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Rigid Foam, Sheathing, and Metal Siding

css1813 | Posted in General Questions on

Hello:

I read up on this but I didn’t find our exact scenario so I wanted to verify our thoughts here if possible.

We are in lower Michigan (zone 5) and have a 40x80x16 pole barn with uninsulated concrete floor, that is constructed with 6×6 treated posts.  The outside wall currently consists of sheathing, house wrap, and metal siding over that.  I was thinking of gluing or fastening rigid foam to the inside surface of the sheathing, then put up sheathing over the foam to protect it on the inside.  Just to summarize, the layers from the outside in would be:  metal siding, house wrap, sheathing, rigid foam, sheathing.  The goal is to keep the temp inside the barn more consistent on very hot and cold days.  No plans to heat it or anything.

Is there any issue with this, for example there may be a slight air gap between the outside sheathing and the rigid foam (any potential moisture/condensation issues)?  My thought on doing this idea instead of closed cell spray foam is mainly cost but also I thought it may be a little cleaner and easier to work with.

Thank you very much , as always!

Chris

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Replies

  1. Steve Knapp CZ 3A Georgia | | #1

    Hi Chris,

    I'll give your post a bump. As an FYI, there are quite a few GBA threads that focus on pole barns. I don't see an issue with your plan, but let's see if one of the professional builders can offer some input. If you decide to move forward, try to source reclaimed foam. It's much more affordable than the brand new stuff.

  2. css1813 | | #2

    Thank you Steve. I did read through the other posts, and I see mostly they deal with pole barns that have the bare metal siding. In our case, we have a moisture barrier (house wrap) and sheathing both, which is a little more unique so yes if there's any feedback on our plan that would be wonderful. Also thank you for the suggestion on the reclaimed foam. Thank you!

  3. Expert Member
    Michael Maines | | #3

    Steve, I don't think this is a pole barn issue as much as an insulation/sheathing issue. In a heated building, unvented gaps between insulation and sheathing can accumulate moisture, leading to problems. Air leaks and vapor drive due to temperature differentials are the main culprits allowing the moisture to accumulate. Your assembly may not be airtight, but as long as the indoor space is close in temperature and relative humidity to the outdoors, you should not have a problem. But the fewer gaps you can leave, the better.

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