Air distribution (duct) systems in U.S. homes are typically only 50 to 75% efficient due to a combination of air leaks and thermal losses. The current best practice for sealing leaks in duct systems is to use a combination of ductleakage measurements, to determine if duct sealing is needed and to locate duct leakage sites. Ducts are then sealed manually on the basis of these measurements as well as on the basis of visual inspections that identify obvious or potential leakage sites based on what weatherization crews have learned from past experience. Duct sealing work includes reattaching ducts that have become disconnected, repairing major leakage sites, and manually applying sealants to all visible and accessible leaks and joints. Cost-effective energy savings have been demonstrated from this technology approach in multiple field tests sponsored by the U.S. Department of Energy (DOE) in a range of climates.