Termite mound inspired building that cools itself in Zimbabwe

The Eastgate in Harare Zimbabwe is the largest office and shopping complex in the entire country. The complex was designed by Architect Mick Pearce in collaboration with Ove Arup engineers, Pearce’s practice is in Harare, and he specialises in buildings which are low cost, low maintenance, and have low environmental impact. It is the first building in the world with this amount of sophistication that cools itself.

It opened in 1996 on Robert Mugabe Avenue and Second Street, and provides 5,600 m² of retail space, 26,000 m² of office space and parking for 450 cars.

Mick Pearce says the design of Eastgate centre was inspired by the African termite mound. This came when an investment group in Harare Zimbabwe hired him to design a sustainable shopping and office complex in the country, but didn’t want to pay for the expensive air conditioning. A HVAC installation would mean importing from a foreign country which would eat into the foreign reserve of Zimbabwe.

Mick Pearce thought of a sophisticated yet easy to maintain building complex, he decided to harness the ingenuity of a termite mound and incoperate in his design. This is referred to as biomimicry in architecture. Now how does the termite mound work?

Termites mounds may appear solid from the outside but are full of vents and openings on the inside. Termites store fungus which is their primary food source, this fungus has to be kept at a particular temperature during night and day. So the termites make openings here and there in the mound from which air is sucked in through the lower vent, is circulated round the mound, and goes out through the upper vent. During this procedure, the fungal temperature inside is preserved.

Mick used this termite formula to achieve passive cooling in the building. He started by placing fans on the first floor of the building that blows in fresh air into the building; which in turn is passed round the seven floors of Eastgate through openings in the ceilings of each floor.

The engineering firm Ove Arup, gave Pearce a set of rules.

“They said that no direct sunlight must fall on the external walls at all and the north façade [direction of summer sun] window-to-wall area must not exceed 25%. They asked for a balance between artificial and external light to minimise energy consumption and heat gain. They said all windows must be sealed because of noise pollution and unpredictable wind pressures and temperatures, relying on ducted ventilation. Above all, windows must be light filters, controlling glare, noise and security”.

Eastgate is made of concrete slabs and brick, instead of glass and steel common with buildings of such complexity and function. It comprises two buildings side by side linked together by a glass roof. Concrete and bricks have a large thermal mass, they can absorb a lot of heat without changing temperature.

Below this, steel bridges and lifts suspended on cables from steel lattice beams span over the atrium below. The lifts connect with a suspended glass skywalk which runs the length of the atrium at level 2. The centre of the skywalk is connected to street level by escalators and the street leads to the city’s web.

The windows have adjustable blinds, but Pearce also used deep overhangs to keep direct sun off windows and walls,shading the walls completely from sun, while allowing sun to warm the building in the morning.

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