It was just about five years ago that I sat down with my colleague Alanna Stang to begin work on a survey of ecoconscious residential design, ultimately published as The Green House: New Directions in Sustainable Architecture (Princeton Architectural Press, 2005). The book’s thesis was straightforward: The green-design and high-design wings of the architecture profession, which had looked at one another for so long across a chasm of mutual disdain, were beginning to find common ground.

In some ways, the task he set before me was similar to the one Alanna and I took on at the start of our research. In both cases, the goal was to find a group of residential designs that pursued ecoefficiency and architectural excellence, even innovation, with equal vigor. Still, it seemed foolish to ignore the fact that the way Americans think about sustainable design has shifted dramatically in the intervening period. Five years ago, there were still many leading architects who equated green architecture with communal, back-to-the-land efforts of the movement’s earliest days. Now it is impossible to walk through the offices of a corporate firm without viewing a model for a green building. And thanks to the U.S. Green Building Council’s LEED ratings—which have caught on with remarkable speed since their introduction in 2000—architects, contractors, and clients alike have a baseline standard for measuring a building’s commitment to the environment.

Meanwhile, green design has gone mainstream. Vanity Fair and other mass-market magazines rushed to get special green issues on newsstands, filling them with stories about Hollywood celebrities outfitting their Venice bungalows with solar panels and gray-water systems. Al Gore won an Oscar, then a Nobel Prize, for his work on global warming.

It didn’t take long, though, for what’s been dubbed “eco chic” to tip into excess. In some cases, it has headed straight toward parody. Earlier this year, the Robb Report—a glossy lifestyle magazine aimed at readers with assets of $5 million and higher—published a special Green Living issue, featuring “Homes That Tread Lightly on the Land.” Those homes, of course, were in each case about the size of a college dorm and executed in a buttery, grandiose, marble-heavy style that might be called Château Vert.

Part of the problem is simply defining something as amorphous as living or building in an environmentally friendly way. The LEED program, for example, has come under heavy scrutiny lately; architects, including Thom Mayne, whose 2007 San Francisco Federal Building pursues a number of innovative green-design strategies, have complained that it promotes a checklist mentality and pays too much attention to how buildings are constructed and not enough to how they perform over time.

To which I would add: The problem in this country with any rating system is that once our responses to a problem can be quantified and ranked—as with LEED points—it is only a matter of time before they’re wielded primarily as marketing tools.

By contrast, the coverage of sustainability that I find myself learning the most from these days moves away from a promotional or self-satisfied tone. Consider Michael Specter’s essay in a February issue of The New Yorker, which reports that “the calculations required to assess the full environmental impact of how we live can be dazzlingly complex.” Specter points out that the concept of the “food mile”—a measurement of how far a banana or potato has to travel to reach your local grocery store—can be highly misleading, because it relies on overly simplistic assumptions about what’s good and bad for the environment. “The environmental burden imposed by importing apples from New Zealand to Northern Europe or New York,” Specter writes, “can be lower than if the apples were raised fifty miles away.” What matters is not just distance, but other factors such as how efficiently the apples are grown or whether they are shipped or trucked to their destination. Like a LEED rating, the food mile is an attempt to measure something very complicated in very simple terms, and results, perhaps, in a kind of reductionism.

Similarly surprising was Brandon Koerner’s recent dispatch on Slate.com, asking whether it’s more ecofriendly to read your morning newspaper in print form or online. It turns out there isn’t much difference in terms of total energy consumption: Powering your computer and its monitor burns nearly as much carbon as the printing plants and delivery trucks that get the old-fashioned newspaper to your front door.

These articles suggest that the best way to understand and pursue green strategies, whether political or architectural, is to dispense with the bromides and the easy labels and to start recognizing that the answers are more complicated.

Ultimately, we decided to approach this year’s Record Houses in the same spirit. Every architectural movement gets less coherent and more fascinating as it evolves; architects have always found opportunity in the cracks that appear as the edifice of theoretical certainty begins to crumble. That was true for the Gothic, the Baroque, and Classicism. It was certainly true for Modernism. And it’s becoming truer every day for green design.

There are many architects who feel strongly that cities, with their density and shared infrastructure, should be the centerpiece of any budding green culture. Others see more opportunity in an effort to live holistically, with an efficient little house perfectly sited on a piece of land just big enough for a vegetable garden. Still others see aggressive government action—here and in the developing world—as the only path to sustainability.

All of them deserve to be called green architects. It is in the aggregate of these various approaches that real progress will emerge. Taken as a group, the projects we ultimately chose suggest not only that sustainable architecture is getting harder to define with any precision but also—and here’s the key—that we should find that difficulty encouraging. To put it another way: Disagreements are good. So are factions. Instead of charting a confluence, as our book did five years ago, the goal here is to document a rich and growing variety of approaches to sustainability—and maybe complicate the definition of green architecture along the way.

Those approaches can be sorted into four rough piles. The first makes a point of turning compactness to architectural as well as ecological advantage. The Rolling Huts, in Washington State, by Olson Sundberg Kundig Allen, come in at 440 square feet apiece, while Darren Petrucci’s VH R-10 gHouse, in Massachusetts, has a 600-square-foot footprint. They likely rank as the two smallest projects ever featured in a Record Houses issue.

The second strategy answers sustainability’s challenge with technical innovations. Hi-tech green design—exemplified in this issue by Werner Sobek’s sleek, remarkable H16, near Stuttgart, Germany—puts a premium on materials and systems to make houses hyperefficient. Sean Godsell’s Glenburn House, in Australia, also uses a matrix of sophisticated green systems, though importantly without compromising its elegantly latticed, low-slung form.

The third approach has its roots in organic architecture and the Arts and Crafts movement: It’s powered by old-fashioned, low-tech solutions like siting, passive heating and cooling, local materials, and general economy. Rather than aiming for a kind of spare, Modernist universalism, in the manner of Sobek, it takes its formal cues from its region, landscape, and context—and then, significantly, coats it with a sheen of sophistication that reflects the challenges of building locally in a globalized world. This sensibility is illustrated by Studio Mumbai’s stunning Palmyra House on the Indian Ocean, Nora House by the endlessly creative Toyko firm Atelier Bow-Wow, and Wall House, outside Santiago, Chile, by FAR frohn&rojas.

The fourth and final approach focuses on preservation and community. As Richard Moe, president of the National Trust for Historic Preservation, put it recently, “The bottom line is that the greenest building is one that already exists.” The Maltman Bungalows, a preservation project by Drisko Studio Architects, promotes history, density, neighborliness, and walkability—all in the middle of a city, Los Angeles, that isn’t known for any of those things. Skene Catling de la Peña’s Dairy House, in England, meanwhile, not only brought a 1902 structure back to life but did so using local materials, craftsmen, and know-how, expanding the notion of green design to include what the client calls “social sustainability.”

By defining sustainability in such a broad and thoughtful way, the Dairy House also offers a way to summarize the attitude of this year’s Record Houses as a whole. As Diana Lind writes in her description of the project, “When you get down to it, whether a work of architecture is green is usually a shade of gray.”