It's been 2 ¹/2 years since the architect began building his eco-friendly home, and friends, neighbors and clients are still asking Cross if he'll be giving tours of his 3,000-square-foot, two-story home once it's done.

Even as the finishing touches are being applied—tiles laid and appliances installed—Cross can't say when that completion date will be.

"Part of why I'm taking my time is that I'm trying to do it as green as possible," he says. "I've spent a lot of time looking for materials and finding things that are reused or recycled."

The house itself is made of recycled earth, waste product from a quarry in Sonoma. Contractors from Napa's Rammed Earth Works Inc. brought in 20 truckloads of earth, each weighing 20 tons, to build the 18-inch-thick walls and construct the floor tiles. Of that material, only a small pile remains in the Crosses' backyard.

Besides having walls made of earth, which provide a natural heating and cooling system, the house features other environmentally friendly and energy-efficient designs. The ceilings are insulated with shredded denim, and the water is heated via a ground source pump. The large beams in the ceiling are made from reclaimed lumber.

Cross installed photovoltaic solar panels on the roof that produce all the electricity he and his family require. Cross and his wife, Amy, received a $700 credit from PG&E for going off the grid. They used half the money to pay off their gas bill.

This environmental architecture extends outdoors, where the beams in the half-constructed garage are made from composite materials. While some green building materials require homeowners to spend more green, Cross says composite beams cost less and are three times as strong as those made from a single wood.

"Lots of people use them who aren't even thinking green," he adds. "Lumber is half as strong as it used to be because they're growing trees really fast, so beams have to be bigger."

Cross says it's fairly easy to find environmentally friendly substitutes for standard building materials. He's done just that with the wood-framed houses he's designed, including several in Willow Glen. "We've included dozens of little things to make it more green," Cross says. "We do this with all our projects. It's not like you have to go to this extreme."

Cross often buys lumber that's been certified by the Forestry Stewardship Council, which ensures that no ecosystems or wildlife were harmed when the wood was harvested. And he steers clear of carpet, which contains formaldehyde, and vinyl flooring, which is made from PVC and produces dioxin. In his own home, he's considering bamboo flooring for his daughters' bedrooms.

"It's a sustainable crop," he explains. "It grows in four years and it's as hard as oak, but you're not cutting down a 100-year-old tree."

In designing other people's homes, Cross also thinks in eco-friendly terms from the ground up. The process used to manufacture cement used in standard housing produces almost as much carbon dioxide as petroleum manufacturing. So Cross replaces 15 to 25 percent of the cement he uses with fly ash, a waste product from coal manufacturing.

The Crosses have been living in a wood-framed home themselves while work on their new domicile continues.

But there is one finishing touch the Crosses won't have to worry about, painting, since earth walls are extremely low maintenance in that regard. Cross says rammed-earth structures can last for years with no visible wear and tear.

"The whole idea is that I don't have to paint it—ever," he added.