A window is an opening in a wall, door, roof, or vehicle that allows the passage of light and may also allow the passage of sound and sometimes air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a framein the opening; the sash and frame are also referred to as a window. Many glazed windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows may have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.
In addition to this, many modern day windows may have a window screen or mesh (often made of aluminum or fibreglass) to keep bugs or insects out when the window is opened.
Types include the eyebrow window, fixed windows, hexagonal windows, single-hung, and double-hung sash windows, horizontal sliding sash windows, casement windows, awning windows, hopper windows, tilt, and slide windows (often door-sized), tilt and turn windows, transom windows, sidelight windows, jalousie or louvered windows, clerestory windows, lancet windows, skylights, roof windows, roof lanterns, bay windows, oriel windows, thermal, or Diocletian, windows, picture windows, Rose windows, emergency exit windows, stained glass windows, French windows, panel windows, double/triple-paned windows, and witch windows.
The Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt, in Alexandria ca. 100 AD. Paper windows were economical and widely used in ancient China, Korea, and Japan. In England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century. In the 19th century American west, greased paper windows came to be used by itinerant groups. Modern-style floor-to-ceiling windows became possible only after the industrial plate glass making processes were fully perfected.
The English language-word window originates from the Old Norse vindauga, from vindr ("wind") and auga ("eye"), i.e., "wind eye".In Norwegian Nynorsk and Icelandic, the Old Norse form has survived to this day (in Icelandic only as a less used word for a type of small open "window", not strictly a synonym for gluggi, the Icelandic word for window ), in Swedish the word vindöga remains as a term for a hole through the roof of a hut, and in the Danish language 'vindue' and Norwegian Bokmål 'vindu', the direct link to 'eye' is lost, just as for 'window'. The Danish (but not the Bokmål) word is pronounced fairly similarly to window.
Window is first recorded in the early 13th century, and originally referred to an unglazed hole in a roof. Window replaced the Old English eagþyrl, which literally means 'eye-hole,' and 'eagduru' 'eye-door'. Many Germanic languages, however, adopted the Latin word 'fenestra' to describe a window with glass, such as standard Swedish 'fönster', or German 'Fenster'. The use of window in English is probably because of the Scandinavian influence on the English language by means of loanwords during the Viking Age. In English, the word fenester was used as a parallel until the mid-18th century. Fenestration is still used to describe the arrangement of windows within a façade, as well as defenestration , meaning to throw something out of a window.
In the 13th century BC, the earliest windows were unglazed openings in a roof to admit light during the day. Later,[ when? ] windows were covered with animal hide, cloth, or wood. Shutters that could be opened and closed came next.[ when? ] Over time, windows were built that both protected the inhabitants from the elements and transmitted light, using multiple small pieces of translucent material, such as flattened pieces of translucent animal horn, thin slices of marble, for example, fengite, or pieces of glass, set in frameworks of wood, iron or lead. In the Far East, paper was used to fill windows. The Romans were the first known to use glass for windows, a technology likely first produced in Roman Egypt. Namely, in Alexandria ca. 100 AD cast glass windows, albeit with poor optical properties, began to appear, but these were small thick productions, little more than blown glass jars (cylindrical shapes) flattened out into sheets with circular striation patterns throughout. It would be over a millennium before a window glass became transparent enough to see through clearly, as we think of it now.
Over the centuries techniques were developed to shear through one side of a blown glass cylinder and produce thinner rectangular window panes from the same amount of glass material. This gave rise to tall narrow windows, usually separated by a vertical support called a mullion. Mullioned glass windows were the windows of choice among European well-to-do, whereas paper windows were economical and widely used in ancient China, Korea, and Japan. In England, glass became common in the windows of ordinary homes only in the early 17th century whereas windows made up of panes of flattened animal horn were used as early as the 14th century.
Modern-style floor-to-ceiling windows became possible only after the industrial plate glass making processes were perfected. Modern windows are usually filled with glass, although a few are transparent plastic.
A cross-window is a rectangular window usually divided into four lights by a mullion and transom that form a Latin cross.
The term eyebrow window is used in two ways: a curved top window in a wall or an eyebrow dormer; and a row of small windows usually under the front eaves such as the James-Lorah House in Pennsylvania.
A fixed window is a window that cannot be opened,whose function is limited to allowing light to enter (unlike an unfixed window, which can open and close). Clerestory windows in church architecture are often fixed. Transom windows may be fixed or operable. This type of window is used in situations where light or vision alone is needed as no ventilation is possible in such windows without the use of trickle vents or overglass vents.
A single-hung sash window is a window that has one sash that is movable (usually the bottom one) and the other fixed. This is the earlier form of sliding sash window and is also cheaper.
A sash window is the traditional style of window in the United Kingdom, and many other places that were formerly colonized by the UK, with two parts (sashes) that overlap slightly and slide up and down inside the frame. The two parts are not necessarily the same size; where the upper sash is smaller (shorter) it is termed a cottage window. Currently, most new double-hung sash windows use spring balances to support the sashes, but traditionally, counterweights held in boxes on either side of the window were used. These were and are attached to the sashes using pulleys of either braided cord or, later, purpose-made chain. Three types of spring balances are called a tape or clock spring balance; channel or block-and-tackle balance, and a spiral or tube balance.
Double-hung sash windows were traditionally often fitted with shutters. Sash windows can be fitted with simplex hinges that let the window be locked into hinges on one side, while the rope on the other side is detached—so the window can be opened for fire escape or cleaning.
A foldup has two equal sashes similar to a standard double-hung but folds upward allowing air to pass through nearly the full-frame opening. The window is balanced using either springs or counterbalances, similar to a double-hung. The sashes can be either offset to simulate a double-hung, or in-line. The inline versions can be made to fold inward or outward. The inward swinging foldup windows can have fixed screens, while the outward swinging ones require movable screens. The windows are typically used for screen rooms, kitchen pass-throughs, or egress.
A horizontal sliding sash window has two or more sashes that overlap slightly but slide horizontally within the frame. In the UK, these are sometimes called Yorkshire sash windows, presumably because of their traditional use in that county.
A casement window is a window with a hinged sash that swings in or out like a door comprising either a side-hung, top-hung (also called "awning window"; see below), or occasionally bottom-hung sash or a combination of these types, sometimes with fixed panels on one or more sides of the sash.In the US, these are usually opened using a crank, but in parts of Europe, they tend to use projection friction stays and espagnolette locking. Formerly, plain hinges were used with a casement stay. Handing applies to casement windows to determine direction of swing; a casement window may be left-handed, right-handed, or double. The casement window is the dominant type now found in modern buildings in the UK and many other parts of Europe.
An awning window is a casement window that is hung horizontally, hinged on top, so that it swings outward like an awning. In addition to being used independently, they can be stacked, several in one opening, or combined with fixed glass. They are particularly useful for ventilation.
A hopper window is a bottom-pivoting casement window that opens by tilting vertically, typically to the inside, resembling a hopper chute.
A pivot window is a window hung on one hinge on each of two opposite sides which allows the window to revolve when opened. The hinges may be mounted top and bottom (Vertically Pivoted) or at each jamb (Horizontally Pivoted). The window will usually open initially to a restricted position for ventilation and, once released, fully reverse and lock again for safe cleaning from inside. Modern pivot hinges incorporate a friction device to hold the window open against its weight and may have restriction and reversed locking built-in. In the UK, where this type of window is most common, they were extensively installed in high-rise social housing.
A tilt and slide window is a window (more usually a door-sized window) where the sash tilts inwards at the top similar to a hopper window and then slides horizontally behind the fixed pane.
A tilt and turn window can both tilt inwards at the top or open inwards from hinges at the side. This is the most common type of window in Germany, its country of origin. It is also widespread in many other European countries. In Europe, it is usual for these to be of the "turn first" type. i.e. when the handle is turned to 90 degrees the window opens in the side hung mode. With the handle turned to 180 degrees the window opens in bottom hung mode. Most usually in the UK the windows will be "tilt first" i.e. bottom hung at 90 degrees for ventilation and side hung at 180 degrees for cleaning the outer face of the glass from inside the building.
A window above a door; in an exterior door the transom window is often fixed, in an interior door, it can open either by hinges at top or bottom, or rotate on hinges. It provided ventilation before forced air heating and cooling. A fan-shaped transom is known as a fanlight, especially in the British Isles.
Windows beside a door or window are called side-, wing-, margen-lights, and flanking windows.
Also known as a louvered window, the jalousie window consists of parallel slats of glass or acrylic that open and close like a Venetian blind, usually using a crank or a lever. They are used extensively in tropical architecture. A jalousie door is a door with a jalousie window.
A clerestory window is a window set in a roof structure or high in a wall, used for daylighting.
A skylight is a window built into a roof structure.This type of window allows for natural daylight and moonlight.
A sloped window used for daylighting, built into a roof structure. It is one of the few windows that could be used as an exit. Larger roof windows meet building codes for emergency evacuation.
A roof lantern is a multi-paned glass structure, resembling a small building, built on a roof for day or moon light. Sometimes includes an additional clerestory. May also be called a cupola.
A bay window is a multi-panel window, with at least three panels set at different angles to create a protrusion from the wall line.
This form of bay window most often appears in Tudor-style houses and monasteries. It projects from the wall and does not extend to the ground. Originally a form of porch, they are often supported by brackets or corbels.
Thermal, or Diocletian, windows are large semicircular windows (or niches) which are usually divided into three lights (window compartments) by two mullions. The central compartment is often wider than the two side lights on either side of it.
A picture window is a large fixed window in a wall, typically without glazing bars, or glazed with only perfunctory glazing bars (muntins) near the edge of the window. Picture windows provide an unimpeded view, as if framing a picture.
A multi-lite window is a window glazed with small panes of glass separated by wooden or lead glazing bars, or muntins , arranged in a decorative glazing pattern often dictated by the building's architectural style. Due to the historic unavailability of large panes of glass, the multi-lit (or lattice window) was the most common window style until the beginning of the 20th century, and is still used in traditional architecture.
An emergency exit window is a window big enough and low enough so that occupants can escape through the opening in an emergency, such as a fire. In many countries, exact specifications for emergency windows in bedrooms are given in many building codes. Specifications for such windows may also allow for the entrance of emergency rescuers. Vehicles, such as buses and aircraft, frequently have emergency exit windows as well.
A stained glass window is a window composed of pieces of colored glass, transparent, translucent or opaque, frequently portraying persons or scenes. Typically the glass in these windows is separated by lead glazing bars. Stained glass windows were popular in Victorian houses and some Wrightian houses, and are especially common in churches.
A French doorhas two rows of upright rectangular glass panes (lights) extending its full length and two of these doors on an exterior wall and without a mullion separating them, that open outward with opposing hinges to a terrace or porch, are referred to as a French window. Sometimes these are set in pairs or multiples thereof along the exterior wall of a very large room, but often, one French window is placed centrally in a typically-sized room, perhaps among other fixed windows flanking the feature. French windows are known as porte-fenêtre in France and portafinestra in Italy, and frequently are used in modern houses.
Double-paned windows have two parallel panes (slabs of glass) with a separation of typically about 1 cm; this space is permanently sealed and filled at the time of manufacture with dry air or other dry nonreactive gas. Such windows provide a marked improvement in thermal insulation (and usually in acoustic insulation as well) and are resistant to fogging and frosting caused by temperature differential. They are widely used for residential and commercial construction in intemperate climates. In the UK, double-paned and triple-paned are referred to as double-glazing and triple-glazing. Triple-paned windows are now a common type of glazing in central to northern Europe. Quadruple glazing is now being introduced in Scandinavia.
A hexagonal window is a hexagon-shaped window, resembling a bee cell or crystal lattice of graphite. The window can be vertically or horizontally oriented, openable or dead. It can also be regular or elongately-shaped and can have a separator (mullion). Typically, the cellular window is used for an attic or as a decorative feature, but it can also be a major architectural element to provide the natural lighting inside buildings.
A guillotine window is a window that opens vertically. The guillotine windows are opening from bottom to top or from top to bottom with more than one sliding frames. The remote control can be used to open and close guillotine windows.
EN 12519 is the European standard that describes windows terms officially used in EU Member States. The main terms are:
The United States NFRC Window Label lists the following terms:
The European harmonised standard hEN 14351–1, which deals with doors and windows, defines 23 characteristics (divided into essential and non essential. Two other, preliminary European Norms that are under development deal with internal pedestrian doors (prEN 14351-2), smoke and fire resisting doors, and openable windows (prEN 16034).
Windows can be a significant source of heat transfer.Therefore, insulated glazing units consist of two or more panes to reduce the transfer of heat.
These are the pieces of framing that separate a larger window into smaller panes. In older windows, large panes of glass were quite expensive, so muntins let smaller panes fill a larger space. In modern windows, light-colored muntins still provide a useful function by reflecting some of the light going through the window, making the window itself a source of diffuse light (instead of just the surfaces and objects illuminated within the room). By increasing the indirect illumination of surfaces near the window, muntins tend to brighten the area immediately around a window and reduce the contrast of shadows within the room.
Frames and sashes can be made of the following materials:
|Material||Thermal resistance||Durability||Maintenance||Cost||Recycled content||Comment|
|Wood||very good||variable||low||average||high||a well-maintained wood window built before 1950 can last 50–100 years|
|uPVC ("vinyl")||very good||very good*||very low||average||very low||has a life span of 25–50 years in average|
|Aluminum||very good**||good||very low||low||typically > 95%||mostly thermally broken by a thermal insulation profile|
|Composites||very good||good||very low||high||high||used in modern buildings|
|Steel||medium||superior||very low||high||> 98%||typically welded at corner joints|
|Fiberglass||very good||very good*||very low||high||medium|
Composites (also known as Hybrid Windows) are start since early 1998 and combine materials like aluminium + pvc or wood to obtain aesthetics of one material with the functional benefits of another.
A special class of PVC window frames, uPVC window frames, became widespread since the late 20th century, particularly in Europe: there were 83.5 million installed by 1998with numbers still growing as of 2012.
Low-emissivity coated panes reduce heat transfer by radiation, which, depending on which surface is coated, helps prevent heat loss (in cold climates) or heat gains (in warm climates).
High thermal resistance can be obtained by evacuating or filling the insulated glazing units with gases such as argon or krypton, which reduces conductive heat transfer due to their low thermal conductivity. Performance of such units depends on good window seals and meticulous frame construction to prevent entry of air and loss of efficiency.
Modern double-pane and triple-pane windows often include one or more low-e coatings to reduce the window's U-factor (its insulation value, specifically its rate of heat loss). In general, soft-coat low-e coatings tend to result in a lower solar heat gain coefficient (SHGC) than hard-coat low-e coatings.
Modern windows are usually glazed with one large sheet of glass per sash, while windows in the past were glazed with multiple panes separated by glazing bars, or muntins, due to the unavailability of large sheets of glass. Today, glazing bars tend to be decorative, separating windows into small panes of glass even though larger panes of glass are available, generally in a pattern dictated by the architectural style at use. Glazing bars are typically wooden, but occasionally lead glazing bars soldered in place are used for more intricate glazing patterns.
Many windows have movable window coverings such as blinds or curtains to keep out light, provide additional insulation, or ensure privacy. Windows allow natural light to enter, but too much can have negative effects such as glare and heat gain. Additionally, while windows let the user see outside, there must be a way to maintain privacy on in the inside.Window coverings are practical accommodations for these issues.
Historically, windows are designed with surfaces parallel to vertical building walls. Such a design allows considerable solar light and heat penetration due to the most commonly occurring incidence of sun angles. In passive solar building design, an extended eave is typically used to control the amount of solar light and heat entering the window(s).
An alternative method is to calculate an optimum window mounting angle that accounts for summer sun load minimization, with consideration of actual latitude of the building. This process has been implemented, for example, in the Dakin Building in Brisbane, California—in which most of the fenestration is designed to reflect summer heat load and help prevent summer interior over-illumination and glare, by canting windows to nearly a 45 degree angle.
Photovoltaic windows not only provide a clear view and illuminate rooms, but also convert sunlight to electricity for the building.In most cases, translucent photovoltaic cells are used.
Passive solar windows allow light and solar energy into a building while minimizing air leakage and heat loss. Properly positioning these windows in relation to sun, wind, and landscape—while properly shading them to limit excess heat gain in summer and shoulder seasons, and providing thermal mass to absorb energy during the day and release it when temperatures cool at night—increases comfort and energy efficiency. Properly designed in climates with adequate solar gain, these can even be a building's primary heating system.
A window covering is a shade or screen that provides multiple functions. Some coverings, such as drapes and blinds provide occupants with privacy. Some window coverings control solar heat gain and glare. There are external shading devices and internal shading devices.Low-e window film is a low-cost alternative to window replacement to transform existing poorly-insulating windows into energy-efficient windows. For high-rise buildings, smart glass can provide an alternative.
A door is a hinged or otherwise movable barrier that allows ingress into and egress from an enclosure. The created opening in the wall is a doorway or portal. A door's essential and primary purpose is to provide security by controlling access to the doorway (portal). Conventionally, it is a panel that fits into the portal of a building, room, or vehicle. Doors are generally made of a material suited to the door's task. Doors are commonly attached by hinges, but can move by other means, such as slides or counterbalancing.
In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unlike active solar heating systems, it does not involve the use of mechanical and electrical devices.
A shōji is a door, window or room divider used in traditional Japanese architecture, consisting of translucent sheets on a lattice frame. Where light transmission is not needed, the similar but opaque fusuma is used. Shoji usually slide, but may occasionally be hung or hinged, especially in more rustic styles.
A curtain wall system is an outer covering of a building in which the outer walls are non-structural, utilized only to keep the weather out and the occupants in. Since the curtain wall is non-structural, it can be made of lightweight materials, thereby reducing construction costs. When glass is used as the curtain wall, an advantage is that natural light can penetrate deeper within the building. The curtain wall façade does not carry any structural load from the building other than its own dead load weight. The wall transfers lateral wind loads that are incident upon it to the main building structure through connections at floors or columns of the building. A curtain wall is designed to resist air and water infiltration, absorb sway induced by wind and seismic forces acting on the building, withstand wind loads, and support its own weight.
A mullion is a vertical element that forms a division between units of a window or screen, or is used decoratively. When dividing adjacent window units its primary purpose is a rigid support to the glazing of the window. Its secondary purpose is to provide structural support to an arch or lintel above the window opening. Horizontal elements separating the head of a door from a window above are both a head jamb and horizontal mullion and are called "transoms".
Window film is a thin laminate film that can be installed to the interior or exterior of glass surfaces in automobiles and boats and also to the interior or exterior of glass in homes and buildings. It is usually made from polyethylene terephthalate (PET), a thermoplastic polymer resin of the polyester family, due to its clarity, tensile strength, dimensional stability, and ability to accept a variety of surface-applied or embedded treatments.
Storm windows are windows that are mounted outside or inside of the main glass windows of a house. Storm windows exist in North America, but are uncommon in Europe, where double, triple or quadruple glazing is prevalent. Storm windows can be made of glass, rigid plastic panels, or flexible plastic sheets; and may be permanently or temporarily mounted. They function similarly to insulated glazing. The term may also refer to a small openable flap found in the side window on light aircraft.
A sash window or hung sash window is made of one or more movable panels, or "sashes". The individual sashes are traditionally paned windows, but can now contain an individual sheet of glass.
A thermal break or thermal barrier is an element of low thermal conductivity placed in an assembly to reduce or prevent the flow of thermal energy between conductive materials. The opposite of a thermal barrier is a thermal bridge.
A sliding glass door, patio door, or doorwall is a type of sliding door in architecture and construction, is a large glass window opening in a structure that provide door access from a room to the outdoors, fresh air, and copious natural light. A sliding glass door is usually considered a single unit consisting of two panel sections, one being fixed and one a being mobile to slide open. Another design, a wall-sized glass pocket door has one or more panels movable and sliding into wall pockets, completely disappearing for a 'wide open' indoor-outdoor room experience.
A muntin (US), muntin bar, glazing bar (UK) or sash bar is a strip of wood or metal separating and holding panes of glass in a window. Muntins can be found in doors, windows and furniture, typically in western styles of architecture. Muntins divide a single window sash or casement into a grid system of small panes of glass, called "lights" or "lites".
Building insulation is any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.
Solar gain is the increase in thermal energy of a space, object or structure as it absorbs incident solar radiation. The amount of solar gain a space experiences is a function of the total incident solar irradiance and of the ability of any intervening material to transmit or resist the radiation.
A casement is a window that is attached to its frame by one or more hinges at the side. They are used singly or in pairs within a common frame, in which case they are hinged on the outside. Casement windows are often held open using a casement stay. Windows hinged at the top are referred to as awning windows, and ones hinged at the bottom are called hoppers.
Window insulation reduces heat transfer from one side of a window to the other. The U-value is used to refer to the amount of heat that can pass through a window, called thermal transmittance, with a lower score being better. The U-factor of a window can often be found on the rating label of the window.
Rock Lawn is a historic house in Garrison, New York, United States. It was built in the mid-19th century from a design by architect Richard Upjohn. In 1982 it was listed on the National Register of Historic Places along with its carriage house, designed by Stanford White and built around 1880.
Glazing, which derives from the Middle English for 'glass', is a part of a wall or window, made of glass. Glazing also describes the work done by a professional "glazier". Glazing is also less commonly used to describe the insertion of ophthalmic lenses into an eyeglass frame.
Insulating glass (IG) consists of two or more glass window panes separated by a vacuum or gas-filled space to reduce heat transfer across a part of the building envelope. A window with insulating glass is commonly known as double glazing or a double-paned window, triple glazing or a triple-paned window, or quadruple glazing or a quadruple-paned window, depending upon how many panes of glass are used in its construction.
A skylight is a light-transmitting structure that forms all or part of the roof space of a building for daylighting purposes.
A Chicago window is a large fixed glass panel flanked by two narrower sashes of the same height, filling a structural bay. The large pane is a single panel of plate glass, and the flanking elements are vertical double-hung sash windows with no dividing muntins. The fenestration was first used by architect Charles B. Atwood in the 1895 Reliance Building, and immediately after by Louis Sullivan at the 1899 Carson Pirie Scott department store, both in Chicago, Illinois. The window design was made possible by advances in glass-making technology and steel structural framing, and became a defining feature of the Chicago school style. The design offered both abundant natural light and practical ventilation. Projecting oriel bays are a common variant of the Chicago window.
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