Windcatcher
From Freepedia
Image:Borujerdiha.jpgA windcatcher, Badgir or (بادگیر) in Persian, is a traditional Persian architectural device used for many centuries to create natural ventilation in buildings.It is not known who first invented the windcatcher, but it still can be seen in many countries today.
Windcatchers come in various designs, such as the uni-directional, bi-directional, and multi-directional.
It is believed that the windcatcher functions based on the difference of height between base and tip. The difference creates a slight pressure gradient between the base and tip of the windcatcher's internal column whenever a breeze or wind passes through the tip of the windcatcher (that is not felt at the base). The pressure gradient then helps lift rising warmer air leaving the cooler air behind at the base. The accumulating effect over a 24 hour period is quite noticeable.
When coupled with thick adobe that exhibits high heat transmission resistance qualities, the windcatcher is able to chill lower level spaces in mosques and houses in the middle of the day to frigid temperatures.
So effective has been the windcatcher in Persian architecture that it has been routinely used as a refrigerating device for ages. Many traditional water reservoirs are built with windcatchers that are capable of storing water at near freezing temperatures for months in summer.
