Blower door

A blower door is a machine used to measure the airtightness of buildings. It can also be used to measure airflow between building zones, to test ductwork airtightness and to help physically locate air leakage sites in the building envelope.

There are three primary components to a blower door: (1) a calibrated, variable-speed fan, capable of inducing a range of airflows sufficient to pressurize and depressurize a variety of building sizes, (2) a pressure measurement instrument, called a manometer, to simultaneously measure the pressure differential induced across the face of the fan and across the building envelope, as a result of fan airflow, and (3) a mounting system, used to mount the fan in a building opening, such as a door or a window.

Air Tightness Testing is usually thought of in residential settings. It is becoming more common in commercial settings. The General Services Administration (GSA) requires testing of new US federal government buildings.

A variety of blower door airtightness metrics can be produced using the combination of building-to-outside pressure and fan airflow measurements. These metrics differ in their measurement methods, calculation and uses. Blower door tests are used by building researchers, weatherization crews, home performance contractors, home energy auditors, and others in efforts to assess the construction quality of the building envelope, locate air leakage pathways, assess how much ventilation is supplied by the air leakage, assess the energy losses resulting from that air leakage, determine if the building too tight or too loose, determine if the building needs mechanical ventilation and to assess compliance with building performance standards.

Blower door technology was first used to measure building airtightness in Sweden around 1977. This earliest implementation used a fan mounted in a window, rather than a door. Similar window-mounted measurement techniques were being pursued by Caffey in Texas, and door-mounted test fans were being developed by Harrje, Blomsterberg and Persily at Princeton University to help them find and fix air leaks in homes in a Twin Rivers, New Jersey housing development. Harold Orr has also been identified as a member of a group in Saskatchewan, Canada who was pursuing similar testing methods.

These early research efforts demonstrated the potential power of blower door testing in revealing otherwise unaccounted for energy losses in homes. Previously, air leakage around doors, windows and electrical outlets was considered to be the primary leakage pathway in homes, but Harrje, Dutt and Beya used blower doors to identify “thermal bypasses”. These bypasses were air leakage sites, such as attic utility chases, that accounted for the vast percentage of air leakage energy losses in most homes. Use of blower doors in home energy retrofitting and weatherization efforts became known as “house doctoring” by researchers on the East and West coasts.

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Wikipedia