Testing has been done on 70 central Florida homes to assess and characterize pressure differentials in new (age five years or less) Florida homes. Blower door testing was done to determine house airtightness and air distribution system leakage. The 70 homes had an average airtightness of 7.23 air changes per hour at 50 Pascals (ACH50). Significant leaks were found in the ductwork in a majority of homes tested, both on the supply and return sides of the air handler. When the air distribution system was sealed off, house ACH50 decreased to 6.42, indicating that 11.2% of the house leak area is in the duct system.
Florida Solar Energy Center and Cummings, James, "Radon Pressure Differential Project, Phase I" (1990). FSEC Energy Research Center®. 862.