Is cellulose an appropriate choice for insulating against board sheathing?
Stephen Horvath| Posted inGeneral Questionson
My old house in Pittsburgh, PA has brick veneer walls sheathed with 1×8 boards and covered with what looks like kraft paper on the exterior of the boards (on the brick side). The boards have a gap between them, on average about 6mm, but sometimes as much as a full cm. Wall studs are standard 2×4 cavities and wall covering is plaster and lath.
Is it appropriate to fill these cavities with dense pack cellulose given there are gaps between the boards and the other wall details and my region?
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Replies
Stephen,
If your house had clapboard siding, I would say, "No problem." But the brick veneer complicates the question. I would consult local weatherization contractors to get their advice.
Is the reason the brick complicates the matter because brick holds more moisture? There is a 1" gap between the brick and the sheathing.
Stephen,
I'm not sure how you evaluated the width of the gaps between the boards -- presumably you have opened up a few stud cavities from the inside.
How strong is the kraft paper? Is it relatively intact or deteriorating?
The question is how much cellulose is likely to be blown through the gaps between the sheathing boards into the space between the brick veneer and the boards. That ventilation and drainage space should not contain any cellulose.
That's right. I'm working on a structural renovation project and have opened up some walls, so I can see the sheathing boards clearly. The kraft paper is on the other side of the sheathing, between the bricks and the sheathing, so I can't see most of it. But when I shine my flashlight between the sheathing gaps it looks to be in fine condition.
So it sounds like the ability of the kraft paper to not allow cellulose into the cavity is the determining factor. How likely would it be for dense-pack cellulose to make it's way through the gaps in the sheathing? I guess it matters how much pressure any that goes through would put on the kraft paper. After 80 years I can't imagine the paper can withstand a whole lot of pressure against it without coming undone.