Past Is Prologue

With today's focus on "green" buildings, it's no wonder that so many of the new towers scraping the Chicago sky are heralded for their benign impact on the environment. But what about the thousands of other high-rises and humbler structures already here? Improving the energy profile of older buildings is a much harder feat. Before virtuous materials and systems can be installed, the old stuff has to be ripped out and hauled off. Managers of existing buildings also have to keep operations humming so as not to disrupt rent-paying tenants. "It can be like performing surgery while the patient is still awake," says Mark Bettin.