Blower Door Test

Blower Door Test

The Blower Door consists of a powerful, calibrated fan that is temporarily sealed into an exterior doorway.

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What is a Blower Door?

The Blower door is a very powerful diagnostic tool designed to measure the air tightness of buildings (homes) and to help locate air leakage pathways. Building air tightness measurements are used for a variety of purposes including:

  • Documenting the construction air tightness of buildings.
  • Estimating natural infiltration rates of houses.
  • Measuring and documenting the effectiveness of air sealing activities.
  • Measuring duct leakage in forced air distribution systems.

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 difference between inside and outside. This pressure difference forces air through all of the holes and penetrations in the exterior (envelope) of the building. By simultaneously measuring the air flow through the fan and its effect on the air pressure of the building, the Blower door system measures the air tightness of the entire building envelope. The tighter the building (e.g. fewer holes), the less air you need from the Blower Door fan to create a change in building pressure.

In addition to assessing the overall air tightness level of the building envelope, the Blower Door can be used to estimate the amount of leakage between the conditioned space of the building and the attached structural components such as garages, attics and crawlspaces. It can be used to estimate the amount of outside leakage in forced air duct systems. And because the Blower door forces air through all of the holes and penetrations that are connected to outside, these problem spots are easier to find by using additional diagnostic tools such as: small traces of chemical smoke, an infrared camera or simply feeling with the back of your hand. The air tightness measurement can also help to assess the potential for back-drafting of natural draft combustion appliances by exhaust fans and other mechanical devices, and help determine the need for mechanical devices.

The Blower Door is one piece of the diagnostic puzzle used to gather information on your home to determine the most cost effective plan of action to air sealing your home. We not only want to lower your utility bills for the future, we want to keep your retrofit costs reasonable by using strategic air sealing methods.


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