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Termite Mounds Inspire Design of
Zimbabwe Office Complex


HARARE, Zimbabwe -- Africa owes its termite mounds a lot. Prospectors mine them, looking for specks of gold carried up from hundreds of feet below. Africans building mud huts love them, because the grainy soil inside is just the right consistency for hard-packed floors. And of course, to aardvarks and other insectivores they are giant helpings of baked alaska.

Now, Africa is paying an offbeat tribute to these ugly towers of bug-holed mud. Harare's newest office complex is said to be the only one in the world to use the same cooling and heating principles as the termite mound.

That's no mean feat. Termite mounds are marvels of engineering. Deep inside, the insects farm a fungus, their only food. It must be kept at exactly 87 degrees, while the temperatures on the African veld outside range from 35 degrees at night to 104 degrees during the day.

They do it by venting breezes in at the base of the mound, down into chambers cooled by wet mud carried up from water tables far below, and up through a flue to the peak. Toiling with the tireless, compulsive work ethic of all ants, they constantly dig new vents and plug old ones to regulate the temperature.

Temperature regulation is a struggle familiar to any architect. Mick Pearce of the Pearce Partnership was given a challenge by Old Mutual, an insurance and real estate conglomerate: build an office block that would be livable with no air-conditioning and almost no heating.

Eastgate, the result, has been open for only nine months, but so far Pearce seems to be succeeding: the complex has been using less than 10 percent of the energy of a conventional building its size. Old Mutual saved $3.5 million on a $36 million building because an air-conditioning plant didn't have to be imported. More important, the savings on electricity are passed along to tenants, so rents are 20 percent lower than in a new building next door.

The complex is actually two buildings linked by bridges across a shady, glass-roofed atrium open to the breezes. Fans suck fresh air in from the atrium, blow it upstairs through hollow spaces under the floors and from there into each office through baseboard vents. As it rises and warms, it is drawn out through ceiling vents. Finally, it exits through 48 round brick chimneys that make the roof look to some like the chimney pots of Dickensian London and to others like the smokestacks of the Queen Mary.

To keep the harsh highveld sun from heating the interior, no more than 25 percent of the outside is glass, and all the windows are screened by an unusual form of sunshade: racks of cement arches that jut out more than a yard.

During summer's cool nights, big fans flush air through the building seven times an hour to chill the hollow floors. By day, smaller fans blow two changes of air an hour through the building, taking advantage of what Pearce calls "the coolth in the slab." For winter days, there are small heaters in the vents.

This is all possible only because Harare is 5,400 feet above sea level, has cloudless skies, little humidity and wide temperature swings -- days as warm as 88 degrees commonly drop to 58 degrees at night.

"You couldn't do this in New York, with its fantastically hot summers and fantastically cold winters," Pearce said. But then his eyes lit up at the challenge. "Perhaps you could store the summer's heat in water somehow ..."

The engineering firm of Ove Arup & Partners, which worked with him on the design, monitors daily temperatures outside, under the floors and at knee, desk and ceiling level. "This isn't all dancing around in the moonlight," Pearce said. "It's real science."

Ove Arup's graphs show that the building has generally fluctuated between 73 and 77 degrees, with the exception of the annual hot spell just before the summer rains in October (the seasons are reversed in the Southern Hemisphere) and of three days in November, when a janitor switched off the fans at night. The atrium, which funnels the winds through, can be much cooler.

"It's only about three weeks of the year we get complaints," Pearce said. "The rest of the year is fine." Turning on the fans later at night during hot spells seems to help.

Tenants confirmed that.

"It was absolutely too hot in October," said Debbi Hawkins, who designed IBM Zimbabwe's offices in the building. "We all ended up opening our windows. Now, it's absolutely fine. I do find it a little stuffy. I'm not too keen on air-conditioning, but I like fresh air from outside."

The air is fresh, Pearce said -- far more so than in air-conditioned buildings, which recycle up to 30 percent of theirs. It just enters unobtrusively, through vents at ankle height.

As far as beauty goes, Eastgate, more than most buildings, has a lot of function for form to follow. True to the idea of a termite mound, the first word that comes to mind is "busy" -- inside and out. Pearce, disdaining smooth glass skins as "igloos in the Sahara," calls his building "spiky." While other buildings that expose their girders and pipes seem to be built of Erector sets, Eastgate looks like Lego.

Other elements tumble over the viewer: the signature "tiaras" over the entrances are meant to resemble the porcupine-quill headdresses of the local Shona tribe, but to non-Shonas they look like the innards of supermarket bread-slicing machines. Elevators were designed to look like mine-shaft cages; their controls resemble ship binnacles. The fan covers, chevrons in granite, are echoes of Great Zimbabwe, the ruins that give the country its name.

The deluge of designs "is one of my problems -- I'm a bit Gothic" Pearce admitted.

Standing on a roof catwalk, peering down inside at people as small as termites below, he said he hoped the plants would grow wild and pigeons and bats would move into the atrium, tempering the whole "natural machine" metaphor with a bit more nature -- like that termite fungus. "But," he confided, with a bounce of his eyebrows, "the client hates it when I talk like that."

New York Times, February 13, 1997, made available on "Green Building News" list.
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