MICHELLE KAUFMANN BELIEVES THAT buying an environmentally friendly home should be as simple as ordering a pair of sneakers. Sitting at her laptop in her Oakland, California, office, the architect goes to the Nike Web site, chooses a shoe, and clicks a few buttons. Moments later her customized sneakers are ready for review: white with orange laces and an orange swoosh, the initials "MK" stitched on the tongue.

The process for ordering one of Kaufmann's solar-ready, sustainably built, water- and energy-efficient modular homes isn't that different. She offers three basic designs, each of which uses ecofriendly materials like bamboo flooring, recycled-glass tiles, and efficient dual-flush toilets. Clients choose a model, then Kaufmann meets with them to figure out the details and price. They can customize finishes, select the number of bedrooms and bathrooms, and decide whether to have the house fitted with solar panels. A few months after final permits have been granted, trucks roll up to the client's building site and deliver the house in sections. It takes only a couple of hours to position the modules, and another four to six weeks to complete the finish work. The prefab model costs 20 percent less than an identical site-built house and takes a third less time to construct. All this is key to Kaufmann's mission: making green architecture accessible to everyone. "People want to do the right thing," she says, "but it has to be affordable."

Kaufmann's career in home building started out more conventionally. A native of Iowa, she got her master's degree in architecture at Princeton University and then spent five years working with Los Angeles architect Frank Gehry, who is known for building exuberant landmarks like the Guggenheim Museum in Bilbao, Spain. But when Kaufmann moved to the San Francisco Bay Area in 2001, she flew straight into the buzz saw of an overheated local real-estate market. She and her eco-builder husband, Kevin Cullen, spent six months being outbid on houses. "It was awful," Kaufmann recalls.

At last the two decided to build their own house. They bought a narrow lot in the semirural Marin County town of Novato, and Kaufmann designed a building that would embody the values she had grown up with in Iowa: efficiency, practicality, and a deep connection with the outdoors. She likes rooms that have multiple functions, courtyards and other outdoor spaces that make a house seem bigger than it is, and designs that exploit cross breezes for ventilation and clerestory windows for light. "I grew up around barns," she says. "A friend of mine once said that it's hard to find a badly designed barn. They're designed for functionality and for climate."

Kaufmann and Cullen dubbed their home the "Glidehouse" because it has so many sliding components, including doors and exterior sunshades that can be used to control light and temperature. Friends who saw the house when it was still under construction asked if they could get one too. "I thought, 'Good question,'" she says. "And I began researching mass production."

Kaufmann found a factory that specialized in prefab housing and was willing to try something new. It built a three-bedroom Glidehouse identical to her home in Novato in only four months at a cost of $182 per square foot. (The Novato house took 14 months to construct and cost $233 per square foot.) Kaufmann was on her way.

Prefab has so long been associated with flimsy trailer homes that it's a bit of a mental adjustment to realize that it can actually improve on traditional, on-site building methods. The controlled environment of a factory means that construction materials don't sit outside for weeks, getting moldy or warped. And because a factory can store leftover materials, little gets thrown away--which is critical given that construction debris takes up nearly a third of the nation's landfills. In other countries, prefab is already the standard; more than 70 percent of new homes in Sweden are factory built.

Judging from the amount of attention Kaufmann's work has gotten, prefab could catch on in the United States too. More than 100,000 people walked through a Glidehouse when it was on display at the National Building Museum in Washington, D.C., earlier this year.

Today Kaufmann has built 17 prefab homes and has 75 more moving through the pipeline. She bought her own factory near Seattle, a location she chose because it is close to the mills that produce her framing, cabinetry, and flooring. The factory can now complete a Glidehouse in a month. Kaufmann's houses cost between $185 and $250 per square foot, depending on the model and location, and she'd like them to be cheaper yet. "Because we want them to be accessible to all, we want the costs to go down," she says.

While her first customers tended to fit the stereotype of the Prius-driving, NPR-listening eco-consumer, Kaufmann is increasingly fielding inquiries from people who just want an attractive, affordable house. "People think 'green home' means straw bale or made out of recycled tires," she says. "Or they think they can't afford it. We're trying to demonstrate that people can have green homes simply by making smart choices."

Photo by JMC Photography; used with permission.