by Michael J. Crosbie, PhD, AIA

Did you know . . . how to use the sun to make your design creations shine?

Summary: In the green frenzy currently coursing its way through architectural practice, you might overlook a basic tool that is the key to creating sustainable buildings: the sun. With attention focused on such hot-button features as green roofs and biomass, don’t overlook the hottest button of them all. Le Corbusier may have said that architecture is “ . . . forms assembled in the light,” but the sun makes architecture more than just sculpture. It pumps through a building’s veins, bringing architecture to life.

Here’s the plan
A number of this year’s AIA Committee on the Environment “Top Ten Green Projects” show how to use the sun to its greatest green advantage, squeezing the rays for energy efficiency, thermal comfort, and cooling (believe it or not). Take, for example, the Government Canyon Visitor Center in Texas, designed by Lake/Flato Architects. This is a small building, but it maximizes its time in the sun. The plan is shaped like two long rectangular bars running east to west, maximizing the south and north exposures. The plan’s narrow width helps to get the sun deep into the building, which accentuates natural lighting throughout. This project delivers natural light to 90 percent of the interior. You want to control the sun on the east and west exposures, so making them much smaller compared to the north/south elevations is the way to go. A long building on an east/west axis is so sun-friendly that it ought to be the natural response for any architect who wants to make a building effortlessly green. Remember, the secret is making the right green moves early in design so that you don’t have to figure out ways to “fix” the design later on as it passes on through design development (when it is too late). At the same time, in the arid Texas climate, you want to minimize direct sunlight into the building so that it doesn’t overheat, so Lake/Flato used deep porches and overhanging roofs.

The secret is making the right green moves early in design

Bringing light deep inside
Another Top Ten winner, the Hawaii Gateway Energy Center on the Big Island of Hawaii by Ferraro Choi and Associates, similarly uses a long, thin building oriented east/west to bring light deep inside. But in this building, the architects used an inventive technology to cool the building with the sun’s rays. Constructed off the building’s north edge is an elaborate space-frame, supporting a 20-kilowatt photovoltaic array that provides all of the building’s electrical power. The building’s gently arched roof is covered with copper, which gets good and hot in the sun. Buried within the roof is a plenum space that collects the heat generated by the sun, which is then exhausted through the top north edge of the roof through a series of “thermal chimneys.” The chimneys create a convection current, which pulls air from beneath a vented floor plenum, where it is cooled by 45-degree seawater pumped through coils. In this case, the sun’s heat works to move air through the building for natural cooling. How efficient is this system? Well, according to the architects, the building does not need a conventional air-conditioning system, yet maintains temperatures between 72 and 76 degrees.

A similar technique is used at the Sidwell Friends Middle School in Washington, D.C., designed by Kieran Timberlake Associates. The architects used sunshades on the east and west facades for maximum illumination with minimal heat gain. Along the roof are solar chimneys, essentially tall skylights within which the heat from the sun creates convection currents to exhaust the hot air and pull cool air through north-facing open windows. This building also keeps people cool without air conditioning, thanks to the smart use of the power of the sun.