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Thread: Wet duct

  1. #1
    Join Date
    Feb 2012
    Posts
    42

    Wet duct

    Hopefully this doesn't tread too far toward DIY territory, but
    I've got a little problem with a cold-air intake that someone
    might have some insight into. You guys must deal with
    fresh-air inlet ducts in some fashion once in a while...

    This is the inlet to an HRV, and is a piece of PVC pipe
    that comes in through a sealed wall penetration. It's
    PVC instead of metal to avoid thermal bridging to outside,
    but it's still passing cold air so the whole pipe is
    naturally going to get a little chilly. It connects
    immediately to a piece of insulated 6" flex that runs
    right down into the HRV inlet. In the original setup,
    the outer jacket + fiberglass of the flex was snugged
    up around the PVC pipe tight to the wall, to try and not
    expose any of the cold bits. Last night I discovered
    that air circulation around that area had nonetheless
    caused condensation to form in the end of the fiberglass
    and start soaking down into the flex duct *and* into
    the wood of the wall that the pipe passes through.

    When y'all do a fresh-air duct penetration for cold
    climates, how do you prevent condensation problems
    on the inside??

    tnx

    _H*

  2. #2
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,438
    Definitely DIY, but I doubt that it 'treads on the trades' here.
    Haven't tried it, but Spray Foam certainly seems like it would be a good insulator AND sealant.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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