Windcatcher

Windcatcher

A windcatcher (Persian: بادگیر "Bâdgir", Arabic: بارجيل "Baarjiil") is a traditional Persian architectural device used for many centuries to create natural ventilation in buildings. It is not known who first invented the windcatcher, but it still can be seen in many countries today. Windcatchers come in various designs, such as the uni-directional, bi-directional, and multi-directional.

Background

Central Iran has a very large day-night temperature difference, ranging from cool to extremely hot, and the air tends to be very dry all day long. Most buildings are constructed of very thick ceramics with extremely high insulation values. Furthermore, towns centered on desert oases tend to be packed very closely together with high walls and ceilings relative to Western architecture, maximizing shade at ground level. The heat of direct sunlight is minimized with small windows that do not face the sun.

Function

The windcatcher functions on several principles:

First, a windcatcher is capped and has several directional ports at the top (Traditionally four). By closing all but the one facing away from the incoming wind, air is drawn upwards using the Coanda effect, similar to how opening the one facing the wind would push air down the shaft. This generates significant cooling ventilation within the structure below, but is not enough to bring the temperature below ambient alone - it would simply draw hot air in through any cracks or windows in the structure below.

Therefore, the key to generating frigid temperatures seems to be that there are very few cracks at the base of the thick structure below, but there is a significant air gap above the qanat. A qanat has quite a lot of water inside, because there are frequent well-like reservoirs along its path. Completely shaded from the sun, a qanat also aggregates the cold, sinking air of the night, which is then trapped within, unable to rise up to the less dense surface air. A windcatcher, however, can create a pressure gradient which sucks at least a small amount of air upwards through a house. This cool, dry night air, being pulled over a long passage of water, evaporates some of it and is cooled down further.

Finally, in a windless environment or waterless house, a windcatcher functions as a stack effect aggregator of hot air. It creates a pressure gradient which allows less dense hot air to travel upwards and escape out the top. This is also compounded significantly by the day-night cycle mentioned above, trapping cool air below. The temperature in such an environment can't drop below the nightly low temperature. These last two functions have gained some ground in Western architecture, and there are several commercial products using the name windcatcher.

When coupled with thick adobe that exhibits high heat transmission resistance qualities (R-value), the windcatcher is able to chill lower level spaces in mosques and houses (e.g. shabestan) in the middle of the day to frigid temperatures.

So effective has been the windcatcher in Persian architecture that it has been routinely used as a refrigerating device (yakhchal) for ages. Many traditional water reservoirs (ab anbars) are built with windcatchers that are capable of storing water at near freezing temperatures for months in summer. High humidity environments destroy the evaporative cooling effect enjoyed in the dry conditions seen on the Iranian plateau; Hence the ubiquitous use of these devices in drier areas such as Yazd, Kashan, Nain, and Bam. This is especially visible in ab anbars that use windcatchers.

A small windcatcher (badgir) 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 be more designed as a pure ventilating device, as opposed to temperature regulators, as their larger cousins in the central deserts of Iran are.

Gallery

A Wind Tower (Persian:"bad gir",Arabic: "barjeel" or "badghir"(from Persian)) is a structure seen on ancient buildings of the Middle East, particularly Iran, Dubai and Bahrain. This acted like a natural air conditioner creating a soothing effect in the harsh conditions of the desert.

The emergence of a traditional Bahraini and Persian Gulf style of architecture arose as people migrated to Bahrain with the growth of the pearl trade. With newfound wealth, the merchants built houses of note in the 18th and 19th centuries. The people of Ahvaz in Iran, for example, came and brought with them new architectural designs, including the distinctive wind tower which can be seen so prominently in the Awadiya area and elsewhere in Bahrain. This distinguishing feature was adapted locally with its own distinctive decorative motifs. The wind tower, an early and very effective form of air conditioning, has in fact been around for about 500 years and was developed from the early Wind Scoops first built about 2,000 years ago in Iran.

In Muharraq and also in parts of Manama there are many buildings, which are no more than two stories high and houses built with natural ventilation, using wind towers and "badghirs", the devices for speeding up the flow of air and which consists of horizontal slats in the lower part of the walls. "Badghir" means ‘wind trap’ and is also the word used to describe the wind tower.

ee also

*Persian architecture
*Yakhchal
*Solar chimney

External links

*cite journal | last = Bahadori | first = Mehdi N. | month = February | year = 1978 | title = Passive Cooling Systems in Iranian Architecture | journal = Scientific American | volume = 238 | issue = 2 | pages = 144–154 | url = http://paccs.fugadeideas.org/disclaimer/fairuse.php?file=cooling_syst_iran.html&title=Passive%20Cooling%20Systems%20in%20Iranian%20Architecture | accessdate = 2007-07-17
*cite journal | last = Bahadori | first = Mehdi N. | year = 1994 | month = August | title = Viability of wind towers in achieving summer comfort in the hot arid regions of the middle east | journal = Renewable Energy | volume = 5 | issue = 5-8 | pages = 879–892 | doi = 10.1016/0960-1481(94)90108-2
*cite web |url = http://www.inive.org/members_area/medias/pdf/Inive%5Cpalenc%5C2005%5CAzami2.pdf |title = Badgir in traditional Iranian architecture |accessdate = 2007-07-17 |author = A. A'zami |format=PDF
* [http://www.ibchamber.org/Magazine%208/yazd.htm Yazd, the city of windcatchers.]
* [http://www.gimizu.de/cgi-bin/Orient.cgi?de:/2004/yazd/bagh-e_dolatabad:0913_d13 The famous Dowlat-abad windcatcher in Yazd]
* [http://www.yazd.com/images/Yazd%2020001127.jpgWindcatchers are incorporated into the architectural expression of traditional Persian buildings. Notice this sample, with 6 symmetrical badgirs, in Yazd.]
* [http://gotouring.com/razzledazzle/articles/libertyphoto010.html ventilation cowl on a ship]


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Appropriate technology — (AT) is technology that is designed with special consideration to the environmental, ethical, cultural, social and economical aspects of the community it is intended for. With these goals in mind, AT typically requires fewer resources, is easier… …   Wikipedia

  • Ab Anbar — phrase literally translates as water reserve .The architectural elements making up an ab anbar are presented in this article.The structureTo withstand the pressure the water exerts on the containers of the storage tank, the storage itself was… …   Wikipedia

  • Pirates at Ocean's Edge — is Wizkids ninth expansion in the Pirates of the Spanish Main series. This set was released in April 2007. It features giant crabs, prehistoric sharks and sea dragons. It also features the return of the junk ship from Pirates of the South China… …   Wikipedia

  • Увлажнитель — климатический прибор, использующийся в первую очередь для повышения влажности воздуха в помещениях. Функциональность увлажнения также может присутствовать в сложных приборах кондиционирования воздуха и вентиляции. В свою очередь, в увлажнителях… …   Википедия

  • One Thousand and One Nights — Arabian Nights redirects here. For other uses, see Arabian Nights (disambiguation). For other uses, see One Thousand and One Nights (disambiguation). Arab World …   Wikipedia

  • Arabic music — Bayad plays the oud to The Lady. from the Riyad Bayad, Arabic tale Arabic music or Arab music (Arabic: الموسيقى العربية al mūsīqā al ‘Arabīyah) is the music of the Arab World, including several genres and styles of music ranging from Arabic… …   Wikipedia

  • Wind power — Wind power: worldwide installed capacity [1] …   Wikipedia

  • Mihrab — Arab World This article is part of the series: Arab Culture …   Wikipedia

  • Breyten Breytenbach — (born September 16, 1939) is a South African writer and painter with French citizenship.Breyten Breytenbach was born in Bonnievale, Western Cape in the Western Cape, approximately 180 km from Cape Town and 100 km from the southernmost tip of… …   Wikipedia

  • Ventilation (architecture) — Ventilation is the intentional movement of air from outside a building to the inside. It is the V in HVAC. With clothes dryers, and combustion equipment such as water heaters, boilers, fireplaces, and wood stoves, their exhausts are often called… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”