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-   -   Minimum foam board thickness over OSB (http://www.diychatroom.com/f19/minimum-foam-board-thickness-over-osb-91953/)

Arky217 01-10-2011 11:45 PM

Minimum foam board thickness over OSB
 
For a mixed humid climate (Arkansas),
what would be the minimum thickness or R-value of foam board over OSB wall sheathing to prevent condensation in the colder months on the inner surface of the OSB when the wall cavity batts are R-19 ?

Thanks,
Arky

Ron6519 01-11-2011 09:02 AM

If you're getting condensation on the interior side of the OSB, it sounds like there is no vapor barrier on the interior(or it's leaking,badly).
Ron

Arky217 01-11-2011 01:07 PM

Quote:

Originally Posted by Ron6519 (Post 567583)
If you're getting condensation on the interior side of the OSB, it sounds like there is no vapor barrier on the interior(or it's leaking,badly).
Ron

According to buildingscience.com, no interior vapor barrier should be used for a mixed-humid climate; just the vapor retarding of the latex paint over the drywall. Their reasoning is that the wall should be able to dry in both directions in a mixed-humid climate.
The walls haven't been built yet, I just want to keep the osb board warm enough in the cold months, as per their (buildingscience.com) recommendation, to prevent condensation on the inner surface of the osb.

Gary in WA 01-11-2011 11:13 PM

I would not use OSB or R-19; http://www.buildingscience.com/docum...d%20in%20walls
http://bct.nrc.umass.edu/index.php/p...d-and-plywood/
http://www.diychatroom.com/f98/how-b...ulation-90438/

http://www.greenbuildingadvisor.com/...foam-sheathing

Gary


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