Sunday, March 2, 2008

Nature's Architects

On the left is a typical termite mound; on the right is Zimbabwe’s largest office and shopping complex: The Eastgate Center. Both are built based on the same principles.

Termites build massive mounds inside of which they farm fungus, their primary food source. In Zimbabwe, the temperature outside of the mound ranges from 2 C at night, to 40 C during the day, but the fungus must be kept at exactly 31 C. The termites achieve this by frequently opening and closing a series of heating/cooling vents throughout the mound over the course of a day. Air is sucked in the lower part of the mound, down into the enclosures with muddy walls, and back up through a channel to the top of the mound.

The Eastgate Center has a ventilation system that operates similarly. At the start of the day the building is comfortably cool. During the day, the shining sun, machines and people generate heat, which is absorbed by the fabric of the building. Gradually the temperature inside increases. In the evening, when the outside temperature drops, the warm internal air is vented through chimneys. This movement is assisted by fans, but also rises naturally due to the less dense nature of hot air. This draws in cool air at the bottom of the building. The process continues over night until an ideal temperature has been reached for the next day.

By applying the termite's ventilation method, known as passive cooling, Eastgate uses only 10% of the energy needed by a similar conventionally cooled building.

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