Secondary Author(s)

Withers Jr., Charles; McIlvaine, Janet; Sonne, Jeffrey; Lombardi, Matthew

Report Number




HVAC; Buildings; Air Flow; Ducts; Energy Efficiency; Residential


Testing was performed to characterize air leakage in 30 air handler cabinets and at connections to supply and return ductwork. Operating pressures were measured in the air handler and plenums. Q 0.1 (Q 25) in the air handler averaged 23.9 cfm (11.3 l/s) in 30 homes. Leakage at the return and supply ductwork connections averaged 3.9 Q 0.1 (1.8 l/s Q 25) and 2.2 Q 0.1 (1.0 l/s Q 25), respectively. Actual return side leakage of 77.5 cfm (36.6 l/s) and supply side leakage of 3.1 cfm (1.5 l/s) are calculated based on Q 0.1 (Q 25) and measured operating pressures, which is 6.4% of the system air flow.

Duct leakage (including the air handler) was also measured in a sub-sample. Return Q 0.1 (Q 25) for 21 homes was 88 cfm (42 l/s). Supply Q 0.1 (Q 25) for 11 homes was 132 cfm (62 l/s). Return leakage is estimated to be 170 cfm (80 l/s) or 13.4% of system air flow and supply leakage is estimated to be 167 cfm (79 l/s) or 13.2% of system air flow.

Date Published



Reference Publication: Cummings, J.B., Chuck Withers, Janet McIlvaine, Jeff Sonne, and Matt Lombardi. "Air Handler Leakage: Field Testing Results in Residences". ASHRAE Transactions, Volume 109, Part 1, 2003.

Local Subjects

Buildings - Air Flow; Buildings - Ducts; Buildings - Energy Efficiency; Buildings - HVAC; Buildings - Residential


FSEC Energy Research Center® Collection



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