Toni Marie
3/22/2016
Greetings, We have a building that we are retro-fitting as a cabin/in-law suite and it has an existing metal roof. There is no vapor barrier or sheathing of any kind, the metal roof sits right on the rafters. We are concerned about condensation when we go to insulate, my question is, is there an effective way to install a vapor barrier without having to take the roof off to do so? Also, what would be the best vapor barrier product to use? We purchased a large roll of vapor barrier which we were planning on running between rafters then insulating over that. I would appreciate any feedback provided.
Todd Miller
Isaiah Industries, Inc.
3/22/2016
One option would be to spray foam the underside of the roof with closed cell urethane foam insulation.
Eric Novotny
An informed customer is the Best Customer!
3/23/2016
+1 SPF is the prescriptive fix here. I would see about installing some rigid foam in the rafters to spray the foam against. I never like spraying metal directly if I can avoid it.
Guest User
4/2/2016
So spray foam is the only option here?
Eric Novotny
An informed customer is the Best Customer!
4/3/2016
Not the only option, just the most easy to have done correctly. I would recommend that you talk to a few contractors and as I mentioned previously, I prefer to put in a layer of rigid foam as compared to spraying right to the metal underside.

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