A window is an opening in an otherwise solid and opaque surface through which light and, sometimes, air can pass. It is usually glass or strong, transparent plastic. For example, a window can be in the wall of a house, or in a scientific measurement device that permits reading of certain wavelengths.

Etymology

The word Window originates from the Old Norse vindauga, from vindr "wind" and auga "eye." It 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." Most Germanic languages however adopted the Latin word fenestra to describe a window with glass. In English the word fenester was used as a parallel until the mid-1500s.

Opening in wall

A window is an opening in the wall of a building that allows light and air to enter a room and people to see out. At previous times in history they were merely small oval or square holes in the walls.

Very early windows were shielded with hide or cloth stretched over the opening or with wooden shutters. Later, various types of windows were invented that allowed light but not weather to pass into a building: mullioned glass windows, which joined multiple small pieces of glass with leading, paper windows, flattened pieces of translucent animal horn, and plates of thinly sliced marble. Mullioned glass windows were the windows of choice among European well-to-do, whereas paper windows were economical and widely used in ancient China 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 Northern Britain. Modern-style floor-to-ceiling windows became possible only after the industrial glass making process was perfected. Evidence of glass window panes in Italy dates back nearly 3000 years.

Modern windows are customarily large rectangles or squares with glass surfaces. Churches traditionally have stained glass windows.

Today a window can be made in practically any shape and size desired.

Window styles

Modern domestic windows come in many styles. The choice of design varies throughout the world, and is largely dictated by the prevailing weather conditions. Coastal climates tend to have smaller outward-opening windows due to the stronger winds experienced - e.g. England. Continental climates tend to have larger windows, many of which open inwards - e.g. France and Germany. Styles available include:

Double-hung sash window : The traditional style of window in the USA, 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. Nowadays, most new double-hung sash windows use spring balances to support the sashes, but traditionally, counterweights held in boxes 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. Double-hung sash windows were traditionally often fitted with shutters. Sash windows may be fitted with simplex hinges which allow the window to be locked into hinges on one side, while the rope on the other site is detached, allowing the window to be opened for escape or cleaning.

Single-hung sash window : one sash is movable and the other fixed. This is the earlier form of sliding sash window, and is obviously also cheaper.

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 window : A window with a hinged sash that swings in or out like a door comprising either a side-hung, top-hung, 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 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.

Tilt and slide : 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 window which can either tilt inwards at the top, or can open inwards hinged at the side.

Jalousie window : A window comprised of many slats of glass that open and close like a Venetian blind, usually using a crank. A Jalousie door is a door with a Jalousie window.

Clerestory window : A vertical window set in a roof structure or high in a wall, used for daylighting.

Skylight : A flat or sloped window built into a roof structure for daylighting

Bay window : A multipanel window, with at least three panels set at different angles to create a protrusion from the wall line.

Oriel window

Fixed window : A window that cannot be opened, whose function is limited to allowing light to enter. Clerestory windows are often fixed.

Picture window : A very large fixed window in a wall, intended to provide an unimpeded view as if framing a picture.

Divided-light window : A window made up of smaller panes that are held together by muntins. New windows are often a single pane with faux muntins glued on to give the appearance of an old dividing-light window. This is cheaper and more energy efficient.

Emergency exit window / egress window : A window big enough and low enough so that occupants can escape from the openable part in an emergency, such as a fire. In the United States, exact specifications for emergency windows in bedrooms are given in many building codes. Vehicles, such as buses and aircraft, sometimes have emergency exit windows as well.

Technical terms

Etymologically speaking, any window can be called a "light". However, within the window industry, particularly in insulated glass production, the term "lite" (so-spelled to keep the meaning differentiated from actual sunlight) is used to mean a single glass pane, several of which may be used to construct the final window product. For example, a sash unit, consisting of at least one sliding glass component, is typically composed of two lites, while a fixed window is composed of one lite. The terms "single-light", "double-light" etc refer to the number of these glass panes in a window.

In the USA, the term replacement window means a framed window designed to slip inside the original window frame from the inside after the old sashes are removed. In Europe, however, it usually means a complete window including a replacement outer frame.

The USA term new construction window means a window with a nailing fin designed to be 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).

In the UK and Europe, windows in new-build houses are usually fixed with long screws into expanding plastic plugs in the brickwork. A gap of up to 13mm is left around all four sides, and filled with expanding polyurethane foam. This makes the window fixing weatherproof but allows for expansion due to heat.

Window materials

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Modern windows, in developing countries in colder climates, typically have insulated glazing, called insulated glass when made from glass, which for insulated glazing is usually double paned but might be triple paned.

Modern windows are made from large sheets of glass while windows in the past were made from multiple panes held together by a grille within the sash. Such a grille is called "glazing bars", "astragals", "muntins", "muntin bars" or "mullions". Today, decorative muntin bars tend to be attached to the surface of the glazing or sandwiched between the panes of the insulated glazing. In the UK, the term glazing bars is currently the most popular term. Most companies in the USA use the term grille for a set of decorative muntin bars within a sash. In the UK, the term "grille" tends to be used when there are bars only within the glazing unit, and not stuck to the outsides of it.

Frames and sashes were traditionally made of wood, but metal, vinyl, and composites are also common. Solid metal frames and sashes are inefficient because metals conduct heat quickly. Some frames are made of vinyl-clad or aluminum-clad wood. Modern metal window parts typically consist of two halves separated by insulating spacer material.

A beam over the top of a window is known as the lintel or transom.

Many windows have movable window coverings such as blinds or curtains to keep out light, provide additional insulation, or ensure privacy.

See also

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• Window film
• Window cleaner
• Insulated glazing
• Window tax
• Defenestration
• Smart windows
• porthole

External links

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• Roman Glass from Metropolitan Museum of Art
• History of Stained Glass

Window stubs

Прозорец | Okno | Fenster | Ventana | Fenestro | Fenêtre | חלון | Ablak | Venster (muur) | 窓 | Vindu | دېرىزە | Okno (budownictwo) | Janela | Окно (дом) | Window | Okno | Прозор | Ikkuna | Fönster | 窗