Some in the industry argue that buyers never truly craved all that surplus space and took it only because that was the way the marketplace measured the worth of their investment. “We have to get out of the dollars-per-square-foot mind-set,” says Sarah Susanka, an architect and author of “The Not So Big House.” “I’ve been on a crusade to get people to think this way for years.” She says she was inspired to write her book — which recommends that home-buyers adjust their space expectations downward by a third and spend the money they save on creating a well-designed interior — after years of hearing the same sentiment from her clients: they were hoping to make a profit at resale, so they had to meet the market’s space expectations, not their own. Susanka says that the success of “The Not So Big House,” which has sold hundreds of thousands of copies since its publication 12 years ago, proves there is room for alternate conceptions of value.

In today’s marketplace, homebuilders are finding that smaller models are selling more reliably, and many are reassessing old marketing assumptions. “In many of our markets, there was an attitude that whatever you buy, you need to stretch, because in two years you’ll be able to sell it for double,” says Jeffrey Mezger, the chief executive of KB Home, one of the nation’s largest builders. With quick profit expectations dispelled, the average size of a KB house has fallen by almost 20 percent since the peak. The company recently introduced a line called the Open Series, homes that have flexible floor plans and low energy costs and run as small as 1,200 square feet.

The trend does not necessarily indicate, however, that Americans have suddenly decided they desire less. Homebuilders are shifting to compete with the cut-rate prices of foreclosures. Nowhere in KB’s marketing for the Open Series will you glimpse the word “small.” Even some enemies of the McMansion say it’s impossible to make a selling point of asceticism.

“Everybody hates the Calvinist sacrifice; they just don’t want to hear of it,” says the architect Andrés Duany, a founding father of the New Urbanist movement and a mentor of Marianne Cusato’s. Duany argues that the sprawling homes of the last decade actually met a need, albeit imperfectly, by reproducing internally what suburban communities lacked: an exercise room substitutes for a park, a home theater for the Main Street cinema. Buyers will only accept smaller homes, he says, if their surroundings compensate them. “The idea that you can promote things — that a developer is actually going to come out and say, ‘Marianne’s house is more virtuous,’ is ridiculous,” Duany says.

A real, live edition of the Home for the New Economy now stands near the end of a street in North Augusta, S.C., behind a white picket fence in a residential development called Hammond’s Ferry. The house owes its existence, in part, to the ideals of LeylandAlliance, which builds communities in the New Urbanist vein, but it’s also a practical concession to the distressed times. Hammond’s Ferry, which is situated along the Savannah River, hit the market in 2006, initially offering up a street of antebellum-style residences that ran as large as 4,000 square feet and cost an average of $500,000. The Home for the New Economy, priced at about half that much, represents a definite adjustment.

“If there was a tactical error we made, it was in the direction of going more toward the ‘wow,’ ” said Turner Simkins, the general manager of the project, as we stood atop a condominium building and surveyed a street of generously proportioned homes with columned two-story porches. On a color map of the Hammond’s Ferry master plan, the building was surrounded by some 450 beige rectangles, lots mainly set aside for single-family homes. So far, 88 houses have been built, 78 of them sold, and many of the lots on the map were still covered by uncleared bramble. Simkins said the homes that were finding buyers, unsurprisingly, were those priced below $250,000, but the developer had found it difficult to convince upscale Southern builders that there was money in modesty. Marianne Cusato’s house was there, as much as anything, to provide a different model.

Some skeptics have questioned whether the Home for the New Economy actually demonstrates much of a change. “I really think the whole thing is a marketing ploy,” Witold Rybczynski says. “Seventeen hundred square feet is not a small house.” Yet in North Augusta, the problem with the place appeared to be quite the opposite: people had trouble imagining how you could sell something so minuscule. One day I had lunch with Cusato and Thomas Blanchard Jr., whose firm was marketing Hammond’s Ferry. Blanchard explained that along the Georgia border, the crash had actually caused new houses to grow even larger. Crown Communities, an Atlanta-area builder, had snapped up suburban land at depressed prices and was erecting billboards that crowed, “Houses from $47 a square foot.” One of its largest models was called the Titan.