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Spray foam for garage ceiling and basement rim joists

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  #1  
Old 09-08-11, 05:58 AM
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Spray foam for garage ceiling and basement rim joists

Hello all. I have a cold bonus room above my garage that I am planning on reinsulating with spray foam as well as my basement rim joist. I had one company come out so far and was quoted 2500 to do the entire job. That included removing sheet rock and replacing with new, and disposal of fiberglass. He would spray 8 inches of open cell into the garage ceiling for an r value of 32 and 6 inches into each of the rim joists. I asked him if closed cell would be better for both applications and he said only on the concrete walls after I frame the basement. He said open cell is fine for rim and garage ceiling. I'm sure the debate is endless, I just want to make sure I am putting the right stuff on. In terms of vapor barrier or retarder is the open cell fine to use? I know I have read on building science or somewhere, that even open cell sprayed at certain depths or inches can be about as good as closed cell for vapor. Also, the information sheet he gave me says the open cell is class I fire rated at 4 inches. Would there still need to be a fire retarder sprayed on or would sheet rock be enough. This may be a question for the local inspector. I live in upstate NY.

Thanks , Ty163
 
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  #2  
Old 09-08-11, 06:15 AM
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Open cell spray foam does not provide any type of protection against vapor. There is no debate on this. If you read that it did on buildingscience.com, I would like to see where. You need at least 2 inches of closed cell spray foam for vapor protection. You can spray open cell on top of it.

If sheetrock is not installed over the foam, it will not meet the standards for a class I fire rating.
 
  #3  
Old 09-08-11, 06:57 AM
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At building science.com under enclosures that work and critical seal at rim joists, it says both types of spray foams are acceptible. There Is a diagram that shows
High r foundations 07 and high r foundation 10 that uses open cell.
The predicted relative humidity for the applications according to them appear to be at safe levels. To me, and maybe I'm reading too much into this, would seem to say at certain sprayed depths, open cell is just as acceptable as closed cell.


Ty163
 
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