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

Dense-pack retrofit cellulose insulation for basement walls?

philray | Posted in Energy Efficiency and Durability on

I recently had an energy audit done existing 1958-built tri-level in climate zone 5 (Ann Arbor MI). Looking for advice from the GBA experts to sanity-check some of the recommendations before making decisions; I’ll try to keep it to one question per post. One recommendation was to add dense-pack cellulose into the existing above-grade and below-grade (finished) walls. I see from the How to Insulate a Basement Wall article that cellulose and other air-permeable insulation materials are never recommended against the basement concrete wall.

Are there reasonable options between leaving the uninsulated below-grade walls as-is, and fully demolishing to the concrete and adding rigid insulation then rebuilding the stud walls?

Current state of the basement is fully-finished, with walls of .75″ drywall, 3.5″ studs with no insulation, fiber board (asphalted?). Not sure from there to the outside because I wasn’t ready to cut through that fiber board to inspect further – maybe an airgap or not, then poured foundation wall. The auditor estimated R9 but that seems optimistic. Above-grade exterior is brick veneer and that extends below grade a bit. No under-slab insulation. Moisture situation is good (overhang, gutters) but grading on one side is not ideal. Thanks for recommendations.

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. user-1072251 | | #1

    It would be helpful to know if there is space behind the fiberboard; whether its against the concrete or if there is a gap that could perhaps be filled.

  2. GBA Editor
    Martin Holladay | | #2

    Phil,
    Determining the risk of installing cellulose insulation in this situation is hard.

    Obviously, cellulose isn't a great choice here, and you would only consider its use to save the hassle and expense of the right solution (which is ripping out the drywall).

    The low-risk situation would be if (a) your house has a functioning footing drain and good exterior dampproofing or waterproofing details, (b) your basement has no history of water entry, and (c) the fiberboard you're talking about is asphalt-impregnated fiberboard.

    Under those circumstances, the risk is low.

    If, on the other hand, (a) The footing drain is partially clogged, (b) The surrounding soil is damp, especially after a heavy rain in April, (c) The basement has had a few water-entry events, and (d) The fiberboard isn't asphalt-impregnated, then you'd be nuts to install cellulose.

  3. philray | | #3

    Thanks Bob for the follow-up, and Martin for helping me avoid a mistake. I'll put basement insulation wall at the bottom of the list of possibilities, only to worked if we end up with enough budget to take the drywall down.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |