Caption title. At head of title: Project summary. "Mar. 1992." "EPA/600-SR-92-008."

The report gives results of tests on 70 central Florida houses to assess and characterize pressure differentials in new (age 5 years or less) Florida houses. Blower door tests determined house airtightness and air distribution system leakage. The 70 houses had an average airtightness of 7.23 air changes per hour at 50 Pa (ACH50). Significant leaks were found in the ductwork in most houses tested, both on the supply and return sides of the air handler. When the air distribution system was sealed off, house ACH50 decreased to 6.421, indicating that 11.2% of the house leak area is in the duct system. Differential pressure measurements were taken between the main body of each house and sub-slab areas, out-doors, and many locations within the house. These measurements indicated significant pressure differentials in the house due to a number of factors. Return leaks produced a maximum whole-house pressurization of 5.5 Pa. Supply leaks produced a maximum whole-house depressurization of -4.8 Pa. Closed interior doors produced a maximum closed-room pressurization of 37 Pa and maximum main-body depressurization of -14.8 Pa. Turning on all exhaust fans and interior dryers typically depressurized the house to 0 to -4 Pa, but one very tight house was depressurized to -37 Pa. One of the most important findings of this study is that large-magnitude localized depressurization occurs because of return plenum leaks. Subslab depressurization of up to 6 Pa have been found 5.5 m from the return plenum. Depressurization of -6 Pa in a garage and a -4 in a utility room has been observed.