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Oilerfan
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# Posted: 10 Jul 2013 02:20pm
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Ok I no this topic has been covered in length on this forum but i want to clarify a few things considering my situation....
I am planning to have a catheral ceiling in my 12x16. The rafters are 2x10s on 16" O.C. I live in a northern climate so it is -20C in the winter and max 30C in the summer. Heating with a wood stove. No running water, power, etc. Bare bones...off the grid. Cabin will only be weekend use, with the odd week long trip maybe a couple times a year.
So....
The question is do I have to vent or can I just install batt with vapour barrier below the ceiling. I know in a perfect world i would likely want to vent but if this is only a weekend use cabin am I still asking for trouble if I don't vent??
Curious if anyone can help me weight the risks.
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OwenChristensen
Member
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# Posted: 11 Jul 2013 06:17am
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You should vent. Even if it's just Cobra style ridge. This will help keep your shingles from over cooking in the hot sun. 2x10's are over kill , but it gives a nice open area above the insulation.
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countrygirl
Member
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# Posted: 11 Jul 2013 10:27am
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we have vaulted roof on our cabin and live in central Canada. You need a ridge cap roof vent. We had a space for air above the insulation, and put the ridge vent in this spring, the heat that come out of that space was hot! Happy we put it in, will save the life of our shingle.
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Oilerfan
Member
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# Posted: 11 Jul 2013 10:52am
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Ya I think I already knew the right answer but I wanted the lazy way out...ha ha. Venting it is. I think I will go with 8inches of batt with a 2 inch airspace.
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OwenChristensen
Member
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# Posted: 11 Jul 2013 07:02pm
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Perfect!
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creeky
Member
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# Posted: 12 Jul 2013 09:57am
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i vote for the ridge cap roof vent also. easy to install and they work really well.
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ICC
Member
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# Posted: 12 Jul 2013 09:59am
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Quoting: creeky i vote for the ridge cap roof vent also. easy to install and they work really well.
as long as you remember the soffit vents too... goes without saying I know, but...
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Trapper
Member
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# Posted: 25 Jul 2013 09:27pm
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Has anyone tried using the breathable stuff (sorry I don't know the proper name) that fits between the metal roofing and the ridge cap? It is much cheaper than vented ridge cap. The local Mennonite place that sells metal roofing is suggesting it. He does sell both.
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bldginsp
Member
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# Posted: 28 Jul 2013 10:22am
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Just to answer your original question about weighing the factors...
It's moisture in the warm inside air, coming into contact with a cold roof deck above the insulation, and then condensing, that is the problem.
If you use it only on weekends and have no shower to produce moisture in the air, then the only other sources of moisture in the air will be cooking and you breathing. Using a woodstove for heat you are probably going to leave the window open cause it will be too hot.
In this case, I might opt for only a serious vapor barrier. By serious I mean 10 mil, not 2 mil, applied to the bottom of the rafters below the insulation and sealed around the perimeter and at any cuts/penetrations.
But better safe than sorry. Venting is the long term solution.
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OwenChristensen
Member
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# Posted: 28 Jul 2013 07:05pm
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True, In most weekend cabins there's not much moisture. I didn't vent mine and it's been fine for twenty years now, but non the less Cobra vent wouldn't hurt.
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