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High Density Cellulose Insulation Drying Time

GBA Editor | Posted in Energy Efficiency and Durability on

I’ve sprayed a wet mix high density cellulose in my stud bays
The weather here in the NW has been good…

How long do I need to wait before drywall?

Even then, because of the 2×6 stud bay, I’m skeptical it will be completely dry. My exterior sheathing is plywood, typar and hardi planks with 1/2 drywall interior. Will I have problems if some moisture is in the cellulose?

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  1. GBA Editor
  2. Christopher Briley | | #3

    It will not be completely dry. I had a house where we did a moist applied cellulose installation (7" cavity) we let it dry for a week with as much heat as we could put in the house without resorting to salamander propane heaters (don't use those). It was surface dry, but if you plunged your hand into it, it was moist (about 21%) we had no choice, we put up the sheetrock and the builder fought humidity issues though spring (condensation on windows, trim and doors always on the move) but in the end, after a good summer, it all worked out though it took about a year for the house to settle in. There were also some tweeks to the ERV (which we changed to an HRV, by swapping a filter). And then humidity has been well under control since. We decided we would never do that again for a winter install but we have numerous times in the summer.

    Let it dry for as long as you possibly can. Postpone sheet rock finishing as long as you can. If you want you could ask the installer to come back with his moisture meter and tell you what the moisture content is before you sheet rock. That puts a little burden on them to tell you its okay. I have this item in my house specs, though it is usually overlooked (or ignored) by the "common" builders.

    You're probably going to be fine.

  3. davidmeiland | | #4

    I use a Drizair dehumidifer on almost every job. It comes in as the drywall board is stocked, and stays thru interior painting. It is amazingly effective at removing excess moisture from the job, and it might help in your case. When it's running I am monitoring the RH and temp as well as the MC of framing members and sheathing in various places.

  4. Frank | | #5

    Thanks for the feedback. The cellulose pdf file you passed recommends NO Vapor Barrier.
    From what I understand, the drywaller tape and texture sub applies a vapor barrier as part of his operation. Should he forego this? or is his application actually a vapor retarder and will not interfere with the cellulose drying to the interior (diffusion through drywall)?

  5. GBA Editor
    Martin Holladay | | #6

    That sounds like a question for your drywall sub. I will repeat my previous advice: don't install interior polyethylene or vinyl wallpaper.

    If you or your building inspector want to see a vapor retarder that comes in a roll (instead of interior paint), install MemBrain, a "smart" retarder with variable permeance.

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