What is a blower door test? A Blower Door is used on buildings in order to quantify the amount of air leakage through its enclosure. During this test, a calibrated fan is installed in an otherwise sealed door or window, while all the other openings to the exterior are closed. When the fan is turned on, it creates a pressure difference between the outside and the inside. Typically done under negative pressure, the fan sucks the air out of the home, causing it to come in through whatever pathways it can find — many of which are unintentional. These unintentional leaks are what we measure when we conducting these tests. While the pressure inside is steady, the air going through the fan is the sum of all the leaks in the building. Because the fan is calibrated, its airflow at various pressures is known. If we keep the pressure differential constant, then we know that the volume of air moving through the fan is the same as the volume of air that is leaking through the cracks
