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  1. #1
    Join Date
    Mar 2007
    Chicago, IL

    Default Wooden plenum for unconditioned air?

    Second-floor of single-family residence would attic immediately above.

    Owner has installed a "whole house" exhaust system for the second-floor consisting of a wooden "plenum"containing an exhaust fan and connected intake lines running from a return grill in each room and exhausting to the interior of the attic (where, hopefully is in turn exhausting through passive vents installed or the ridge).

    1) A violation of the rules against combustible ductwork used for environmental air?

    2) No different from a joists space headed off to install a conventional whole-house ceiling exhaust fan?

    3) "Aw, come on Mike. Who gives a ****? Let it go and move on."?

    Opinions (preferably documented by a code or other reference)?

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  2. #2
    Join Date
    Jun 2010
    Rochester, NY

    Default Re: Wooden plenum for unconditioned air?

    No mention of whole house intake, so assume none?

    4. Test worst case CAZ, fail water heater and furnace. Tell them they have a dangerous ccondition and need sealed combustion appliances to cure.

  3. #3
    Join Date
    Feb 2008
    Chicago IL

    Default Re: Wooden plenum for unconditioned air?

    Whether it is 'allowed' or not would be my secondary concern. My more immediate concerns would be.
    - potential overheating and fire potential for a motor sealed in a wood box in an attic, what kind of motor and is it rated for such an enclosure, is it properly wired, is there any reasonable way to access it, etc
    - potential contaminant build-up on the wood and creep back into the occupancy space when the motor isn't running, presumably most of the winter
    - what does this say about the temps up on the 2nd floor, if the owner did this, I'm guessing no AC or crappy AC install and it gets boiling hot up there.
    - house depressurization concerns
    "The Code is not a ceiling to reach but a floor to work up from"

  4. #4
    mike huntzinger's Avatar
    mike huntzinger Guest

    Default Re: Wooden plenum for unconditioned air?

    another problem is moist air would have mold growing on the inside of the wood box


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