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Community and Q&A

Blower door test and HVAC ducts

Jeremy K | Posted in Energy Efficiency and Durability on

We had our house blower door tested recently. I didn’t think about it at the time however we have a geothermal heat pump. The geothermal HVAC unit sits inside the walkout garage and ductwork runs into the conditioned space of the home being tested.

During a blower door test, how significant would the leakage be if any from air being pulled through the cabinet of the geo unit? Do you normally seal of the ductwork at the unit for the blower test?

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  1. David Meiland | | #1

    During a normal test, no modifications are made to the ductwork, furnace cabinet, etc. The HVAC is part of the air barrier of the house. If it's leaky, or if it's tight, it impacts the result.

  2. GBA Editor
    Martin Holladay | | #2

    David's right.

    And by the way, there are many reasons why you don't want to put a heat pump, an air handler, and ductwork in your garage. It is not only possible for this equipment to affect your blower-door results -- meaning that the ductwork penetrations can make your house leakier -- but the ducts can pull fumes from your garage into your house.

  3. Jeremy K | | #3

    Thank you for the replies. Technically the air unit is in a utility room adjacent to the garage but still unconditioned space. Ducts do run through the garage bay as its a walkout with master bedroom above. Thanks for pointing out the potential issue with fumes as even though its technically separate from the garage, I did not focus on sealing this room as well from the garage as we did the conditioned space. On the plus side there are no open vents or returns in the ductwork and all seams are sealed with mastic. I was just curious about sealing the unit during testing as we did not. Sounds like it was tested correctly. The house tested well at 1.9Ach50,

    Edit: Fireplace is a glass door insert and flu or outside air intakes were not ballooned either during testing.

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