A louver or louvre (British English), from the French

French language

French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 l'ouvert; "the open one") is a window, blind

Window blind

A window blind is a type of window coverings. There are many different kinds of window blinds, using different systems and materials. A typical window blind is made with slats of fabric, wood, plastic or metal that adjust by rotating from an open position to a closed position by allowing slats to...

 or shutter

Window shutter

A window shutter is a solid and stable window covering usually consisting of a frame of vertical stiles and horizontal rails...

 with horizontal slats

Slats

A Slat is a long, thin, flat piece of lumber or plasticSlat or Slats may also refer to:*Leading edge slats fitted to aircraft*Mini blinds - for windows*SLAT, for Slow, Low, Aerial Target, a pejorative nickname for the A-10 Thunderbolt II...

 that are angled to admit light and air, but to keep out rain, direct sunshine, and noise. The angle of the slats may be adjustable, usually in blinds and windows, or fixed.

History

Louvers originated in the Middle Ages

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 as lantern-like constructions in wood that were fitted on top of roof holes in large kitchens to allow ventilation while keeping out rain and snow. They were originally rather crude constructions consisting merely of a barrel. Later they evolved into more elaborate designs made of pottery, taking the shape of faces where the smoke and steam from cooking would pour out through the eyes and mouth, or into constructions that were more like modern louvers, with slats that could be opened or closed by pulling on a string.

Construction

More modern louver windows comprise slats of glass, opened and closed with a metal lever, or they may be shutters of wood, plastic or other material.

Use

Some modern louver systems serve to improve indoor daylighting

Daylighting

Daylighting is the practice of placing windows or other openings and reflective surfaces so that during the day natural light provides effective internal lighting. Particular attention is given to daylighting while designing a building when the aim is to maximize visual comfort or to reduce energy...

. Fixed mirror

Mirror

A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...

ed louver systems can limit glare and of redirect diffuse light. Such louvers may be integrated in between two panes of double glazing.

Louvers are rarely seen as primary design elements in the language of modern architecture, but rather simply a technical device. However, there are examples of architects who use them as part of the overall aesthetic effect of their buildings. The most well-known example is Finnish modernist architect Alvar Aalto

Alvar Aalto

Hugo Alvar Henrik Aalto was a Finnish architect and designer. His work includes architecture, furniture, textiles and glassware...

 who would create aesthetic effects in the facades of his buildings through the combination of different types and sizes of louvers, some fixed some moveable, and made mostly from wood (e.g. the various buildings of the Helsinki University of Technology

Helsinki University of Technology

Aalto University School of Science and Technology , was the temporary name for Helsinki University of Technology during the process of forming the Aalto University...

). A second example, taking influence from Aalto, is the second-generation modernist architect Juha Leiviskä

Juha Leiviskä

Juha Ilmari Leiviskä is a prominent architect from Finland.- Life and career :The son of engineer Toivo Ilmari Leiviskä and teacher Sonja Jämsén-Astala, Leiviskä studied architecture at Helsinki University of Technology, qualifying as an architect in 1963...

.

Additionally, louvers are used as semi-passive means of thermal control on spacecraft

Spacecraft

A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

. They are also available as an accessory for some automobiles.