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Right Idea, Wrong Result: A Cellulose Insulation Job Goes Off Track

Too much cellulose in the wrong place creates a winter nightmare

Too much of a good thing. Cellulose oozing between roof slates is soaking up winter moisture and creating problems inside the house.
Image Credit: Jason Shapiro

Jason Shapiro took the plunge and invested in more insulation for his house: blown cellulose for his attic and dense-packed cellulose in the exterior walls. No doubt he’d like to be enjoying a warmer house and lower energy bills. Instead, he’s dealing with a mess.

“We have now had significant snowfall and freezing rain, and today I noticed a leak from the top of a window casing in the wall that was dense-packed,” Shapiro writes in a Q&A post at GreenBuildingAdvisor. “When I went up on a ladder to look at the gutter, I found a significant amount of frozen cellulose protruding from a gap between the slate roof tiles and the sheathing underneath.”

It looks like the cellulose was wicking up moisture from the outside and allowing it to get into the wall, but why is the excess cellulose there in the first place? Shapiro says foam insulation baffles were placed between each rafter before the cellulose was blown in, and the top plate was sealed with spray foam.

“The soffits appear to be filled with cellulose that is poking out through the vents, and which can be easily seen from the outside of the house,” Shapiro says. “I am also able to reach up through and behind the gutter and under the sheathing and can feel a large amount of wet cellulose. The contractor is saying that there must have been a problem with the roof that allowed the cellulose to communicate to the exterior in this way. He is also saying that there is no need to remove the wet cellulose because it is treated with borate and will not mold.”

Source of the problem

GBA senior editor Martin Holladay points to one potential cause:…

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2 Comments

  1. Nicholaus Baxter | | #1

    Pull down the soffit
    I suggest pulling off a section of your soffit to see where the insulation is coming from. It should be evident if it came from the wall or the roof. It is the insulation contractor's responsibility to remove and replace wet insulation as well as repair any damages from the poorly installed insulation. Be careful in allowing them to do work beyond the insulation task, if you have insulation installers out there removing and replacing soffits, 9 times out of 10 they will do a shotty job and you will need to get it redone anyway.

    Get a second opinion. Find a general contractor that can assess the damages, the cause, and the solution for you. This will help you know what the insulation installers need to do. Get a quote from the contractor to fix the damages, if there are areas that need to be fixed or replaced such as soffits, siding, roofing, or gutters, outside of what the insulation installers are capable of, it will be the insulation installers responsibility to pay your contractor for the repairs.

    It is a messy situation dealing with poorly done work, and likely you will end up paying for something out of your pocket, but you most definitely do not want to leave any sort of water intrusion issue alone. It will not dry out, and nothing in the building world just goes away, it only gets worse. Down the road you can end up with rot, or water intrusion issues that make their way into your home.

  2. Matthew Amann | | #2

    Obvious previous leaks.
    If there weren't openings in the assembly to start with, there wouldn't be wet cellulose. Sounds like the baffles sealed the deal, either weren't wide enough, or not tall enough, and/or the installer was blowing sloppily. Cellulose obviously shouldn't be in soffits or against ANY skip sheathing.....missing fascia?

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