Windcatcher Facts For Kids

Windcatcher is a simple roof tower or scoop that helps move air through a house without machines. People have used windcatchers, also called wind towers or wind scoops, for hundreds of years in hot places to cool rooms and bring fresh air inside. They come in many shapes and sizes because builders change the design for the usual wind direction, the height of the building, how hot or humid the weather is, and how dusty the air might be. Even when there is little wind, windcatchers can still work by using differences in temperature between inside and outside.

A windcatcher works by changing the air's push and pull. When wind hits the open face, it makes a higher pressure that pushes air into the tower. On the other side of a building, the wind can make lower pressure, or suction, that pulls air out. Together this push and pull make air travel through rooms and out the low-pressure side.

Warm air also helps move the breeze because warm air rises. This effect, called convection, mixes with wind pressure. Even small roof breezes that slip over buildings can create extra suction, so the tower keeps air moving through the house for cooling and fresh air.

Night flushing is a way windcatchers use cool night air to clean and cool a house. After a hot day, the outside air becomes cooler at night. Cool air is heavier, so it sinks into open courtyards and low rooms. Windcatchers let this cool air flow in and push the warm indoor air out, like giving the house a long, cool breath.

This process is part of diurnal cooling, which just means the daily cycle of hot days and cool nights. Builders design rooms and courtyards to fill with cold night air so the house stays comfortable the next day without using fans or refrigerators.

Subterranean cooling means using the coolness found below the ground to lower air temperature. A few meters under the surface, soil and groundwater keep a steady temperature close to the year’s average. When air is sent through underground passages or over cool water, it loses heat to the earth and comes back cooler.

Builders sometimes link windcatchers to buried ducts, shaded wells, or stone chambers so the incoming air can cool down before entering rooms. In some places, very cold night air is sent underground to make and store ice long before electric freezers existed, showing how effective the ground can be at holding coolness.

In many hot, dry places windcatchers use evaporative cooling to make the air feel cooler. Warm air is pulled down or through the tower and passes over water: as some water turns into vapor it takes heat from the air, so the air that enters rooms is cooler. Buildings often use a nearby underground channel called a qanat to bring cool water to the tower.

Sometimes towers have wet mats or thin-sheet fountains called salasabils to increase the water surface. That makes more evaporation, but it can slow airflow or cause cool air to sink quickly. A simple name for this sinking effect is passive downdraught evaporative cooling (PDEC). Spray nozzles or cold coils can also make PDEC, but they need care when water is hard.

Windcatchers appear across North Africa, West Asia, and India, but they look different from place to place. In Iran a tower is called a bâdgir and can have one, four, or eight openings. Cities like Yazd often use four- or eight-sided towers. In Egypt the same idea is called a malqaf (plural malaaqef) and many are shaped like tall triangular prisms that face the wind.

Taller, many-sided towers are common in dusty coastal or gulf regions. Some are grand and show status; smaller ones, like the shish-khan, work mostly as ventilators. Orientation matters: a tower works best when it faces the wind closely, usually within about ten degrees.

People today mix old ideas with new materials to make windcatchers work in modern buildings. For example, Council House 2 in Melbourne has three-story “shower towers” made of cloth that is kept wet by a showerhead. Air cools as it passes the wet cloth and drops down into the rooms below.

Another modern example is the Zénith in Saint-Étienne, France, which has a very large aluminium windcatcher. It is lighter than old masonry towers and is shaped so it can work no matter which way the wind blows. These designs show the old idea still helps cool buildings today.

Using windcatchers can cut how much electricity a building needs for cooling and so lower its carbon footprint. In the right climates they can make indoor air about 8 to 12 °C (14 to 22 °F) cooler than outside air, which means air conditioners run less or not at all.

Tests show a simple window windcatcher can reduce a building’s total energy use by around 23.3 percent. Still, they work best where the air is dry; in humid places evaporative cooling is less strong. When used well, windcatchers are a clever, low-energy way to keep people comfortable and help the planet.