Ancient Wind Towers Passively Cool Buildings

Wind towers catch cooler breezes that prevail at a higher level above the ground and direct it into the interior of  buildings. Typically, a wind tower is capped and has openings on its sides toward four directions. It will either act as a solar chimney to draw hot air out of the building, or will allow cooler breezes to come down the chimney to cool the spaces below. These ancient structures were originally developed in the Mid-East, constructed mostly of thick adobe or ceramic walls with extremely high insulative values. Also known as windcatchers, wind towers can be located over an underground reservoir of water known as a qanat. Completely shaded from the sun, a qanat aggregates the cold, sinking air of the night, which is then trapped within, unable to rise up to the less dense surface air. The wind tower creates a pressure gradient which sucks at least a small amount of air upwards through the building. This cool, dry night air, being pulled over a long passage of water, evaporates some of it and is further cooled. Some modern buildings are now using wind towers as a strategy to save energy by cooling buildings using this ancient, passive principle of air flow. http://www.solaripedia.com/13/205/wind_towers_catch_the_breezes_%28mid_east%29.html