Wind Towers or wind catchers, known as Badgir in Persian, are examples of indigenous architecture that incorporate a natural ventilation system, which can also be used as refrigeration. In Iran, they exist mainly in the smaller form called shish-khan which is purely a ventilation system. They are also found along the south-east coast of the Arabian Peninsula from Bahrain to Ra’s al-Khayma. In 1973, Dr Geoffrey King from the School of Oriental & African Studies, London, heard reports of a wind-tower on the island of Tarut, built by a family who had migrated from Bahrain, and says that otherwise the wind tower is not seen in Saudi Arabia. This type of architectural device is also seen in Pakistan. Roman wall paintings dated 10 BC are believed to show examples from Alexandria.
Towns built on desert oases tend to consist of buildings that are packed tightly together with high walls and ceilings. This is seen in its most dramatic expression in the mud brick buildings of Shibam in the Hadramaut area of the Yemen. The height and compactness of the buildings maximize shade in the hot desert climate. Direct sunlight is eliminated by the small size of the window openings as can be seen in this photograph taken by Wilfred Thesiger.
Where the wind- catcher system is used for ventilation, it can be one directional or multi-directional. A wind catcher consists of a capped tower-like structure on the superstructure of a building, which traditionally has four directional ports at the top. Air is drawn upwards when all except the one facing away from the incoming wind are shut. Opening only the port facing the wind would have the effect of pushing air down the shaft. Some wind catchers are designed purely for ventilation and others use the system in conjunction with the qanat, an underground water system, to regulate the temperature inside the building. For this system to operate effectively the base of the structure must be as free of cracks as possible and there must be a good air gap above the qanat. The cool dry night air, sucked by the pressure created by the wind catcher, is evaporated and cooled by its passage over the cold water of the qanat. The wind tower also has a function in a windless environment and a waterless house. It allows less dense hot air move upwards and escape, and in conjunction with the high heat transmission resistance qualities of adobe, can cool the lower spaces in houses and mosques in the middle of the day.
Among the collection of The Metropolitan Museum of Modern Art are frescoes from a villa at Boscoreale northeast of Pompeii, excavated in 1900, and another at Boscotrecase near Vesuvius, excavated in 1903, both of which depict “cityscapes and landscapes which display unusual architectural features”. E. R. Knauer relates them to the wind towers of non- classical antiquity, and describes those from Boscotrecase one of which is believed to be the villa of Agrippa Posthumus the son of a friend of the Emperor Augustus who conquered Ptolemaic Egypt. A common feature of the wall paintings is that all of the buildings in question have “latticed or arcaded openings” just below the top rather than windows. It is thought that the inhabitants of the Nile Valley learned to make use of the steady north and north-easterly winds during their early history. Models recovered from the tombs of the Old Kingdom period show half cupolas on the upper terrace floors facing the direction of the prevailing winds, which are believed to have served the function of wind-catchers. Depictions of houses from New Kingdom tombs show louvered windows designed to regulate the flow of air, with triangular structures on the flat roof intended to catch the winds from various directions. It is believed that similar structures were used in Mesopotamia but no records exist.
A pent roofed ventilator on the roof of an 18th century Cairene building shows latticed bays and rows of arched openings similar to those described from the New Kingdom paintings. Although some studies suggest that the wind-catching device was introduced into Egypt from Iran during the Fatimid period, Elfriede Knauer and others believe that they arise from an “unbroken indigenous tradition”.
Iran has the highest number of wind-catchers, situated primarily in the hot humid southern area and around Yadz in the hot dry area of the central plateau. The wind catcher is similar to a chimney with its top over the roof and its end in the underground of the house. Four sided wind-catchers are those most commonly seen in Yadz and are made of mud-brick or brick. In Bandar Lengeh in Hormozgan province, plaster and plaster of lime is used, as it prevents humidity penetrating the walls of the wind-catcher. Wind-catchers come in various forms, rectangular, square, hexagonal and octagonal, and as their function is to capture the wind and transfer it to the inner space the ratio of length to height and width are important. The wind-catcher helps to balance the temperature of a house both day and night. Dry warm wind passing over a central pool becomes cool and wet with evaporation before flowing into the rooms.
In Iran today wind-catchers are used in water-reservoirs as well as houses. A city reservoir is likely to have seven wind-catchers interacting with each other. Field water-reservoirs will usually have a unidirectional or bilateral wind-catcher facing the appropriate winds. Believed to have been used in Iran from antiquity the wind-catcher is a prime example of architecture designed to suit local climatic conditions. Iranian examples show clear parallels to the structures depicted in the Roman wall paintings especially the isolated towers with latticed openings below the roof. Whereas the Roman examples have slanted roofs, the Iranian tower structures are flat roofed. The tower is subdivided into shafts by brick walls with the vents open to the winds. They function in the absence of wind when the brick shaft warms during the day creating an upward draft which causes the air within to circulate. In recent years, interest in wind towers has been regenerated as they represent a traditional cooling system that does not require the use of fossil fuels.
