Lawn-covered suburbs seem like they would be more suited to green living than cramped cities. But more people are gravitating to urban areas in the name of ecology. City dwellers drive less and typically live in smaller homes, which require less energy to heat and cool. Services are usually clustered together, encouraging walking and better use of available land. Suburban families use three times as much energy as urban families of the same size, according to researchers at the Brookings Institution. Visiting fellow Christopher Leinberger says more people would choose to live in more populated areas if housing was easier to come by. "Only 10% to 15% of our housing stock is walkable urban," he says. "We have pent-up demand for one and overproduction of the other." Leinberger, who's also the director of the graduate real estate program at the University of Michigan, estimates that half of Americans would prefer to live in a town or city, where they can run errands by foot. "In these sprawling suburbs you can't walk, can't take a train, can't ride a bike, your kids can't walk to school," he says. "People are getting bored with having to drive everywhere." This is why urban neighborhoods and suburbs with good public transit have held their value in the real estate crash better than remote suburban enclaves, he says. Luckily, he says, as more people migrate back to towns and cities in the coming years urban life is only likely to get better.