Iran's wind towers, age-old air conditioners
Wind towers (Badgir) are important elements in traditional Iranian architecture, providing natural air-conditioning in hot, dry and humid climates for thousands of years.
These towers rise not only on ordinary houses but also on top of water cisterns (Ab-anbar) and mosques.
The function of the cistern found below most wind towers in warm dry regions was to help balance humidity inside the structure.In many desert buildings, wind towers were built on top of a lavabo (howzkhaneh, which functioned as a summer courtyard). The wind was directed over the pool where it evaporated the water and took the cool air into other rooms.The first historical evidence of wind towers in Iran dates back to the fourth millennium BC.To counter the harshly variable climates of the country, Iranians invented wind towers which still stand in various desert towns except in areas where the city was located in a valley or in places experiencing frequent violent storms.
Wind towers are an inseparable part of the architecture of central and southern Iran, namely Yazd, Kashan, Bam and villages on the Persian Gulf coast.
In desert areas houses are closely set together, high-walled and made of baked brick with small windows facing away from the sun to minimize heat and maximize shade.In order to provide occupants with constant comfort, wind towers were built with a four-directional orientation to catch wind from all directions and guide it into the house.
Wind towers consist of four parts: the body containing shafts, air shelves which catch hot air and prevent it from entering the structure, flaps which redirect wind circulation, and a roof covering.
Wind travels through the shafts on top of the tower to reach the interior of the building. The air flow inside the structure travels in two directions, up and down.The temperature difference between the interior and exterior of a building causes pressure variations which results in the creation of air currents.
In cities where the wind blows only from one single direction, only one of the shafts operates to receive the breeze and the other three work as air outlet passages.
There are three types of wind towers:
1- The most elementary type of wind tower was built over cellars and underground water reservoirs known as ab-anbar.
These cellars kept food refrigerated and also served as sitting rooms where people could remain cool on hot summer days.
In hot climate cities, one to six wind towers were used to cool the water. They prevented stagnant air and the formation of dew or humidity inside, resulting in pure, clean and cold water all year round.
2- The second type transferred the flow into the basement where it hit damp walls and its humidity increased while its temperature decreased. The flow could be directed into other rooms using valves.
3- The third type of wind tower was taller and mainly used in multi-roomed one-story buildings. A dome-roofed hall under the tower helped ventilation.
Decorated with tiles or patterned or painted bricks, wind towers make full use of the elements of Iranian architecture, prompting passers-by to admire their beauty.
Among the country's famous wind towers are the historical Borujerdi house's tower and the Abbasian Badgir in Kashan.
The Dowlatabad garden wind tower in Yazd, presumably the world's tallest, is said to be 250 years old and about 33 meters high. It is surrounded by intricately hand-carved wooden lattice panels and stands atop the Dowlatabad cistern.
Another noteworthy wind tower is the 26-meter tall Emarat-e Badgir (wind tower monument) which is located in the eastern part of the compound of Tehran's Golestan Palace, once the Qajar royal complex.
The tower, elaborately decorated with blue, yellow and black tiles, is built on top of a lavabo (howzkhaneh).
Wind towers display the compatibility of human-built architectural designs with the natural environment and the ingenuity of Iranian engineers.
Following the introduction of western architecture, traditional structures such as wind towers gradually became part of the past though many still remain in use.With today's growing emphasis on reducing energy consumption, modern architecture can make use of traditional Iranian methods to utilize air currents and evaporation in cooling and air-conditioning living quarters.