Secondary Author(s)

Moyer, Neil; Dunsmore, Rico

Report Number




Ducts; Buildings; HVAC; Air Flow; Blower Door; Cooling; Florida


Testing for duct leakage was done in 91 homes. Tracer gas tests found that infiltration rates were four times greater when the air handler was operating than when it was off. Return leaks were found to average 10.0% of air handler total flow. House airtightness, in 63 of these homes, determined by blower door testing, averaged 12.38 air changes per hour at 50 Pascals (ACH50). When the duct registers were sealed, ACH50 decreased to 10.93, indicating that 11.7% of the house leaks were in the duct system.

Duct repairs were made on 25 homes. Blower door tests found 12.30 air changes per hour at 50 Pascals pressure (ACH50). When the registers were sealed off, ACH50 decreased to 10.58, indicating that 14.0% of the house leaks are in the duct system. Repair of duct leaks reduced house ACH50 from 12.30 to 11.13, indicating that 68% of the duct leaks were repaired. The duct repairs caused infiltration with the air handler operating to decrease from 1.13 air changes per hour (ach) to 0.54 ach, and return leaks to decrease from 16.7% to 4.5%.

Cooling energy use was monitored on 24 homes before and after duct repair. Air conditioner energy use decreased by 18.0% because of duct repair. At an average cost of $200 per home, duct repairs have a simple payback of less than two years. Duct repairs are also shown to reduce winter peak demand in electrically heated Florida homes by about 1.6 kW per house at about one-sixth the cost of building new electrical generation capacity.

Date Published



Reference Publication: Cummings, J. B., Tooley, J. J., Moyer, N. A. and Dunsmore, R., "Impacts of Duct Leakage on Infiltration Rates, Space Conditioning Energy Use, and Peak Electrical Demand in Florida Homes," Proceedings of the ACEEE 1990 Summer Study, Pacific Grove, CA, August 1990.

Local Subjects

Buildings - Air Flow; Buildings - Blower Door; Buildings - Cooling; Buildings - Ducts; Florida; Buildings - HVAC


FSEC Energy Research Center® Collection



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