The biggest losers in your house may be leaky ducts used for central air conditioning or forced-air heating systems, as well as your attic insulation or lack thereof.
About 66 percent of homes have leaky air ducts used for air conditioning and heating systems. According to the U.S. Department of Energy’s Energy Star program, leaky ducts in attics or crawlspaces can account for 20 percent or more of a home’s heating and cooling energy losses. In a study of energy efficient measures, sealing the ducts yielded by far the greatest energy savings of 12 measures studied, at the lowest cost. In 100 homes in Phoenix, sealing ducts cut leakage by 30 percent.