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toyota_mdt_tech
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# Posted: 30 Oct 2012 01:03pm - Edited by: toyota_mdt_tech
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Quoting: vandersysml # Posted: 30 Oct 2012 12:23 Reply Quote Sorry to butt in here, but I'm having a dilemma now that I've seen this post... It looks like Rifraf's cabin is built pretty much the same as mine, same style that is. But I do not have a ridge vent, or soffit vents. I have fiberglass insulation that I was planning on installing this weekend in my ceiling/roof with no venting at all. I'm in Arkansas, so the weather is fairly mild, not super cold conditions like some of ya'll. Am I inviting disaster by insulating this way? What options do I have at this point? The ceiling doesn't really HAVE to be insulated here to be comfortable. Am I better off without it given my perdiciment? I feel like such an amateur for not thinking of condensation.
If you dont have a vaulted ceiling, insualte it. If its vaulted, but a 2X6 in there (might have to scab onto your 2X4) then add 2X4 insulation, buty open between each rafter, ie the rafter tailes, (bird block) and ridge vent. Make the ridge vent wide enough.
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MtnDon
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# Posted: 30 Oct 2012 01:19pm - Edited by: MtnDon
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Quoting: vandersysml Am I inviting disaster by insulating this way?
very well could be. Here's a link to a document from the Arkansas dept of energy. Read it and then see if yiu have further questions. I skimmed it and saw they do talk some about vapor barriers, but I did not look at it in depth.
And THIS has recommendations for R values in Arkansas
and the Arkansas energy code
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Rob_O
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# Posted: 30 Oct 2012 09:29pm
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Quoting: Rifraf sounds like you read me to mean a plastic sheet between the fiberglass insulation and finishing material..
He is
Don has done a very good job of explaining the problems you can have when "human error" is introduced into the equation. It's difficult at best to completely seal the plastic vapor barrier. You also need to seal every seam on the foam with caulk, canned foam or whatever to keep air movement from happening in the sealed space... any air infiltration will bring in moisture and that's a bad thing
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PA_Bound
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# Posted: 31 Oct 2012 09:00am
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Rif... I have a basic question. I know you have this condensation problem on the foam in the areas where the final (car siding) ceiling has not be installed. But what about in the areas where it has been installed? We need to find that out. I say that because if the problem is not occuring there, then the wood itself is providing enough additional insulation/vapor barrier that nothing more need to be done- other than finishing the ceiling. If the problem is occuring behind the finished ceiling also, that is likely an indicator that just finishing the ceiling is not going to resolve the issue, and we need to look at additional steps. Is there any way to determine if condensation is also occuring behind the finished ceiling?
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Rifraf
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# Posted: 31 Oct 2012 09:53am - Edited by: Rifraf
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PA,
ive wondered how to do that too, aside from tearing it down I havent come up with anything yet  mh, as I sit here im thinking I may be able to feed a soft line up the soffit and pull it back to see if its wet in those areas.
still thinking. It will be a month or more before i can afford more car siding to put up on the unfinished areas, so until then ill be thinking and pondering and asking, and praying to get some answers..
Rob,
Yeah I know MTNDON explains everything very very well. ive never met him but have a respect for his experience and willingness to share. I hope he doesnt take my indecisiveness as an indicator that I dont value that data. My problem in this case is more than a data and numbers one. I have to try and find cheap solutions if they exist , while trying to understand said data. Hence my delay
I dont have any plastic sheets I have foam (1/4 thick) boards with perferated dimples for breathing. This was recommended for my application.. I think the human error is simply my joist cavity depth.. I probably should have gave in on the lost loft space and furred it out to at least 6". So here I am looking for a magic trick to use. And im hopeful that finished ceiling may provide just the right thing to make it "work" but I need to test that first
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toyota_mdt_tech
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# Posted: 31 Oct 2012 10:32am
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RifRaf, could it just be breath and people coming in with wet clotches in a small heated space? I think like Don said, its moisture from the inside based on where its collecting. We can assume you are OK in the ceiling around the insulation as its open to outside air with air flow (adequate ventilation). I know other issues, ie fresh drwyall and mud work will create moisture/dew until its all dried. Same goes for any construction materials you brought from outside that may have been wet. As soon as the interior components drys fully (and you'd know this better than I would) then you may be OK. Just bouncing some ideas off ya.
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Rob_O
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# Posted: 1 Nov 2012 12:20am
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Quoting: Rifraf I dont have any plastic sheets I have foam (1/4 thick) boards with perferated dimples for breathing. This was recommended for my application..
I was suggesting you add the sheeting, but that was before I knew the foam had the vent holes that would prohibit it from acting as a vapor barrier. Depending on the vapor permeability of the foam you have it may breath enough to prevent moisture buildup with an interior vapor barrier
At this point the best suggestion I can offer is to hang tar paper (not plastic or tyvek) between the wood and the fiberglass. The other options are "do nothing" or "spend a lot more money" and I don't believe "nothing" is a good choice for a small structure with 5 occupant dumping moisture in the air
Good luck with your project
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