Currently, the exterior walls have batt insulation. It has the paper face on one side. A few months ago, I removed a window due to watered down drywall caused by the window. At the time, I didn't check to see if the insulation was the kind with a vapor barrier. (there is no plastic, that I know for sure) However, I dont know if the insulation installed was the kind with a vapor barrier.

Now, we have decided to do cellulose at some point. We are currently doing a remodel of 2 rooms so I need to decide if I should remove the drywall and the insulation and then get cellulose blown in. Or if I should leave the drywall and insulation as is and when we get new siding at some point, have cellulose blown in with the batt insulation.

Are there any advantages/disadvantages of leaving the batt insulation alone? Do I need to worry about there possibly not being a vapor barrier?


Dense-packed (and only dense-packed, not loose-blown) cellulose is better in walls than fiberglass batts, for a couple of reasons.

  1. It has a slightly higher R-value per inch.
  2. Is is hygroscopic, meaning that it can take up moisture; in doing this, it can protect the structural wood should it ever get wet.
  3. Dense-packed cellulose can improve the airtightness of a stud wall; Fiberglass cannot, and is very strongly negatively affected by a non-airtight wall (furnace filters are made of fiberglass, which shows you how much air can move through them!).
  4. Cellulose is loaded with borate, which makes it pretty much mold-proof. Fiberglass can, paradoxically enough, grow mold if it gets wet and stays wet, especially with the kraft paper facer.

That said, unless your fiberglass batts are wet or moldy, it's probably not cost-effective to remove them, especially if leaving them in means you can avoid tearing off perfectly good drywall. The kraft paper facer on most batts is not a vapor barrier, it's a vapor retarder, which is fine. Very few batts have foil facers, which are vapor barriers. Even if your batts have vapor barrier facers, I see that you live in Wisconsin, which is a place where you can get away with having a vapor barrier without it being too bad (most of the time you don't want a vapor barrier in your walls). I'd leave the batts in.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.