most part, the green housing market mirrors the megahouse trends in the conventional homebuilding market. "My clients want to build green, but they want to build bigger," says George Ostrow, principal of Velocipede Architects, a leading sustainable design firm in Seattle. Ostrow links big green houses to fuel-efficient SUVs and other green-living oxymorons. "It's a contradiction of our culture," he said. Whether it's a McMansion or an architect-designed estate, big green homes offer a recognizably American take on eco-friendly trends sweeping the country. There's the 4,200-square-foot solar-powered home featured in Salon last month -- a house "so spacious it includes an entire guest wing the couple never uses." Rob Harrison, another Seattle architect who specializes in sustainable design, cites a 4,100-square-foot home -- including garage and attached greeenhouse -- he recently designed for a single family household in Redmond, Wash. Among other features, the house will incorporate advanced framing, Forest Stewardship Council-certified lumber, hardwood floors and plywood, as well as sustainably harvested cork floors. The main roof slopes south for future photovoltaic panels, and there is porous paving on the driveway. "We had many green features," Harrison said. "But ultimately, because of the size, we are still using more resources." The client's personal requirements, including room for a regulation-size pool table and a music performance atrium for 30 people, made it impossible to reduce the footprint of the house, Harrison said. "House size," he says, "is probably the most important criterion and often the most difficult one for us to meet." Not all green designers and builders hew to the notion that less is more. Take William McDonough, the visionary green architect who likes to invoke the cherry tree -- in which thousands of blossoms provide fruit so that one pit might take root and grow -- as a model for sustainable production. "No one would ever look at the ground littered with cherry blossoms and say 'how inefficient how wasteful,'" writes McDonough in his book, "Cradle to Cradle." Instead, he observes, the blossoms decompose and provide nutrients for soil, plants and other organisms. Nature, in his view, is both abundant and productive -- qualities that "eco-effective" design (a McDonough alternative to "eco-efficient" design) can and should emulate. Allison Ewing, a residential architect at McDonough's Charlottesville, Va., firm, applies this theory to the 4,000-square-foot-plus green homes she designs. "Our belief is that if it's solar powered, you can have all the hot water you want," she said. "As long as you have cradle-to-cradle design, we say, celebrate abundance." Responding to a question about house size and ecological footprint, Ewing reiterates another favorite McDonough saying: "We're not in the business of telling people to be less bad," she said. "We're about 100 percent more good." Ewing cites a recently designed 4,500-square-foot residence that incorporates geothermal energy sources, radiant floor heating and sustainably harvested wood -- a house that apparently catalyzed a local market for sustainably harvested lumber. A smaller residence, she said, would not have had the same impact on the local green economy. As a metaphor, design principle and incubator for sustainable markets, the idea of productive abundance is compelling. It's much less compelling when viewed in context of American consumption habits. Is nature abundant? Or is it frugal? When it comes to picking design metaphors, the natural world is, conveniently, a free market. And as Ostrow and Harrison point out, the trend toward large green houses is driven in large part by the lack of awareness surrounding square footage and ecological footprint, not because of any lofty ideas about nature's fecundity. A reflection of American priorities and lifestyles, the march toward bigger homes also gets a push from complex zoning regulations and real estate and banking practices. Mortgage banks lock in large house sizes by requiring the value of the home to be three times the value of the land, said Art Castle, executive vice president of the Home Builders Association of Kitsap County, Wash. "If you put a house outside of these perimeters, you create a market aberration," he said. "A lot of lenders are unwilling to support smaller houses." The bias toward large homes has even penetrated green-building rating programs, according to an analysis performed last year by the Pittsburgh-based Integrated Building and Construction Solutions (IBACOS). The study found that the Home Energy Rating System, a federal program that rates energy efficiency performance for new and existing homes, requires smaller houses to incorporate more advanced energy features than larger houses, assuming a given occupancy. "The whole motivation for doing the analysis was that house size is not being taken as seriously as it should be, " said Eric Newhouse, an IBACOS systems integration designer and the coauthor of the report, "Analysis of Energy Consumption, Rating Score and House Size." The paper was presented at the U.S. Green Building Conference last year. In 1998, Environmental Building News published an article comparing energy and materials use in large and small houses. Using data compiled by the NAHB and Energy Balance, the article showed that a 1,500-square-foot home with low energy performance standards will use less energy for heating and cooling than a 3,000-square-foot house with high energy performance standards. Because big houses tend to have more design features, the NAHB also estimated that large homes consume proportionately more materials. Thus a 5,000-square-foot house will consume three times as many resources as a 2,085- square-foot house, even though its square footage is only 2.4 times greater. Six years later, experts say the correlation between square footage and resource and energy use is still valid. Size matters even if a residence incorporates solar power, rainwater catchment and other "off the grid" technologies, says Newhouse. "Bigger houses use more materials," he said. "and there's no perfectly environmentally friendly material." Acknowledging the issue, some green-building rating programs have started to incorporate a matrix for house size. Like many green residential programs, PGE's Earth Advantage certification in Portland, Ore., is based on a combination of required measures and additional points that can be earned for a home's green features. Last summer, Earth Advantage created four advanced levels of certification, two of which incorporate a matrix for house size. For example, under the new Earth Advantage Gold Environmental and Water Efficiency package, a 2,500-square-foot home needs to earn 50 more environmental responsibility or resource efficiency points than a 1,999-square-foot home in order to earn the same ranking. The Vermont Built Green (VBG) program, which piloted last year and is recognized as the most comprehensive program in the country, takes this idea one step further. To earn VGB certification, a home must meet 54 requirements and earn at least 100 points. Under this system, the easiest way to earn certification is to meet the minimum requirements and build a very small house. For example, a two-bedroom house earns 100 points if it's 1,000 square feet; 25 points at 1,500 square feet. By contrast, a four-bedroom house at 5,200 square feet loses 100 points, meaning that the house will have to earn 200 poin