Ductwork is the network of metal, fiberglass, or flexible conduit that distributes conditioned air from the HVAC system throughout a building. Properly designed and installed ductwork is essential for efficient, even heating and cooling.
Duct systems include supply ducts (delivering conditioned air to rooms), return ducts (pulling air back to the HVAC system), and the plenum (the main duct directly connected to the air handler). Duct design is governed by ACCA Manual D calculations.
Leaky ductwork is one of the most significant sources of energy waste in American homes — the EPA estimates that the average home loses 20-30% of conditioned air through duct leaks. Signs of duct problems include uneven temperatures, high energy bills, and excessive dust. Duct sealing with mastic compound or UL-listed tape (not standard duct tape) can dramatically improve efficiency.