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dpschuste Posted: Dec 02, 2017 02:58 PM	how much closed cell foam? I live in south central PA--zip 17349. My zone map says I should have R38 on the cathedral ceiling. My spray foam contractor says 4" of cc is plenty to do the job--beyond 4" there is no benefit. Is this enough? I am particularly worried about condensation in the ceiling, as I've had that in a prior, badly insulated home. I would appreciate any advice!
dpschuste Posted: Dec 02, 2017 03:06 PM	I should also add that recommended R on the walls for my area is 13, but there he is proposing 2.5"--when it seems like 2" should be enough? I would appreciate any advice on this as well! Many thanks!
jimcoler I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs. I've expanded my knowledge into t Posted: Dec 02, 2017 03:46 PM	I have typically worked up in Rochester, NY which can be a colder climate than south central PA. I feel 4” of closed cell should be fine in most attics and 2” if closed cell will prevent moisture from condensing on the insulation, but i would be more concerned about the roof rafters or the studs in the walls as wood is only an R-1/inch. So, this only provides an R-2 if you only spray 2” of closed cell in the walls or an R-4 if you only spray 4” in the ceiling. I would suggest spraying over the roof rafters with at least 1-2” of foam to prevent moisture from condensing even in our climate zone. I know I’ve sprayed 6” of open cell in the attic and 3-3.5 in the walls which is less expensive and we’ve had zero issues with condensation in over 15 years! So, you might want to look into this as it’s a less costly solution which still provides equal or R-value with more thickness which is what you want in your situation!

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Comments

dpschuste

Posted: Dec 02, 2017 02:58 PM

how much closed cell foam?

I live in south central PA--zip 17349. My zone map says I should have R38 on the cathedral ceiling. My spray foam contractor says 4" of cc is plenty to do the job--beyond 4" there is no benefit. Is this enough? I am particularly worried about condensation in the ceiling, as I've had that in a prior, badly insulated home.
I would appreciate any advice!

dpschuste

Posted: Dec 02, 2017 03:06 PM

I should also add that recommended R on the walls for my area is 13, but there he is proposing 2.5"--when it seems like 2" should be enough? I would appreciate any advice on this as well! Many thanks!

jimcoler

I have over 10 years of experience specifying and installing open and closed cell spray foam. I've sold my business but I'm still selling for the new owners and consulting on large and custom specific jobs.

I've expanded my knowledge into t

Posted: Dec 02, 2017 03:46 PM

I have typically worked up in Rochester, NY which can be a colder climate than south central PA.

I feel 4” of closed cell should be fine in most attics and 2” if closed cell will prevent moisture from condensing on the insulation, but i would be more concerned about the roof rafters or the studs in the walls as wood is only an R-1/inch. So, this only provides an R-2 if you only spray 2” of closed cell in the walls or an R-4 if you only spray 4” in the ceiling. I would suggest spraying over the roof rafters with at least 1-2” of foam to prevent moisture from condensing even in our climate zone.

I know I’ve sprayed 6” of open cell in the attic and 3-3.5 in the walls which is less expensive and we’ve had zero issues with condensation in over 15 years! So, you might want to look into this as it’s a less costly solution which still provides equal or R-value with more thickness which is what you want in your situation!

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