Can Big Be Green?

The house Joe Monfredo built in Anne Arundel County has seven bedrooms, 6 1/2 baths and four fireplaces. There are a recreation room, a study, a media room, a gym, a second laundry room and a second kitchen.

The home, in Davidsonville, near Annapolis, is almost five times the size of the average new American house.

And it's good for the planet, Monfredo claims.

The two concepts of "green" and "big" hardly seem compatible. After all, green is synonymous with conservation. Big is closely linked with waste. Yet some eco-friendly homes these days are not just big, they're huge, and the relationship between size and greenness is not as clear-cut as one might think.

All else being equal, a small home is more eco-friendly than a big one. It eats up less in raw materials, emits less greenhouse gas and is more energy-efficient simply because it's smaller.

But who is to judge how much space a person needs, asked David B. Goldstein, energy program director at the Natural Resources Defense Council, an environmental group. If one 10,000-square-foot house owned by a family of four is "a bad thing," what about two 5,000-square-foot houses owned by the same family?

"It's really a matter of moral or economic judgment as to whether the home you're asking for makes environmental sense," Goldstein said. "Only the individual homeowner is in a position to know how much size satisfies basic needs, how much satisfies basic wants and how much is silly extravagance."

For decades, Americans have believed that bigger is better. The average size of a new home swelled by two-thirds from 1970 to 2007, from 1,500 to 2,500 square feet, according to the National Association of Home Builders. The "supersize me" phenomenon unfolded even as the average family size shrank, suggesting that people are buying bigger for lifestyle reasons, not function.

The way builder Jerry Zayets sees it, the desire to go green has not diminished that craving for space.

That's why he built a 6,500-square-foot house in Northwest Washington, now on the market for $1.59 million. With seven bedrooms, six baths and a dramatic two-story entry, the house feels vast.

"I know people walk into this house and think it's the Ford Excursion of homes," said Zayets, owner of Nexxt Builders in the District. "It's not. The energy costs of this home are less than my 1,200-square-foot rambler in Silver Spring. Many small homes consume more energy than the one I've built."

The Envelope, Please

The key is the envelope of the house, Zayets said. Each surface that touches the outside is insulated with a low-density foam that sprays on like a cream but expands to 100 times its size, seals air leaks and takes the shape of whatever space it's filling, he said. Traditional fiberglass insulation must be cut with a utility knife, making it tough to use for irregular angles and crevices.