The Blower Door Test

The Blower Door Test method of measuring airtightness has become a standard part of passive house certification.

Measurement setup for Blower Door Test With lightweight buildings, the Blower Door Test procedure is carried out before the cladding is fixed, to allow the rectification of possible weak spots. With solid construction methods, it is done after the building has been rendered.

Prior to extensive renovation, however, it may be useful to a combine the Blower Door Test with thermography, as the latter pinpoints leaks and weak spots.


Blower Door Test movie

Blower Door Test procedure

With windows and doors closed, a fan creates a pressure difference of 50 Pascal (Pa) between inside and outside the building, and then determines the flow rate needed to maintain this pressure difference. The test indicates the degree of leakiness, since the volume of air needed to maintain the pressure difference is equal to that leaking out of the building.


The planning and building authorities in some European countries have made a certificate of airtightness a requirement as part of a drive to increase quality and workmanship in buildings.