The purchase of a home is the largest and most important investment most people ever make. And one of the most influential factors in that decision is the energy efficiency of the house. In fact, a National Association of Home Builders (NAHB) survey has found that two out of three homebuyers list energy efficiency as a primary consideration when buying a new home. And more and more potential home buyers are becoming concerned with energy efficiency as experts still predict energy costs to increase throughout the decade.