The Wind Towers of Yazd Cool a House Without Electricity — Epoche B1
Above the flat roofs of Yazd, a desert city in central Iran, stand tall rectangular towers called badgirs, or wind catchers. Each is a shaft that rises above the roofline, catches the moving air and sends it down into the rooms beneath. Many are centuries old, and they cooled houses long before electricity arrived. How the tower works A badgir is open on one or more sides, and internal walls divide the shaft into channels. Wind striking the open face presses air downwards; on the sheltered face, the passing wind draws stale air up and out. The difference in pressure between the two sides keeps the air moving. At the foot of the shaft, the air often passes over a pool or the damp channel of a qanat — an underground water tunnel — and evaporation cools it further. The house below The tower does not stand alone. It belongs to a courtyard house, whose rooms face inwards onto a garden with a basin of water, and it feeds a sardab — a cellar room where the family sits through the worst hours of the afternoon. Where the wind blows mainly from one direction, the shaft is turned to face it. The tallest, at the Dowlatabad Garden, rises roughly thirty metres. Why it still matters UNESCO added the historic city of Yazd to the World Heritage List in 2017, citing this earthen architecture and the water system that serves it. Architects have since borrowed the principle back: wind towers on modern buildings in the Gulf and in Europe move air by pressure and heat alone, with no fuel and no compressor. The lesson is not that air conditioning should be abandoned. It is that the desert had already answered the question, and the answer was made of mud brick and patience. References Bahadori, M. N. (1978). Passive cooling systems in Iranian architecture. Scientific American, 238(2), 144-154. Roaf, S. (1988). The Windcatchers of Yazd. PhD thesis, Oxford Polytechnic. UNESCO World Heritage Centre (2017). Historic City of Yazd. World Heritage List. Paris: UNESCO.