Q&A Forums
OC over CC Post New Topic | Post Reply
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Will Reed
Posted: Apr 06, 2009 09:49 PM
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OC over CC
In your opinion do you see any problems with spraying 3.5" of open cell over 2" of close cell in a 2x6 wall in a cold climate? That is, a CC lift against exterior sheathing and then filling the rest of the bay with OC. My concern is vapor drive. Should I be worried? Do you foresee any other issues with this type of system?
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mason
Posted: Apr 07, 2009 07:21 AM
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Most building scientist agree that 2 inches of closed cell foam will in most environments provide adequate vapor retarder properties so that you can install a higher perm rated material over it (such as open cell SPF, cellulose or fiberglass) If the interior humidity exceeds 50% or if the temperatures in winter are extremely cold for months at a time, you would want to perform some hygrothermal modeling (such as a WUFI or MOIST simulation) to determine the amount of closed cell foam required to minimize the potential for condensation. |
