How the Blower Door test works:

A basic blower-door system includes three components: a calibrated fan, a door-panel system and a device to measure fan air flow and building pressure. The blower-door fan is temporarily sealed into an exterior doorway using the door-panel system. The fan is used to blow air into or out of the building, which creates a small pressure difference between inside and outside. This pressure difference forces air through all holes and penetrations in the building enclosure. The tighter the building (e.g. fewer holes), the less air is needed from the blower door fan to create a change in building pressure.

The Blower Door method offers the opportunity to:

1. Determine location and strength of air leakage (qualitative);
2. Determine air flow (V50 in m³/h) as the sum of all leaks in the building at a test pressure of 50 Pa (quantitative);
3. Calculate the hourly air change rate (V50/Vroom = n50) measured at 50 Pa;
4. Calculate the air permeability of building envelope (V50 / envelope area = q50) measured at 50 Pa.