Roof insulation

I have an a frame cabin with 2 inch tongue and groove decking with metal on top. There is no way to insulate the inside. I want to foam the outside. I can't get consistent answers on how to do it. I would like to remove the metal, put something over the wood, build a 2x4 frame, foam the cavity with closed cell foam, put osb decking on the frame work and put the metal back on. What kind of under lament should I use? Do I need any venting? I need some suggestions,		Guest User 3/23/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20222/find/
It sounds like what you're building will not require venting. That said, venting and a thermal break in the system would only be helpful, not harmful. I would suggest a layer of quality synthetic underlayment, or whatever the roofing manufacturer requires.		Todd Miller Isaiah Industries, Inc. 3/23/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20223/find/
So if I remove the existing roof, put an under lament, shark skin or similar. Then build the frame work with 2x4, foam the cavity full (3 1/2) inches, with closed cell. Put osb decking felt paper or ?, then put the metal back. Would that work?		Guest User 3/23/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20224/find/
The underlayment I was referring to would be on top of the decking, directly beneath the roofing. What you are referring to would be more of a vapor barrier. Installing a vapor barrier would not be a bad idea. I would probably do an impermeable vapor barrier for that rather than a roofing underlayment through.		Todd Miller Isaiah Industries, Inc. 3/23/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20225/find/
Why not just use rigid foam over the roof sheathing? This type of system is fine. You can air seal the T&G boards by just putting peal and stick membrane over it.		Eric Novotny An informed customer is the Best Customer! 3/23/2015	Share Or copy this URL: https://www.metalroofing.com/spirit/comment/20226/find/

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