Replies

1. Expert Member
   Michael Maines | Aug 06, 2023 11:52am | #1

   Carl, this article should answer all of your questions: https://www.greenbuildingadvisor.com/article/calculating-the-minimum-thickness-of-rigid-foam-sheathing.

1. 
   Csk | Aug 06, 2023 12:03pm | #2

   Thanks for the help it is appreciated

   Carl

2. Expert Member
   BILL WICHERS | Aug 06, 2023 12:24pm | #3

   I prefer polyiso, for maximum R per inch. You can usually use either foil or fiber faced rigid foam on the exterior, as long as your walls can dry to the interior. The big difference is that foil or poly faced rigid foam is a vapor BARRIER, and allows ZERO drying. Fiber faced rigid foam is a pretty tight vapor RETARDER, and allows a LITTLE drying. In practice though, walls built with exterior rigid foam are normally intended to dry to the interior, so it ends up not making much difference which type of facer is on the exterior rigid foam. If you have interior polyethylene that you can't remove, that's when I'd use fiber faced rigid foam, or rigid mineral wool (even better for drying, buy lots more expensive).

   Bill

1. 
   Csk | Aug 06, 2023 01:07pm | #4

   Thanks for the advice bill

   Carl

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   Deleted | Aug 06, 2023 05:04pm | #5

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