GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X 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

Sealing & Insulating Asphault/Felt Impregnated Fiberboard

NorCalNate | Posted in General Questions on

I am in the planning phase of renovating a single story house built in 1958. Removing the inside wall paneling, we found that the sheathing was asphalt/felt impregnated fiberboard (no insulation in the wall cavity). We want to insulate the walls before putting on dry wall, but are not sure how to do so correctly. Removing siding or sheathing is not an option for financial reasons, so we’re hoping someone can give us insights how to seal/insulate the interior cavity knowing we’re dealing with asphault/felt impregnated fiberboard.

FYI the outside siding is wooden board and batten, they put some type of exterior house wrap, and the sheathing is obviously the fiber board which is connected to 2×4″ studs. 

Help please!

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.


  1. Expert Member
    Akos | | #1

    If you have house wrap on the outside, you can insulate with standard batts. I would check around window and openings for sign of water leaks. Those must be fixed otherwise you end up with a moldy mess down the road.

    Air sealing fiberboard is impossible without spray foam. The low cost air barrier would be your drywall. Make sure to install vapor tight device boxes with a gasketed flange as these leak much less than standard units.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |