Over 90% of existing buildings located throughout North America have air duct systems that contain small holes and cracks that reduce the level of comfort and increase heating and cooling costs. Leaks are caused by a variety of factors including the age of the dwelling, type of construction, type of ductwork and local building codes. Repairing and patching leaks in HVAC duct systems saves cooling, heating, and fan energy. In air-based systems, ducts deliver all of the heating and cooling to conditioned spaces. Any duct leakage translates into extra air that must be supplied so sufficient heating or cooling reaches the conditioned space. This not only increases effective heating and cooling loads, it also increases fan energy due to increased flow and/or run time. Sealing duct leaks reduces the amount of heated or cooled air the supply fan must handle to deliver the same amount of air to the conditioned space.