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I am building a pre-cut kit this summer and it comes with a metal roof. This kit has no vapor barrier or insulation and the roof is 2x6 24" OC rafters. I want the post and beam wood wall look to stay but the ceiling is stick built rafters. So I am trying to figure out how to get this right the first time! I have a metal roof on my garage with plywood decking, purlins and then the roofing and it is VERY HOT! I don't want to see plywood inside my beautiful P&B. So, I've been thinking...
1) from the rafters out-Plywood decking, underlayment, Reflectix radiant barrier, purlins, then roofing. From the inside, 2" rigid foam, nailers and then recessed barn boards to keep the look. Seems like too much work.
2) from the rafters out-Barn boards, vapor barrier, 1.5" rigid foam silver face out to reflect summer heat, purlins, the roofing.
3) Inside rafters, I install a vapor barrier, then boards for a finished continuous flat board look. From the outside, I lay pink insulation, Decking, underlayment, Reflectix, purlins, then roofing. (nervous about the pink in this scenario)
I know there is controversy over Reflectix bubble foil but I have installed it between the rafters with air gaps at top and bottom and it has done a great job with channeling the heat out to the roof vent.
It is not a year-round cabin and doesn't need a huge R rating. Keeping summer heat from the roof out is every bit as important and sealing it up to hold heat in.
I have attached some pics in case they may help.
I have read through a bunch of these threads and you guys are great!
This is the kit as is
This is what they suggest but it uses pink and I see no purlins. Does this seem right?
You could use your last option and substitute rigid foam insulation for the pink fiberglass. Battens will probably be helpful. I would suggest they may not be essential but, if you can't ventilate between your insulation and your roof deck, I think battens are wise as they will provide a thermal break from the metal to the decking.
Thanks for the thought.
The pink fiberglass will be easier to deal with. What are your thoughts on the reflective material (Reflectix)? It is not in the illustration, but I am going to put purlins down over the roofing vapor barrier. Do you think that will provide enough ventilation?
Does anyone have any better suggestion?
Reflectix is more for radiant heat reflection -- keeping the structure cooler in warm weather -- than for anything else, correct?
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