Window

Modern-style floor-to-ceiling windows became possible only after the industrial plate glass making processes were fully perfected.

In the 13th century BC, the earliest windows were unglazed openings in a roof to admit light during the day.

Specifically, in Alexandria c. 100 CE, 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.

In 1154, Al-Idrisi described glass windows as a feature of the palace belonging to the king of the Ghana Empire.

This gave rise to tall narrow windows, usually separated by a vertical support called a mullion.

among the European well-to-do, whereas paper windows were economical and widely used in ancient China, Korea, and Japan.

Peter Smith discusses overall trends in early-modern rural Welsh window architecture: Up to about 1680 windows tended to be horizontal in proportion, a shape suitable for lighting the low-ceilinged rooms that had resulted from the insertion of the upper floor into the hall-house.

After that date vertically proportioned windows came into fashion, partly at least as a response to the Renaissance taste for the high ceiling.

[11] The spread of plate-glass technology made possible the introduction of picture windows (in Levittown, Pennsylvania,[12] founded 1951–1952[clarification needed]).

Windows are primarily designed to facilitate a vital connection with the outdoors, offering those within the confines of the building visual access to the everchanging events occurring outside.

Of these criteria, windows that are designed to provide views of nature are considered to be the most important by people.

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

The two parts are not necessarily the same size; where the upper sash is smaller (shorter) it is termed a cottage window.

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.

[2] 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.

The casement window is the dominant type now found in modern buildings in the UK and many other parts of Europe.

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.

[24] A French door[25] 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.

French windows are known as porte-fenêtre in France and portafinestra in Italy, and frequently are used in modern houses.

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.

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

Performance of such units depends on good window seals and meticulous frame construction to prevent entry of air and loss of efficiency.

Windows allow natural light to enter, but too much can have negative effects such as glare and heat gain.

Such a design allows considerable solar light and heat penetration due to the most commonly occurring incidence of sun angles.

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.

Photovoltaic windows not only provide a clear view and illuminate rooms, but also convert sunlight to electricity for the building.

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.