Window

A **window** is an opening in a wall, door, roof or vehicle that allows the passage of light, sound, and air. Modern windows are usually glazed or covered in some other transparent or translucent material, a sash set in a frame in 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 often have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.

Types include the eyebrow window, fixed 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, skylights, roof windows, roof lanterns, bay windows, oriel windows, thermal, or Diocletian, windows, picture windows, emergency exit windows, stained glass windows, French windows, panel windows, and double - and triple paned 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.

## History

In the 13th century BC, the earliest windows were unglazed openings in a roof to admit light during the day. Later, windows were covered with animal hide, cloth, or wood. Shutters that could be opened and closed came next. 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.

## Types

### Cross

A cross-window is a rectangular window usually divided into four lights by a mullion and transom that form a Latin cross.

### Eyebrow

The term eyebrow window is used in two ways: a curved top window in a wall or in an eyebrow dormer; and a row of small windows usually under the front eaves such as the James-Lorah House in Pennsylvania.

### Fixed

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.

### Single-hung sash

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.

### Double-hung sash

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.

### Foldup

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 for egress.

### Horizontal sliding sash

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.

### Casement

*Main article: Casement window*

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 USA, 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.

#### Awning

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 be used independently, they can be stacked, several in one opening, or combined with fixed glass. They are particularly useful for ventilation.

#### Hopper

A hopper window is a bottom-pivoting casement window that opens by tilting vertically, typically to the inside.

### Pivot

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 own 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.

### Tilt and slide

A tilt and slide window is a window (more usually a door-sized window) where the sash tilts inwards at the top and then slides horizontally behind the fixed pane.

#### Tilt and turn

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.

### Transom

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.

### Side light

Windows beside a door or window are called *side*-, *wing*-, and *margen-lights* and *flanking windows*.

### Jalousie window

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.

### Clerestory

A clerestory window is a window set in a roof structure or high in a wall, used for daylighting.

### Skylight

A skylight is a window built into a roof structure. This type of window allows for natural daylight and moonlight.

### Roof

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.

### Roof lantern

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.

### Bay

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.

#### Oriel

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

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.

### Picture

A picture window is a large fixed window in a wall, typically without glazing bars, or glazed with only perfunctory glazing bars near the edge of the window. Picture windows provide an unimpeded view, as if framing a picture.

### Multi-lite

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.

### Stained glass

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.

### French

A French door  has 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

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. Triple-paned windows have been commercially manufactured and marketed with claims of additional benefit but have not become common. In the UK double-paned and triple-paned are referred to as double-glazing and triple-glazing.

### Hexagonal window

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.

## Terms

EN 12519 is the European standard that describes windows terms officially used in EU Member States.
The main terms are:

* **Light**, or **Lite**, is the area between the outer parts of a window (transom, sill and jambs), usually filled with a glass pane. Multiple panes are divided by mullions when load-bearing, muntins when not.
* **Lattice light** is a compound window pane madeup of small pieces of glass held together in a lattice.
* **Fixed window** is a unit of one non-moving lite. The terms *single-light*, *double-light*, etc., refer to the number of these glass panes in a window.
* **Sash unit** is a window consisting of at least one sliding glass component, typically composed of two lites (known as a *double-light*).
* **Replacement window** in the United States means a framed window designed to slip inside the original window frame from the inside after the old sashes are removed. In Europe it usually means a complete window including a replacement outer frame.
* **New construction window**, in the US, means a window with a nailing fin that is inserted into a rough opening from the outside before applying siding and inside trim. A nailing fin is a projection on the outer frame of the window in the same plane as the glazing, which overlaps the prepared opening, and can thus be 'nailed' into place.

* **Lintel** is a beam over the top of a window, also known as a transom.
* **Window sill** is the bottom piece in a window frame. Window sills slant outward to drain water away from the inside of the building.
* **Secondary glazing** is an additional frame applied to the inside of an existing frame, usually used on protected or listed buildings to achieve higher levels of thermal and sound insulation without compromising the look of the building
* **Decorative millwork** is the moulding, cornices and lintels often decorating the surrounding edges of the window.

## References

1. ↑ 1.0 1.1 1.2 1.3 Window. Britannica. Retrieved on May 19, 2012.
2. ↑ 2.0 2.1 2.2 Window. The Free Dictionary By Farlex. Retrieved on May 19, 2012.
3. ↑ Curl, James Stevens (2006). *Oxford Dictionary of Architecture and Landscape Architecture*, 2nd ed., OUP, Oxford and New York, p. 214. ISBN 978-0-19-860678-9.
4. ↑ Harris, Cyril M.. *American architecture: an illustrated encyclopedia*. New York: W.W. Norton, 1998. Print.
5. ↑ Will Tilt-and-Turn Windows Gain Market Share in North America? | Window & Door. Windowanddoor.com (March 29, 2010). Retrieved on February 11, 2012.
6. ↑ Curl, James Stevens. "Flanking window". *A dictionary of architecture and landscape architecture*. 2nd ed. Oxford England: Oxford University Press, 2006. 285. Print.
7. ↑ Picture window. The Free Dictionary By Farlex. Retrieved on May 19, 2012.
8. ↑ Stained glass. The Free Dictionary By Farlex. Retrieved on May 19, 2012.
9. ↑ *French Door*, The Merriam-Webster Dictionary, access date July 4, 2017
10. ↑ *French Window*, The Merriam-Webster Dictionary, access date July 4, 2017

## External links

* Roman Glass from Metropolitan Museum of Art