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Community and Q&A

Spot HRV distance from openable portion of window

rossn1 | Posted in Building Code Questions on
I am installing some Lunos e2 Spot HRVs in a residence – they alternate between pushing and pulling of air out/in the home. Do I understand correctly that these must adhere to IRC M1506.3 “Air exhaust openings shall terminate not less than…; 3 feet from operable and nonoperable openings into the building…”?
If so, and there is a ’slider’ type window, is the requirement 3’ from the openable portion of the window, or the entire window? I wasn’t clear about ‘operable and *nonoperable* openings’.
Will IRC allow an extension outside the home to make the 3’?


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  1. Expert Member
    Peter Engle | | #1

    A code Nazi could possibly interpret the code that way, but that would totally not be the intent.

    The intent of 1506.3 is that exhausts from ventilation equipment like kitchen and bathroom fans are not to be located close enough to an opening that the exhaust can get sucked back into the opening. In the case of an operable window, you don't want your kitchen smoke and grease coming back in the window.

    If you have your windows open, there's no point in having the Lunos system operating, is there?

    And, if someone really wanted to use this argument, the Lunos fan itself violates this code provision because it is both an intake and an exhaust and it is not separated from itself. If we don't care about it rebreathing its own exhaust, why would we care if its exhaust happened to come back in through an open window? Remember, the exhaust from the Lunos is just room air. There's nothing harmful or offensive in it.

    As far as your specific question, yes, the IRC does allow snorkels, extensions and other vent terminations to extend the distance from an opening. That won't help with the Lunos however, because the longer the extension, the more of the air you just exhausted is stored in the pipe, and then that stale air is definitely brought back into the house when it cycles. Shorter is better for this system.

    1. Expert Member
      MALCOLM TAYLOR | | #3


      What's still troubling is the reference to setbacks from the inoperable portion of the window. I don't understand that at all.

  2. rossn1 | | #2

    Thanks for your thoughts, Peter.

    I entirely agree on the concept you've stated, but taken literally these are both exhausting and in-taking air and my local building department is very strict to code, which doesn't differentiate between types of mechanical ventilation. It's possible for me to switch windows that I'm installing today, but definitely not preferred. Wish this was clearer in the IRC.

    I'd see a snorkel as a temporary measure.

  3. rossn1 | | #4

    County did confirm no issues with the spot HRVs next to an openable window.

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