{{short description|Window protection with horizontal angled slats}} {{other uses|Louvre (disambiguation)}} {{redirect|Louvre (window)|windows composed of louvres|Jalousie window}} {{more citations needed|date=May 2013}} {{use dmy dates|date=October 2025}} [[File:Louver (PSF).png|thumb|250px|right|Concept drawing of a louver [[gable]] vent]] [[File:Inside a single louvered stevenson screen.jpg|thumb|250px|right|Louvers used in a [[Stevenson screen]]]] [[File:Villa Olmi K.jpg|thumb|Louver exterior shutters in Italy]] [[File:Drayton green sch.jpg|thumb|250px|right|Louvered [[cupola]] bell house]]
A '''louver''' ([[American English|American]]) or '''louvre''' ([[Commonwealth English]]; [[American and British English spelling differences#-re, -er|see spelling differences]]) is a framed opening fitted with horizontal [[wikt:slat|slats]] in a structure. These slats (also sometimes called louvers/louvres) are angled to [[daylighting (architecture)|admit light]] and [[ventilation (architecture)|air]], as well as to [[weatherization|keep out rain]] and direct [[sunlight|sunshine]]. The angle of the slats may be adjustable, usually in [[window blind|blinds]] and [[jalousie window|windows]], or fixed, such as in exterior [[window shutter|shutters]].<ref name=TFD-1>{{cite web |url=https://thefreedictionary.com/louver |title=louver |via=[[The Free Dictionary]] |access-date=2014-03-02}}</ref><ref>{{cite web |url=https://shuttercraft.co.uk/blog/window-dressings/what-should-i-choose-shutters-vs-blinds |title=Shutters vs. Blinds |publisher=Shuttercraft Ltd |access-date=2025-02-07}}</ref>
== History == Louvers originated in the [[Middle Ages]] 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.<ref>Henisch (1976), pp. 96–97.</ref>
== Construction == Modern louvers are often made of [[aluminum]], metal, wood, or glass. They may be opened and closed with a metal lever, pulleys, or through motorized operators.<ref name=EB-1>{{cite encyclopedia|title=Louver from "Encyclopædia Britannica"|url=https://www.britannica.com/EBchecked/topic/349399/louver|encyclopedia=Encyclopædia Britannica|access-date=2014-03-02|url-status=live|archive-url=https://archive.today/20140302084725/http://www.britannica.com/EBchecked/topic/349399/louver|archive-date=2014-03-02}}</ref>
The Australian Standard specifies requirements for the construction of buildings using louver in [[wildfire|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.<ref>{{Cite web|url=https://safetylinejalousie.com.au/specifying-louvres-in-bushfire-prone-areas/|title=Specifying Louvres in Bushfire Prone Areas|date=2018-09-18|website=SafetyLine Jalousie|language=en-AU|access-date=2018-09-18}}</ref><ref>[https://www.planning.vic.gov.au/guides-and-resources/guides/all-guides/building-in-bushfire-prone-areas "Building in designated bushfire prone areas"]. ''[[Department of Transport and Planning]]''. [https://shadeitblinds.ca/ Shade It]. 2023-11-21. Retrieved 2025-10-08.</ref> 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 [[Jalousie window|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.<ref>Architectural Terms & Definitions Textbook</ref>
== Use == ===In architecture=== [[File:Cathédrale St Étienne Sens 18.jpg|thumb|The belfry louvers of [[Sens Cathedral]], France]] Louvers are rarely seen as primary design elements in the language of [[modern architecture]], but rather simply a technical device. Louvers are part of the design of [[Demerara window]]s to help keep 18th and 19th century buildings cool in hot climates and block direct sunlight.<ref name="Westmas">{{Cite news|url=https://www.stabroeknews.com/2010/guyana-review/05/31/architecture/|title=Architecture - Building Under the Sun|last=Rory|first=Westmas |date=2010-05-31 |work=Stabroek News |access-date=2018-06-02}}</ref><ref name="Murtland">{{Cite news |url=https://www.kaieteurnewsonline.com/2017/04/23/the-demerara-window-the-colonial-ac/ |title=The Demerara Window – the Colonial 'AC' |date=2017-04-23 |work=Kaieteur News |first=Murtland |last=Haley|access-date=2018-06-02}}</ref> Some modern louver systems serve to improve indoor [[Daylighting (architecture)|daylighting]]. Fixed [[mirror]]ed louver systems can limit glare and of redirect diffuse light. Such louvers may be integrated in between two panes of [[double glazing]].<ref>Dariusz Heim and Kamil Kieszkowski: [http://www.unige.ch/cuepe/html/plea2006/Vol2/PLEA2006_PAPER786.pdf Shading Devices Designed to Achieve the Desired Quality of Internal Daylight Environment] {{webarchive|url=https://web.archive.org/web/20110607033118/http://www.unige.ch/cuepe/html/plea2006/Vol2/PLEA2006_PAPER786.pdf |date=2011-06-07}}, PLEA2006 - The 23rd Conference on Passive and Low Energy Architecture, Geneva, Switzerland, 6–8 September 2006</ref> In industrial facilities such as steel [[Foundry|foundries]] and [[Power station|power plant]]s, louvers are very common. They are utilized for natural ventilation and temperature control.
Louvers are frequently found in [[bell tower]]s, 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]]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.<ref>{{Cite web|url=https://safetylinejalousie.com.au/a-timely-reminder-why-louvre-windows-were-specified-in-queensland-cyclone-shelters/|title=A Timely Reminder Why Louvre Windows Were Specified in Queensland Cyclone Shelters|date=2017-03-29|website=SafetyLine Jalousie|language=en-AU|access-date=2017-03-29}}</ref> Cyclone homes have always been synonymous with louver windows, louver blades have been tested for 'debris type B' for cyclonic regions.
===In transportation=== [[File:1970 AMC Javelin SST with 304 V8 black red C-stripe AMO 2015 meet 2of4.jpg|thumb|Louvers mounted to the rear window of a 1970 [[AMC Javelin]]]] [[Window deflector#Rear window louvers|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 rod]]s, 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]] as well.<ref>{{cite web|title=Frequently asked questions / Rosetta / Space Science / Our Activities / ESA|url=http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions|url-status=live|archive-url=https://archive.today/20130304181220/http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions|archive-date=2013-03-04|access-date=2014-05-24}} "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"</ref>
Louvers may also be used on [[traffic light]] [[Traffic light#Programmable visibility signals|lenses]] to prevent traffic from seeing the wrong traffic signal.
==See also== {{wiktionary}} * [[Air conditioning]] * [[Jalousie window]] * [[Window shutter]]
==References== {{commons category}} ;Notes {{reflist|30em}}
;Bibliography *Henisch, Bridget Ann ''Fast and Feast: Food in Medieval Society''. The Pennsylvania State Press, University Park. 1976. {{ISBN|0-271-01230-7}} *{{cite web|title=Foundation Flood Vents|publisher=National Association of Home Builders (NAHB) Research Center|date=2001|url=http://toolbase.org/about.aspx|archive-url=https://archive.today/20251008084929/https://web.archive.org/web/20130116013400/http://toolbase.org/about.aspx|archive-date=8 October 2025}}
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[[Category:Windows]] [[Category:Window coverings]] [[Category:Ventilation]] [[Category:Architectural elements]] [[Category:Shading (architecture)]]