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SJohns
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# Posted: 16 Jun 2021 16:50
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I had a 14' x 32' "shed" style cabin built for me as a 'caretaker' cabin for my mom. I'm trying to figure out the insulation for the vaulted barn shaped ceiling. The rafters are 2x4s and there are no gaps/venting at the eaves. At the ridge, the OSB does not meet and I can see the black paper that is between it and the metal roof ridge. The cabin is pretty air tight. been working on if for four years during weekend trips and have no mice/ insect invaders yet. I have read so many different things about vent channels, foam board, batting, foil, my head is about to explode from it all. The cabin is in southern Kansas and I will be heating with tiny wood burning stove and cooling with window unit. From all my research it sounds like I'm supposed to run 1x2 cross wise the rafters and fill in with 2" and 1/2" foam boards to have a 1" air space between the OSB and 2 1/2" foam board with a radiant barrier, sealed with tape on room side, then attach my finished ceiling material (probably tongue in groove)the the room side of the 1x2's, which will allow for 1" air gap between ceiling material and the radiant barrier. I attached two photos from before I started work. I've framed in a bathroom and closet at the end opposite door and have already installed electrical, plumbing, and wall insulation (faced Pink R13). Also, should I put some vents on the walls near the ridge on each end? I'm considering enclosing the end loft as a storage area. (excuse any bad terminology) Thanks for any advise and guidance!
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spencerin
Member
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# Posted: 16 Jun 2021 19:26 - Edited by: spencerin
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Assuming you're keeping it vaulted, I think most on here would advise you spray foam it all and then attach your finished ceiling material directly to the rafter studs.
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SJohns
Member
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# Posted: 19 Jun 2021 21:32
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Thank you, I was hoping to avoid the expense of spray foam, but at least it will be less labor for me.
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Brettny
Member
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# Posted: 19 Jun 2021 23:06
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2x4 rafters and you still want an air gap? That really dosnt leave much if any for insulation. Have you thought about leaving the whole 2x4 for an air gap and putting foam board directly on the under side of the rafters?..then useing furring strips to hold the ceiling material on?
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spencerin
Member
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# Posted: 19 Jun 2021 23:12
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You can buy DIY spray foam kits, and if you're in southern KS, you might be able to make it go further. You could always do a layer of spray foam and then a second layer below it of foam board. One big advantage of spray foam is that is creates a tight seal.
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SJohns
Member
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# Posted: 20 Jun 2021 13:12
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How thick of foam board would I need if I did the refers as air vap?
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SJohns
Member
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# Posted: 20 Jun 2021 13:16
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If I did DIY foam spray, I just need to spray one layer between the rafters? How thick? Would 2" foam board be enough? And should I just attach it to the rafters like Brettny said? It got down to below zero last winter for almost two weeks and summers can be over 100 with humidity in the 90s.
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Brettny
Member
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# Posted: 20 Jun 2021 18:41
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Look up the Insulation code/map for your area. That will give you a needed R value. Is someone going to be living in this or a weekend cabin?
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SJohns
Member
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# Posted: 22 Jun 2021 09:25
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I'm on the border on zone 3/4, on the Z4 side. My local hardware store had told me R13 was good for the walls. It shows R30 for z3 and R38 for z4. It also mentions R25 for floor. I hadn't thought of floor. I did 6ml plastic on the ground in the crawl space with vents on each side. I will be living in it. I also reached out for foam insulation, but they want to charge extra for distance. I may have to DIY on that.
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Brettny
Member
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# Posted: 22 Jun 2021 11:01
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I believe spray foam is r6-7 per inch and if sprayed to the bottom of the roof you dont need an air gap. Either way you will be useing some foam board on the bottom of the rafters.
For the floor..heat rises but making it hard for cold air to come in down low makes to hard for hot air to escape out of the building. So sealing and Insulating the floor is nearly important.
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SJohns
Member
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# Posted: 23 Jun 2021 21:15
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I have a few weeks so I'll keep looking for someone for spray foam while I research the DIY option. I'll be moving in next spring, so I can do the floor insulation before next winter hits. Maybe I'll get lucky and find someone to spray foam both for a price I can handle. Thanks for the advise!
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