GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Does the facing of polyiso insulation matter when mechanically attaching to a block wall?

Paul J | Posted in Building Code Questions on

The 2009 IRC allows for unvented crawl spaces. To acheive the R-10 for my zone (Maryland) I plan on using recycled 2″ polyiso roof insulation attached with Tapcon screws to the CMU walls. 85% of the CMU is below grade. The facing of the roof insulation I intended to use has a heavy tar paper facing both sides. Does this facing preclude using this roof insulation in this application?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. TJ Elder | | #1

    Paul,

    This is probably okay if the wall has effective waterproofing and stays dry. The polyiso will be nearly impermeable, but you don't really want moisture to migrate into the insulation. You just need to be sure there's no wetting of the block, or water could collect under the polyiso, and probably end up dripping out onto the floor. The worst thing you can do is add insulation to the warm side of a wet wall.

  2. Paul J | | #2

    Thank you for your reply.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |