In 1991, the multinational Old Mutual investment group approached the Zimbabwean architect Mick Pearce with an audacious assignment. The group wished to construct a retail and office complex called the Eastgate Centre in Zimbabwe’s capital city of Harare that, at 55,000 square meters, would be the country’s largest commercial building. What Old Mutual didn’t wish to do was pay the high cost of air-conditioning such a massive space. Could Pearce, working with the Arup construction firm, devise a design that relied solely on passive, natural climate control?
Pondering the problem, Pearce found inspiration in the termite mounds that dotted the savannas across his country. The largest mounds could reach several meters in height, dwarfing the legions of termites who built them just as a modern skyscraper towers over an individual construction worker. Each funneled air underground through networks of channels into a spherical nest that housed termites by the millions, and even larger numbers of fungi and bacteria. In all, a typical nest contained about a small cow’s worth of hot, breathing biomass. Based on the ideas of the Swiss entomologist Martin Lüscher, many researchers believed the mounds acted as air conditioners, maintaining a nest’s pleasant temperature, humidity, and oxygenation by continuously exchanging hot air rising from deep inside a colony with cooler drafts diffusing down from the surface. According to Lüscher, the mounds’ towering height allowed the “hot breath” of the colony’s biomass to drive this convective exchange. Lüscher’s theory came to prominence in 1961, reaching a wide audience through an article in Scientific American.