When a real estate survey released last week sparked a slew of news stories trumpeting "The Death of the McMansion," it sounded like great news for the environment. After all, smaller homes are more efficient to live in and less resource-intensive to build.

But on second thought, what will become of all those foreclosed-upon faux chateaus sitting unoccupied? Sure, a handful might be repurposed, but aren’t the rest doomed to demolition -- adding tons of debris to the waste stream, not to mention the materials and energy used to rebuild and redevelop those subdivisions?

Which really would be better for the environment: building smaller new homes or sticking it out with the existing starter castles, however oversized?

“The death of the McMansion is probably a good thing in the long run,” says Justin Horner, a smart growth expert and transportation policy analyst for NRDC. "Though there is a significant environmental impact to demolition and rebuilding, it’s not such a big impact that we have an environmental interest in keeping people living in these things."

Though it obviously would have been better to have gotten it right the first time, it will eventually pay off to try to do better moving forward. That way, hopefully, small homes built in the future will not only run more efficiently, they’ll also still be in-demand (and therefore less likely to be demolished) for years to come. This seems particularly likely since American households are shrinking (smaller families, more singles, and more couples waiting longer to have kids). Demolishing the right way -- with maximum repurposing and recycling of material -- will also tip the scales a little further.

Another point in favor of excising those Hummer-houses: a preference for more petite digs tends to go along with a desire to live in a walk-able community closer to an urban center, which has the advantage in what’s called "location efficiency."

"Large, new homes also tend to be built on the outskirts of towns [where lots are big and zoning restrictions are few]," Horner says. "Not only are you using more water and electricity at home, you’re also driving in from the middle of nowhere to go buy a carton of milk."

So go ahead and feel relieved if you see a wrecking ball heading for an exurban cul-de-sac full of garage Mahals. But keep your fingers crossed, hoping that developers have finally learned their lesson.