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Damp spray insulation voids

Mr_Gerbik | Posted in Green Building Techniques on

Looking for some advice.

I recently had my walls damp sprayed with cellulose. Upon checking everything out after they left, I noticed some voids (or dimples) in the installation where the cavity wasn’t quite filled. They are between .5 to 1 inch deep by maybe a square foot. Not a big deal in terms of r value (stud cavities are true 6″), but I had a couple questions:

Is this to be expected? Some part of me imagined these cavities should have all been 100% full, as it doesn’t seem it would be hard to overload them as the scrubber takes care of the rest.

Is this a problem? I’m not an engineer, or a very smart guy. I just want to be sure the gap between drywall and insulation will not pose a problem.

The insulation seems quite damp yet, I know every place has said this is fine, but seems disconcerting. I will not be using an internal vapor barrier and that should aid in drying, I don’t suppose the cold winter is helping.

I invested in the cellulose over batt insulation because of irregular cavity sizes, among other things. I just want to make sure that I got what I paid for.


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  1. GBA Editor
    Martin Holladay | | #1

    Talk to your insulation contractor. If the contractor is reputable, he or she will come back and make sure that the installation is satisfactory. It isn't unreasonable to expect every stud bay to be completely filled. That said, I don't know if you are talking about one small area, or a significant percentage of your walls.

    The energy penalty from this type of problem is small. However, it's conceivable that this type of void could lead to settling or slumping over time.

  2. user-1140531 | | #2

    When inspecting a job like this, how would a person know that there are not more voids hidden on the exterior side against the sheathing?

  3. Mr_Gerbik | | #3

    There were not a whole lot of spots, overall I am pretty happy with it. It is amazing the difference cellulose insulation makes. We have always insulated with fiberglass, but the cellulose was immediately noticeable, especially with sound reduction. I watched a bit of the installation, and the voids seemed to be an issue of just the lack of fill, not necessarily a faulty installation. From what I could see and how tightly the cellulose was packed it would be near impossible to have an undiscovered void.


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