Fan airflow is determined using CFan and nFan values that are provided by the blower door manufacturer, and they are used to calculate QFan. The multi-point blower door test procedure results in a series of known values of Qn, Fan and ∆Pn, Building. Typical ∆Pn, Building values are ±5, 10, 20, 30, 40 and 50 pascal. Ordinary least squares regression analysis is then used to calculate the leakage characteristics of the building envelope: CBuilding and nBuilding. These leakage characteristics of the building envelope can then be used to calculate how much airflow will be induced through the building envelope for a given pressure difference caused by wind, temperature difference or mechanical forces. 50 Pa can be plugged into the orifice-flow equation, along with the derived building C and n values to calculate airflow at 50 pascal. This same method can be used to calculate airflow at a variety of pressures, for use in creation of other blower door metrics.