Open-cell foam on attic floor
David Coker| Posted inGeneral Questionson
My house is about 10 years old and the attic floor has open cell spray foam. There are places where the foam is only 3-4 inches thick. I am considering adding 10+ inches of cellulose on top of the open cell. Will that cause problems with moisture? The makeup of the ceiling is painted sheetrock, ceiling joists with cavities filled with open cell in a vented attic space. I am in the upper most top of zone 4 in Arkansas. I’ve done a lot of research in here and on the internet but everything i’ve read is directed at closed cell on the attic floor. Your thoughts and ideas please?
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Replies
David,
Q. "I am considering adding 10+ inches of cellulose on top of the open-cell spray foam. Will that cause problems with moisture?"
A. No. before installing the cellulose, inspect the attic carefully to make sure that air leaks were properly addressed. Just because the attic floor has spray foam, doesn't mean that all air leaks were sealed properly. Once you've verified that air sealing work is complete, go ahead and pile on the cellulose.
David,
Do you have HVAC ducts or equipment in the attic?
Yes, i've already inspected the attic and there was a few places I had to use can foam. Thank you for he information and i've learned a lot from this forum.
David,
It would be better to have the HVAC and ducts within the home's conditioned space. This would require installing new insulation at the roof line. See these two articles for additional information:
//m.etiketa4.com/articles/dept/musings/how-install-rigid-foam-top-roof-sheathing
//m.etiketa4.com/articles/dept/musings/combining-exterior-rigid-foam-fluffy-insulation
If moving the insulation layer is not possible, you would want to make sure your ducts are completely sealed and well insulated before installing the additional cellulose.