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Community and Q&A

How to use polyiso as interior insulation on a pole barn?

jackzylkin | Posted in Green Building Techniques on

I have an unfinished pole barn with board and batten siding in Pennsylvania. I’d like to insulate the inside with polyiso panels, because that way I won’t have to frame out the walls, and the polyiso will create a handy air barrier and thermal break. I can also find used 3″ panels for ~$20 around here. My plan is to glue 3 inches of polyiso directly to the inside of the Purlins, tape the seams, then screw OSB, plywood, or drywall on top with long screws. These screws will go all the way through the foam to the barn’s 2×4 purlins.

However, my worry is that these screws will become very cold during the winter, because they basically reach all the way to the outside of the insulated space. Maybe this won’t make any impact on my heating bills, but I worry that the ice-cold screws will form magnets for condensation all over (and inside) my walls. Is this fear justified, or is my plan workable?

I have been told that I could forgo all the screws and glue everything instead. That doesn’t sound too secure, especially if I’ll be hanging up tools, etc, on the walls.

I tend to way overthink things like this (to the point where I get nothing done!) so I would appreciate any guidance.

Thanks very much.

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  1. GBA Editor
    Martin Holladay | | #1

    Your screws will indeed be colder than the rest of your wall, but not enough to cause problems. Don't worry about it.

    Your biggest problem will be making the entire wall assembly airtight, especially where the polyiso meets your vertical poles, and where the polyiso meets your slab floor (or dirt floor?). Depending on the way your pole barn was built, and your air-sealing skills, this plan may or may not work.

  2. jackzylkin | | #2

    Thank you very much!

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