A louver (

American English American English, sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United States. English is the Languages of the United States, most widely spoken lang ...

) or louvre (

Commonwealth English The use of the English language in current and former Member states of the Commonwealth of Nations, countries of Commonwealth of Nations, the Commonwealth was largely inherited from British Empire, British colonisation, with some exceptions. Eng ...

; see spelling differences) is a window blind or shutter with horizontal slats that are angled to admit light and air, but to keep out rain and direct sunshine. The angle of the slats may be adjustable, usually in blinds and windows, or fixed, such as in shutters.

History

Louvers originated in the

Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...

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

Modern louvers are often made of

aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, metal, wood, or glass. They may be opened and closed with a metal lever, pulleys, or through motorized operators. The Australian Standard specifies requirements for the construction of buildings using louver in bushfire-prone areas in order to improve their resistance to bushfire attack from burning embers, radiant heat, flame contact and combinations of the three attack forms. The revised building standard details various construction methods and materials that must be used depending on the homes level of bushfire risk. This includes changes to the window and glazing requirements for homes located in a Bushfire Attack Level category greater than BAL-Low.

Jalousies

Often used interchangeably by mistake, the key difference between louvers and jalousies is that louvers are fixed position. Jalousies are installed within a movable adjustable mechanism which positions all jalousies into any parallel position with respect to each other.

Use

In architecture

Louvers are rarely seen as primary design elements in the language of

modern architecture Modern architecture, also called modernist architecture, or the modern movement, is an architectural movement and style that was prominent in the 20th century, between the earlier Art Deco and later postmodern movements. Modern architectur ...

, but rather simply a technical device. Louvers are part of the design of Demerara windows to help keep 18th and 19th century buildings cool in hot climates and block direct sunlight. Some modern louver systems serve to improve indoor daylighting. Fixed

mirror A mirror, also known as a looking glass, is an object that Reflection (physics), reflects an image. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera ...

ed louver systems can limit glare and of redirect diffuse light. Such louvers may be integrated in between two panes of double glazing. In industrial facilities such as steel foundries and

power plant A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an electr ...

s, louvers are very common. They are utilized for natural ventilation and temperature control. Louvers are frequently found in bell towers, where they are utilised to let out as much sound as possible, while having the bells remain unexposed to the weather. There are examples of architects who use louvers as part of the overall aesthetic effect of their buildings. The most well-known example is Finnish modernist architect Alvar Aalto 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). A second example, taking influence from Aalto, is the second-generation modernist architect Juha Leiviskä.

In infrastructure

Louvers may be used as a type of flood opening, usually covered by one or more moving flaps. They are designed to allow

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

waters to enter and leave the building, equalizing hydrostatic pressure on the walls and mitigating structural damage due to flooding. Louver windows are a staple in the design of homes and perfect to withstand the pressures of future cyclonic conditions. Cyclone homes have always been synonymous with louver windows, louver blades have been tested for ‘debris type B’ for cyclonic regions.

In transportation

1970 AMC Javelin SST with 304 V8 black red C-stripe AMO 2015 meet 2of4

Rear window louvers are also available as an accessory for some automobiles. They have also been used over the years in hoods, trunk lids, and other various body panels; typically hot rods, but by no means exclusive to that period. Their purpose in this regard is both as a functional means of ventilation, but also as a styling modification. Louvers are used as semi-passive means of thermal control on airplanes and

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

as well. "The system devised for Rosetta employs several new techniques, including the installation of louvres over the radiators, to keep spacecraft hardware at proper operating temperatures" Louvers may also be used on

traffic light Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at intersection (road), road intersections, pedestrian crossings, and other locations in order t ...

lenses to prevent traffic from seeing the wrong traffic signal.

References

;Notes ;Bibliography *Henisch, Bridget Ann ''Fast and Feast: Food in Medieval Society''. The Pennsylvania State Press, University Park. 1976. * {{Use dmy dates, date=April 2017 Windows Window coverings Ventilation Architectural elements Shading (architecture)