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Community and Q&A

Dense-Packed Cellulose for Old Walls

cfowens | Posted in General Questions on

I live in upstate New York in a home built in 1958.  The home has no insulation in any of the exterior walls.  From some research I’ve done, it seems like the only retrofit option available without pretty much tearing all of the drywall down is dense packing the stud bays with cellulose from the outside.  This entails removing rows of siding, drilling 2 inch holes through the sheathing, dense packing the stud bays, plugging the holes with a wood cutout, sealing, and replacing the siding.

There seem to be conflicting opinions on whether this is a good approach or not.  Some seem to make the argument that older homes of this era were designed/built to be able to ‘breathe’, and by dense packing the walls with cellulose you essentially cut that ability to ‘breathe’ off, setting the stage for mold and moisture issues.  Some literally state that this is a surefire way to destroy(!) an old home, and your studs will inevitably rot out by doing this.  Sounds pretty scary!

On the other hand, I’ve seen others suggest that so long as there are no known/active water leaks in your home, one could argue that there is little opportunity for the cellulose to get wet in the first place, and so the risk of this rot occurring is relatively low.

It’s worth noting that my house is vinyl sided, and the vinyl is, at least tin my opinion, in pretty good shape.  I’m not aware of any major cracks, leaks, etc.

As I mentioned, I live in upstate New York, where temperatures have been below zero degrees Fahrenheit on and off for the past few weeks.  So the lack of insulation in my exterior walls currently isn’t doing my utility bill any favors, and i’d really like to do something about it.  As aforementioned, seems like dense packed cellulose might be my only retrofit option here, but if that’s going to rot my house out, i’m not sure I want to proceed with that.

I’ve been driving myself nuts here the past few days reading conflicting opinions on this approach on various sites across the internet.  I’m doing my best to educate myself, but also understand that sometimes reading too much can just muddy the waters more.

Appreciate any insight anyone here who’s probably way smarter than me on this topic might have to offer.

Thanks in advance!

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  1. user-6623302 | | #1

    I filled my walls in my 1830 house with cellulose thirty years ago with no apparent problems. How are the walls constructed? Boards, not plywood? Cellulose is a good moisture manager and will dry to the outside if it is not sealed in. Have you looked into the State energy efficiency program.

    1. cfowens | | #3

      Thanks for the reply here!

      That's encouraging to hear that you did something like this and haven't had any apparent issues in 30 years.

      I assume you're asking what the sheathing is? If so, I'm not positive, but I don't think it's boards or plywood. One of my rooms that has a built-in dresser that runs alongside an exterior wall. I pulled one of the drawers and can see right into the stud bays. This is what told me there is no insulation in the exterior walls to begin with. Anyhow, as I can see into the stud bays, I can see the back side of the sheathing. It appears to be some type of like textured compressed/particle board. Kind of hard to describe, as I can't say i've seen it before. It's definitely not plywood, though. See the picture I attached here, for reference.

      Do you suppose what it's made of makes a difference?

      I am familiar with the EmPower and Assisted Home Performance programs that help cover either all or a portion of the cost to upgrade the insulation in your home. They both appear to be income-based, however, and after taking a look at the income limits, I don't think I would qualify, unfortunately.

      Are these the programs you're thinking of, or is there something different out there? I'd love to be able to take advantage of one of these if I could qualify.

  2. walta100 | | #2

    I have a few things I would want know before deciding .

    Are you sure there is no knob and tube wiring in your walls?

    Do you have plywood sheathing under your siding?

    Is there a layer of tar paper under the siding?

    I had cellulose blown into the walls of my 1959 house. It had vinyl siding over the original redwood tar paper and skip sheathing. It worked well for us there was one bay the insulators did not want to fill for some reason I was always amazed at how cold that part of the wall was. One wall had a brick veneer so the insulation was blown thru holes on the drywall I was the only one that could see the plugs.


    1. cfowens | | #4

      Thanks for the response here!

      No knob and tube wiring that I'm aware of. It's older 2 conductor wire without a ground in most of the house but, again, no knob and tube that i'm aware of. The electrical entrance was also updated not too long before I bought the place 8 years ago. So it's relatively modern.

      See the photo I attached to my earlier reply to Jonathan Blaney, for what I believe to be the back side of the sheathing (inward facing side). As noted, i'm not sure what material this is, but it doesn't appear to be plywood. It looks like some type of textured compressed/particle board. Not sure if this presents an issue or not.

      As the picture also shows, there doesn't appear to be any type of tar paper or moisture/vapor barrier. Guessing that's less than ideal (?)

      The walls are currently quite cold, as it sounds like the one section of yours that didn't get insulation is. That is what i'm trying to fix here!

  3. walta100 | | #5

    Seeing your photo reminded me that my old hose had the same insulation board under the siding. We lived in that house for 20+ years after we had the wall filled without a problem.

    Seems to me your house is the perfect candidate for blowing in cellulose

    I don’t recall feeling like the wall were cold before we had the cellulose blown in.


  4. mn_johnb | | #6

    That picture looks like a fiberboard sheathing like celotex. Think structural homosote.

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