Blower Door Test | Energy Star Home

By Todd Fratzel on Energy Conservation, Feature Story, Insulation

Energy Star Home

Over the past few months we’ve been building an an Energy Star Certified Home for a customer. This new home features some really nice energy efficient details including triple pane windows, spray-in-place cellulose insulation, high efficiency propane boiler and Energy Star certified appliances. Building an Energy Star Home involves a team effort from designers, contractors and third party inspectors. As part of the final process in certifying the new home for Energy Star we hired a third party inspector to inspect the home during construction and to perform a blower door test.

Blower Door Test EquipmentBlower Door Test

The blower door test provides a measurable comparison of the homes “tightness” compared to industry standards. The air-tightness of a home is a good prediction of how well the houses thermal envelope will perform. It has been shown that air infiltration is a bigger cause for poor thermal performance than the amount of insulation or “R” value. This is true because air infiltration actually reduces the effective “R” value of the total insulation “system”.

The blower door test is performed using the equipment shown in the photos. A temporary “air-lock” door is placed in the  main door of the home. The blower door as it’s referred to has a fan mounted in it that allows the house to be pressurized with negative air pressure.

Blower Door Test EquipmentThe calibrated fan is equiped with measuring devices that monitor fan flow and air pressure. The inspector can then calculate a standard CFM50 score for the house. CFM50 is definted as the air flow in cubic feet per minute required to create a 50 pascal pressure difference in the house compared to outside. The CFM50 value is then used to compare the home to standards set by the Energy Star Home certification program.

The blower door test is also very useful in identifying areas of the home that may have a significant air infiltration problem. While the blower is running you can walk around the house and listen and feel for drafty areas that may not be sealed properly.

Problem areas that might be identified include: electrical outlets, doors, windows, attic access panels, pocket door frames, shower stalls and holes for utilities. It’s amazing to walk around and find areas that didn’t seem to be a problem during construction. So this test is really helpful in identifying those areas so corrections can be made.

Blower Door Test Results

We should get the results back in the next week or so from the Blower Door Test. I have no doubt the house will score well knowing the care that was taken to air seal the framing and the use of the spray-in-place cellulose insulation. Also, the inspector thought the field measurements were very good when compared to other homes he’s tested. I’ll be sure to post the results when we get them so you can see how well this Energy Star Home rated.


If you’d like to see the results of the blower door test then read our Blower Door Test Results article.

About the author

Todd Fratzel

I'm full time builder for a large construction company in New Hampshire. I run their design-build division that specializes in custom homes, commercial design-build projects and sub-divisions. I'm also a licensed civil and structural engineer with extensive experience in civil and structural design and home construction. My hope is that I can share my experience in the home construction, home improvement and home renovation profession with other builders and home owners. I'm also the Editor-in-Chief and Founder of Tool Box Buzz. Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site.

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  1. security locks says:

    fantastic web site, the internet i starved of good content like this, keep it up, the web needs it.

  2. Bob says:

    I’d be interested in seeing the blower test results if you ever got them back.

    • Todd says:

      Bob – Great question. The results for this house were as follows (I’ll update the article to include this as well):

      ACH 50 = 2.17 from the Blower Door Test.

      The following are guidelines for a basic understanding of that value.

      ACH 50 below 5.0 Is indicative of a Tight house.
      ACH 50 between 5.0 and 10.0 is indicative of a Moderate House
      ACH 50 above 10.0 is a Leaky House

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