Replies

1. Expert Member
   Zephyr7|Apr 20, 2020 08:52pm|#1

   Looks like tar paper to me, which is usually a kraft paper material with a black coating. If it’s thick and tough it might be asphaltic fiberboard.

   I think both materials act as smart vapor RETARDERS, not full vapor BARRIERS. These materials aren’t like a sheet of polyethylene, for example.

   Bill

1. 
   Austin G|Apr 20, 2020 09:20pm|#2

   Any possible way to determine perm rating on something this old? I sprayed closed cell on the interior knowing that the exterior was only 1/2” of eps... but only just realized this papaer was hiding under the eps.