The balanced fan depressurization method has been modified for application to high-rise apartment buildings in order to measure the overall air leakage and the wall air leakage of an apartment unit simultaneously. The method requires the use of two sets of fan pressurization apparatus. One is installed at the door of an apartment unit for measuring the air leakage rate of the exterior wall, and a much larger apparatus is installed at an exterior door of the building for measuring the overall air leakage rate. The pressures between the test unit and the adjacent units are balanced to minimize the air leakage through the party walls by adjusting the airflow of the larger apparatus and the door opening of the adjacent apartments. The method was successfully applied to two high-rise apartment towers before and after they were retrofitted to improve airtightness of the envelope. In addition, the tracer gas decay method was applied to the same buildings to obtain the infiltration rates of selected apartment units.

The methods used to measure the airtightness values and the air infiltration rates and the test results of the two apartment towers are discussed.