Paul Kennedy and Teresa Kennedy, 40 and 33

Austin, Texas

The Kennedys are downsizing from a 3,600-square-foot spread to a custom-built, totally green 2,400-square-foot contemporary house, in hopes of keeping a tighter lid on energy and water bills. "We're spending money to heat and cool space we don't use," says Paul.

It will be made with a 10-inch-thick energy-efficient insulated concrete wall and topped with an insulated metal roof. The couple will draw water from a collection tank that filters rain, and reuse it for irrigation. Ground broke in December; the house is expected to be complete in August.

How much extra it cost: $12 a square foot, but Paul says he "expects to save money in the long term."

Would going green work for you?