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jowens80 02-12-2009 11:21 AM

metal roof condensation
My dad has an aluminum roof covering his back porch. It was an open air area but he decided to close it in. We framed the stud walls with 2x4's and sheated with 7/16" osb. Immediatley the rain started from the underside of the roof. I decided to put up a plastic vapor barrier and 1 1/2" foam insulation. The roof has about 4" valleys and peaks so we were able to get some 2x2"s in the peaks for a screwing surface. We are still seeing some condensation though. I removed some of the foam to inspect and saw that moisture was forming on the bottom of the plastic especially were it was in direct contact with the aluminum. I've run out of ideas short of tearing the roof off and building a conventional roof but the problem with that is that he only has about 2"-3" of slope. Can somebody PLEASE HELP?????????????????????????

jogr 02-13-2009 02:23 PM

You put the plastic on the wrong side of the foam. So water vapor is slipping between the foam board joints and condensing on the cold plastic. If you seal well between the foam sheets then the foam itself can act as a vapor barrier. Otherwise put the plastic on the warm side of the insulation (the interior). That should stop the rain.

AaronB 02-17-2009 09:23 PM

and add more insulation in order to get the dew point within the insulation assembly.

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