heat transmission through framing and shuttering members / mild steel and aluminium windows / two main classes of glazing materials / clear vision / obscures / clear material the light reflected back / obscuring materials / brightness of the view wide range of diffusion patterns / thermal and optical performance / multi-paned lites of glass / conductive and convective heat transfer / shading coefficients / visible transmittance / U-VALUE / rate of heat transfer or heat loss / window with standard glass / double glazed window with standard glass / SHADING COEFFICIENT (SC) / ratio of solar heat gain / solar heat gain coefficient (SHGC) / absorbed, convected, and inwardly radiated solar energy / high SHGC / low SHGC / VISIBLE TRANSMITTANCE (VT) / optical property / visible light transmitted / higher VT / spectrally selective tinted or coated glazing / infrared energy / higher levels of visible light transmittance / selective low-e coating on the interior surface / increased day lighting / building energy usage / TASK HANDLING / visual tasks / use of eyes / visual tasks relief.

Windows are the primary source of illumination. In tropical climates, in small houses when a door is open, which is the nominal case most of the time, it provides both ventilation and illumination. The window thus becomes a minor opening used only occasionally for ventilation. In a tropical house admission of light is usually accompanied by heat gain, but the breeze coming through a door balances the interior environment. In tropical climates interiors tend to be darker to reduce the heat gain compared to colder climates more illumination is preferred. We associate darkness with coolness and brightness with warmth as a matter of experience and also due to the psychological conditioning. Naturally illuminated lit spaces are perceived to be healthier.

Sunlight is an electromagnetic form of energy arriving from the sun. It is composed of a range of electromagnetic wavelengths, such as: Ultraviolet (UV), Visible, and Infrared (IR), referred collectively, as the solar spectrum. The short, UV wavelengths are largely invisible to the naked eye, but are responsible for fabric fading and skin damage. Visible light is made up of those wavelengths detectable by the human eye. This light contains about 47% of the energy in sunlight. Longer IR wavelengths are also invisible and contain about 46% of the energy in sunlight. The earth receives a small fraction of the very large luminous flux from the sun. On a bright sunny day the illumination can be more than 100,000 lux (about 10,000 fc). The luminance of a cloudy sky can be nearly 1/ 3^rd of that, and much lower if the clouds are dense and dark.

DAY-LIGHTING: Day-lighting is the practice of placing windows or other openings, so that, during the day, natural light provides effective internal illumination. The aims are to maximize visual comfort and reduce energy use.

The amount of light coming through any opening depends on factors like: sun's position, sky conditions and the nature of surroundings. The nature of illumination in an interior space depends on the size, number, location, distribution, orientation of openings, types of glazing, and components of the window system such as: external shading devices, internal appendages like curtains, Venetian blinds. The quality of illumination is affected by reflections from external and internal surfaces.

There are three basic sources of day-lighting for buildings, the direct radiation from the sun -Direct component, the light reflected from the sky (more apparent when direct sunlight is not available) -the reflected or Sky component, and illumination reflected from the ground and other surfaces -the Reflected component.

Day lighting when insufficient, requires augmentation by artificial illumination. Artificial illumination was available from burning. Burning fuels was very costly and also gave out smoke and soot. It was the chief source of degradation of interior spaces and also a health hazard. People planned their activities requiring acute illumination between sunup and sundown periods.

In upper latitudes daylight periods are very short and skies overcast reducing the hours of working light. Buildings in these zones, are planned with as large perimeter as possible, to enlarge the external surface area. Rooms requiring day lighting were made wider and placed with a wider side on the exterior face. Rooms were made large instead of many small units. Windows stretched for full height. Compared to these, buildings in arid zones minimize the exposure to an external surface, by compact massing. Window openings are smaller and distributed. Problems of the glare were solved by cross opening, which also helped in better aeration of space.

Large size openings for illumination offer greater warmth during day time, but at night the outward conduction of heat is very high. Windows in all climate zones require very careful planning and detailing.

ENERGY CONSERVATION: In the 19^th C, gas and petroleum-liquids provided an option for cleaner illumination. It still caused problems of smoke and fumes. But, later electrical illumination marked a cleaner and non polluting a source of illumination. Cellars and deep-set interior spaces now could be lit without the worries of ventilation. Day-lighting was given a passover, as electric illumination was easy, consistent and flexible.

Since fuel crisis, conservation of energy has been accepted as a go-green policy. 'Day-lighting represents the single largest 'new' opportunity for energy savings in commercial lighting today and for the foreseeable future', said Professor of Architecture Dale Brentrup.

WINDOW LOCATION: A window with an interior wall at a right angle distributes the light well, reducing the glare, compared to a centric window that causes contrast and so glare. A window in a wall with interior colour of lighter shade seems less contrasting than a window in a dark coloured wall. Chamferred or splayed sides of the window opening over inner edges creates planes of intermediate brightness and thereby dispersion of illumination. Similar chamferring of the outer edges enlarges the sky component and thereby greater intake of illumination. A chamferred sill illuminates sections close to the wall. Windows located high in a wall or in the roof trusses and clerestories result in deeper penetration of light and better distribution. A rule-of-thumb is that the depth of daylight penetration is about two and one-half times the distance between the top of a window and the sill. Light-coloured floors allow daylight reflection to the ceiling section.

Light is a visible energy, and the lumen refer only to visible power. One watt of radiant power at 555 nm - the wavelength at which the typical human eye is most sensitive - is equivalent to a luminous flux of 680 lumen.

Brightness is a perceived or subjective attribute of light, because the sensitivity of the eye decreases as the magnitude of the light increases. It cannot be measured, but checked as between very dim and very bright (brilliant). If the luminance of a viewed light source is increased 10 times, viewers do not judge that the brightness has increased 10 times. The relationship is, in fact, logarithmic: the sensitivity of the eye decreases rapidly as the luminance of the source increases. It is this characteristic that allows the human eye to operate over such an extremely wide range of light levels.

Glass blocks or glass bricks have been used in walls and floors to illuminate deep interior spaces. Glass blocks in floors allow traffic loads so are used in multi storeyed underground parking.

MODELLING: For a designer 'modelling' of objects is as important as their functional aspects are. Opening systems like windows, skylights, clerestories provide the necessary natural luminance (brightness or intensity) to show the form, colour and texture of objects. Objects are perceived mainly due to the direction of light and its ever-changing nature. These are often enhanced, contrasted or subdued by reflectance and also by artificial illumination. Corbusier has used planes strategically placed against openings to model the interior spaces. The size and intensity of the luminance determine the shadow density and so affect the 'modelling'.

For visual effectiveness, some contrast in brightness levels is desirable in a space. Dull uniformity in lighting leads to tiredness and lack of attention. Windows on multiple orientations and height levels must be combined to produce the right mix of light for interiors.

Light from a single bright source overemphasizes the shadows and textures, and therefore creates a model that may be all right only from certain points of observation. Light from a large diffuse source softens the texture and dulls the neat delineation of the object (modelling), but permits mobile objects to be seen. Light from multiple directions and if in different intensities accentuates differences between different planes of the object. However, a very large diffuse source eliminates the texture. Light which comes from a large top source like a roof, seems shadow-less and so featureless, compared to light from a side, which enhances the horizontal dimension and creates a definition.

REFLECTANCE OF ROOM SURFACES: Reflectance of the room surfaces significantly impacts the quality of day-lighting. 'It is desirable to keep ceiling reflectance more than 80%, walls more than 50%, and floors around 20%'. Of the various room surfaces, floor reflectance has the least impact on Day-lighting penetration. The amount of light received by the walls, ceiling or floor determines the amount of illumination in a room, but the colour of the surface affects the reflectance into the interior space.

'Reflection of light either is specular (mirror-like) or diffuse (retaining the energy, but losing the image) depending on the nature of the interface. A mirror provides the most common model for specular light reflection, and typically consists of a glass sheet with a metallic coating where the reflection actually occurs. Reflection is enhanced in metals by suppression of wave propagation beyond their skin depths. Reflection also occurs at the surface of transparent media, such as water or glass. When light strikes a rough or granular surface, it bounces off in all directions due to the microscopic irregularities of the interface. Thus, an 'image' is not formed. This is called diffuse reflection. The exact form of the reflection depends on the structure of the surface'. For specular surfaces, such as glass or polished metal, reflectivity will be nearly zero at all angles except at the appropriate reflected angle. For diffuse surfaces, such as matte white paint, reflectivity is uniform; radiation is reflected in all angles equally or near-equally. Such surfaces are said to be Lambertian. Most real objects have some mixture of diffuse and specular reflective properties.

GLARE: A glare is a visual discomfort that occurs due to field of excessive brightness (usually of window or door opening but could be any source of light) that contrasts with rest of the area within the field of view. The human eye can function quite well over a wide range of luminous environments (within certain time frames or sections), but does not function well if extreme levels of brightness are present in the same field of view (within same time sections). The glare arises due to the contrast between the aperture and the adjacent field, and can be eliminated by many different methods. The bright light coming from a window or door aperture is from direct solar radiation or due to highly reflective sky or surface in the surroundings. The opening can be masked by translucent glazing or by placing shading devices (chhajjas, awnings, curtains, blinds, etc.). By increasing the interior brightness of the room the contrasting effect glare can be reduced. Interior brightness can be increased by a lighter colour scheme, auxiliary openings on the opposite or roof side and by additional artificial illumination. The glare can also be avoided if task is handled by placing the glare causing aperture on the back side.

MIXING NATURAL AND ARTIFICIAL ILLUMINATION: A good day-lighting design not only makes use of variety of opening types, their position and orientation but also optimally uses architectural features such as partitions, walls, ceilings, contours and levels, and utilises interior design elements like furniture layouts, furnishings, openings' treatment systems, etc. A good day-lighting arrangement must persist even through early hours of evening and in many commercial establishments through the night. The change over from day-lighting to night-time illumination may come about suddenly or the transition is developed imperceptibly. But a well-thought scheme for transition and integration with the electric lighting system is necessary. With advanced controls, it is now possible to adjust the level of electric light depending on the scale and quality of day-lighting available. Two, day-lighting and artificial illumination functions as one coherent illumination system through preprogrammed logic.

Daylight during the twilight zones, just around the sunrise and sunset periods are most difficult to cope up. The light changes are occurring very fast and colour diffraction of horizontal sunrays almost unpredictable. Artificial illumination or a back-up system to the day-lighting, for these few moments are very difficult. 24 hours open facilities like Airports, Bus stops, sea ports, night clubs, bridges, public spaces, parks and gardens and monuments, are some of the examples where day-lighting and artificial illumination must be mixed. Windows with large sky-components that are with a large open horizon, specifically on east and west sides are more affected by the twilight zone.

Three types of controls are commercially available: On-off switching controls are of two types: One that adjusts the opening of windows and shading devices, etc. to control the daylight input, Two, that turn of electric lights off randomly as well as selectively, when there is ample daylight. Stepped and Dimming controls continuously adjust the opening size or adjust the brightness level of electric lighting fixtures. Reflectance controls enhance or decrease the reflection available in an interior space, by varying the quality (texture and colour), angles and position of such surfaces.

GLAZING MATERIALS: The simplest method to maximize daylight within a space is to get largest sky component by placing windows as high up as possible, using clerestories and skylights. With the availability of glass, daylight was increased simply by increasing the glazing area. Glazed openings have a thin body entity, so larger glazed area also meant high rates of heat conduction across the surface. Poor thermal performance also results from the heat transmission through framing and shuttering members. The chief framing material wood was a poor conductor of heat, but in recent period mild steel and aluminium windows are widely used. These metal windows conduct heat, inward and outward depending on the internal and external ambient conditions.

There are two main classes of glazing materials: One that allows clear vision and the other that obscure it. For clear material the light reflected back for direct or sunlight at or near normal incidences could be 4 to 8 %, and for obscuring materials it could be as high as 60 %. In clear vision materials the brightness of the view depends upon the light absorption by the glass. However, these materials admit the light in a downward direction and thus a high percentage of it is absorbed by the floor furniture, etc. with little or no diffusion of the transmitted light. Obscuring materials, on the other hand, provide a wide range of diffusion patterns. Single sheet obscuring materials scatter the transmitted light within a relatively small cone having the direction of the incidence as an axis.

Glazing can easily and inexpensively be changed, to increase both thermal and optical performance. Glazing manufacturers employ a wide variety of tints, metallic and low-emission coatings, and surface treatments like etching, grinding, etc. for obscuring the glass. Multi paned lites of glass are also available with inert-gas fills, such as argon or krypton to reduce conductive and convective heat transfer. Gas fillings reduce U-values without affecting shading coefficients or visible transmittance.

To optimize a fenestration system three characteristics of glass need to be understood: U-value, Shading Coefficient, and Visible Transmittance.

U-VALUE: U value represents the rate of heat transfer or heat loss due to temperature difference across a glazing material. It is indicated in units of watts per square metre per degree. A material with low U Value will allow lesser heat to escape or enter into a space. A single glazed window with standard glass will have a typical centre pane U Value of 5.6, while a double glazed window with standard glass will have a U Value of 2.8 (i.e. 1 sq. mt single-glazed windows will transmit 5.6 and a double glazed window 2.8 watts of energy). Many countries however specify windows with U value of 2.0 or lower.

SHADING COEFFICIENT (SC): It is a ratio of solar heat gain of a window or skylight to transmit solar heat, relative to that for 3 mm clear single glass. The shading coefficient is expressed as a number without units between 0 and 1. The lower a window's solar heat gains coefficient or shading coefficient, the less solar heat it transmits, and the greater is its shading ability.

Shading coefficient is now being phased out in favour of the solar heat gain coefficient (SHGC), and is approximately equal to the SHGC multiplied by 1.15. The SHGC is similar to the SC, but also accounts for absorbed, convected, and inwardly radiated solar energy. The solar heat gain coefficient (SHGC) refers to the fraction of solar radiation admitted through an entire window, door, or skylight assembly either transmitted directly or absorbed and subsequently released as heat into the space behind. SC and the SHGC are both values which represent the solar heat gain through the glazing from the total solar energy spectrum, but do not necessarily have a direct correlation to visible light transmittance.

The lower the SHGC, the less solar heat the object transmits and the greater its shading ability. An object with a high SHGC is more effective at transmitting solar heat gains inside during the winter. An object with a low SHGC is more effective at reducing cooling loads during the summer by blocking heat gain from the sun. SHGC for a window, door, or skylight should be determined by factors such as the climate, surface orientation, and external obstructions.

VISIBLE TRANSMITTANCE (VT): It is a measure of how much visible light is transmitted through a given glazing material, as some daylight is reflected within the glazing while some visible light is allowed through. It is an optical property that indicates the amount of visible light transmitted through glazing. It is a fraction of the visible spectrum of sunlight (380 to 720 nanometre), weighted by the sensitivity of the human eye. VT is expressed as a number between 0 and 1, but most values are between 0.3 and 0.8. A product with a higher VT transmits more visible light. VT required for space through an opening system is determined whether one needs to reduce the interior glare in a space. Some tinted glasses reduce solar heat gain but also cut the amount of visible light transmitted, which is not efficient for day lighting. A spectrally selective tinted or coated glazing, however, can help reduce the solar gain while providing as much visible light as clear glass.

A spectrally selective glass has special properties that actually block or re-radiate the infrared energy from the sun, reducing solar gain through the windows, while maintaining higher levels of visible light transmittance. Such properties are achieved by a selective low-e coating on the interior surface of insulating glass units.

Day lighting the interior space is an important consideration for building design. It is directly related to the number of windows, curtain walls, skylights, and other fenestration products that are installed on the building envelope. Increased day lighting improves productivity, health, feeling of well being, but larger areas of openings also add to the heating or cooling loads of a building. A proper strategy of day-lighting helps reduce extreme contrasts of illumination and thereby eliminate the need for backup of artificial lighting. Day lighting can save anywhere from 30% to 60% in building energy usage when integrated with appropriate lighting controls such as photocell activated lighting or automated shading systems.

TASK HANDLING: For conducting tasks illumination is an important factor. The level of illumination also indirectly presents the available ventilation and other parameters of comforts and well being. Visual tasks involve use of eyes, so the field of vision, its depth, contrasts, glare, etc. need to be considered. Some fundamental factors involved in visual tasks are: size of the task, contrast at the task (brightness or colour contrasts), brightness of the task, duration of the task. A task is part of a continuum and it occurs as a sequence and so not only the current environment of the place but conditions before and after must be considered. A visual task often requires a relief such as change of view or brightness level. Opening systems provide the relief by their position, orientation, nature of construction and controls. Excessive brightness in the vicinity of critical visual tasks causes poor visibility and discomfort. Direct beam daylight such as from small skylights on critical visual tasks must be avoided.

4.2.8.2 THERMAL MANAGEMENT : INSULATION

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: openings on exterior face of a building / thin body structures / efficient management of the solar radiation / Thermal management by siting / exposed to unequal levels of solar radiation / movement of air / Thermal management by ventilation / Thermal management by window design / structure of the opening system is thin bodied / Thermal performance of a window / Thermal management by window design -glazing / Thermal management by window design -low-emissivity coatings / reflect 40 to 70 percent of infrared radiation / spectrally selective low-e coatings / advanced forms of low-e coatings / 99 percent of the ultraviolet radiation / Thermal management by window design / -reflective coatings / angle-selective coating / Thermal management by window design -directionally selective materials / Thermal management by window design -dynamic glazing / photo-chromatic properties / polarized glazing materials / Thermal management by window design -frame of the window / rubber gaskets, polyurethane fill-in and other thermal breaks / non touching entities / Thermal management by window design -joint Design / air tightness / manner of fixing at the site / very short life cycle / Thermal management by shading devices / interior shading devices.

Windows are openings on exterior face of a building and so play a very important role in thermal management of a building. Windows are thin body structures so have a poor thermal performance, but with appropriate design it can improve its function. Windows take up nearly 10 to 25 % of the exterior surface of homes, and much higher proportion for commercial buildings. Windows contribute 25 % of typical houses' heating load or 50 % of the cooling load in heating-dominated or cooling-dominated climates, respectively. Improved thermal behaviour of windows can reduce the heat loss in colder climates or minimize the solar heat gain in warmer climates.

Thermal performance of a window reflects all conditions leading to efficient management of the solar radiation. It includes many diverse conditions such as the siting of the window, its nature of exposure to the solar radiation, time management (scheduling), shapes, size, construction details of the window, and add-on systems that modulate the solar radiation.

Thermal management by siting: A building gets exposed to unequal levels of solar radiation on its various faces. By planning various activities appropriately one can advantageously use the solar radiation exposure. The side facing the pole (North or South) and beyond the tropic of Cancer -23N, and Capricorn 23S, may not receive direct solar radiation. East and West faces solar radiation in the morning and evening respectively. The temperature difference between the exposed side and shaded side causes the movement of air which can be used to alter the thermal behaviour of the building.

Thermal management by ventilation: Openings are means of ventilation and so must be opened frequently or remain open permanently. In warm climates the ventilation facilitates the heat transfer and it is handled by managing opening-closing of various sections of the window. Scheduling an opening system heat can be conserved or diffused in the building.

Thermal management by window design: The structure of the opening system is thin bodied and so heat transfer is far quicker then with any other component of the building. Thermal performance of a window is a function of three elements: glazing, frame and perimeter details.

Thermal management by window design: Glazing is transparent to translucent material that allows transmission of heat across it. Its thin wall has low thermal insulation capacity. But glazing systems with multiple layers, cavity and modern low-e coatings show improved thermal performance. Windows with lower U-factors or higher R-values perform better in colder climates and windows with lower solar heat gain coefficients (SHGC) perform better in warmer climates.

Thermal management by window design: Low-emissivity coatings have the ability to reflect a part of the radiant energy outward, which otherwise passes through the glass to the interior spaces. Low-e coatings have high VT and reflect 40 to 70 percent of infrared radiation. Low-e coatings offer a reduction of 5 to 37 percent in ultraviolet radiation. Low-e coatings are applied directly on the glass or as coated plastic film, during manufacturing or assembly of glazing within a window system. The installed performance of a low-e coating varies in relation to the climate and placement of the coating within the multiple layered glazing unit. Such coatings are inevitable part of the multi layered double / triple glass glazing units. Low-e coatings are applied to one glazing surface facing the air gap of the insulating gas (IG) unit. The location of this surface does not affect the thermal conductivity, but does affect the solar heat gain properties. Spectrally selective low-e coatings are made to be selective to specific wavelengths of light. Advanced forms of low-e coatings are also being developed to further select the transmission of visible light and reflection of solar infrared, and this can block up to 99 percent of the ultraviolet radiation.

Thermal management by window design: Reflective coatings are made of reflective particles deposited on a glazing material. Reflective materials can be deposited on glass of clear, tinted, or otherwise treated varieties. They generally reduce visible-light transmission but less effective for curtailing infrared radiation. Like mirrored glazing, they cause annoying reflection over neighbours' buildings, often causing a heat build up there. Frit is the most common angle-selective coating. It consists of a ceramic coating, either translucent or opaque, which is screen-printed in small patterns on a glass surface. The pattern used on the glass controls the light based on its angle of the incidence. The colour of Frit controls the reflection or absorption and the control of view or visual privacy. Visual transparency can also be controlled by applying Frit to both sides of the glass so that at some angles it appears transparent, and at other angles it appears opaque.

Thermal management by window design: Directionally Selective Materials: Directionally selective materials reject or redirect incident solar radiation based on a geometric relationship between radiation and the material. This glazing can redirect light to a predetermined location. They include glass blocks, silk-screened glazing, prismatic devices, enclosed louvers, holographic films, and embedded structures.

Thermal management by window design: Dynamic Glazing is called switchable optical windows or smart windows, because the photo-chromatic properties of the glazing can be altered with change in level of illumination or by an electric current. Dynamic glazing also includes polarized glazing materials, which with a change in its inclination curtail view and light (as in rear view mirrors of automobiles). Switchable materials can provide glare reduction, privacy, daylight and solar control, and reduction of ultraviolet transmission.

Thermal management by window design: The frames of the window, its materials, geometry and method of fabrication (e.g. thermal breaks in metal frames) determine thermal behaviour of the opening system. Low conductance materials, such as wood, vinyl, and fibre glass, perform better than high conductance materials such as aluminum. Perimeter details of commercial or low-cost windows are extremely poor and have high thermal leakage across joints and junctions. High end windows have rubber gaskets, polyurethane fill-in and other thermal breaks (layers of insulation materials that isolates the internal and external surfaces / components). These need to be continuously checked and replaced. Proper placement of insulation material in the voids at the window perimeter and maintaining continuity of the air barrier reduces drafts and energy loss around windows. It is not possible to separate the inside and outside faces of a window, as the frame and shutter each are single body construction. A complete thermal isolation can be best achieved by having two sets of windows placed as non touching entities.

Thermal management by window design: Joint Design. Windows are multi component systems with many joints which cause leakage of energy. Windows are now tested and rated for air tightness. A rating, of 0.2 cfm/ft (cubic feet per minute of air leakage per linear foot of window edge) or lower, is considered good. A good window has a rating of 0.1 cfm/ft or lower. Windows with low-emission and solar control coatings, low-conductance gas fills, improved thermal breaks and edge spacers, and better edge sealing techniques cannot be taken granted for the thermal performance. The manner of fixing at the site can alter the thermal behaviour of the window. A window well made and properly fixed at the site still needs to be periodically maintained, as the thermal breaks have a very short life cycle (requiring frequent replacement).

Thermal management by shading devices: This is designed to take optimum advantage of seasonal angles of a solar incidence. The solar gain occurs primarily in reference to the plane of the window, so an alternate method could be to have a variable plane of the window, but that may be architectural style wise not a very viable option. However external shading devices keep the glazing surface in shade while cutting off the direct solar radiation. Shading devices such as Venetian blinds or vertical louvers are not very effective on the internal face of the opening, as the solar gain has already been admitted into the interior space. But interior shading devices offer glare control, and visual comfort.

4.2.8.3 VENTILATION

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: ventilation is required to dilute / ventilation depends on / natural ventilation / rooms with interior doors / movement of air between indoor spaces / transfer-air / air-infiltration / unintentional gaps and cracks / natural driving forces of wind and temperature / vents and other openings / ventilation design / heavier needs of ventilation / for toilets, kitchens, production areas and public spaces / planned openings like windows / opposite sides and on same axis / draught-breeze over the body and the task / shutters opening outward / offset hinges or friction stays / hoppers, awning and jalousie windows / depth of window and its surround / splayed sides / minimum opening area / actual ventilation requirements are higher / unoccupied rooms / viscous or laminar flow / outward leakage of internal air / adequate ventilation / air changes per hour, ACH / requirements for air for well being / floor area basis / differences in temperature and pressure / air leaves should be larger / direction and strength of air movement / OUTDOOR AIR / filtration devices integrated within the opening system.

Ventilation of smoke from cooking or warming fires was one of the prime irritants of human abode. Smoke escaped mainly from the door gap but more effectively from loose roofing materials like thatch, tiles or slate or through roof level apertures and smoke pipes. Ventilation is required to dilute the odours, moisture, carbon dioxide, airborne pollutants such as dust, smoke, volatile organic compounds (VOCs), latent heat from air, objects, etc. and encourage evaporation of body moisture and thereby cause cooling. Ventilation depends on many factors, such as: on the nature of opening (cracks, crevices, holes), size of opening, number, distribution, location, orientation, external climatic conditions (snow, rain, windy), and internal occupation (activity) etc. Natural ventilation advantageously uses wind movement speeds, pressure-driven flows, and temperature differences (stack effect) to supply and remove air through enclosed space.

Windows provide ventilation, more effectively in rooms with interior doors (that is doors not opening outside) and especially during periods when a door is closed for security. Movement of air between indoor spaces, and not the outside, is called transfer-air, and has a limited role in ventilation. In a building substantial amount of ventilation occurs through air-infiltration from unintentional gaps and cracks in the building envelope. The rate of air-infiltration is also dependent on the magnitude of the natural driving forces of wind and temperature. Vents and other openings incorporated into a building as part of ventilation design, become more effective when the unintentional gaps are unavailable and outside conditions do not support air movement across it. Cracks and gaps being unintentional are usually insufficient for heavier needs of ventilation and cooling or heating, such as for toilets, kitchens, production areas and public spaces. Planned openings like windows on external face provide for such needs at the location, elevation, depth and in required quantity (such as a rate of air change -dilution, and the rate of air flow). The effectiveness of windows in achieving desired ventilation depends also on which windows are opened, how far they open, and the nature of shutter fixing.

Windows placed on opposite sides and on same axis are better ventilating devices. The position of window vis a vis the work plane or task is determined wether one wants a draught-breeze over the body and the task or avoid it. The nature of shutter opening also determines the direction of the internal air movement.

Windows with shutters opening outward often obstruct the wind path, but double hung sash windows and sliding shutters which open within the frame are better as receptors. Casement window shutters with offset hinges or friction stay which create a small gap on the jamb side help in catching the breeze. Hoppers, awning and jalousie windows direct the breeze due to the angle of opening. The depth of a window and its surround also affects the nature of ventilation. Splayed sides create funnel effect to catch the breeze.

Windows are also used for illumination, view out and egress. These requirements are often contradictory and nullifying each other. Typically in western India, at a location like Ahmedabad the prevalent breeze direction during April to August is S and SW, and during afternoons the same side also receives direct solar radiation, making it very tricky to design a fenestration system and an appropriate shading device.

Most building codes have suggest minimum opening area (including doors, etc.) at 4 to 5% of the floor area. But actual ventilation requirements are higher as during rainy days moisture content is very high, and when lot of people gather in a room, as during celebrations and social events. Nominally openings (including doors) of 20 % of the floor area are sufficient for the purpose of ventilation provided some sections are located within the human height (1.75 mts). Even in unoccupied rooms some ventilation is required to remove fumes and moisture generated by materials, plants and condensation. Minimum requirement for ventilation is 23 to 25 CMT per person per hour, and 12 to 16 CMT per Kg of fuel burnt. Large sized openings create turbulent air movements whereas cracks and crevices create a viscous or laminar flow. Ventilation is required for a fire emergency from areas like corridors, stairs, etc. Openings for ventilation are necessary for all climate conditions, but control requirements are very acute in warm and extremely cold climates, due to outward leakage of internal air.

For adequate ventilation the site of the building must take full advantage of prevailing breezes. This includes consideration of: seasonal and diurnal wind patterns, land contours and other topographical features, shape and form of the building, height of the openings, axial position of the openings, work or task plane, physical state and age of the occupants, etc. Other important conditions are position of the window, the form of the surrounds and projections and design of the window shutter.

Commonly ventilation is measured in terms of entire interior volume of air gets replaced per hour, it is called air changes per hour, ACH, but requirements for air for well being per person are also specified. Minimum 0.35 ACH but the supplied air must be no less than 15 cfm/person or 7.5 l/s/person. Since 2003, the standards for ventilation have been changed on floor area basis which is from 3 CFM/100 sq. ft. or 15 l/s/100 sq. m. to the 7.5 CFM/person or 3.5 L/s/person. To find the total amount of outside air required, one needs to add 3 cfm/100 sq. ft. or 15 l/s/100 sq. m. to the 7.5 cfm/person or 3.5 l/s/person. Thus, the air change rate requirement will vary by the size of the house and the occupancy.

In 1973, in response to oil crisis and conservation concerns, ASHRAE had reduced required ventilation from 10 CFM (4.76 L/S) per person to 5 CFM (2.37 L/S) per person. This was found to be a primary cause of 'sick building syndrome'. Current ASHRAE standards (Standard 62-89) states that appropriate ventilation guidelines are 20 CFM (9.2 L/s) per person in an office building, and 15 CFM (7.1 L/s) per person for schools. In commercial environments with tobacco smoke, the ventilation rate may range from 25 CFM to 125 CFM.

'In certain applications, such as submarines, pressurized aircraft, and spacecraft, ventilation air is also needed to provide oxygen, and to dilute carbon dioxide for survival. Batteries in submarines also discharge hydrogen gas, which must also be ventilated for health and safety. In any pressurized, regulated environment, ventilation is necessary to control any fires that may occur, as the flames may be deprived of oxygen'.

Air moves because of differences in temperature and pressure across the supply and exhaust points. In single storey houses, the movement of air due to pressure differences is more governing a factor then the differences in temperature across the supply and exhaust points. A high-pressure area is created when air strikes a building and low-pressure areas are created as the air moves over and around the building. Within a room, to encourage the movement of air, the openings, through which the air leaves should be larger, than those through which it enters. The direction and strength of air movement are altered due to draperies, furniture items, people, local heat sources (heating, cooking, machines) and air movement devices (fans).

OUTDOOR AIR: Outdoor air at any location is relatively less polluted because it has greater scope of dilution compared to any restricted interior air mass. However in densely developed urban localities and at locations near known pollution causing activities such as power plants, industry, open mines, etc. outdoor air can be a source of pollution. High level of humidity in certain coastal locations and during very heavy rainy seasons can be considered a contaminant of air. Where such air is used to replace the interior air, some control or processing by passive or active filtration devices, integrated within the opening system, are required.

4.2.8.4 PASSAGE AND CONTROL

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: PASSAGE / act of defenestration / Defenestration / defenestration of Prague / safety pioneer Hugh De Haven / mechanical analysis of survival in falls / survival in defenestration / development of the seat belt / CONTROLS / positional / kinetically active / linked system / sequence or concurrently / automatic controls / programmed logic or fuzzy logic system.

PASSAGE: Windows were conceived as defence apertures to throw objects like pitch, hot water and oil, garbage, offal, dung, arrows, spears, over intruders. Although defenestration can be fatal due to the height of the window through which a person is thrown, or lacerations from the broken glass, the act of defenestration need not be carried out with the intent or result of death. Defenestration results from desire to reject non useful things by moving them away from the vicinity or visual field.

Defenestration is the act of throwing someone or something out of a window. The term was coined around the time of an incident in Prague Castle in the year of 1618. The word comes from the Latin de (from; out of) and fenestra (window or opening). Historically, the word defenestration was used to refer to an act of political dissent. Notably, the defenestration of Prague in 1419 and 1618 helped to trigger prolonged conflict within Bohemia and beyond. It is said that some Catholics ascribed the survival of those defenestrated at Prague Castle in 1618 to divine intervention.

In 1942 safety pioneer Hugh De Haven published the classic Mechanical analysis of survival in falls from heights of 50 to 150 feet. De Haven's work on survival in defenestration was instrumental in the development of the seat belt.

CONTROLS: Windows become efficient opening systems because parts or subsections of it are individually controllable. The controls: hold a shutter open or closed, govern the speed with which a shutter opens or closes, allows functioning of various add-on devices, manipulation of shading devices, ensures privacy and security, and prevents intruders and escapees. Inclusions of anti ligature elements make a windows safe for prisons and children's rooms.

Most controls are positional that is become active or effective when placed in certain physical position. Controls are kinetically active that is becoming active-non active in a synchronous manner. Controls also occur as linked system that is become active in sequence or concurrently. Automatic controls have mechanical logic system but could have programmed logic or fuzzy logic system.

4.2.8.5 SAFETY AND SECURITY

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: breach or break-point / emergency exit by the occupants / entry point for rescue personnel / SAFETY / means of egress / emergency entry / exit / entry-exit through windows / facilities of egress openings to outside / accidentally fall out / maliciously thrown out -defenestered / grills or protection bars / SECURITY / breaking in through the window / someone or something falling out of it / tall plinth / high sill level / security and store rooms / security assurance / better management of the estates / larger size glass for openings / toughened and layered glass / electronic surveillance systems.

A building is an enclosure and every breach or breakpoint in that poses a hazard. Windows are hazardous by themselves but can also become elements to mitigate other risks. In a crisis situation the doors which abut a passage or stair are themselves at risk, whereas windows over exterior face are less encumbered and so better for evacuation and rescue. Windows are natural points of an emergency exit by the occupants of the building and entry point for rescue personnel.

SAFETY: The term 'means of egress' refers to the facility to exit a structure, in the event of an emergency, such as a fire, earthquakes, etc. Facilities of egress are of three categories: 'the path to an exit, the exit itself, and the exit discharges (the path to a safe area outside)'.

Emergency entry / exit requirements vary for different types of buildings and their functional sub units. Entry/exit through windows are required for many different purposes: fire fighting, calamity exits, out door painting, repair, maintenance, and demolition. Such facilities of egress openings to outside must be provided: at one unit within every 15 R. Mts of distance within any enclosed space, least one on every external face of the building, and one for every floor, apartment or rent-ownership unit.

The size of public escape must be 840 x 450, at a height less than 1.75 mts from inside floors. Window apertures must be without glazing or grill, or at least both must be easily removable, without tools. Non public openings to be used by trained maintenance persons could be smaller.

Windows are openings through which things could accidentally fall out or maliciously thrown out (defenestered). Window openings require grills or protection bars. The aperture size of such grill openings must be less than for a 100 dia sphere to pass through (standards same as applicable to railings and barricades). If the window opening is beyond the nominal reach of an infant, the aperture size could be larger then 100 width.

SECURITY: It is the state of being or feeling secure. Windows bring forth two sets of fears: someone breaking in through the window opening, or someone or something falling out of it. A tall plinth and a high sill level both reduce the chances of forceful entry from outside. A window placed on extreme outside face or with none or sloping ledges assures greater security. Otherwise, windows of all types on exterior faces are security risk. Security and store rooms (for arms, ornaments, bank vaults) are placed away from the external edges, or have few and very small openings. Glazing is a very fragile material and was avoided in domestic buildings for a very long time. But a glazed window is as safe as the outside conditions are politically assuring. The post-Industrial age large glazed windows were a functional necessity in industrial plants, hospitals, railway stations and commercial buildings. The security assurance for glazed building was provided by better management of the estates. Large housing and commercial estates have their own security arrangements resulting into use of larger size glass for openings. Post WW II production of toughened and layered glass heightened the security assurance. Police all over the world prefer a see-through shop for security assurance. A house with light seen through a window at night is considered safer. Electronic surveillance systems now provide even greater security assurance.

4.2.8.6 VISION IN-OUT

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: eyes / doors / familiar and negotiable terrain / windows / less known territory / windows on familiar territories / vision depends on several factors / cone of vision / width of the window / depth of the room / corner side window / centrally positioned window / rbbon like windows / panoramic openings / spot windows / picture openings / VISION-OUT / size up objects / positional depth / note the change or movement / stratification of the view / higher view / middle view / lower view / horizontal baffles / horizontal chhajja bottom / higher view from the upper section of a multi-storeyed building / higher view in a low rise building / mid level views on busy streets / low level view from upper floors / floor to ceiling window / zarokhas / bay windows / street side openings / Dutch door / French door / window's functionality / VISION-IN / small aperture openings / commercial spaces / shop fronts / ensures security.

Windows are eyes (origin old Norse, from words meaning 'wind' + 'eye') to look out. Doors were points of entrance and so placed towards a familiar and negotiable terrain like a known street, a courtyard, etc., but windows could be placed over a less known territory, such as side or back of the building as an opening. Such windows were small apertures, as the small size provided security yet a connection to the outside world. Windows on familiar territories, such as the front face, tend to be full height, almost like doors, with perhaps a safety barricade in the lower section.

Vision depends on several factors, such as: the sill level, lintel level, shading devices, internal and external openings' treatments, external surroundings, internal furnishings, window design or configuration, quality of glazing, level of maintenance, amount of glare, tasks, orientation, climatic conditions, lighting conditions, need for protection and privacy, etc.

The cone of vision is determined by the width of the window and depth of the room. A corner side window cuts off the view compared to a centrally positioned window. Ribbon like windows are called panoramic openings, whereas spot windows are called picture openings.

VISION-OUT: An interior space is a very safe area, person viewing out is assured that any action here may not be noticed or only partially revealed. The cover is enhanced by lattice, structure of the surrounds, interior treatments like curtains, blinds, etc. Windows frame a view. A mask that changes the perception of the view through it. Windows provide a scale reference that helps size objects and judge their positional depth. Windows as a stationary and known object allow one to note the change or movement occurring in the scene.

Vision through windows causes stratification of the view. Windows show views in three references: The higher view (above the horizontal eye level or head level), the middle view (within the nominal cone of vision) and the lower view (eye and the head both bend downward).

The stratification of view is obvious when working some distance away (typically equal to one height measure of the room) from the window. A person working close to the face of a window may get all three views from a mid level opening. The strata are more pronounced in windows with horizontal baffles as shading component. A horizontal chhajja bottom vividly reflects the light off the grounds below.

Higher view from the upper section of a multi-storeyed building shows up only sky, a very static view. But higher view in a low rise building shows upper section of surrounding buildings, mid portions of trees, and horizon, a slightly changing view but not strong enough to cause any distraction.

Mid level views on busy streets are distracting due to continuously moving objects outside and varying illumination and reflections in the interior space. Mid level views from any floor are ergonomically not exerting for most of the tasks.

Low level view from upper floors show up the grounds, gardens, lower terraces, water bodies, etc. All of these surfaces very strongly reflect the changes in solar illumination, shadows, moving objects, etc. The ceiling surfaces become extremely vivid due to the upward reflections, not an ideal proposition for bed rooms, rest rooms and hospital wards.

A fully stretched floor to ceiling window shows all the three views concurrently, and as a result there is no stratification of the view. The strata can be supported or diffused by including or eliminating horizontal elements in window design.

Open Zarokhas, bay windows and Latticed balconies, like at the Jaipur Hawa Mahal or Mashrabiya of middle east, are two opposite versions of street side openings. A Dutch door with its upper section and French door, are doors facilitating windows' functionality.

VISION-IN: Historically windows have not been used for viewing in the interior spaces. Though small aperture openings, alone or as part of the doors, were used for eavesdropping, spying or casual observation (darshan). These were small sized because the eye was placed very close to the aperture. Display cabinets and Aquarium have glazed fronts to display the items. Office and cabin doors have view windows. Commercial spaces require people to see the interiors' spaces and the goods and activities therein. Shop fronts are large format fixed glass windows. A shop front design depends on the angle of observation, difference between outside-inside illumination, angles of light source, its size and intensity. Shop fronts are designed for clear and glare free view, achieved by treatments over glass, external shading devices and through back up illumination. The quality of glass and its cleanliness become very important issue. A view-in window like the shop front ensures security as a person breaking-in is likely to be observed.

4.2.8.7 OTHER ISSUES

(Click here to go to sub index 4.2.8.0 Functions of Windows)

Keywords: ACOUSTIC PERFORMANCE / acoustic performance of windows / exterior noise / SERVICEABILITY / ECOLOGICAL CONCERNS / functional efficiency / effective usage / for reuse, and ultimate disposal / rationalises energy usage / passively, without the use of extra power / multi component systems / easily replaced and upgraded / correct a technological obsolescence or deficiency / second-use market / DISPOSAL AND RECYCLING / disposal of old windows / replacement of old windows / FIRE SAFETY / Escape and Rescue / Spread of fire / Fire Resistant Ratings / FRR / Integrity of the window / structural adequacy / integrity /fire protection-rated glazing / Ventilation of smoke and Fumes.

ACOUSTIC PERFORMANCE: The acoustic performance of windows is primarily a function of the largest surface, the glazing. An increase in the mid glazing cavity in multi glass system and use of a sound absorbent spacer between the glass panes, and the quality of glazing affects the sound transmission through the plane of the window. Sound insulation of windows can be improved by increasing the mass of the frames or better by hollow filled-in framing. Thermal breaks, gaskets and such other elastomeric lining restrict the sound transmission. Isolation or separation of window units from the masonry sides by resilient materials, reduces the vibrations related noise-ingress. Exterior noise must be stopped on the outside face of the building by structural shading devices and baffles rather then through provisions within or at the window. Interior noise can be suppressed by use of cavity glazing, space separated double glazing system, by use of curtains and blinds.

SERVICEABILITY: The service life of even the most durable window is likely to be shorter than that of the surrounding wall construction. Therefore, the design of the window and perimeter construction should permit removal of window and replacement of it without affecting the adjacent wall components.

The service life expectancy of components that are mated with the window into an assembly should match the service life expectancy of the window itself. Require durable flashing materials, noncorroding attachment hardware and fasteners, and moisture resistant materials in regions subject to wetting.

ECOLOGICAL CONCERNS: Windows need to address ecological concerns on several fronts: One, as an environmental component whose functional efficiency leads to comfort and economy, Two, as a widely used and frequently replaced building component, whose effective usage can save precious raw materials and energy, and Three, as a substantially sized object which requires special strategies for reuse, and ultimate disposal by way of productive recycling, or through natural degradation.

A window's functional efficiency, immediately rationalise the energy usage of a building. A good window once installed continues to provide many levels of comfort passively, without the use of extra power. Typically adequate illumination reduces the conservation of electricity. Its thermal performance rationalizes cooling-heating loads.

Windows are multi component systems within a larger system, the building. But windows are nearly self-sufficient system, so can be easily replaced and upgraded. It is very easy to correct the technological obsolescence or deficiency in windows. Upgrades make an economical sense but problems and cost of disposal of removed material makes it a very daunting task. Typically windows of wood or metal are easy to dispose but the old paint coatings on it are toxic and nearly inseparable. Similarly plastic extruded sections have toxic mastic compounds and foam fill-ins. Glass is considered recyclable but its unfixing out of the frame is very difficult due to high-end elastomeric compounds. Windows, even when have a predictable service cycle, its components are made over-lasting to ensure a fail-safe product. A large second-use market for domestic doors and windows exists in many developing countries, but commercial windows and large glass fronts have no secondary users.

There is a raging controversy about correct choice between replaceable materials like wood, and high-end technological materials like plastics and aluminium alloys. The former ones are not preferred because these are not easy to replace resources, the later ones consume substantial quantity of water, energy, etc. in the production processes.

DISPOSAL AND RECYCLING: Natural materials are disposable, as many of them degrade biologically and without many toxic residuals. Metals, where separable are recyclable, but secondary processed like plastics or manufactured materials like composites are very difficult to recycle. Treated materials, such as with paints, coatings, co-extrusions, galvanic coatings, metalizing, are not easy to recycle. Intervening elements like gaskets, mastic compounds, sealants, spacers, thermal breaks, cavity fill-in foam, are of very complex nature and often contain toxic compounds, and are difficult to process.

Disposal of old windows or its parts is an issue for every community. The need for disposal occurs due to replacement of old windows during building's renovations and complete removal (destruction) of less functional building. Disposal includes removal from the site, transporting the debris to a disposal yard, separation of components and materials' elements, all of which are very costly procedures. Resale value is more a location-based value, unavailable in densely populated localities.

FIRE SAFETY: Windows' fire safety is checked on several counts: Escape and Rescue, Spread of fire, Integrity of the window in fire conditions, Ventilation of smoke and fumes.

ESCAPE AND RESCUE: Doors are the preferred means of a rescue in fire and other incidences, but because nominally windows are placed on exterior faces psychologically and practically are the prime ways of escape and also a rescue. For sizes of egress through windows, ref to 4.2.8.5 Safety and Security.

SPREAD OF FIRE: A fire spreads out of a window unit when its frame, glazing or the surrounding structures are affected. Fire-resistant Ratings FRR refers to periods in minutes for fire resistence of the window. Minimum rating time is 30 minutes, which is how long the glass will hold the flames and hot gases. FRR is given to a tested complete window assembly, but it also depends on how and where the window unit is fitted. The other requirement is 'insulation' which also starts at 30 minutes. Insulation is the ability of the glass to additionally hold back the heat of the fire to keep the glass temperature below specified levels.

INTEGRITY OF THE WINDOW: Integrity of window results from adequate functioning of several of its components. Combustibility of its framing, integrity of the glazing in fire, insulation or resistence capacity at high temperature conditions, blasts resistance. Structural adequacy or integrity refers to the ability of the window frame to maintain stability and adequate load-bearing capacity even through the fire. Wood even though a combustible material, may not collapse or get dis-shaped with fire, and allows maximum time for escape. Steel on the other hand expands and gets dis-shaped very early in fire. Plastics have a tendency to soften and often shrink in size. Integrity is the glazing's ability to resist the passage of flames and hot gases. Fire-resistant glass is also often required in buildings for preventing spread of fire to neighbouring properties and for providing safety zones or passageways for escape. Fire protection-rated glazing such as wired glass is mandatory for all openings in industrial buildings.

VENTILATION OF SMOKE AND FUMES: Windows and other openings play a key role in ventilation of gases and heat during a fire. But their operational success depends on their location and ability to remain open or open out automatically on such occasions. Opening systems such as skylights, hatches, etc. when open create a draught and cause the fire to move to that direction, making other sections safe and accessible. Openings also ventilate unburnt but combustible gases before they become a flammable mixture, avoiding chances of explosion and sudden bursts of flames.

4.2.9.1 EMERGING TECHNOLOGIES

Keywords: view out / clutter of mid-members / unrestricted in scale / colour tinge or impurities / glare or shimmer / one way or private / panoramic view / view out function / certain depth within a building / inside is a restricted world / bear the structural loads / planner and lateral stiffness / outside view / do not provide an alternative view / glazing incorporating a pattern or scene generator / interior climate and outside atmospheric conditions / special functions / high noise insulation windows / theft and vandal proof windows / explosion proof windows / radiation proof units / gold dust sprayed windows / dampening gaskets / curtain wall / vacuum cavity sealed / barrier systems / a see through wall / membrane technology / permeable membrane materials / future windows / colour tonal and hue saturation qualities / light and colour / unusual window systems / outside edge / make-believe opening system.

One of the ever increasing purposes of windows has been view out:

A view, that is unhindered by clutter of mid-members like mullions, transoms, shutter-frames, etc.

A view unrestricted in scale, by the size of the glazing material. A view unaffected by the colour tinge or impurities of the glazing material.

A view without the glare or shimmer.

A view that is one way or private.

A window providing a panoramic view even through singly curved and doubly curved surfaces.

Modern windows offer all these. The view out function is achieved at a great cost, but it is available up to a certain depth within a building. Inner areas are cutoff from outside. A glazed entity cuts off the fresh air, odours, the varying external atmospheric conditions, sounds and noises of nature and surroundings. Glazed buildings have to depend on HVAC means for climate control. Future windows will bring in or recreate the natural climate like features. A glazed entity is a consistent reminder that inside is a restricted world but outside even though not benign offers surprises. The architecture in coming years will be addressing these issues, with new forms of windows and perhaps architecture itself.

A window in spite of being used as a curtain wall cannot bear the structural loads. It needs supports of concealed or revealed 'sticks' which must connect at floors. Glass has limited planner and lateral stiffness, and so requires frequent supports on a multi-storeyed facade. A 'stick'-less glazing, a joint-less uninterrupted surface and automatic or self-regulating mechanism offering seamless adjustments, are some of the design needs for windows to come by.

On lower floors of a multi-storeyed building, outside view through a curtain wall glazing, showing the opposite building or its terrace is not at all endearing. To curtail the unattractive view barricades like curtains or blinds is used, but this does not provide an alternative view. Perhaps the glazing incorporating a pattern or scene generator (such as LCD) is very much necessary.

The interior climate and outside atmospheric conditions are often complete-mismatch, perhaps some selective equalization is necessary. These can be done by transposing some of the external conditions like moisture, smell, breeze, etc. to the interior side. Such fine tuning of environment will be in reference to the window, its position in interior space.

Windows, nowadays are required to serve very special functions: High noise insulation windows are double glass panes with a sealed cavity, used for buildings in the vicinity of highways and air ports, in foundries and forging plants. Theft and vandal proof windows in commercial establishments and museums are made with toughened glass. Explosion proof windows, in war prone zones are layered with membrane sheets. Radiation proof units for nuclear plants have metal or chemical sprayed on the surface or ingrained in the glass. Space stations have gold dust sprayed windows to eliminate the effect of cosmic rays. Sound proof windows for recording studios are designed with dampening gaskets.

Today a window as an opening system is no longer a vertical flat unit. It is being shaped and placed in all orientations, including horizontal, facing skyward and downward. Window units as a curtain wall have replaced the wall by effectively taking over most of the functions. The major problem with a large size glass window is that, it is too thin (a poor insulator) and allows large amounts of inward or outward transmission of energies like heat, sound etc. This is now being overcome by compositions like a vacuum cavity sealed window units. Non frosting windows have embedded micro heating nets. Photo-chromatic glass controls the radiation. Artificial ventilation systems have obviated the need for a window to be 'open'.

Till now, barrier systems were opaque, however curtain wall systems have created a see-through wall. An opaque barrier system like the traditional wall enforced a very sharp and sudden (drastic) change between inside and outside. Windows with glass have helped in diluting this transition.

Glass has till now been a flat material, and occasionally moulded. Acrylics and other plastic (poly carbonate) sheets allow easy bending and moulding. Glass being morphic material is shattered on impact. Surface toughening and film sand-witching provide some resistance. Membrane technology will perhaps provide transparent materials that are non shattering, flexible and non tearing.

Windows have served the purpose of view, to create an environment from which to experience a continuously varying world, without the associated climatic discomforts. High density urban growth, however, does not offer a suitable panorama through a window. Perhaps a glass with embedded LCD will solve the problem. Glass and similar materials are morphic in nature and are virtually opaque to the air or moisture transmission. Perhaps in future permeable membrane materials that are light and transparent but will allow air and moisture transmission will replace glass.

Future windows will have ingrained systems to not only control the amount of light but also the colour tonal and hue saturation qualities. It will perhaps generate illumination of appropriate light and colour on its own, or modify the visual-scape / scene to suit the mood of the user. It will perhaps as a membrane take over the function of ventilation from centralized plants. All these futuristic systems will be self regulating or intentionally controlled by the user. A window may not remain a window, but instead become an interactive barrier system.

Unusual window systems are already in use in submarines, space crafts, mines, under ground power generation plants, observation booths located in large warehouses and industrial plants. These are areas where an outside edge is not available for window making. Make-believe opening systems emulating all functions of a window will be used.

4.2.9.2 WINDOWS MYTHS AND LEGENDS

Keywords: taste of reality / intentional physical transition / sensorial connection / protection of the window / act of defenestration / Finestrata / fire or emergency exit doors / egress windows / defenestration / defenestrate / J. R. R. Tolkien / C. Riley Auge / transition / sensorial connections / negotiable threshold / impassable barrier / Bari / access to light and ventilation / a natural right / Window Tax / windows or window-like openings of all buildings / trompe l'œil windows / mark of status and wealth / Laws Ancient lights / acquired an easement to the light / statutory length of time / windowed room / windowless cell / rooms with a window looking out / room at the corner of an office / M. K. Gandhi / Eastern Doors / Western Windows window of the soul / windows are eyes of the house / window for directions / door for alms / single window clearance / window of opportunity / window of vulnerability / launch window / credit window / window knockers / Louis Kahn / Tadao Ando.

A window is more restrictive then a door. Everything to the left, right, above and below the window is out of view. The view is straight just across it. Yet, a window allows the taste of reality from the safety of our abode. The safety of indoors, behind a window, is often worth more then being out of doors and free.

Windows and doors, both are penetrable surfaces, but a door allows intentional physical transition, whereas a window allows only sensorial connection. A perception through the window is invariably obtrusive. A window is a manipulated opening. 'Many a doctrine is like a window pane, we see truth through it but it divides us from truth' -Khalil Gibran. 'The eyes are the windows of the soul', but eyes see what the mind decides to perceive.

In fiction 'people who look through windows have a narrow view, and are standoffish. These people will watch the world go by from their window, but not do anything about it. People who are scared to look out the window are people that do not want to know what is going on in the world around them. Even though they are still protected by the glass, they are still worried that the world will be too shocking to behold. Sometimes, these people will open the window just to holler out. These are the ones that believe that they have a say in the world that they are not truly a part of'.

The protection of the window instigates us to do things which one may not dare across a door. We cast off unwanted things out of the window because nothing is likely to bounce back from here. For punishment or revenge people have been thrown out of the windows 'as an act of defenestration'. In some expediencies some enter or jump out of the window like a Romeo. Gaining an entry through a door is much more authoritative then breaking in like a thief through a window. Finestrata in Italian is slamming a window shut in anger.

Defenestration is the act of throwing someone or something out of a window. The term was coined around the time of an incident in Prague Castle in the year of 1618. The word comes from the Latin de (from; out of) and fenestra (window or opening). Although defenestration can be fatal due to the height of the window through which a person is thrown, or lacerations from broken glass, the act of defenestration was an act of rejection rather then with the intention death.

The painful experience of going across a window makes one extra ordinarily careful before venturing in or out of a window. Fire or emergency exit doors do not cause as much alarm and skepticism as much as egress windows do. An opening becomes a window due to hindrances it offers, so slight raising of the threshold turns a door into a French window. It is said heavens have doors only for entry, because no one would want to leave it ever, though there are windows to look down and realize the difference between here and there, or perhaps to defenestrate a mischief maker!

Italians try to avoid buttare il denaro (throwing money) out the window. 'Mangi la minestra o salti la finestra,' is the threat an Italian mamma gives to a child who doesn't want to eat the food she's prepared. (Eat the soup or jump out the window is the Italian equivalent of, Take it or leave it).

Going out of a window could be hazardous, but going out through a door is a conscious move but full of dilemmas. However, Italians in trouble find a way to uscire dalla porta e rientrare dalla finestra (leave by the door and sneak back in by the window) with apologies.

'A doorway has a narrow view of the world, but a person can walk through the doorway. The doorway is their opportunity to actually make a difference in the world. People who are more willing to make a difference in the world have an easier time walking through the doorway then others. Characters in stories that are too scared to walk through a door are also scared about what the world might do to them. They would rather keep that doorway as their shell from the rest of the world'.

'Windows, seems to have suggested a different physical and psychological interpretation to J. R. Tolkien. Unlike other openings, one doesn't usually use a window as a passageway, but rather as a means by which to see and assess the world before using the door to step into it. Because of their relatively smaller size, windows often present a limited view or frame of the world. Tolkien frequently uses this idea to frame a particular character's view of present circumstances. Virtually every mention of windows includes a reference to light or lack thereof. Because the view through a window is limited, characters may perceive the situation to be better or worse than it actually is, depending upon the perspective the window affords them. In other instances, Tolkien frames the situation for the readers by referring to the level of light seen in a window or by the protective measures applied to the window. Windows generally offer less protection from dangerous intrusion than doors, so their number, size, and treatment reveal the world view of the house's inhabitants. Hundreds of windows as at Brandy Hall imply a sense of peace, prosperity, and security, as opposed to the heavy-shuttered and curtained windows found in Bree where suspicion and caution rule.' -Crossing the Threshold, Openings and Passageways in J. R. R. Tolkien's The Hobbit and The Lord of the Rings. By C. Riley Auge.

If a door is an expression of transition, of the physical reality of passing through, a window is an extension of sensorial connections. A window represents the psychological idea of safety, and is the physical reality of protection. A door has a negotiable threshold but a window is an impassable barrier. In tropical climates an open door due to its larger size and floor reaching gaps provides better environmental involvement, but in extreme weather locales a smaller opening like window or hole is an omnipresent lifeline.

Ahmedabad pols were interconnected through a small Bari, a high threshold door like a gap. Baris are also used in fort gates. The word bari derives from bahari -meaning on the external face of the building or with an outside view. Zarokhas are often latticed covered with a small clear aperture called Bari.

The access to light and ventilation has been of great importance and considered a natural right. Any attempt to tax the natural right is rarely popular. A window Tax was conceived on the very stuff of life, i.e. light and air. English monarch, William III was short of money, and so devised the much-despised Window Tax. The tax was imposed on the windows or window-like openings of all buildings. The English were literally denied access to the daylight by the Window Tax. People went to great pains to avoid paying the tax. Many windows were bricked up or sometimes with painted-on trompe l'œil windows for that reason. That's daylight robbery. However, the upper classes paid the tax as a mark of status and wealth, and also continued to build new homes with more windows. The Hardwick Hall (built 1590's) of the Cavendish family, was famous for its light and airy interiors, and as the celebrated rhyme suggests it was more glass than wall.

Laws Ancient lights in English property law, is the right of a building or house owner to the light received from and through the windows. Windows used for light by an owner for 20 years or more could not be obstructed by erection of a barrier or by any other act by the adjacent landowner. This rule of law originated in England in 1663, based on the theory that a landowner acquired an easement to the light by virtue of the use of the windows for that purpose for the statutory length of time. The doctrine did not acquire wide acceptance by courts in the United States.

A windowed room such as orangery, conservatory, studio, barasati or Chhatri is a privilege, but a windowless cell like a dungeon is for confinement and a punishment. In legends highly a possessed damsel was confined to a room with a view of all sides, but in difficult to access or escape one column abode. Servants of European palaces were housed in cellar rooms or attic rooms, both with deficient window provision. Balconies serve the purpose of very wide opening. Spanish, French, other European and Latin American rulers come to a balcony to greet the public. The upper floor balcony has a French door or window opening overlooking a large ground, plaza or busy street.

Records on recovery after cholecystectomy of patients in a suburban Pennsylvania hospital between 1972 and 1981 were examined to determine whether assignment to a room with a window view of a natural setting might have restorative influences. Twenty-three surgical patients assigned to rooms with windows looking out on a natural scene had shorter postoperative hospital stays, received fewer negative evaluative comments in nurses' notes, and took fewer potent analgesics than 23 matched patients in similar rooms with windows facing a brick building wall.

The room at the corner of an office building is prerogative of the owner. Windows on two or more sides provide greater vista and metaphorically better control over the outside. Status in corporations and organizations is shown by the size of the office and the amount of window view the person has. Staff pools of lower ranked employees occupy central spaces with no windows.

'Aircraft windows: It is not the view through the window that seemed interesting to me but rather the connection between this view and the window itself. The connection between the boundless possibility of freedom, symbolized by the opening and the complete confinement represented by the aircraft. The aircraft flies, and we don't. Our body is actually tied to our seat; it is nothing. And yet this 'nothing' is the bearer of our thoughts. The view through the window sheds light on that contradiction'.

Windows carry associations with wide variety of experiences. Windows and doors have been used by writers to discuss, directly as well as metaphorically, personal issues of characters. A pessimist stays against a window, but an opportunist passes through the door. 'I want a house with all its windows and doors open where the cultural breezes of all lands and nations blow through my house. But I refuse to be blown off my feet by any'. by M. K. Gandhi. Doors and windows exemplify our selfish attitude. 'Increased global contacts have necessitated that Western managers acquire greater understanding of the Eastern Doors', i.e. come down here and enter the space, and 'Eastern managers look beyond the Western Windows', i.e. may not leave their abode but just look out. The door threshold allows some degree of indecision, but a window has no threshold, only a sill that lets one to stand against it, but is not for crossing over. If doors are the gates for body then windows are openings for the soul. Doors have realistic connection, but windows have more of the metaphoric relationship. If, the eyes are the windows of the soul, then windows are eyes of the house.

An Indian sadhu (Hindu, Jain, or Buddhist) is advised to go to a window for directions, and to a door for alms (bhiksha). A damsel looks intriguing, partly concealed through a window then fully revealed in the door.

Windows appear in our dealings, in real, ethereal and metaphoric forms. A single window clearance need not come through a window. If a window of opportunity is the chance of action or attack outward then the window of vulnerability is the weak spot inward. The space science looks for perfect time and space, a launch window to push a craft. A credit window is the possible financial opportunity. Doubt comes in at the window when inquiry is denied at the door. Opportunity knocks on the door to the future. But in 1900's, to awaken the workers for early morning shifts in industrial housing colonies across the UK, 'window knockers' were retained to tap the bedroom windows.

'Consider the momentous event in architecture when the wall parted and the column became -Louis Kahn'. And the epochal 20^th C, when the windows as glass curtain wall came with a vengeance to cover the columns.

'Such things as light and wind only have meaning when they are introduced inside a house in a form cut off from the outside world. The isolated fragments of light and air suggest the entire natural world. The forms I have created have altered and acquired meaning through elementary nature (light and air) that give indication of the passage of time and the changing of the seasons…' Tadao Ando 1982