On a frigid morning in early February, about 30 building-industry executives gathered in the conference room of Bovis Lend Lease, on the ninth floor of the MetLife building. It was by all appearances an unremarkable event, except that this group of seasoned architects, developers, engineers, contractors, designers, and planners had come to plan an environmental revolution. They do this on the first Wednesday of every month, before scurrying off to jobs at many of the most prestigious building firms in the city.

The topic was indoor air quality, and Catherine Bobenhausen, a mild-mannered industrial hygienist who is one of New York State's foremost experts on the subject, had been invited to address the group about testing for pollutants. She used a lot of jargon, but she didn't mince words. Rather than constantly testing for noxious chemicals in our air ducts, said Bobenhausen, we should construct buildings that are less toxic and better-ventilated.

The assembled construction experts, most of them members of the U.S. Green Building Council, didn't disagree, but neither did they let Bobenhausen off easy. For the next hour, she fielded a barrage of pointed, technical questions about how to build for cleaner indoor air. Time is too precious for an academic discussion. These hands-on pros want to design and construct their buildings "greener": to use energy more efficiently, preserve clean air and water, provide healthy indoor environments, ease strain on the infrastructure, and last for the long haul. Natural daylight as an alternative to electric lights, central air filters to flush out pollutants--old ideas, perhaps, but in the cost- and risk-averse world of real estate development, such measures are still radical.

Similar early-morning conferences are regularly taking place around the country. Not looking to be martyrs for a half-baked cause, industry people are signing on to green building precisely because they believe it has a real chance of becoming standard practice. They are betting that over time more of their colleagues will agree. "Sustainable, high-performance building is an opportunity for a cleaner, leaner and greener future," says Susan Kaplan, a manager of green-building projects for the Battery Park City Authority, which mandates that all new construction in Battery Park follow a strict environmental code.

But don't look to the New York City Department of Buildings, which regulates construction, to force the city's developers to build green. Even now, nearly 400 volunteer experts from all areas of the industry are working in 13 technical committees to rewrite New York City's massive building code, combing through it word by word, and there's little chance that the revisions will include requirements for green building.

The committees are working from a shared desire to reduce construction costs, maintain safety standards, and strip out mandates they consider nonessential. They are trying to adopt a "performance-based" code, which sets minimum benchmarks for, say, a building's energy efficiency, but does not explicitly state ways to meet the standard. "The heart of the difference between prescriptive and performance-based codes is that prescriptive can strangle out development of new concepts and new technologies," says Marzio Penzi, an associate commissioner at the Department of Buildings, responding to the suggestion that the new code could require builders to go green. "We want to include language that will enable new technology--if the designers chose to do it. We want to point in the right direction, but we're not going to tell you exactly how to get there, because we want you to always be coming up with better ways."

Most of the country follows the same approach when it comes to regulating construction. While interest in green building is booming, only a few cities--notably Boulder, Colorado, and Richmond, Texas--have written mandates into their building codes.

The green-building vanguard have concluded they're better off not fighting for government regulations. Instead, professionals like those gathered at Bovis think it's more essential to convince their colleagues that adopting sustainable building practices is simply good business. They reason that once enough builders and developers start using the materials, mechanisms and techniques they've pioneered, those products will become less costly and more available, skills will spread, and practices that are now unusual will become the norm.

"The government could just outright legislate it, but I believe in choices in this world," says Petr Stand, a New York architect who specializes in urban renewal projects and has been opting to build green for years. "The goal is to get a building that is joyous, not just another box with windows. But there will be resistance to the city telling builders how to build. So we should at least give developers the choice, and they could be incentivized. That route is more palatable politically and economically."

Think back to pesticide bans or regulations that limit logging in old-growth forests. By relying on the marketplace to promote positive change, the green building movement is utterly different from most earlier environmental campaigns. And there is a lot at stake. Residential and commercial buildings in the U.S. collectively consume more than a third of the nation's energy, two-thirds of electricity and 40 percent of raw materials. They also account for large shares of greenhouse gas emissions, solid waste and air pollutants linked to respiratory illnesses such as asthma.

How buildings are made, and what they are made of, has huge consequences for the health of their occupants, too. "There is strong evidence that characteristics of buildings and indoor environments significantly influence the occurrence of communicable respiratory illness, allergy and asthma symptoms," concluded William Fisk, a scientist at Lawrence Berkeley National Laboratory, in a landmark 2000 study. The Environmental Protection Agency agrees: It lists indoor air quality as one of the top five environmental health risks facing Americans today. The buildings we live and work in, it seems, can actually make us sick.

Fisk's research points to solutions. He offers evidence that improving the air filtration in existing buildings can result in tens of millions fewer cases of asthma, colds, flu, and other afflictions known or thought to be environmentally related.

But green building advocates know they can't win their case with developers based on public health benefits alone. "Decisions about energy performance and efficiency are always bottom-line decisions," explains Alan Traugott, a principal at the global engineering firm Flack + Kurtz.