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doodledawn
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# Posted: 8 Aug 2019 01:59pm - Edited by: doodledawn
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Hi everyone,
Long time lurker, first time poster.
I am refurbishing my uncle's old trappers cabin. It is currently a 14x18 framed with 2x6s with a 6 ft covered front deck on skids with shallow (edit) gable roof trusses. I am tearing off the old roof, adding 2 feet along with a loft overhanging the deck and putting on an equal angle gambrel style cathedral roof. I live in northern Alberta, Canada so it can get below -40 (same in Celsius and Fahrenheit) and up to 30C in the summer (86F) but is a pretty low humidity climate year-round.
Because it is a gambrel roof, my guess is that I need to do an unvented style (it will be metal). I know I should be using rigid foam on the outside of the sheathing that exceeds the r-value of the interior batting but that is going to cost big bucks. If I insulate entirely under the sheathing, would my mold risk go up significantly? Also if anyone has any other tips for me, I am open to all advice. This is definitely a learn-on-the-go project!
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Brettny
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# Posted: 8 Aug 2019 02:40pm
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This application it would be best to use spray foam. Or you can do wrap and strap useing foam board. Either way you cut it the fiberglass insulation that fits in a 2x6 ceiling is only going to be r21. Thats not enough.
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ICC
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# Posted: 8 Aug 2019 03:16pm - Edited by: ICC
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Why s gambrel roof? In your climate a gable roof with insulation in the ceiling is easier, cheaper and much more energy efficient.
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doodledawn
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# Posted: 8 Aug 2019 03:57pm - Edited by: doodledawn
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I picked a gambrel because I wanted some clearance for the loft, as it was a pretty small space to start. And as for the r-21, that's what I was afraid of. One option I read would be to scab on some 2x4s the trusses. Honestly I could have built something from scratch for a similar price, but the building has sentimental value.
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Princelake
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# Posted: 9 Aug 2019 06:55am
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What about building a knee wall like 3-4feet then use 2x10 or 12 and stick frame a regular roof
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Brettny
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# Posted: 9 Aug 2019 07:37am
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Look into the "wrap and strap" method. Basicly you build the roof sctucture, sheeth it, then put foam board down, put furring strips down and around the outside and around the foam board then put your metal roof on. Cheaper than spray foam but seals better than cutting foam and sticking it in the bays. You can also add fiberglass later if you feel the need so an r30-r48 in foam isnt needed.
What is your desired R vale for the roof? A gambrel roof holds alot of hot air up in the roof so a higher R value may really help.
I built this gambrel shed a few years back with all rough cut. I can give you a few pointers if you would like?
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Scott G
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# Posted: 9 Aug 2019 10:07pm
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My cabin is gambrel. Only 2*4 rafters with r15 extruded foam. New addition I made 2*6 rafters, r20. It's small and the stove makes up for it. I'm in New Brunswick, plenty of cold here too.
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doodledawn
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# Posted: 20 Aug 2019 05:54pm
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The gambrel trusses are already built so no switching to another roof type, unfortunately.
Quoting: Brettny What is your desired R vale for the roof? A gambrel roof holds alot of hot air up in the roof so a higher R value may really help. I built this gambrel shed a few years back with all rough cut. I can give you a few pointers if you would like?
Pointers are welcome. I was aiming for minimum R-31 (going by the climate chart on the Home Depot website). The place doesn't necessarily need to be to code but also don't want to have to redo the darn thing later.
@Scott G, does the stove make a big difference with condensation? That will be my primary heat source for now.
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