When many people hear the term "green home," the first image that comes to their minds is one of a sleek, ultramodern home that uses space-age technology to minimize its impact on Earth. Green homes, these people reason, are only effective if they use the absolute latest in modern technology, design and construction.
But some green homes have been here for a while. In fact, many of the so-called "green" design features that modern homebuilders use to improve new homes' efficiency have their roots in very old -- and sometimes ancient -- design and construction techniques.
Human beings have been adapting their homes for efficiency for millennia. Some of the earliest homes, such as those of the ancient Pueblo people of the American Southwest, feature green designs and techniques that were later seen in homes built by famous architects, such as Philip Johnson and Frank Lloyd Wright.
If you're considering building a green home or making green improvements to your existing home, check out this list of historic green homes. Your project may be separated from these structures by hundreds -- or thousands -- of years, but the basic principles that made them efficient could work for your own project.