What is a blower door test?


What is a blower door test?

Asked by Paul Lennon

What does it usually cost? What information does it tell me?

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Florian Speier's picture

A blower door test is a measurement of how airtight your house is.

In essence, an energy auditor places a large fan into an exterior door of your house. The fan pumps air out of your house, lowering the air pressure inside the house. This will make fresh air try to infiltrate your house wherever there is a leak.

You can get two types of information with a blower door test:

  • how quickly air leaks into your house (a measure of the overall tightness of your home), and
  • where the leaks are (by using a smoke pencil to trace airflows).

The results will let you make informed decisions about where it is most important to seal your house.

It will not, however, give you any information about the R-value of your insulation in different areas of your house. To get an overview about where your house needs to be insulated more, you can use infrared photography.

  • The resulting picture will show your house in colors from red over yellow and green to blue, depicting the surface temperatures of your home.
  • Higher surface temperatures indicate less good insulation in these areas as the heat makes its way out of the house and warms its outer surface.
  • You can then concentrate on insulating the areas that are warmest, shown in red.

Many utilities offer these two services, IR photography and blower door testing, bundled in a home energy audit.

Prices depend on the utility; in my area this is about $120.

For more information:

Check our energy auditordirectory to find a professional near you.

Read "I keep hearing that I should get a home energy audit. What should I expect to pay and expect to get?" a Q&A answered by Steve Saunders.