The National Association of Home Builders released its Model Green Home Building Guidelines earlier this year (to get a free copy, click here); the Sustainable Building Council released its Green Building Guidelines in 2002; and the U.S. Green Building Council currently is developing a residential counterpart to its Leadership in Energy and Environmental Design (LEED) guidelines for commercial buildings.
Additionally, the Department of Energy’s Building America Program, which has long been developing strategies for green and energy efficient construction, has begun to release building guides by climate zone.
While technology–advanced glass and insulation products, for example–plays a role in some of these documents' guidelines, other ideas will seem familiar to anyone who grew up in a house built before central air conditioning became the norm. In fact, you'll probably see many of these ideas in use today in your area's older homes.
"When air conditioning came along, people could rely on something mechanical," explains Debra Rucker Coleman, an architect whose Sun Plans Inc. practice focuses on designs that maximize natural heating and cooling, reducing the need for air conditioning to the summer's hottest months.
Debra lives in southwestern Alabama, so she understands the need for air conditioning very well. "It used to be you relied on common sense," she says. "These are not complex strategies."
Debra outlines her approach, called "passive solar" design, in her book, The Sun-Inspired? House, due out in October 2005. Many of her ideas also are described in the new NAHB guidelines. Following are a few of the common-sense tactics she considers when designing high-efficiency custom homes:
- Consider your siting. Minimize east- and west-facing wall areas, because these elevations feel summer sun most intensely. Shade windows on these facades with porches or trees.
- Maximize south-facing glazing. This strategy also helps minimize winter heating bills. Right-sized overhangs placed above south-facing windows can help minimize heat gain during the summer, when the sky is high in the southern sky, yet still admit warming rays during winter months.
- Maximize use of operable windows. Aim for operable-window space equal to 6 to 7 percent of floor space. (Only the operable portion of a double-hung window counts toward this percentage, while all of a casement window's space counts toward the total.)
- Use thoughtful window placement. Place windows diagonally across from each other, rather than directly opposite, to encourage ventilation through, rather than across, a space.
- Incorporate whole-house/attic fans. Coleman says today's units are more powerful and efficient than models you might remember from your grandmother's home. In the evening, with windows and attic doors open, these fans can help flush out daytime heat quickly.
