# metal roof - condensation question



## bestbarnever (Jan 25, 2014)

Gentlemen,

I have an existing pole barn that has been enclosed with walls. Also a plywood and shingle roof has been put over the existing sheet metal roof. I am installing 3/4" rigid insulation on the ceiling inside to stop the condensation. My question is this (please see the attached photo). 

Would it be better to install the insulation on the bottom of the rafters and create an air gap between the insulation and the underside of the roof or cut the insulation and install it between the rafters, directly to the underside of the metal?

Thanks in advance for your help!


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## shazapple (Dec 3, 2010)

Condensation is forming on the metal because the warm moist interior air is meeting the cold metal. The real problem here is keeping the interior air away from that metal (aka air sealing). I think it would be difficult to accomplish a good air seal by cutting the insulation to fit between the joists. 

Why not install batt insulation (fiberglass or mineral wool) between the joists and then board insulation on the bottom? The batt insulation would act as your main insulator and the board could be air sealed by taping the seams.


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## TedLeger (Feb 24, 2014)

*Insulation*

I don't know if I would use all batting. It would be a pain to work with, though it would still work. But that is just me. I think you can use batting on the rafters, and then just insulate between the rafters with regular sheets. No airgap though, as the last post said, it is because of the warm air hitting the cool metal that it drips, and that would put an end to it by just putting the insulation against the sheet. You can always use something like liquid nails to get it from the underside.


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