If your air conditioning unit sits out in the sun, consider planting trees or shrubs...

A house in a box? In construction, prefabrication means creating the pieces of a building-complete with interior walls, flooring, windows, and all the pipes and wiring-in a factory. The pieces are then hauled to the building site for assembly-a practice that saves time, money, and, in many cases, resources. Prefab housing, first popularized almost a hundred years ago, has been undergoing a resurgence in recent years, showcasing a more modern look and touting itself as a green way to build. Some critics argue that prefab construction can be just as wasteful as on-site construction, and that many prefab homes are built with eco-unfriendly materials such as vinyl. As with many other purchases, buyers might want to ask some questions to be sure the companies they are working with are as environmentally responsible as they claim.

The two most important things to consider when shopping for "green" furniture are: What is the...