How it began
The Eastgate Centre is a shopping center and office block in central Harare designed by the Zimbabwean architect Mick Pearce and engineered by Ove Arup and Partners. Construction began in 1993 and the building opened in 1996. Pearce drew on the idea, current at the time, that termite mounds keep a stable internal climate through a structure that drives passive airflow.
Before it existed
Harare's climate usually requires buildings to be cooled year-round, which meant buying, installing and maintaining a conventional air-conditioning system with its immediate and long-term costs. The challenge set for Eastgate was a self-regulating ventilation system that would keep the building comfortable without one.
How it works
The building materials have a high thermal capacity, so the structure stores heat by day and releases it at night. Fans run on a cycle timed to that pattern. Heat from occupants and appliances helps drive air upward through large internal spaces to rooftop chimneys, and 48 brick funnels carry cool air up from the base and let warm air escape at the top. Arup's computer analysis required that no direct sunlight fall on the external walls and that windows on the north facade not exceed 25 percent of the wall area.
What changed first
The building saved about 10 percent of its cost up front by not buying an air-conditioning system; one account puts the saving at 3.5 million US dollars. It is reported to use about 10 percent of the energy of a conventionally cooled building of similar size, and rents are lower than in nearby buildings because of the energy savings.
What lasted
Eastgate became a standard example of biomimicry in architecture and a forerunner of green building technology in sub-Saharan Africa. Portcullis House in London, completed in 2001, emulates its system of large chimneys. Later research changed the understanding of termite mounds, which are now thought to work more like lungs for gas exchange, but the building still achieves a controlled internal climate with the mechanisms the mounds inspired.
