Passive Homes Save Energy

It may be possible to heat your living space by hosting a dinner party. With cutting-edge, well-insulated “green” homes, you may not even need a furnace or boiler, just your body heat.

“It’s like living in a glass thermos,” says Dr. John Eckfeldt, a physician who built a passive home in bitter-cold Isabella, Minn. Eckfeldt notes the temperature inside remains comfortable even as he watches snow falling outside.

In these homes the windows never feel cold, nor do the concrete floors, even though they don’t have in-floor heating. The homes also are super quiet because of insulation.

The technology started in Europe, where thousands of such homes have been built. Now it’s starting to catch on in the United States as consumers seek to cut energy bills.

Passive homes don’t require expensive solar panels or wind turbines. Instead, they focus on old-tech building science that is capable of reducing energy use up to 90 percent.

Blast From Past?

These homes are different from passive solar homes of the 1970s – south-facing windows for heating, thick walls and roofs, as well as efficient appliances and lighting.

The secret today is in superior insulation and air sealing. A mechanical system brings in fresh air, and it is heated or cooled as needed.

“It’s growing exponentially,” says Tom DiGiovanni, who heads the Passive House Alliance, a nationwide nonprofit group established last year to promote the standard.

Proponents say the passive standard’s prime tenets – insulation and air sealing – also can be used by owners of traditional homes because windows are becoming more affordable and building codes are demanding greater efficiency.

“It could be mainstream in five years,” says Nate Kredich, vice president of residential market development for the private U.S. Green Building Council, which has its own “green” rating system. The group, comprised of community of leaders, is working to make green buildings available to everyone within a generation.

By The Numbers

Passive homes cost 6 percent to 12 percent more than other types of new homes, but they recoup their investment in lower utility bills in seven to 12 years, according to DiGiovanni.

“The biggest extra cost is the windows,” he says, noting U.S. companies only recently began making triple-pane types. California’s Serious Materials makes ultra-efficient dual-pane windows which some U.S. passive homes have used.

“It’s innately reasonable,” says architect David Peabody, who designed the first passive homes in Washington, D.C.

He says the extra cost was about 8 percent, but the annual utility bills for the 4,200-square-foot homes are projected to be about $750.

U.S. households spent an average of $2,639 on energy for homes that size in 2005, the most recent year for available data.

Home Designs Limited

Most passive homes have limited windows and a boxy shape. Homes with curves and larger footprints require extra insulation and sealing, adding cost. Huge curved windows with upscale finishes can cost $450 per square foot.

John Semmelhack, a passive house consultant from Charlottesville, Va., says the criteria are very stringent. This is especially true if the owner is trying to achieve the top rating from the U.S. Green Building Council.

Regardless of location, passive homes cannot have a heating or cooling load above 4,755 BTUs per square foot. This is about one-tenth that of homes built to current building codes.

Passive homes also must be airtight, with meticulous sealing of ducts, joints, and hairline cracks.

To avoid overheating, the house must have exterior shading, ventilation and a cooling system. Generally, only a small solar panel is needed to meet the requirements of a “zero energy home.”

The Green View

WMB believes passive energy homes may provide many opportunities for manufacturers and suppliers to meet consumer demands, from materials to design.

As energy costs – particularly those for heating fuel oil – continue to jump at alarming and unpredictable rates, the consumer market will benefit from growing availability of passive homes.

It’s time to think inside, not outside, the box!

TechMan