WHETHER it's 100 degrees or freezing outside the Botswana Technology Centre (BTC), employees are comfortable inside, with almost no additional heating and no cooling, thanks to a combination of American know-how and techniques as old as the sun. This four-year-old, energy-efficient Centre, funded in part by the United States Agency for International Development, last month received a US Presidential Design Award for projects using federal funds. It had won an award of merit for unusual competence in passive solar design for commercial buildings at the 1982 Knoxville World's Fair, as well as one from Progressive Architecture magazine.

The Centre, in the capital city of Gaborone, has windows on the peak of the roof to exhaust hot air and provide light. In the main building, small private offices surround a large central open space. Attached is the library, a large room with stacks and other offices. The walls and roof are heavily insulated, and because the walls are masonry, they absorb excess daytime heat and release it back at night. Most windows face north or south, and louvers keep direct sun out. Outside, shading devices and deciduous plants mitigate the summer's heat.

Perhaps even more important than the comfort of the building is its use of runoff water. The pool in the center of the courtyard symbolizes the importance of water in the parched region. Enough water is collected from the roof, the site, and the parking lot to supply all the needs of the workers. ``Which is a good thing,'' says architect David Norris, ``because the city refused to hook us up to its water supply.''

A follow-up study found the Centre office design reduces the cooling load of a conventional building by 77 percent, and the heating load by 51 percent.

Associates in Rural Development Inc. (ARD), in Burlington, Vt., won the AID contract for a multimillion-dollar renewable energy project, of which this is a part. The firm subcontracted the design and building of the office and a model solar home to Peter Temple, a senior solar researcher at Total Environmental Action, in Harrisville, N.H., a now-defunct solar design and engineering firm. Mr. Temple hired Mr. Norris, a former co-worker, who lives in New York.

``We did a lot of preparation work here; researched the climate, geography, and types of materials,'' says Temple, looking out at an iced-over New Hampshire lake. ``It was hard to do for a place like Botswana.''

The design team spent six weeks there, sharing temporary offices in a converted garage. ``We talked to local weather people, builders, and architects, finding out materials, contacted the government architecture office, got their opinions on various issues. We took trips to villages to get familiar with the local architecture, to get a sense of what works. Mainly people build round mud buildings with thatched roofs.''

The design team found a rapidly urbanizing Botswana, with people moving out of rondavels, or round huts, into rectangular buildings. ``One of the issues we found was,'' says architect Norris, ``Were people comfortable in rectangles? Could rectangles be made to carry over some of the feeling of the village, to make it more comfortable? In fact, that kind of thinking affected the way I designed the BTC. That program called for an administrative center, a library, technical workshop, and demonstration center. I put them around a courtyard, which is a traditional planning device in villages. The design also borrows from the colonial history of the country, with the deep overhangs, and the steeply sloped metal roofs.''

The most high-tech part of it, he said, was that Temple worked out his energy analysis on a hand-held programmable calculator.

Botswana is a country the size of Texas with a climate like northern Mexico; hot and dry, but cool in the winter. Batswana cook and heat with coal and wood; deforestation is a problem.

``The intent was to reduce the need for either electrical heat or coal-fired heat, as well as to make the building cool in summer,'' says George Burrill, director of ARD. ``An overall goal is to reduce the need for electricity, since a lot of it comes in from South Africa. The Batswana are trying to bring in power from Zimbabwe. For the past six to eight years they've been involved in strategic planning, looking to broaden the electrical supply.''

The Centre is part of a pilot project between the Botswana Ministry of Mineral Resources and Water Affairs, and USAID. It is designed to introduce to villages renewable energy technologies that are easily reproduced and inexpensive, and to reduce the country's dependence on fossil fuels. ARD worked with more effective stove designs, water pumping systems, windmills, and solar pumps.

``It's very dry there,'' says George Burrill. ``It's big cattle-raising country. We went into the communities to install photovoltaics for vaccine refrigeration and lights for health clinics and in schools.''

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