The McMansion phenomenon is likely to survive both the residential property slump and the popularity of green design, but communities are increasingly opting to regulate house size. Even Los Angeles, often blamed for spawning the culture of sprawl, is evaluating a measure that would limit the size of single-family infill housing—some 300,000 properties.

Although there is no single set of nationwide data on such ordinances, the National Trust for Historic Preservation tracks the issue through its anti-teardown initiative. In a May 2006 study it found that more than 300 communities in 33 states have taken steps to combat teardowns and overbuilding by imposing demolition delays, limits on square footage, and creating conservation districts. “We’re finding that it’s as much about what goes up afterward as what comes down,” says Adrian Fine, director of the Trust’s Northeast field office in Philadelphia.