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Is duct sealing considered part of infiltration measures in older homes?

xUoWsdaw6X | Posted in Building Code Questions on

The basic scenario is in a older home when you seal the ducts it causes infiltration numbers of the blower to drop significantly. By code would you count that to the infiltration measures or keep it separate. And if you keep it separate what would be the right way of running the test and completing the work.
Thank you very much

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  1. GBA Editor
    Martin Holladay | | #1

    Your question is unclear. What part of the code are you talking about?

    The 2012 IECC includes requirements for envelope tightness (measured with a blower door) as well as requirements for duct tightness (usually measured with a Duct Blaster).

    For more information on blower door testing, see Blower Door Basics.

    For more information on duct testing, see Duct Leakage Testing.

  2. xUoWsdaw6X | | #2

    Okay well from my understanding on preexisting homes the duct work and the infiltration work are two separate measures that are suppose to be done individually to ensure accurate results. Thing is if I do the work separately I get always get false numbers.
    So let say I seal a preexisting home with a pre blower door of 3000cfm and I infiltrate the home and I bring the post blower reading at 50 pascals to 2000cfm. The I work on the ac unit and run the post duct test air leakage to outside and I get a 3% air loss. If I run the post blower door again I would get around 1700cfm on the door blaster because I seal the ac unit.
    Keep in mind this is a government program to target older homes and make then more energy efficient, and they have this rule do infiltration first then do the ducts and don't include ducts in infiltration measures. I talk to all the program mangers and nobody has a clue to why that is. Its just one of those unexplained rules.

  3. davidmeiland | | #3

    If they want you to exclude duct leakage to outside from your blower door number, they should give you a procedure to follow for doing so, but collecting the necessary data is fairly straightforward. If you are going to do both a blower door test and a duct blaster test, do the blower door first without masking the ducts. Then, mask the ducts and perform a total duct leakage test. Then, with the ducts masked, cap the duct blaster fan and run the blower door a second time. This should give you a reasonable approximation of shell leakage minus duct leakage. Last, turn the fan around and get a duct leakage to outside with both fans running. If they put you on the stand, give them all four numbers and explain what they mean. What else could they ask for?

  4. xUoWsdaw6X | | #4

    okay that actually helped now explaining to them why there wrong is the hard part thank you David you were very helpful

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