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Community and Q&A

Air exchange in spray foam attic

MaureenB | Posted in General Questions on

We live in northern IL and are spray foaming our attic where both water pipes and heating ductwork are located; on a slab. How do we exchange the air within the attic space? Do we have install a air exchanger in the attic or ? Concerned with moisture and heat buildup in attic.

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  1. Expert Member
    DCcontrarian | | #1

    The short answer is that the reason you do spray foam is so you don't have to worry about heat and moisture building up in your attic.

  2. Expert Member
    BILL WICHERS | | #2

    If you do the spray foam right and seal the attic space from the outdoors, the attic is now inside the envelope of your building and is conditioned space just like any other room. Normally you would put a single supply and return register in the attic space to keep some air flowing through whenever your HVAC system runs. You don't need anything fancy.


    1. MaureenB | | #3

      Will there be off gassing that occurs from the spray foam? The attic will be sprayed but not covered with drywall. Perhaps we should cover and put in a supply and return?

      1. Expert Member
        BILL WICHERS | | #5

        Properly cured spray foam shouldn't really do much in the way of off gassing after a few days to a week or two.

        Your local code may require that the spray foam be covered for fire protection, so that is something you may need to do. A quick call to your local building department will get you an answer, and I expect that they will tell you "yes", you need to put the drywall up for protection. Note that you don't need a fancy drywall job for this, just hang the drywall and tape/mud the joints. I do recommend priming the drywall though, although that's not really necassary for fire protection alone.


  3. Deleted | | #4


  4. walta100 | | #6

    Can you bring yourself to say “I will have a conditioned attic and am committed to heating and cooling it to more or less the same temp and humidity as the rest of my house”?

    If so, be sure you remove any and all the existing insulation now on the attic floor. Without the old insulation your old ducts may well be leaky enough to condition the attic. I would be tempted monitor the temp and humidity and would be prepared to change the return ductwork so most on the air was pulled from the attic and add vents to allow room air to enter the attic.


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