Replies

1. Expert Member
   BILL WICHERS | Jun 28, 2023 09:09pm | #1

   So OSB backed polyiso? I've not heard these called "hunter panels" before, but I suppose it's just another trade name type name like Johns Manville's Nailboard, or Zip-R, or.... Kleenex :-)

   You could certainly try making such a panel yourself, but you'd have no engineering data behind it, and no agency approvals or listings, which could cause you problems at inspection time.

   This is a similar question to "can I make my own version of Huber's Zip-R panels?" which comes up on GBA periodically, and the answer is always "yes you can, but you can't use it the same way, because you don't have the engineering to back up your design, so you won't pass inspection". Most codes include language along the lines of "must be listed for the purpose", which means a third party testing labratory has to test the product and certify it for the intended use. Inspectors will then look for this certification (or at least they should), and will fail your project if you use an unlisted assembly. This issue most commonly comes up whenever you try to do anything the inspector is not familiar with, in which case they tend to look more closely and look for reasons to fail the assembly -- such as using unlisted materials.

   Bill

1. 
   Zins | Jun 28, 2023 09:59pm | #2

   Thanks, Bill. Exactly, Hunter Panel is just the maker that's been mentioned to me most recently so my brain used their name.

   If someone was making these panels with GPS foam I'd be interested, but I haven't found them.

   Since we're replacing an existing roof and only adding insulation local code doesn't require an inspection.

   What mutiple roofers have proposed is either prefab hunter type panel (which has iso). Or fasten down two layers of gps foam, then fasten down the backer layer.

   I'm simply considering a third route, recognizing it may not be an advisable one.

   I'd love to know if anyone has done this with/without success. As you say, possible, certainly, anything is. A decent idea? I don't yet know.

   Thanks again!

1. 
   Zins | Jun 28, 2023 10:01pm | #3

   And I should add, if I use iso I don't need the backer layer under EPDM. This is driven by a desire to use GPS foam.