Open cell vs closed cell spray foam insulation in my attic
I am insulation an old brick house with closed cell on the exterior walls and I am tying to decide between open or closed cell under the roof deck in the unvented attic. Most insulation contractors are recommending open because it’s cheaper and also because if I go with closed cell and the roof leaks it will not penetrate the insulation and could remain stuck between the sheathing and the insulation and could rot the wood and or travel to a more hidden spot of the roof or attic causing worse problems that are harder to notice than if the roof leaked and water penetrated through the open cell which I would be able to see and fix if necessary. I’m putting on a new roof so assuming the roof is water tight and not leaking should I go with open cell? Or maybe a hybrid of a thin layer of closed cell on the roof deck and the rest of my r value in open cell? Anyone have thoughts on this? I read Martins article which makes total sense but it doesn’t address the notion of closed cell being problematic if the roof leaks and can’t penetrate the insulation. I guess the question is whether closed cell is worth the extra money etc. thanks!
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