Drawing on termite nest design and combining the ancient materials of brick and stone with contemporary steel and glass, this retail and office complex transformed building heating and cooling systems.
It might terrify anyone who finds one near or in their home, but Zimbabwean architect Mick Pearce realised that a termitary, a home for termites, is actually one of nature’s architectural wonders. Why? Because those clever little pests build their homes in some of world’s hottest places using a design that never over heats.
Challenged to create a sustainable retail and office development in sub-tropical Harare, Pearce took a closer look at termitary structures. This led to the creation of a ground-breaking scheme, which opened in 1996 and has since inspired sustainable building design worldwide.
Eastgate is formed from two side-by-side buildings linked by a glazed roof, featuring steel bridges and lifts suspended on cables from steel lattice beams spanning the atrium.
The protruding precast concrete facia protects the glazing and interior from the sun and leads to an increased external surface area, which improves the heat loss from the interior at night and minimises daily heat gain. While, columns of steel rings running up and down the exterior are covered in green vines creating vertical gardens.
Keeping things cool
Now we get to the really clever bit influenced by termitary construction. Forty-eight brick funnels sit along the red-tiled roof and these extract the exhaust air from the seven floors of offices below. Under the office floors sits a mezzanine plant room where a bank of fans extracts air from the atrium through filters.
As Mick Pearce explains on his website: “This air is pushed up through the supply section of vertical ducts in the central spine core of each office wing. From the duct, the air is fed through the hollow floors to low-level grilles under the windows. As it is warmed by human activity it rises to the vaulted ceiling where it is sucked out via the exhaust ports at the end of each vault through a system of masonry ducts to the exhaust sections of the central vertical stacks. In the office space, uplighters use the concrete vaulted ceiling to reflect light downwards and absorb their heat.
“The sandwich of the vaulted ceiling and the voided floor above acts as a heat exchanger. The cold night air passing through the void festooned with concrete teeth removes the heat of the previous day and on the following day warm external air is cooled about 3°C by the same teeth before entering the room.”
This heat exchanger means that Eastgate consumes 35% less energy than other local buildings using traditional heating ventilation and air conditioning systems.
Versions of these passive cooling systems are now commonly used in sustainable architecture, making a significant contribution to carbon emissions and energy reduction – all thanks to termites!