Steve Glenn's home in Santa Monica California is the first LEED Platinum-certified single-family house in the country, featuring gray water to irrigate the lawn, and produces near-zero greenhouse-gas emissions.

"I realized that developers, not architects, control what gets created in the built environment," Glenn said. In response, the tech executive is rolling out a line of extreme-green homes similar to his own with KieranTimberlake, an architectural firm that focuses on sustainable design.

Cost is the biggest challenge when it comes to green living, Glenn says. At $250 per square foot for 2,500 square feet (plus another $40,000 for the foundation), the grand total was more than $765,000 to build (not including the price of the land). Glenn's next challenge: green design that's more affordable.

Building a house is expensive, and constructing an environmentally friendly home is astronomical. Glenn's solution for the average American is prefabricated construction. "Prefab allows you to build a house with smaller thresholds for tolerance," Glenn says, "and a tighter energy envelope." Prefab allows expensive up-front costs for green components to be amortized across many homes and mitigates extra rubble left behind, which account 30% of landfills. The Cellophane House (pictured) is on display this summer at New York's Museum of Modern Art.

Matthew Berman (left) and Andrew Kotchen (right) are architects with a cause: reducing the impact of housing on the environment. 50% of all greenhouse-gas emissions are building-related. Yet even as the housing market falls apart, McGraw-Hill Construction predicts that the green market building market will grow from $12 billion this year to between $40 billion and $70 billion by 2012. "There's this grumbling," Berman says, "It grows, it brings things to the center, and then you get this explosion."

Berman and Kotchen have won accolades for their work, including a competition sponsored by Global Green USA and actor Brad Pitt to design "zero energy" housing in the Lower Ninth Ward in New Orleans. Their firm, Workshop/apd, will oversee the construction of their "GREEN.O.LA," which includes five single-family houses and 18 apartments. The units feature solar panels, rainwater-collection systems and trellises to keep the interiors cool. "Good design is inherently more efficient and uses less materials," Kotchen says.

A McGraw-Hill construction study estimates that by 2010 as many as 10% of all American housing starts will incorporate energy-conserving features and appliances, including low-flush toilets and more-efficient heating and cooling systems. However, it will take a serious shift in American culture to push green living to the common homeowner. "Sustainability is a cultural problem, embedded in unsustainable lifestyles," says Wilfried Wang, a chair of architecture at the University of Texas at Austen.