High utility bills? Stuffy rooms? Dusty house? It could be your duct system. In houses with forced-air heating and cooling systems, ducts are used to distribute conditioned air throughout the house. A duct system that is properly sealed and insulated can make your home more comfortable, energy efficient, and safe—all while helping to reduce your energy bills. However, in typical homes, about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly installed ducts. The result is higher utility bills and difficulty keeping the house comfortable, no matter how the thermostat is set.