How It Works

A blower door is a diagnostic tool used to determine how airtight a building is. The blower door is set up in an exterior door of the building facing outward. The unit blows air out of the building and that air is replaced by air coming into the building through leaks. The tool then measures the air moving out through the fan at a pressure of 50 pascals. 

For single family homes, a mandatory air leakage test must show that the rate does not exceed 3 air changes per hour (ACH) at 50 pascals.