What's a Blower Door? H.E.A.T

The Blower Door is a diagnostic tool designed to measure the airtightness of buildings and to help locate air leakage sites. The Blower Door consists of a powerful, calibrated fan that is temporarily sealed into an exterior doorway. The fan blows air into or out of the building to create a slight pressure different between inside and outside. The pressure created simulates 20 mph. winds on all four sides of the building. This pressure difference forces air through all holes and penetrations in the exterior envelope. By simultaneously measuring the airflow through the fan and its effect on the air pressure in the building, this test measures the airtightness of the entire building envelope. The tighter the building (e.g. fewer holes), the less air you need from the fan to create a change in building pressure.

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