If you've been carefully sealing electrical boxes, but buying cheap windows and neglecting to gasket beneath your wall plates, you've probably been throwing dollars to the wind. The story is told by the accompanying chart, which was created by Dennis Creech of the Southface Energy Center in Atlanta, Georgia for use in its builder training courses. The data for the charts came from studies done in different parts of the country. Because the charts are based on rough national averages, they can vary considerably depending on the particular house design. However, they do paint a picture of what generates most of a home's air leakage, and where you should concentrate your energy-saving efforts. Not surprisingly, the data showed infiltration to be a major cause of heat loss, with the biggest culprit being sills and the intersection of walls and ceilings.

Source: Southface Institute