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GrapevineVilla
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# Posted: 14 Jul 2022 04:49pm
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I’m brand new to this forum but I’ve been stalking for a while now. My shabin has arrived and I’m working on getting insulation installed bc I’m in Indiana so we have hot AND cold so I’m not 100% sure how to do my ceilings with respect to moisture accumulation. I have a metal roof (no ridge vent) with underlayment then OSB. I am making the ceiling vaulted. I will likely stain my trusses to make them look good. I’m installing insulation with kraft facing. Since the ceiling is essentially unvented I suspect I need an actual air barrier overtop my insulation or beneath tongue and groove paneling that I will eventually put on? I have a wood stove for heat and a small window ac unit for summer. I have read when to use a vapor vs air barrier guides on the web but they are typically talking about a normal house roof with an attic. In this particular application I’m not sure how to proceed. Do any of you have suggestions how to do this without creating a moisture situation in my walls and/or ceiling? I’m attaching a photo to give you a better idea of what I’m working with.
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Cedar Fever
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# Posted: 14 Jul 2022 05:09pm
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Story of my life. I have not insulated yet but am having similar issues. Spray foam is great since closed de would be a vapor barrier. What I am going to try and do is insulate the outside of the roof with foam board. Or OSB my roof and spray foam it.
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BRADISH
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# Posted: 14 Jul 2022 06:13pm
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You might want to check out WILL1E's build thread for some ideas..
https://www.small-cabin.com/forum/6_10783_3.html
Pages 4, 5 & 6 all have info/pictures of how he approached this issue.
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ICC
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# Posted: 14 Jul 2022 06:33pm
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Quoting: Cedar Fever insulate the outside of the roof with foam board
That would be my choice with such a structure.
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GrapevineVilla
Member
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# Posted: 14 Jul 2022 07:08pm
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Thanks for that! My cabin is fully metal on the outside so I am working to get it comfortable enough to stay the night in to save gas driving back and forth.
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GrapevineVilla
Member
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# Posted: 14 Jul 2022 07:12pm
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I’m not sure why my pictures keep flipping sideways and upside down 🤔
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razmichael
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# Posted: 15 Jul 2022 02:01am
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As mentioned, closed cell spray foam is a great option if your budget allows (and might not be as expensive as you think).
We did ours this way and added in spraying the loft end walls (I had already insulated the rest). No venting or vapor barrier to worry about plus really good insulation both summer and winter. Not to mention the professionals will have it done in no time.
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Brettny
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# Posted: 15 Jul 2022 07:02am
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You will never get enough insulation nor enough air sealing with batt insulation for that ceiling. It's not really about how much heat loss/gain your going to have..air will leak out and meet a cold piece of plywood and cause condensation. Condensation in a enclosed space will mold.
Theres really just no cheap way to insulate a 2x4 truss vaulted ceiling, or even a 2x6-8 vaulted ceiling for that matter.
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GrapevineVilla
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# Posted: 15 Jul 2022 07:44am
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One reason I didn’t use foam boards with spray around the edges was it seemed like it was hard to get a good R Value? I’m not opposed to taking the batts out of the ceiling and using foam board if it means my cabin will last longer. What R value have you all been using when you use foam board insulation?
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toyota_mdt_tech
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# Posted: 15 Jul 2022 08:19am - Edited by: toyota_mdt_tech
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Quoting: GrapevineVilla so we have hot AND cold so I’m not 100% sure how to do my ceilings with respect to moisture accumulation.
How about leave it open, insulate up to the rafter ties below it, leave top area open, but vents on each end and in the rafters leading up to the rafter ties, vents drilled into blocking, protect with heavy screen and install those foam "chutes" in the bay to allow breathing from rafter tail bird blocks to open attic area. and insulate over top of chute without crushing it. Add a crawl space door for access.
Then insulate between rafter ties and close in ceiling.
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Brettny
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# Posted: 15 Jul 2022 09:13am
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Quoting: GrapevineVilla What R value have you all been using when you use foam board insulation?
Use the spec for the R value needed for a ceiling in your area. Google search the R value needed and it will show a map with all the specs.
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gcrank1
Member
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# Posted: 15 Jul 2022 11:48am - Edited by: gcrank1
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Im in south central WI; our 1st cabin build was '83-'84, a 12x24 with a 12x12 loft. I insulated the walls, as well as between the floor joists (before decking it) with 1" blue DOW styro. Nothing in the ceiling; I intended to but didnt get to it. Exposed rafters topped by plywood, roofing was asphalt shingles.We used that cabin for 30+ years, heating with only a poor efficiency antique wood stove and even in the dead of winter had no problem other than the getting up in the middle of the night to climb down from the sleeping loft to refill the stove.
In all that time we found no urgency in getting around to insulating the ceiling, and the exposed rafters and plywood was not a bad look.
It was a recreational/part time cabin, off-grid and dry with rain barrel for utility water. We used it A Lot in the 1st 20yrs. Maybe full time would have made me feel more like insulating but I dont think so. We had lots of dead and dying white oaks that needed to be cleaned up and recycled as firewood wasnt an issue as the cabin was really pretty easy on wood fuel.
Propane cook stove, whatever old 'marine' battery(s) I could scare up for lighting (old type Edison base RV incandescents, what energy hogs!) and a D battery powered radio. At our new cabin (Aug 3, 2020) we still have off-grid, dry with rain barrel (waayyy better filter system), propane cookstove, same radio, but LED lights and 2x 100Ah LFP batteries (Great bats!) powering a 12vdc to 120vac 300W pure sine wave inverter. All is simple wired for 120vac and we also have Fans (wha-hoo) and a small tv with built in vhs player.
Fwiw, I get 2 to 3 times as much power from a 100Ah LFP as I did from a 100Ah 'marine' bat. This year Im just swapping the bats out and bringing the low one home to recharge, but I do have 600W of solar array at the cabin I need to re-do. No rush.
For bigger stuff; ie, microwave, power tools, etc we have a 1700/2000peak inv/gen.
And simple wash pans, no plumbing, a diy composting T and simple grey water French drain.
All that to say, its a rustic cabin, not a miniature 'house', well more creature comforts than our prev one and no hardship living for us (at 70ish).
Dont overthink it unless you have to be code compliant with inspections.
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GrapevineVilla
Member
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# Posted: 16 Jul 2022 10:24am - Edited by: GrapevineVilla
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So with foam board insulation the R values don’t go nearly as high as fiberglass batting. The highest I could find for board insulation in a sane price range (still questionable) was closed cell R 10 that is 2 inches thick. Online I have seen if you create an air pocket on either side of that 2 inch foam board it can increase the R value significantly. The recommended R value in central Indiana is R 13. I see some of you have used batting underneath the foam board of course that was Alaska and I’m pretty sure that cabin needed a higher R value than mine will. Also my understanding is that with closed cell foam boards you do not need an air barrier bc it’s closed cell. I’m not a carpenter so I don’t know the technical jargon for some of this stuff, I apologize.
Also we have extremely hot weather here too so this cabin will have a small window ac unit. I’m not just trying to keep warm but also cool. It’s been nearly 90 degrees here on and off for weeks with muggy humidity so there’s a definite concern for moisture in the ceiling with the metal roof on top.
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gcrank1
Member
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# Posted: 16 Jul 2022 10:45am
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Whatever you do with styro, Do Not get styro 'beadboard', horrible stuff that should be (imo) banned.
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GrapevineVilla
Member
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# Posted: 25 Sep 2022 08:31pm
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Decided to go with two inch foam board with a half inch air space beneath. This has made a massive difference during the hot weather. Now… I have a small wood stove to try and figure out how to install. My main challenge so far has been figuring out the flashing on my metal roof. I see a lot of silicone boots being used. Does anyone have experiences with these? Good? Bad?
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spencerin
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# Posted: 26 Sep 2022 09:17am
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Looks like you did a good job.
Where in central IN are you located? I used to be in Spencer, but sold that place and moved closer to the Ohio River.
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Brettny
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# Posted: 27 Sep 2022 08:56am
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Quoting: GrapevineVilla Decided to go with two inch foam board with a half inch air space beneath. This has made a massive difference during the hot weather. Now… I have a small wood stove to try and figure out how to install. My main challenge so far has been figuring out the flashing on my metal roof. I see a lot of silicone boots being used. Does anyone have experiences with these? Good? Bad?
Yes I have a boot on my chimney for about 3yrs and just checked it last week. No leaks.
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Jackson
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# Posted: 29 Sep 2022 09:02pm
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Quoting: GrapevineVilla I see a lot of silicone boots being used. Does anyone have experiences with these? Good? Bad?
Mine is also 3 or 4 years old and no issues. Will use again given the chance.
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GrapevineVilla
Member
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# Posted: 29 Sep 2022 09:08pm
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I checked the price of those silicone boots a Menards today and about had a heart attack. It was $199.99 for a kit. Does this kit seem expensive for what you get?
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Jackson
Member
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# Posted: 1 Oct 2022 04:55pm - Edited by: Jackson
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Roof boot
This is like what I have, unsure of the temp range on mine vs. what I linked though. I have no idea what all is in that box, but the boot alone was all I needed.
But to answer your question with only my opinion, yes.
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