Katherine Wildermuth, 61, and John Jamison, 58

Walla Walla, Wash.

In 2004 the couple bought a 20-acre parcel of land and, with the help of a $15,000 grant from the Washington State Department of Fish and Wildlife, started restoring the natural habitat, which includes two salmon-bearing creeks. "We've always felt we need to be caretakers of the natural world," says Jamison. Meanwhile, they called on an architect to design a 2,000-square-foot house with energy-saving features.

Notably, the house is built on a convective slab - an insulated layer of concrete blocks laid directly under the floor - that helps keep the house at a constant 67°F year round. Extra-long eaves over the windows will block out high summer sun but let it shine in (and warm the concrete) in the winter. The couple are hoping to move in by March.

How much extra it cost: About $10,000. Wildermuth and Jamison say that they expect to make up for the expense within 20 years.

Would going green work for you?