High-tech habitats. (Innovative Technologies).

A series of demonstration houses in Tennessee is pushing the envelope of energy efficiency--literally. By testing tighter building exteriors, or "envelopes," and other innovations, engineers in the Building America program at the Department of Energy's Oak Ridge National Laboratory (ORNL) are learning what works and what doesn't. The houses are built by volunteers for Habitat for Humanity, and, after initial testing is completed, low-income families take possession. Close monitoring of the houses is producing data that could affect building practices nationwide, says ORNL project manager Jeff Christian.

For example, to test different heating and cooling scenarios, ORNL and Habitat have built two houses with three separate heat pumps each, and multiple heating, ventilating, and air-conditioning (HVAC) ducts. Some of the ducts run, per normal building practice, through the attic and crawl spaces, while others run only inside "conditioned" (warmed and cooled) space. The test houses show that running ducts through conditioned space saves 35% of total heating/cooling energy. Because industry has already improved the energy efficiency of furnaces and air conditioners, Christian says, "[Ductwork] is one of the last big, untapped resources in energy-efficient residential building." The less-efficient equipment will be removed before the homeowners move in.

The goal in another house built in 2002 was to cut total monthly energy bills to zero, courtesy of roof-mounted photovoltaic panels and a slew of other experimental energy technologies. This house became a "living laboratory" when the Habitat homeowner family moved in in early November 2002. ORNL and the Florida Solar Energy Center (part of the University of Central Florida in Orlando) will closely monitor total energy usage and production for 12 months.

The first month's energy bill was $54, about half the average for conventionally built Habitat houses in the same neighborhood. With help from an electricity buyback program from the Tennessee Valley Authority, expected to begin in early 2003, and further fine-tuning of the photovoltaic and HVAC systems, Christian expects the house to approach an energy cost averaging just $20 per month over a 12-month period.

Housing accounts for 20% of U.S. energy consumption. The Building America program is intended to develop, test, and promote energy-efficient housing technology. Since 1995, Building America has helped build 18,000 homes. Project staff promote energy efficiency at 18 trade shows each year, but the Habitat demonstration houses help get the word out in a different way, says Christian: "With each Habitat house, you touch fifty to one hundred local volunteers, and also the subcontractors."

Subrato Chandra, project director for the Department of Energy's Building American Industrialized Housing Partnership at the Florida Solar Energy Center, says much of the interest in energy efficiency stems from the threat of lawsuits over health problems attributed to mold [see "Mold Insurance: Crafting Coverage for a Spreading Problem," p. A100 this issue]. But he sees the result as a win-win situation. "We are finding a groundswell of enthusiasm from builders wanting to build good houses," he says. Mold can be reduced by controlling moisture and temperature, which simultaneously improves indoor air quality, increases comfort, and improves energy efficiency.

"These things all go hand in hand," Chandra says. "Once we can show that through proper construction which also means energy-efficient construction--we can solve the mold problem, builders get excited about building better, more energy-efficient homes."