Models for Determining Air Permeability of Buildings by Fan Pressurization Method

The fan pressurization method in ISO9972:201.5 (ISO method) aims to determine the air permeability of buildings. We focus on the effective leakage area (ELA) which is the most typical quantitative parameter of air leakage among a variety of parameters and variables obtained by the method. Herein, we clarify the relation between the ELA and the geometrical area and how a group of leakages are combined to an equivalent leakage. Models expressing the relation include a coefficient. The models provide both the leakage area with the equivalent total area of widely distributed narrow rectangular leakages and the large circular area or wide rectangular leakages located nearby by adjusting the coefficient. The coefficient is estimated to fit the models to the ELA estimated by the ISO method. The coefficient is approximated using the value of pi or pi/4. The ELA of the room itself and that of the room with a size-controllable artificial leakage area are estimated by the ISO method, whereas the given artificial leakage area is discriminated from the ELAs via the models. The area discriminated is well fitted to that set a priori, and is within 2.2%. The error of the geometrical leakage area of the room estimated under different artificial areas of leakages is 2.2%.