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Community and Q&A

Is paper backed polyiso acceptable for use on exterior walls

MOH | Posted in Energy Efficiency and Durability on

I’m in Michigan and planning to reside my small ranch home. I was planning on purchasing and applying new foil faced polyiso insulation prior to putting up the new siding, but have come across an opportunity to purchase paper faced polyiso that would have been used on a roof. Since I’ve never heard of anyone doing this, I would imagine it has some unforeseen consequences. Any advice would be appreciated.

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  1. Expert Member
    BILL WICHERS | | #1

    It'll work fine, and it will allow for a little bit of drying too (typically not a bad thing!). You can't use it as your WRB is all, so you still need something like housewrap over the polyiso.

    About the only downside to the fiber faced roofing polyiso is that it's usually slightly lower density than the foil faced stuff, so you get a teensy bit less R per inch, but not enough difference to really worry about. If you can get this stuff for a good price, go for it!


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