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HVAC Duct Leakage Test Results

airfix | Posted in General Questions on

New construction, climate 6B.  We are not interested in the certifications we are just looking to do a pretty good home that is better than code where it makes sense.

I had plenty of questions on the best way to seal ducts and the aeroseal process that my HVAC guy was trying to push me towards.  See the thread here:

Our duct leakage test results are in.  We ended up getting 151cfm at 50 pascals for our 4000 square foot home that included the air handler.  They did not test the drier vent ducts or ERV ducts because their leakage rate would be too small to measure, they said.

IRC 2015 N1103.3.4 allows the following duct leakage: Rough In Test – less than 4 cfm per 100 sq ft which for my house is about 160 cfm if the air handler is included in the leakage test.
However our local Utah code has a carve out allowing 7 cfm per 100 sq ft.

So we are way better than Utah code and a little under the 2015 IRC code. This was without using aeroseal, only mastic and duct tape.   I imagine a higher portion of the leaked will be in the panned floor joists rather than the supply ducts.

The guy that did the test said that he thought most houses that don’t do duct tests come in about 7 or 8 cfm per 100 sq ft and that my ducts are pretty tight compared to local practices.

On the whole I’m happy enough with the test results and don’t think it is worth doing any more sealing or testing to bring down the numbers anymore.  What do you guys think?


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  1. Jon_R | | #1

    > We ended up getting 151cfm at 50 pascals

    Isn't the standard 25 pascals?

    I'd say that the effect of duct leakage is entirely dependent on where it is.

  2. airfix | | #2


    You are right. I was going from memory. They used 25 pascals.


  3. Expert Member
    Dana Dorsett | | #3

    >"...less than 4 cfm per 100 sq ft ..."

    That means it meets the <4cfm/100' parameter of an Energy Star duct system. Did you also test for balance to see if it meets the Energy star <3 pascals room to room pressure difference part of the Energy Star spec?

  4. airfix | | #4

    No I don't think they did test for pressure balance. It wasn't something on my radar that I requested.

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