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What should I do about this sheathing?

Tom Wheeler | Posted in Energy Efficiency and Durability on

Zone 7 house with D log siding. 2×6 walls.  Some plywood, some polyiso board for sheathing.  The squirrels love to dig in and get to the fluffy pink stuff. 

My question is, after 25 years of visqueen, unfaced fiberglass and this resulting in no detrimental effects, at least in this room. Should I just put the same thing back and air seal from the top?  Or something else?  Seems like the double foil face would be an issue, but that is why I am asking. 

Tons of animal issues, as well as questions of installation since the same room was missing 4 feet of insulation over the double window, and making the roof flat instead of cathedral for better insulation and air sealing, are reasons I gutted it. 


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  1. Jon R | | #1

    Follow the recommendations here. And use a blower door test to verify air sealing.

    Does anyone have a solution that makes entering a house/attic unattractive to squirrels?

    1. GBA Editor
      Brian Pontolilo | | #3


      Outdoor cats do a pretty good job.

  2. GBA Editor
    Brian Pontolilo | | #2

    Hey Tom,

    I'm not sure what you mean by "air seal from the top." Please clarify.

    There's nothing wrong with re-installing fiberglass insulation, though it's difficult to install well, so make sure that you get the details right. This will be helpful:

    You are right to be concerned about re-installing a vapor barrier on the walls with foil faced foam sheathing, both because you could be creating a double vapor barrier situation and because the foam's R-value is probably not high enough to keep the inside surface warm in the winter, particularly if outside air is getting in. Do you know how thick the foam is? Perhaps a smart vapor retarder is a better option than poly sheeting.

    It will also be helpful to develop a strategy for air sealing, as Jon suggests. You'll get more moisture in your walls if they are leaky than you will from diffusion if they are tight. You're best bet is probably airtight drywall:

  3. Tom Wheeler | | #4

    I was planning on using a froth pack on the top plates and to seal the site made baffles.

  4. Tom Wheeler | | #5

    The foil iso is 3/4 or 1/2, not enough to avoid condensation, even with 6 inches of solid wood siding.

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