Local Knowledge About Ductwork Retrofitting

A high quality duct system greatly minimizes ductwork energy loss. Leaks in ductwork can contribute 20 to 60 percent of the air leakage in a house. The system should be airtight and designed to deliver the correct air flow to each room. Depressurization and overpressurization can occur in homes due to faulty duct system characteristics. As a result, air is exchanged (through infiltration and exfiltration) with outside air. Depressurization can be caused by closing interior doors, blocking air that is supplied to rooms from reaching the return air plenum (usually located in a central area of the house). The return air plenum will consequently be starved for air and will pull air from wherever it can. Good system design, improved duct and sealing materials combined with proper installation reduce energy losses. Some design strategies are simple, such as allowing adequate airspace under interior doors to permit air to return to plenums outside of the room.