Information about Windcatcher

A windcatcher (Bâdgir; بادگیر) 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 don't 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

The windcatcher of "Dowlat-abad" in Yazd, is one of the tallest extant windcatchers.

Windtowers, Yazd.

Borujerdi ha House, in central Iran. Built in 1857, it is an excellent example of ancient Persian desert architecture. The two tall windcatchers cool the andaruni section of the house.

A Wind Tower (Persian:bad gir,Arabic: badghir(from Persian)) is a structure seen on ancient buildings of the Middle East, particularly Iran 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.

See also

• Persian architecture
• Yakhchal
• Solar chimney

External links

• Bahadori, Mehdi N. (February 1978). "Passive Cooling Systems in Iranian Architecture". Scientific American 238 (2): 144-154. Retrieved on 2007-07-17. 
• Bahadori, Mehdi N. (August 1994). "Viability of wind towers in achieving summer comfort in the hot arid regions of the middle east". Renewable Energy 5 (5-8): 879-892. DOI:10.1016/0960-1481(94)90108-2. 
• A. A'zami. Badgir in traditional Iranian architecture. Retrieved on 2007-07-17.
• Yazd, the city of windcatchers.
• The famous Dowlat-abad windcatcher in Yazd
• Windcatchers are incorporated into the architectural expression of traditional Persian buildings. Notice this sample, with 6 symmetrical badgirs, in Yazd.
• ventilation cowl on a ship

•  • [ e] Sustainability and Energy development
Future	2000 Watt society Hubbert peak Peak oil
Transportation	Air car Alternative fuel Alternative propulsion Battery electric vehicle Bicycle Bioalcohol Biodiesel Bioethanol Biogas Biomass to liquid Bus rapid transit Ecodriving Electric power-assist system Electric vehicle Hybrid electric vehicle Hydrogen station Hydrogen vehicle Low-energy vehicle Plug-in hybrid Production battery electric vehicle Public transport Pyrolysis Trolleybus TWIKE utility cycling Vegetable oil used as fuel
Energy Conversion	Electricity generation Distributed generation Microgeneration Sustainable community energy system Environmental concerns with electricity generation Biological energy Anaerobic digestion Biomass Mechanical biological treatment Chemical energy Blue energy Fuel cell Hydrogen production Geothermal power Deep lake water cooling Earth cooling tubes Hydroelectricity Run-of-the-river hydroelectricity Tidal power Water turbine Wave power Nuclear power Inertial fusion power plant Fusion Nuclear reactor Radioisotope thermoelectric generator Solar power Active solar Barra system Central solar heating plant Energy tower Ocean Thermal Passive solar Passive solar building design Photovoltaics Photovoltaic module Solar cell Solar combisystem Solar hot water panel Solar pond Solar power satellite Solar power tower Solar roof Solar shingles Solar thermal collector Solar thermal energy Solar tracker Solar updraft tower Trombe wall Waste-to-energy Wind power Wind farm Wind turbine Storage Flywheel energy storage Grid energy storage Hydrogen storage Seasonal thermal store Thermal energy storage
Sustainability	Ecological footprint Ecosystem services Ecovillage Energy conservation Energy Demand Management Green map Human Development Index Infrastructural capital Permaculture Renewable energy Self-sufficiency Simple living Sustainable development Sustainable living The Natural Step TPE Value of Earth World energy resources and consumption Zones (Permaculture) Appropriate technology Air engine Autonomous building Cob (building) Composting toilet Cool roof Earth sheltering Energy-efficient landscaping Green roof Hypermodernity Low energy building Passive house Rammed earth Sheet composting Solar chimney Straw-bale construction Superinsulation Technological singularity Windcatcher Sustainable agriculture Food security Forest gardening Humanure List of companion plants List of repellent plants Seed ball Vermicompost Zero energy building Sustainable design Environmental design Sustainable architecture Sustainable landscape architecture Sustainable econonomics Development economics Green economics Green Gross Domestic Product Hydrogen economy Liquid nitrogen economy Low-carbon economy Triple bottom line Sustainable industries Agroforestry Ecoforestry Exploitation of natural resources Green building Green chemistry Green computing Industrial Ecology Natural building Sustainable energy Sustainable forest management Sustainable procurement Sustainable transport Sustainable waste Living machines Mycoremediation
Management	Commission on Sustainable Development Human development theory Intermediate Technology Development Group Maldevelopment Precautionary principle Rio Declaration on Environment and Development Rocky Mountain Institute Sim Van der Ryn Underdevelopment World Business Council for Sustainable Development World Summit on Sustainable Development

•  • [ e] The architecture of Iran and historical Persia
Elements	Bazaars  The Persian Garden (hayāt)  Windcatchers  Shabestan  Kucheh  Talar  Iwan  Howz  Panjdari  Hashti  Andaruni  Biruni (persian architecture)  Dalan e Vorudi  Qanat  Kariz  Gonbad  Ab anbar  Yakhchal  Caravanserais  Robats  Burj  Khaneqah  Tekyeh  Sahn  Imamzadeh  mosques
Notable traditional cities	Architecture of Tehran  Kashan   Qazvin • Yazd  Isfahan  Shiraz  Qom  Herat  Derbent  Bukhara  Samarkand  Merv  Mashad  Bam  Persepolis  Ctesiphon  Susa  Shahrisabz
History and theory	Traditional Persian residential architcture  Traditional water sources of Persian antiquity  Islamic architecture  Sassanid architecture  Pre-Parsi style  Parsi style  Parthian style  Khorasani style  Razi style  Azari style  Isfahani style
Lists	List of ab anbars of Qazvin  List of historical Iranian architects  List of mosques    List of Ziyarat-gahs