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{{Short description|Architectural element for creating a draft}}
{{Duplicated citations|reason=[[User:Polygnotus/DuplicateReferences|DuplicateReferences]] detected:<br>
* https://web.archive.org/web/20071023174149/http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CRoaf.pdf (refs: 31, 32)
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[[File:Edificios en Yazd, Irán, 2016-09-21, DD 17.jpg|thumb |An ''[[ab anbar]]'' (water reservoir) with windcatchers (openings near the top of the towers) in the central desert city of [[Yazd]], Iran]]
[[File:Aghazade mansion.jpg|thumb |[[Aghazadeh Mansion]] in [[Abarkuh|Abarkooh]], [[Iran]], has an elaborate 18-m windtower with two levels of openings, plus some smaller windtowers.]]

A '''windcatcher''', '''wind tower''', or '''wind scoop''' ({{langx|fa|[[:fa:بادگیر|بادگیر]]}}) is a traditional [[architectural element]] used to create [[cross ventilation]] and [[passive cooling]] in buildings.<ref>{{Cite web |last=Malone |first=Alanna |title=The Windcatcher House |url=http://archrecord.construction.com/features/humanitariandesign/united-states/The-Windcatcher-House.asp |website=Architectural Record: Building for Social Change |publisher=McGraw-Hill |access-date=27 July 2023}}</ref> Windcatchers come in various designs, depending on whether local [[prevailing winds]] are unidirectional, bidirectional, or multidirectional, on how they change with altitude, on the daily [[temperature]] cycle, on [[humidity]], and on how much dust needs to be removed.<ref name=review/> Despite the name, windcatchers can also [[#Convection|function without wind]].

Neglected by modern architects in the latter half of the 20th century, the early 21st century saw them used again to increase [[Ventilation (architecture)|ventilation]] and cut power demand for [[air-conditioning]].<ref name=shady/> Generally, the cost of construction for a windcatcher-ventilated building is less than that of a similar building with conventional [[heating, ventilation, and air conditioning]] (HVAC) systems. The maintenance costs are also lower. Unlike powered air-conditioning and fans, windcatchers are silent<ref name=CFD/> and continue to function when the [[electrical grid]] power fails (a particular concern in places where grid power is unreliable or expensive).<ref name=PDEC/>{{refn|unreliability of American grids<ref name="climate_grids">{{cite news |last1=Plumer |first1=Brad |title=A Glimpse of America's Future: Climate Change Means Trouble for Power Grids |url=https://www.nytimes.com/2021/02/16/climate/texas-power-grid-failures.html |work=The New York Times |date=16 February 2021 |access-date=29 July 2023}}</ref><ref name="reuters">{{cite news |title=U.S. power and natgas prices spike in Texas and California heatwaves |url=https://www.reuters.com/business/energy/us-power-natgas-prices-spike-texas-california-heatwaves-2021-06-15/ |work=Reuters |date=16 June 2021 |access-date=29 July 2023 |language=en}}</ref><ref name="guardian">{{cite news |last1=Singh |first1=Maanvi |title='California and Texas are warnings': blackouts show US deeply unprepared for the climate crisis |url=https://www.theguardian.com/environment/2021/feb/19/power-outages-texas-california-climate-crisis |work=The Guardian |date=19 February 2021 |access-date=29 July 2023}}</ref><ref name="2grids">{{cite web |title=A Tale of Two Grids: Texas and California |url=https://www.nrdc.org/bio/ralph-cavanagh/tale-two-grids-texas-and-california |website=www.nrdc.org |language=en |date=2 March 2021}}</ref><ref name="grid">{{cite news |title=Power grid struggles in Texas similar to those in California |url=https://abc7.com/texas-ice-snow-freeze-power-outages/10349071/ |work=ABC7 Los Angeles |date=18 February 2021 |access-date=29 July 2023 |language=en}}</ref>}}

Windcatchers rely on local weather and [[microclimate]] conditions, and not all techniques will work everywhere; local factors must be taken into account in design.<ref name=PDEC/> Windcatchers of varying designs are widely used in North Africa, [[West Asia]], and India.<ref name="bbc">{{cite news |last1=Abdolhamidi |first1=Shervin |title=An ancient engineering feat that harnessed the wind |url=https://www.bbc.com/travel/article/20180926-an-ancient-engineering-feat-that-harnessed-the-wind |work=www.bbc.com |date=27 September 2018 |access-date=29 July 2023 |language=en}}</ref><ref name=review/> A simple, widespread idea, there is evidence that windcatchers have been in use for many millennia, and no clear evidence that they were not used into [[prehistory]].<ref name="shady">{{cite conference |last1=Attia |first1=Shady |title=Designing the Malqaf for summer cooling in low-rise housing, an experimental study |journal=PLEA2009 – 26th Conference on Passive and Low Energy Architecture |location=Quebec City, Canada |date=22-24 June 2009 |url=https://orbi.uliege.be/bitstream/2268/167581/1/Attia_Designing%20the%20Malqaf%20for%20summer%20cooling%20in%20low-rise%20housing,%20an%20experimental%20study.pdf}}</ref><ref name=review/><ref name="bbc"/> The "place of invention" of windcatchers is thus intensely disputed; Egypt, Iran, and the [[United Arab Emirates]] all claim it.<ref name="bbc"/><ref name="ifp">{{cite news |title=Arab States Obstructing Registration Of Iranian Windcatcher At UNESCO |url=https://ifpnews.com/arab-states-obstructing-registration-of-iranian-windcatcher-at-unesco/ |work=ifpnews.com |date=16 June 2019 |access-date=29 July 2023}}</ref>

Windcatchers vary dramatically in shape, including height, cross-sectional area, and internal sub-divisions and filters.<ref name=review/>

Windcatching has gained some ground in Western architecture, and there are several commercial products using the name ''windcatcher''. Some modern windcatchers use sensor-controlled moving parts or even solar-powered fans to make semi-[[passive ventilation]] and semi-[[passive cooling]] systems.<ref name=review/>

Windscoops have long been used on ships, for example in the form of a [[dorade box]]. Windcatchers have also been used experimentally to cool outdoor areas in cities, with mixed results;<ref name=review/> traditional methods include narrow, walled spaces, parks and winding streets, which act as cold-air reservoirs, and [[takhtabush]]-like arrangements (see sections on night flushing and convection, below).<ref name=Fathy/>{{rp|Ch. 6}}

== Location ==
{{multiple image
| image1            = Wind Tower Dubai.jpg
| caption1          = Wind tower, exterior, [[Dubai Museum]]
| image2            = Inside the windcatcher exhibit at the Dubai Museum.jpg
| caption2          = The same interior. This wind tower has four openings and brown cloth vertical walls on the interior diagonals, so it can catch the wind from a range of directions.
}}
[[File:Souq Waqif, Doha, Catar, 2013-08-05, DD 77.JPG|thumb|upright|An eight-sectioned [[masonry]] windtower in [[Souq Waqif]], [[Doha]], [[Qatar]]]]
[[File:Malkafs (1878) - TIMEA.jpg|thumb|{{transliteration|ar|Malqafs}} in Egypt in 1878. Short wood-and-matting [[right triangular prism]]s, with the vertical side left open and facing directly up or down wind (often one of each per building). This design works well in areas with strong low-level winds from a consistent direction.]]

The construction of a windcatcher depends on the [[prevailing wind]] direction at that specific location: if the wind tends to blow from only one side, it may have only one opening, and no internal partitions.<ref name=review/> In areas with more variable wind directions, there may also be radial internal walls, which divide the windtower into vertical sections. These sections are like parallel [[chimney]]s, but with openings to the side, pointing in multiple directions.<ref name=review/> More sections reduce the flow rate, but increase the efficiency at suboptimal wind angles. If the wind hits the opening square-on, it will go in, but if it hits it at a sufficiently oblique angle, it will tend to slip around the tower, instead.<ref name=review/>

Windcatchers in areas with stronger winds will have smaller total cross-sections,<ref name=azami/> and areas with very hot wind may have many smaller shafts in order to cool the incoming air.<ref name=Fathy/>{{rp|Ch. 5}} Windtowers with square horizontal cross-sections are more efficient than round ones, as the sharp angles make the flow less [[laminar flow|laminar]], encouraging [[flow separation]];<ref name=review/> suitable shaping increases suction.<ref name=Fathy/>{{rp|Ch. 5}}

Taller windcatchers catch higher winds. Higher winds blow [[Wind gradient|stronger]] and [[Lapse rate|cooler]]<ref name=egypt_trad/> (and [[Ekman spiral|in a different direction]]<ref name="houghton">{{Cite book |last=Houghton |first=John |title=The Physics of Atmospheres |publisher=Cambridge University Press |year=2002 |isbn=0-521-01122-1 |edition=3rd |location=Cambridge |pages=135–136}}</ref>). Higher air is also usually less dusty.<ref name=egypt_trad/>

If the wind is dusty or polluted, or there are insect-borne illnesses such as [[malaria]] and [[dengue fever]], then [[air filter]]ing may be necessary.<ref name=review/> Some dust can be dumped at the bottom of the windcatcher as the air slows (see diagram below), and more can be filtered out by suitable plantings or insect mesh.<ref name=egypt_trad/> Physical filters generally reduce throughflow, unless the flow is very gusty.<ref name=review/> It may also be possible to fully or partially close the windcatcher off.<ref name=azami/>

The short, wide right-triangle-prism {{transliteration|ar|malqaf}} are usually bidirectional, set in symmetrical pairs, and are often used with a {{transliteration|ar|[[salsabil (fountain)|salsabil]]}} (evaporative cooling unit)<ref name=review/> and a {{transliteration|ar|shuksheika}} ([[roof lantern]] vent).<ref name=egypt_trad/> Wide {{transliteration|ar|malqaf}}s are more often used in damper climates, where high-volume air flow is more important compared to evaporative cooling. In hotter climates, they are narrower, and air is cooled on its way in.<ref name=Fathy/>{{rp|Ch. 5}} They are more commonly used in Africa.<ref name=review/> {{transliteration|fa|Baudgir}}, on the other hand, are multisided (usually 4-sided), and they are typically tall towers (up to 34 meters tall) which can be closed in winter. They are more common in the [[Persian Gulf|Persian Gulf region]]<ref name=review/> and in areas with [[dust storm]]s.<ref name=azami/> Taller windcatchers also have a stronger [[stack effect]].<ref name=Fathy/>{{rp|Ch. 5}}

== Cooling methods ==

Night-flushing cools the house by increasing ventilation at night, when the outdoor air is cooler; windtowers can assist night flushing.<ref name=egypt_trad/>

A windcatcher can also cool air by drawing it over cool objects. In [[arid climate]]s, the daily temperature swings are often extreme, with desert temperatures often dipping below freezing at night. The [[thermal inertia]] of the soil evens out the daily and even annual temperature swings. Even the thermal inertia of thick masonry walls will keep a building warmer at night and cooler during the day. Windcatchers can thus cool by drawing air over night- or winter-cooled materials, which act as [[heat reservoir]]s.

Windcatchers that cool by drawing air over water use the water as a heat reservoir, but if the air is dry, they are also cooling the air with [[evaporative cooling]].<ref name=review/>  The heat in the air goes into evaporating some of the water, and will not be released until the water re-condenses. This is a very effective way of cooling dry air.<ref name=review/>

Simply moving the air also has a cooling effect. Humans cool themselves using evaporative cooling when they [[sweat]]. A draft disrupts the [[boundary layer]] of body-warmed and water-saturated air clinging to the skin, so a human will feel cooler in moving air than in stagnant air of the same temperature.<ref name=Fathy/>{{rp|Ch. 5}}

=== Airflow forces ===
[[File:malqaf.svg|thumb|A pair of short traditional windcatchers ({{transliteration|ar|malqaf}}); wind is forced down on the [[windward]] side and leaves on the [[leeward]] side. In the center, a {{transliteration|ar|shuksheika}} ([[roof lantern]] vent), used to shade the [[qa'a (room)|qa'a]] below while allowing hot air to rise out of it.<ref name=egypt_trad/>]]

The windcatcher can function in two ways: directing airflow using the pressure of wind blowing into the windcatcher, or directing airflow using [[buoyancy force]]s from [[temperature gradient]]s ([[stack effect]]).<ref name=review/><ref name=CFD/> The relative importance of these two forces has been debated. The importance of windpressure increases with increasing wind speed, and is generally more important than buoyancy under most conditions in which the windcatcher is working effectively.<ref name=review/>

Airflow speed is also important, especially for evaporative cooling (since it only works on dry air, and humidifies the air). It is possible for a windtower-ventilated building to have very high flow rates; 30 air changes per hour were measured in one experiment.<ref name=PDEC/> Uniform, stable flow with no stagnant corners is important. Turbulent flow should therefore be avoided; [[laminar flow]] is more effective at maintaining human comfort<ref name="CFD">{{Cite web |last1=Niktash |first1=Amirreza |last2=Huynh |first2=B. Phuoc |date=July 2–4, 2014 |title=Simulation and Analysis of Ventilation Flow Through a Room Caused by a Two-sided Windcatcher Using a LES Method |url=http://www.iaeng.org/publication/WCE2014/WCE2014_pp1294-1297.pdf |website=Proceedings of the World Congress on Engineering}}</ref> (for an extreme example, see [[Tesla valve]]).

Other elements are often used in combination with the windcatchers to cool and ventilate: [[courtyards]], [[dome]]s, walls, and fountains, for instance, as integral parts of an overall ventilation and heat-management strategy.

==== Wind pressure ====

If a windcatcher's open side faces the prevailing wind, it can "catch" it, and bring it down into the heart of the building. Suction from the lee side of a windtower is also an important driving force, usually somewhat more constant and less gusty than the pressure on the upwind side (see [[Venturi effect]] and [[Bernoulli's principle]]).<ref name=Fathy/>{{rp|Ch. 5}}

Routing the wind through the building cools the people in the building interior. The air flows through the house, and leaves from the other side, creating a through-draft; the rate of airflow itself can provide a cooling effect.{{citation needed|date=August 2020}} Windcatchers have been employed in this manner for thousands of years.<ref name="Fathy">{{Cite book |last=Hassan Fathy |title=Natural Energy and Vernacular Architecture |chapter=The wind factor in air movement |author-link=Hassan Fathy |chapter-url=http://archive.unu.edu/unupress/unupbooks/80a01e/80A01E00.htm |date=1986 |access-date=29 July 2023}}</ref>

The windtower essentially creates a pressure gradient to draw air through the building.<ref name="pressure">{{Cite journal |last1=Shea |first1=Andy |date=April 2010 |title=Measurements of the performance of a wind-driven ventilation terminal |volume=163 |pages=129–136 |journal=Proceedings of the Institution of Civil Engineers - Structures and Buildings |publisher=Thomas Telford Ltd |issue=SB2 |location=London, UK |doi=10.1680/stbu.2010.163.2.129 |s2cid=55886961 |url=https://doi.org/10.1680/stbu.2010.163.2.129|url-access=subscription }}</ref> Windtowers topped with horizontal airfoils have been built to enhance these pressure gradients.<ref name=review/> The shape of the traditional {{transliteration|ar|shuksheika}} roof also creates suction as wind blows over it.<ref name=Fathy/>{{rp|Ch. 5}}

==== Convection ====
{{main|Convection}}
[[File:UFAD Air Stratification Example Diagram.jpg|thumb|Vertical temperature gradient caused by [[stable stratification]] of air inside a room. Note hot air rising from the person.]]

Buoyancy is usually not the main effect driving windcatcher air circulation<ref name="review">{{Cite journal |last1=Saadatian |first1=Omidreza |url=https://www.researchgate.net/publication/233982408 |title=Review of windcatcher technologies |last2=Haw |first2=Lim Chin |last3=Sopian |first3=K. |last4=Sulaiman |first4=M.Y. |date=April 2012 |journal=Renewable and Sustainable Energy Reviews |volume=16 |pages=1477–1495 |doi=10.1016/j.rser.2011.11.037 |issue=3|bibcode=2012RSERv..16.1477S }}</ref> during the day.

In a windless environment, a windcatcher can still function using the [[stack effect]].<ref name=egypt_trad/> The hot air, which is less dense, tends to travel upwards and escape out the top of the house via the windtower.<ref name=review/>

Heating of the windtower itself can heat the air inside (making it a [[solar chimney]] and [[solar updraft tower]]), so that it rises and pulls air out of the top of the house, creating a draft. This effect can be enhanced with a heat source at the bottom of the windtower ([[Energy#Biology|such as humans, ~80 Watts each]]{{citation needed|date=August 2020}}), but this heats the house and makes it less comfortable.<ref name=review/> A more practical technique is to cool the air as it flows down and in, using heat reservoirs and/or evaporative cooling.<ref name=PDEC/>

A [[takhtabush]] is a space similar to the ancient Roman tablinum, opening both onto a heavily shaded courtyard and onto a rear garden court (the garden side being shaded with a {{transliteration|ar|[[mashrabiya]]}} lattice). It is designed to capture a cross-draft. The breeze is at least partly driven by convection (since one court will generally be warmer than the other), and may also be driven by wind pressure and evaporative cooling,<ref name=Fathy/>{{rp|Ch. 6}}<ref name=egypt_trad/><ref name="PDEC">{{Cite journal |last=Ford |first=Brian |url=https://www.cambridge.org/core/services/aop-cambridge-core/content/view/6317345C8FB8B405AADE7BA99CD62E8B/S1359135501001312a.pdf/passive_downdraught_evaporative_cooling_principles_and_practice.pdf |title=Passive downdraught evaporative cooling: principles and practice |date=September 2001 |journal=Architectural Research Quarterly |volume=5 |pages=271–280 |doi=10.1017/S1359135501001312 |doi-access=free |issue=3}}</ref> so the garden and courtyard are used as windcatchers.

Buoyancy forces are used to cause night flushing.

==== Night flushing (colder air) ====
{{main|Passive cooling#Night flushing}}

The [[diurnal temperature cycle]] means that the night air is colder than the daytime air; in arid climates, much colder. This creates appreciable buoyancy forces. Buildings may be designed to spontaneously increase ventilation at night.

Courtyards in hot climates fill with cold air at night. This cold air then flows from the courtyard into adjacent rooms.<ref name=egypt_trad/> The cold night air will flow in easily, as it is more dense than the rising warm air it is displacing.<ref name=Fathy/>{{rp|Ch. 6}}<ref name=egypt_trad/> But in the day, the courtyard walls and awning shade it, while the air outside is heated by the sun.<ref name=egypt_trad/> The cool masonry will also chill the nearby air.<ref name="whither">{{Cite web |date=2012-05-23 |title=Whither the Windcatcher? |url=https://www.conservationmagazine.org/2012/05/whither-the-windcatcher/ |website=Conservation}}</ref> The courtyard air will become [[stable stratification|stably stratified]], the hot air floating on top of the cold air with little mixing.<ref name=Fathy/>{{rp|Ch. 6}} The fact that the openings are at the top will trap the cool air below, though it cannot cause the temperature to drop below the nightly minimum temperature. This mechanism also works in windtowers.<ref name=azami/>

=== Subterranean cooling ===
[[File:Sahebgheraniye Hozkhane.jpg|thumb|A [[shabestan]], a cool [[earth shelter|earth-sheltered]] room in [[Iranian architecture]] which may be ventilated with windcatchers. The fountain pool adds evaporative cooling.]]
{{main|Passive cooling#Earth coupling}}

A windcatcher can also cool air by bringing it into contact with cool [[thermal mass]]es. These are often found underground.

Below approximately 6m of depth, soil and [[groundwater]] is always at about the annual [[mean average|mean-average]] temperature (MATT)<ref>{{Cite web |date=2015-08-23 |title=Groundwater temperature's measurement and significance |url=http://www.ngwa.org/Fundamentals/studying/Pages/Groundwater-temperature's-measurement-and-significance.aspx |url-status=dead |archive-url=https://web.archive.org/web/20150823030910/http://www.ngwa.org/Fundamentals/studying/Pages/Groundwater-temperature's-measurement-and-significance.aspx |archive-date=2015-08-23 |publisher=National Groundwater Association}}</ref><ref>{{Cite web |title=Mean Annual Air Temperature |url=http://www.icax.co.uk/Mean_Annual_Air_Temperature.html |website=www.icax.co.uk}}</ref><ref>{{Cite web |title=Ground Temperatures as a Function of Location, Season, and Depth |url=https://builditsolar.com/Projects/Cooling/EarthTemperatures.htm |website=builditsolar.com}}</ref>  (it is this depth which is used for many [[ground-source heat pumps]], often loosely referred to as "geothermal heat pumps" by laypeople<ref name="survival">{{Cite news |last=Rafferty |first=Kevin |date=April 1997 |title=An Information Survival Kit for the Prospective Residential Geothermal Heat Pump Owner |volume=18 |pages=1–11 |work=Geo-Heat Centre Quarterly Bulletin |publisher=Oregon Institute of Technology |issue=2 |location=Klmath Falls, Oregon |url=http://geoheat.oit.edu/bulletin/bull18-2/art1.pdf |access-date=2009-03-21 |archive-url=https://web.archive.org/web/20120217184539/http://geoheat.oit.edu/bulletin/bull18-2/art1.pdf |archive-date=17 February 2012 |issn=0276-1084}} The author issued an {{URL|http://geoheat.oit.edu/ghp/survival.pdf |updated version}} of this article in February 2001.</ref>). The [[thermal inertia]] of the soil evens out the daily and even annual temperature swings. In [[arid climate]]s, the daily temperature swings are often extreme, with desert temperatures often dipping below freezing at night. Even the thermal inertia of thick masonry walls will keep a building warmer at night and cooler during the day; in hot-arid climates, thick walls with high [[thermal mass]] ([[adobe]], stone, [[brick]]) are common (though thinner walls with high [[R-value (insulation)|resistance against heat transmission]] are more modernly sometimes used).<ref name=egypt_trad/> Windcatchers can thus cool by drawing air over night- or winter-cooled materials, which act as [[heat reservoir]]s.

Windcatchers are also often used to ventilate lower-level indoor spaces (e.g. [[shabestan]]s), which maintain frigid temperatures in the middle of the day even without windcatchers. [[Ice house (building)|Ice houses]] are traditionally used to store water frozen overnight in desert areas, or over winter in temperate areas. They may use windcatchers to circulate air into an underground or semi-underground chamber, evaporatively cooling the ice so that it melts only slowly and stays fairly dry (see [[:File:Edificios en Yazd, Ir%C3%A1n, 2016-09-21, DD 17.jpg|lede image]]). At night, the windcatchers may even bring sub-freezing night air underground, helping to freeze ice.

=== Evaporative cooling ===
[[File:Qanat wind tower.svg|thumb|A windcatcher and [[qanat]] used for cooling]]

In dry climates, the [[evaporative cooling]] effect may be used by placing water at the air intake, such that the draft draws air over water and then into the house. For this reason, it is sometimes said that the fountain, in the architecture of hot, arid climates, is like the fireplace in the architecture of cold climates.<ref name=egypt_trad/>

Windcatchers are used for evaporative cooling in combination with a [[qanat]], or underground canal (which also makes use of the subterranean heat reservoir described above). In this method, the open side of the tower faces away from the direction of the prevailing wind (the tower's orientation may be adjusted by directional ports at the top). When only the [[Windward and leeward|leeward]] side is left open, air is drawn upwards using the [[Coandă effect]]. This pulls air into an intake on the other side of the building. The hot air brought down into the qanat tunnel is cooled by coming into contact with the water flow and the surrounding [[subsoil|earth]]. The soil below ground level stays cool by virtue of being several meters below the surface. The insulation and heat capacity of the overlying earth maintains the same stable temperature day and night, and as nights in arid climates are quite cold, often below freezing, that stable temperature is quite cool. The air is also [[evaporative cooling|evaporatively cooled]] when some of the water in the qanat evaporates as the hot, dry surface air passes over it; the heat energy in the air is absorbed as [[energy of vaporization]]. The dry air is thus also humidified before entering the building. The cooled air is drawn up through the house and finally out the windcatcher, again by the Coandă effect. On the whole, the cool air flows through the building, decreasing the structure's overall temperature.{{Citation needed|date=July 2024}}

A {{transliteration|ar|[[salsabil (fountain)|salasabil]]}} is a type of fountain with a thin sheet of flowing water, shaped to maximize surface area and thus evaporative cooling.<ref name=egypt_trad/><ref name=Fathy/>{{rp|Ch. 7}} Windcatchers are often used with salasabils may be used to maximize the flow of unsaturated air over the water surface and carry the cooled air to where it is needed in the building.<ref name="CFD" />

Wetted matting can also be hung inside the windcatcher to cool incoming air.<ref name=egypt_trad/> This can reduce flow, especially in weak winds. However, it can also produce a downdraft of cool air in windless conditions.<ref name=review/> The evaporative cooling within a windtower causes the air in the tower to sink, driving circulation. This is called [[evaporative cooler#Direct evaporative cooling|passive downdraught evaporative cooling]] (PDEC). It may also be generated using spray nozzles (which have a tendency to get blocked if the water is hard) or cold-water cooling coils (like [[underfloor heating|hydronic underfloor heating]] in reverse).<ref name=PDEC/>

== Windcatchers and climate change ==
Windcatchers can be used for [[Climate change mitigation|mitigation of climate change]] as they can "reduce the [[Building energy efficiency|building's energy consumption]] and [[carbon footprint]]"<ref>{{cite journal |last1=Richard Hughes |first1=Ben |last2=Kaiser Calautit |first2=John |last3=Abdul Ghani |first3=Saud |title=The development of commercial wind towers for natural ventilation: A review |journal=Applied Energy |date=April 2012 |volume=92 |page=606 |doi=10.1016/j.apenergy.2011.11.066 |bibcode=2012ApEn...92..606H |url=https://www.sciencedirect.com/science/article/abs/pii/S0306261911007720 |access-date=28 August 2023|url-access=subscription }}</ref> and for [[Climate change adaptation|adaptation to climate change]] because they facilitate cooling in a warmer climate.<ref>{{cite journal |last1=Carreto-Hernandez |first1=L.G. |last2=Moya |first2=S.L. |last3=Varela-Boydo |first3=C.A. |last4=Francisco-Hernandez |first4=A. |title=Studies of ventilation and thermal comfort in different wind tower-room configurations considering humidification for a warm climate of Mexico |journal=Journal of Building Engineering |date=1 April 2022 |volume=46 |doi=10.1016/j.jobe.2021.103675 |s2cid=244435768 |url=https://www.sciencedirect.com/science/article/abs/pii/S2352710221015333 |access-date=28 August 2023|url-access=subscription }}</ref> Windcatchers can reduce temperature inside the house by {{convert|8|to|12|C-change}} in comparison to the outdoor temperature.<ref>{{cite news |last1=Hambling |first1=David |title=Ancient windcatchers in Iran give architects cooling inspiration |url=https://www.theguardian.com/environment/2023/jul/13/weatherwatch-ancient-windcatchers-iran-give-architects-cooling-inspiration#:~:text=This%20displaces%20warm%20air%20that,building%20by%208C%20to%2012C. |access-date=28 August 2023 |agency=The Guardian |date=13 July 2023}}</ref>

A window windcatcher can reduce the total energy use of a building by 23.3%.<ref>{{cite journal |last1=Nouh Ma’bdeh |first1=Shouib |last2=Fawwaz Alrebei |first2=Odi |last3=M. Obeidat |first3=Laith |last4=Al-Radaideh |first4=Tamer |last5=Kaouri |first5=Katerina |last6=I. Amhamed |first6=Abdulkarem |title=Quantifying Energy Reduction and Thermal Comfort for a Residential Building Ventilated with a Window-Windcatcher: A Case Study |journal=Buildings |date=29 December 2022 |volume=13 |page=86 |doi=10.3390/buildings13010086|doi-access=free |hdl=10919/113078 |hdl-access=free }}</ref>

== Regional use ==
{{globalize||date=August 2020}}

=== Africa ===

==== Egypt ====

In Egypt windcatchers are known as {{transliteration|ar|malqaf}}, pl. {{transliteration|ar|malaaqef}}.<ref name="el-Maqadef">{{Cite web |last1=Ahmed Abdel Wahab Ahmed Rizk |last2=Mohamed Abdel Mawgoud Abdel Ghaffar |last3=Mohamed Hefnawy |date=2007-04-11 |title=The effect of wind-catchers (el-Malaqef) on the internal natural ventilation in hot climates with special reference to Egypt: A study on small physical models |url=http://www.aun.edu.eg/env_enc/march2007/1-12(end).doc |access-date=2016-09-21 |website=www.aun.edu.eg |publisher=[[Assiut University]] |location=[[Asyut]] |page=1 |language=en, ar |format=[[Doc (computing)|Microsoft Word document (.doc)]] |quote=EL-MALAQEF |archive-date=September 23, 2015 |archive-url=https://web.archive.org/web/20150923180222/http://www.aun.edu.eg/env_enc/march2007/1-12(end).doc |url-status=dead }}</ref><ref>{{Cite web |title=Industrial architecture in Egypt in the 19th and 20th centuries, Arsenal in the Citadel of Cairo: workshop hall with timber roof construction and wind catcher (malqaf) |url=http://www.dainst.org/en/project/industriearchitektur?ft=all |url-status=dead |archive-url=https://web.archive.org/web/20130513172320/http://www.dainst.org/en/project/industriearchitektur?ft=all |archive-date=2013-05-13 |access-date=2013-04-22 |publisher=Dainst.org}}</ref><ref name="shady2">{{Cite web |last=Shady Attia |date=June 22–24, 2009 |title=Designing the Malqaf for summer cooling in low-rise housing, an experimental study |url=http://www.plea2009.arc.ulaval.ca/Papers/2.STRATEGIES/2.2%20Heating%20and%20Cooling/POSTER/2-2-28-PLEA2009Quebec.pdf |archive-url=https://web.archive.org/web/20130503010439/http://www.plea2009.arc.ulaval.ca/Papers/2.STRATEGIES/2.2%20Heating%20and%20Cooling/POSTER/2-2-28-PLEA2009Quebec.pdf |archive-date=2013-05-03 |access-date=2013-04-22 |website=26th Conference on Passive and Low Energy Architecture (PLEA2009)}}</ref> They are generally shaped as [[right triangular prism]]s with the vertical side left open and facing directly up or down wind (one of each per building). They work best if oriented within 10 degrees of wind direction; larger angles allow the wind to escape.<ref name=shady/> Windcatchers were used in traditional [[ancient Egyptian architecture]],<ref>{{Cite web |title=Air-conditioning avoidance |url=http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CRoaf.pdf|archive-url=https://web.archive.org/web/20071023174149/http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CRoaf.pdf |archive-date=October 23, 2007 }}</ref> and only started to fall out of use in the mid-20th century. Their use is now being re-examined, as air conditioning accounts for 60% of Egypt's [[peak electrical power demand]] (and thus the need for 60% of its [[Peaking power plant|generating capacity]]).<ref name=shady/>

Windcatchers in Egypt are often used in conjunction with other passive cooling elements.<!--{{expand-inline}}--><ref name="egypt_trad">{{Cite book |last=Mohamed |first=Mady A. A. |url=https://www.researchgate.net/publication/273122348 |title=Traditional Ways of Dealing with Climate in Egypt |work=Sustainable Architecture and Urban Development |publisher=The Center for the Study of Architecture in Arab Region (CSAAR Press) |year=2010 |editor-last=S. Lehmann |series=The Seventh International Conference of Sustainable Architecture and Urban Development (SAUD 2010) |location=Amman, Jordan |pages=247–266 |editor-last2=H.A. Waer |editor-last3=J. Al-Qawasmi}}[https://www.irbnet.de/daten/iconda/CIB22610.pdf low-res bw version]</ref><!--Mamluk period? https://knoji.com/article/the-architecture-of-the-traditional-arab-house/-->

<gallery mode="packed" caption="models" widths="180px" heights="120px">
Byggnadskonsten, Fornegyptiska boningshus, Nordisk familjebok.png|Dwelling house in Ancient Egypt with windcatcher. From a painting at the Pharaonic house of Neb-Ammun, Egypt, which dates from the 19th Dynasty, c. 1300 BC (British Museum).<ref>{{Cite web |title=Air-conditioning avoidance |url=http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CRoaf.pdf|archive-url=https://web.archive.org/web/20071023174149/http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CRoaf.pdf |archive-date=October 23, 2007 }}</ref><ref name=shady/>
Ancient Egyptian House miniature showing windcatchers.jpg|Ancient Egyptian House miniature showing windcatchers, dating from [[Early Dynastic Period of Egypt]], found in [[Abu Rawash|Abou Rawsh]] near Cairo. Now in [[Louvre]].
RPM Ägypten 003.jpg|Model of an Ancient Egyptian house with windcatcher, [[Roemer- und Pelizaeus-Museum Hildesheim]]
</gallery>
<gallery mode="packed" widths="240px" heights="160px" caption="cityscapes">
صور متنوعة من داخل القلعة 26.jpg|Windcatchers and {{transliteration|ar|shuksheika}} roofs shading narrow [[Ventilation shaft|airshaft]] courtyards, [[Cairo Citadel]]
View over Khartoum.jpg|Windcatchers in [[Khartoum]], Sudan
</gallery>

=== Middle East and Asia ===
[[File:Qatar University.Campus.jpg|thumb|The [[University of Qatar]] in Doha has unusual windcatchers.<ref name=review/>]]
[[File:Hyderabad1800s (cropped to windcatchers).jpg|thumb|Simple windcatchers in [[Hyderabad, Sindh]], in the 1800s: two-walled square towers with a diagonally-sloped [[skillion roof|skillion rooves]]]]
Windcatchers are a common feature across many Middle Eastern countries, influenced by the spread of Islamic culture.

==== Iran ====
{{see also|Persian architecture}}

In Iran, a windcatcher is called a ''bâdgir'', ''bâd'' "wind" + ''gir'' "catcher" ({{langx|fa|بادگیر}}). The devices were used in [[Achaemenid architecture]].<ref name="azami">{{Cite web |last=A. A'zami |date=May 2005 |title=Badgir in traditional Iranian architecture |url=http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CAzami2.pdf |access-date=2012-03-21 |publisher=International Conference "Passive and Low Energy Cooling 1021 for the Built Environment", May 2005, Santorini, Greece}} (the English is hard to understancd)</ref> They are used in the hot, dry areas of the Central Iranian Plateau, and in the hot, humid coastal regions.<ref name=azami/>

Central [[Iran]] shows large [[diurnal temperature variation]] with an [[arid climate]]. Most buildings are constructed from thick [[ceramic]] with high [[insulation value]]s. Towns centered on desert [[oases]] tend to be packed very closely together with high walls and ceilings, maximizing shade at ground level. The heat of direct sunlight is minimized with small windows that face away from the sun.<ref name=azami/>

The windcatcher's effectiveness had led to its routine use as a refrigerating device in Iran. Many traditional water reservoirs (''[[ab anbar]]s''), which are capable of storing water at near freezing temperatures during summer months, are built with windcatchers.<ref name=azami/> The [[evaporative cooling]] effect is strongest in the driest climates, such as on the Iranian plateau, leading to the ubiquitous use of windcatchers in drier areas such as [[Yazd]], [[Kerman]], [[Kashan]], [[Sirjan]], [[Nain, Iran|Nain]], and [[Bam, Iran|Bam]].

Windcatchers tend to have one, four, or eight openings. In the city of Yazd, all windcatchers are four- or eight-sided. The construction of a windcatcher depends on the direction of airflow at that specific location: if the wind tends to blow from only one side, it is built with only one [[downwind]] opening. This is the style most commonly seen in [[Meybod]], 50 kilometers from Yazd: the windcatchers are short and have a single opening.

Windcatchers in Iran may be quite elaborate, due to their use as status symbols.<ref name=azami/>

A small windcatcher is called a ''shish-khan'' in traditional Persian architecture. Shish-khans can still be seen on top of ab anbars in [[Qazvin]] and other northern cities in Iran. These seem to function more as ventilators than as the temperature regulators seen in the central deserts of Iran.

<gallery mode="packed">
File:Dolat Abad Garden - Pavilion 02.jpg|The windcatcher of [[Dowlatabad Garden]] in [[Yazd]], [[Iran]]: one of the tallest existing windcatchers
File:Borujerdiha.jpg|[[Borujerdi House]], in Kashan, central Iran. Built in 1857, it is an excellent example of ancient Persian desert architecture. The two tall windcatchers cool the ''[[andaruni]]'' (courtyard) of the house.
File:Windcatcher at Ganjali Khan Complex, Kerman.jpg|Windcatcher of [[Ganjali Khan Complex]], in [[Kerman]], [[Iran]]
File:Badgir-golestan-palace-tehr.jpg|[[Golestan Palace]], in [[Tehran]], Iran
File:نمای زیرین بادگیر.JPG|A windtower from below, inside, showing that it is partly closed-off
</gallery>

=== Australia ===
[[File:CouncilHouse2.jpg|thumb|[[Council House 2]]. Wind towers in [[Urban canyon|concrete canyon]] to the left.]]

[[Council House 2]] in [[Melbourne]], Australia, has 3-story-tall "shower towers", made of cloth kept wet by a showerhead trickling at the top of each one. Evaporative cooling chills the air, which then descends into the building.<ref name=whither/>

=== Europe ===
[[File:Saint Étienne-Le Zénith-20110111.jpg|thumb|The {{lang|fr|Zénith de Saint-Étienne Métropole}} has an extremely wide aluminium windcatcher scoop.]]

==== France ====
The [[Saint-Étienne Métropole]]'s [[Zénith de Saint-Étienne|Zénith]] is a multi-purpose hall built in [[Auvergne-Rhône-Alpes]] (inland southern France). It incorporates a very large aluminium windcatcher,<ref name="bigcity" /> which is much lighter than the equivalent masonry windcatcher would be. The size of the windcatcher allows it to work in any wind direction;<ref name="bigcity" /> the [[cross-sectional area]] perpendicular to the wind flow remains large.

==== United Kingdom ====
The [[Bluewater Shopping Centre]] in [[Kent]] uses windcatcher towers.<ref name="whither" /> The Queen's Building of [[DeMontfort University|De Montfort University]] in [[Leicester]] uses stack-effect towers to ventilate.<ref>{{Cite web|url=https://sitecore.uidaho.edu/scott-explore/error-pages/404|title=404 - University of Idaho|website=sitecore.uidaho.edu}}</ref>

=== Americas ===
[[File:Kensington Oval media centre.jpg|thumb|The [[Kensington Oval]] cricket ground in [[Barbados]] also uses a very wide aluminium windscoop.<ref name="bigcity" />]]

A windcatcher has been used in the visitor center at [[Zion National Park]], [[Utah]],<ref>{{Cite web |title=Zion Canyon Visitor Center |url=https://www.nps.gov/zion/learn/nature/zion-canyon-visitor-center.htm |access-date=2018-10-29 |website=National Park Service }}</ref> where it functions without the addition of mechanical devices in order to regulate temperature.<ref name="bigcity">{{Cite web |date=2012-03-20 |title=How Ancient Persian Architecture Captured Wind Energy Underground to Green Buildings |url=http://thisbigcity.net/how-ancient-persian-architecture-captured-wind-energy-underground-to-green-buildings/ |access-date=2012-03-20 |publisher=This Big City.net}}</ref>

== See also ==
* {{annotated link|Ridge vent}}
* {{annotated link|Passive cooling}}
* {{annotated link|Qanat}}
* {{annotated link|Salsabil (fountain)}}
* {{annotated link|Solar updraft tower}}
* {{annotated link|Vernacular architecture}}
* {{annotated link|Yakhchal}}

== References ==
{{reflist}}

== Further reading ==
* {{cite journal |last=Bahadori |first=Mehdi N. |title=Passive Cooling Systems in Iranian Architecture |journal=Scientific American |publisher=Springer Science and Business Media LLC |volume=238 |issue=2 |year=1978 |issn=0036-8733 |doi=10.1038/scientificamerican0278-144 |pages=144–154 |bibcode=1978SciAm.238b.144B |s2cid=119819386 |ref=none}}
* {{cite journal |last=Bahadori |first=Mehdi N. |title=Viability of wind towers in achieving summer comfort in the hot arid regions of the middle east |journal=Renewable Energy |publisher=Elsevier BV |volume=5 |issue=5–8 |year=1994 |issn=0960-1481 |doi=10.1016/0960-1481(94)90108-2 |pages=879–892 |bibcode=1994REne....5..879B |ref=none}}
* {{cite journal |last=Kassir |first=Radwan M |title=Passive downdraught evaporative cooling wind-towers: A case study using simulation with field-corroborated results |journal=Building Services Engineering Research and Technology |publisher=SAGE Publications |volume=37 |issue=1 |date=2015-09-04 |issn=0143-6244 |doi=10.1177/0143624415603281 |pages=103–120 |s2cid=111048250 |ref=none}}
* {{cite journal |last1=Montazeri |first1=H. |last2=Azizian |first2=R. |title=Experimental study on natural ventilation performance of one-sided wind catcher |journal=Building and Environment |publisher=Elsevier BV |volume=43 |issue=12 |year=2008 |issn=0360-1323 |doi=10.1016/j.buildenv.2008.01.005 |pages=2193–2202 |bibcode=2008BuEnv..43.2193M |ref=none}}
* {{cite journal |last1=Sangdeh |first1=Parham Kheirkhah |last2=Nasrollahi |first2=Nazanin |title=Windcatchers and their applications in contemporary architecture |journal=Energy and Built Environment |publisher=Elsevier BV |volume=3 |issue=1 |year=2022 |issn=2666-1233 |doi=10.1016/j.enbenv.2020.10.005 |pages=56–72 |ref=none|doi-access=free |bibcode=2022EnBEn...3...56S }}

== External links ==
{{commons category|Windcatchers}}
* G.R Dehghan Kamaragi (January 2016). "[https://www.badgirs.com https://www.badgirs.com]".
* {{Cite book |last=Fathy |first=Hassan |title=Natural Energy and Vernacular Architecture |chapter=The wind factor in air movement |chapter-url=http://archive.unu.edu/unupress/unupbooks/80a01e/80A01E00.htm}} ''(free fulltext)''
* {{Cite encyclopedia |last=Roaf |first=S. |url=http://www.iranicaonline.org/articles/badgir-traditional-structure-for-passive-air-conditioning |title=Bādgīr |encyclopedia=Encyclopaedia Iranica |year=1988 |volume=III |pages=368–370 |issue=4}}

{{Application of wind energy}}
{{Iranian Architecture}}
{{Islamic architecture}}
{{HVAC}}

[[Category:Cooling technology]]
[[Category:Iranian architectural elements]]
[[Category:Islamic architectural elements]]
[[Category:Islamic architecture]]
[[Category:Low-energy building]]
[[Category:Architectural elements]]
[[Category:Appropriate technology]]
[[Category:Heating, ventilation, and air conditioning]]
[[Category:Sustainable building]]
[[Category:Architecture in the United Arab Emirates]]
[[Category:Architecture in Egypt]]
[[Category:Passive cooling]]
[[Category:Passive ventilation]]
[[Category:Wind]]