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3 ach50

Kevin Mick | Posted in Mechanicals on

Is there a way to know what the infiltration will be in a house after it passes the test?

If an exhaust ventilation system is used for ASHRAE 62.2 requirements, how do you know that sufficient makeup air will come in through cracks to compensate for what is exhausted?

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  1. GBA Editor
    Martin Holladay | | #1

    Kevin,
    If you have already performed a blower door test, and if the result is 3 ach50, you know more than most people. If you install an exhaust-only ventilation system, your house will almost undoubtedly have enough cracks to provide makeup air for your fan or fans. (I'm talking about a typical 80 cfm bath ran, not a big honking range hood fan.)

    After your bath fan is installed, it is a good idea to verify the air flow rate of the fan. If the airflow rate of the fan meets the design specs, then, by definition, your house has enough cracks to provide makeup air.

    Read these articles to learn more about airflow testing:

    Is Your Ventilation System Working?

    A Failure That Stalls the Certification of Many Energy Star Homes

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