Now is the time, or so the media would have us believe, to be green. Al Gore is preaching the gospel of sustainability in multiplexes across the country. Elle and Vanity Fair magazines published dueling green issues this spring. And tonight, a six-part series on sustainable architecture and design — "Design e2: The Economies of Being Environmentally Conscious" — begins on PBS.

The series is narrated by Brad Pitt, a celeb, architecture buff and father of a new baby girl. (Those two facts are not unrelated, as it turns out: The kid's middle name is Nouvel, presumably in honor of the hip French architect Jean Nouvel.) If it has certain blind spots, particularly what sports fans call East Coast bias, it's also an engaging overview of the most prominent players, recent breakthroughs and stiffest challenges in sustainable architecture. And it's produced with enough panache — particularly in the brooding camera work by Robert Humphreys, which owes something to trendy architectural photographs by Olivo Barbieri — to make its more medicinal lessons go down quite easily.

Pitt starts each episode with a rhetorical introduction: "They use 40 percent of the world's energy and emit 50 percent of its greenhouse gases. They are not the cars we drive. They are the buildings we work, live and grow in." Those statistics aren't new, but they don't seem to have sunk in yet, particularly with the environmental activists who continue to make the SUV the bete noire of the green movement.

Friday's installment, on New York City, is essentially a made-for-public-TV version of an article by David Owen that appeared in The New Yorker magazine last year. Owen made the counterintuitive case that New York is the greenest city in America, simply because it's the densest — because its residents are more likely to use public transportation and to live in apartment buildings that share heating and cooling and water systems. He describes New York as a "community of consumption," and he means that in a good way.

Owen now lives outside the city, in that great, leafy land of leisure that wealthy New Yorkers call "the country," and it is a little odd, but also entertaining, to see him interviewed as he stands in the driveway of his rambling clapboard house, coffee mug in hand, complaining that he and his wife have put on weight because they just don't walk as much as they did in New York.

The episodes that follow look at a handful of community-activist architects. They include Sergio Palleroni, who sends his students at the University of Texas-Austin to build energy-efficient housing in Mexican slums, and Cameron Sinclair, of the nonprofit Architecture for Humanity, who makes the case that the architectural profession is faced with a crucial choice, as he puts it, "between aesthetics and ethics." The series devotes one full installment to Chicago, where Mayor Richard M. Daley has embarked on a green crusade, another to Boston's Big Dig and a third to China, which is now urbanizing more quickly than any society ever has, with consequences for the environment that have already been felt around the world. In fact, Pitt tells us, a full 25 percent of "the particulate matter floating above Los Angeles" can be traced to China. And it could get worse, since China is planning to build housing for 400 million people in the next dozen years.

While those episodes are wide-ranging, making the case that green design is connected not just with architecture but with politics and urban planning, the installment on New York sets the tone for a series that sees virtually no middle ground between urban and rural life. But it has held little meaning in America for several decades. The vast majority of new construction in the country is happening either in cities that the pundits on view here dismiss as insufficiently dense or, more to the point, in sprawling suburbs, exurbs and gated communities.

Since relatively few Americans driving gas-guzzlers and living in McMansions will be persuaded by a PBS special to move into Manhattan — or could even afford to — the most helpful question a series such as this could answer is how dense suburban Southern California or Florida would have to get, or how drastically their building codes would have to change, before they could be considered even remotely green. It might also have enlisted as a dissenting voice the author Robert Bruegmann, who points out in his most recent book that sprawl was pioneered not by Angelenos but by Romans.

It's common these days to hear about the coming "green revolution," as if sustainability were Marxism and already the environmentalists were massing in the streets behind their straw-bale barricades. In fact, truly green design is less extreme and less glamorous than that; it's a balancing act between the global and the local, the holistic and the piecemeal. A typical choice for an architect building a new house and trying to make it green is between buying one kind of building material that's not green but is available locally and another that's fully recycled but has to be trucked in from 2,000 miles away.

The series is most effective when it acknowledges that sustainable architecture will become the norm not when the American public suddenly and dramatically demands a new approach but when universities decide, as they are beginning to do, to make green design a fundamental part of architectural education. Or when architects in their 60s and 70s, who as a generation could hardly care less about sustainability, finally go into retirement.

Revolution, alas, is always more glamorous than gradual change, and it definitely plays better on TV. The producers of this series understand all too well that we live in an odd age in which Hollywood glamour has become entwined with global catastrophe. When we think of Hurricane Katrina, we remember Sean Penn in a boat. And when we hear about Darfur, Sudan, we picture George Clooney on CNN.

For that matter, both of Shiloh Nouvel Jolie-Pitt's parents have been spending most of their time in recent months not on movie sets but on various camera-ready humanitarian missions. Count this series as one more.