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geobuild
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# Posted: 23 Sep 2021 21:18 - Edited by: geobuild
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Hi All,
I’m going to begin insulating the ceiling in our 14x24 cabin next week. Rafters are 2x6 and I’m using R-23 Rockwool. It’s a gable-ended roof with the collar ties at about 9’. I’m planning to finish the interior with T&G boards next summer.
Originally, I planned to do a cathedral ceiling to the ridge and leave the collar ties exposed but that will mean a lot of tricky, for me, cutting of the T&G boards. If I finish the ceiling across the collar ties should I insulate all the way to the ridge in the rafter bays or go across the collar ties?
Second question…… I met an architect building a year-round vacation home nearby here in the northern Adirondacks. He told me about Intello membrane for the interior. Using it in a cabin is probably overkill but the architect tells me I could avoid installing soffit vents and 1x2s on the rafters to create a space under roof plywood.
Thanks in advance.
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DaveBell
Moderator
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# Posted: 23 Sep 2021 23:03
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Quoting: geobuild If I finish the ceiling across the collar ties should I insulate all the way to the ridge in the rafter bays or go across the collar ties?
If you insulate up to the ridge, the ridge vent will allow cold air down to the ceiling. So go across the ties.
Quoting: geobuild Rafters are 2x6 and I’m using R-23 Rockwool
The R-23 rockwool is 5.5 inches thick. A 2x6 is 5.5 inches deep. How will the soffit vents duct to the ridge vent?
Quoting: geobuild Intello membrane for the interior. .....I could avoid installing soffit vents
A roll of Intello is about $400. (Made in Germany) Then you would install it from ridge vent across the tie and back up to the ridge vent. And seal between runs.
All things considered, no soffit vents, seal the attic wood with deck sealer, install small metal gable vents on the gable ends to assist the ridge vent, Tyvec the top of the ties, rockwool insulation the ceiling and walls.
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Brettny
Member
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# Posted: 24 Sep 2021 06:01
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2x6 really isnt enough for ceiling insulation on our climate. Is it also a metal roof?
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geobuild
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# Posted: 24 Sep 2021 11:40
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Quoting: DaveBell The R-23 rockwool is 5.5 inches thick. A 2x6 is 5.5 inches deep. How will the soffit vents duct to the ridge vent?
If I go with the Intello I would not install soffit vents, would install insulation across collar ties and install insulation in rafter bays below collar ties. The insulation would be against the plywood roof deck.
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geobuild
Member
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# Posted: 24 Sep 2021 11:42
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Quoting: DaveBell A roll of Intello is about $400. (Made in Germany) Then you would install it from ridge vent across the tie and back up to the ridge vent. And seal between runs.
I don't understand this. If I go with insulation in rafter bays then across collar ties I thought the Intello would be installed the same way, up the rafter bays then across collar ties.
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geobuild
Member
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# Posted: 24 Sep 2021 11:45
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Quoting: Brettny 2x6 really isnt enough for ceiling insulation on our climate. Is it also a metal roof?
Yes, metal roof on 5/8" plywood. This is going to be used primarily from May to November. Maybe one or two short trips in the dead of winter when it's below zero F.
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geobuild
Member
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# Posted: 24 Sep 2021 11:45
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Thanks DaveBell and Brettny for your feedback!
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Brettny
Member
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# Posted: 24 Sep 2021 15:14
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You may get enough R value if you spray foam under the roof. However if you insulate to just the rafter ties it will allow you to really vent the attic triangle that's left. I have found ridge vents work poorly with cathedral ceilings.
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gcrank1
Member
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# Posted: 24 Sep 2021 20:26
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For 3 season with occasional winter we had NO insulation in a cath ceiling in s-central Wisconsin for 37 years. 5.5" of insul in my 2x6 rafters would have been luxurious, as it was we kept the wood stove idling along and did fine, sometimes living in there in shorts and t-shirt at well below freezing.
I had intended to insul.....then lost my 'roundtuit'; once we found out we could do more than just barely Ok there was no rush, lol.
On yours Id make everything above the collar-ties a mini-attic, fill the lower rafter sections with all they will take and at least that much on that 'attic' floor and have gable vents as mentioned. Bet you will be cozy.
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Brettny
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# Posted: 25 Sep 2021 20:44
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I guess the "wait and see" approach would work here. With metal roof how ever you may be making moisture between your sheething and roof you dont use proper underlayment it can damage the sheething
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geobuild
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# Posted: 27 Sep 2021 16:38
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Quoting: Brettny With metal roof how ever you may be making moisture between your sheething and roof you dont use proper underlayment it can damage the sheething
I checked with the cabin builder and the roof underlayment is Tarco UDL-15 synthetic underlayment.
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