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NorthShoreSLR
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# Posted: 9 Nov 2025 08:19pm
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Hello friends. After framing and getting the cabin build dried in for winter, I'm on to the insulation phase.
I built the rafters from 2x12x18s (big, I know, but needed to span 14') at 16oc and the roof is a mono slope at roughly a 6:12 pitch. We have already completed the metal roofing. Before installing the big rafters, I did sand them in case they are partially exposed.
We are in Northern Minnesota and this is to be a dry cabin with a wood stove and electric.
We are looking for advice on insulating the roof and enclosing the ceiling. We got a deal on 2" foam and we're thinking to install that between studs and then spray foam all the edges. This should be okay for the 2x6 framed walls, right?
But what about the ceiling? Seeing that this will be a "hot roof", I'm getting confused on the air gap and how to handle the depth of the 2x12s.
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NorthShoreSLR
Member
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# Posted: 9 Nov 2025 08:21pm
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Thank you in advance for all expert and kind advice.
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DRP
Member
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# Posted: 10 Nov 2025 07:13am
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This is one good overview;
https://www.youtube.com/watch?v=FsFTsrfhBug&t=566s
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Brettny
Member
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# Posted: 10 Nov 2025 10:50am
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Get that wood stove installed. 2in foam will be good in the ceiling if layered. Idk I would bother with it in the walls. Fiberglass is alot cheaper and you dont have moisture to deal with like the roof possibly will.
We did 2x10 rafter with 4in of polyiso foam, caned foam around all the edges then r21 fiberglass over that. We did r21 fiberglass in the walls and 4in foam in the floor. Only use 2 types of insulation not including the caned foam. In a 24x20' with 8x8 bathroom we used about 40 of the pro sized cans of foam. I have a gambrel roof so lots of angles. I got better at useing less foam as I went.
Put one layer of foam in your ceiling prior to doing any interior walls. They where really in the way for me.
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travellerw
Member
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# Posted: 10 Nov 2025 11:03am
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Here is what I did on our roof.
We used foamboard and made a 1" channel from the soffit to a ridge vent. We did this by using foam spacers that we glued to the bottom of the roof sheeting (on the inside). Those spacers ensured that the foam board couldn't be pushed tight to the sheeting when inserted between the roof rafters.
Once that was complete, we filled the rest of the bay with fiberglass batt, and finally drywall. This gave us an R-value of about 25 as we used 2x8 rafters. Our walls are 2X6 and insulated with fiberglass to an R value of about 21.
Our cabin is in a pretty cold place. -40C at least once a season, but mostly -15c to -20C over winter. The wood stove easily keeps the cabin at +20C even at -40C. In fact at -20C we have used the heat pump once the cabin was up to temp.
Hope that helps and wasn't too confusing.
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