Why is duct leakage a significant problem?
Duct leakage will significantly reduce system performance and increasing kilowatt consumption. Since the air in a duct system is under pressure (most ducts move 1000 to 2000 cubic feet of air per minute), even the smallest leak can waste a lot of cooled or heated air, as well as take in a lot of unfiltered and unconditioned air. If there are leaks in a duct system, closing interior doors can triple the air moving through these leaks. If the air return plenum is isolated from a significant portion of the needed return air, as when registers are closed or interior doors isolate a room from air movement, then pressure imbalances are created that are usually made up from very hot, humid attic air, or dusty, pollen-laden outside air. Air can be drawn through spaces in both interior and exterior walls that are open to the attic or through plumbing penetrations or spaces where the walls are attached to the foundation. Air can even be “back drafted” from your furnace, hot water heater, or fire
