Residents of a Washington, D.C., townhouse are enjoying comfortable indoor temperatures, even during the area’s sweltering summers, thanks to an attractive but unusual design feature added during a recent renovation. Sitting astride a modern rooftop pavilion, a 15-foot-tall solar chimney brings cool, fresh air into the home without conventional air conditioning. In conjunction with other high-performance features, it’s reduced the home’s energy bills by up to 65%, says Rick Harlan Schneider, principal of Washington-based iSTUDIO Architects.

“You can stand in the basement and feel air movement,” he says. “The owners still use AC on the steamiest days, but it’s a lot less than before.”

Using age-old technology, the chimney promotes whole-house airflow by placing an engineered outlet for rising hot air at the top of the stairs. A vented chamber at the top of the chimney is heated up by the sun, causing cooler air to be drawn in through the basement windows. Fresh air moves throughout the four-story townhouse on days when it’s hot but not too humid, and the owners can turn off the air conditioning.

While helping to save money on energy bills, the chimney cost very little to construct--only extra framing materials, a window, and a louver. Because the owner did not have the budget for an active solar system, passive design made the most sense, Schneider says.

“The home had an open stair for three stories, plus the proposed rooftop penthouse which immediately suggested harnessing the stack effect,” he says. “When the owner showed me the window wells in the basement and described the stale air down there, it all clicked.” While skeptical at first, the  residents are sold on the energy efficiency of their new passive solar system, says Schneider, who garnered an AIA Presidential Citation for Sustainable Design for the chimney, one of the first of its kind in the city.  
In addition to the chimney, othe dwelling’s other high-performance features include a high-efficiency air conditioner, rainwater-collecting barrels, cork flooring, and Energy Star-rated appliances and lights.

Jennifer Goodman is Senior Editor Online for EcoHome.