What is a windcatcher (wind tower)?
A windcatcher, or wind tower, is a tower or rooftop unit that catches the wind and channels it into a building, to ventilate and cool it naturally. In Dutch it is called “windvanger” or “windtoren”. The technique is centuries old and best known from the Middle East, where wind towers (called “badgir” in Iran) define the skyline of cities such as Yazd. Modern versions are used today on schools, offices and homes.
How does it work?
- Catching the wind: the opening on the windward side is under positive pressure, pushing air down a shaft into the building.
- Extracting: the leeward side is under negative pressure, drawing warm, stale air out through another channel.
- Stack effect: even with little wind, warm air rises and leaves through the tower, drawing in cooler air lower down.
- Extra cooling: in traditional buildings incoming air was sometimes passed over water, so evaporation cooled it.
Traditional and modern forms
- Traditional: tall masonry towers with vertical partitions dividing the shaft into channels, so there are always openings on the windward and leeward sides.
- Modern: compact roof units with louvres and dampers, often combined with heat recovery or a fan for still days, and controlled by CO2 or temperature sensors.
Tips for use
- Roof position: place it in free wind, above obstacles such as roof structures and trees.
- Rain and insects: fit louvres, a drip drain and mesh.
- Closable in winter: in a temperate climate the unit must close or turn down in winter, or a lot of heat is lost.
- Noise: an open connection to outside also lets noise in. Near busy roads, use acoustic attenuation.
- Regulations: have a ventilation engineer confirm the airflow meets building regulations, and check whether the roof structure needs permission.
Related terms
- Venturi wind turbine
- Wind energy
- Heat pump
- Cogeneration
- Aquifer thermal energy storage
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