Shelter, like many other elements of human existence, comes at an extraordinary cost to our planet and its inhabitants. In the U.S. alone, construction of 1.2 million new homes a year results in a massive drain on Earth's natural resource base. Today, nearly 60 percent of all timber cut in the U.S. is used in building houses, not to mention construction wastes and the huge amounts of resources used in the day-to-day operation of the "modern" household. In addition to environmental costs, there are the personal economic costs—the thousands of dollars each homeowner spends each year to heat, cool, and power our homes.