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Rifraf
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# Posted: 12 Apr 2012 12:12pm - Edited by: Rifraf
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My budget is thinning rapidly so ive been thinking of ways to shave dollars here and there.. one was with my baffle venting from soffits/eves to ridge. One idea is to use 1.5 inch thick foam trim on the inside of the rafters and span that with 1/4 inch foam panels that are sold in 50ft runs, folded up.
This is still a little pricey at 120.00
The next thought would be to use spare 1x2s and buy some screen door material ( i have some thats plastic, but not sure if it will hold up for years) and run that down the rafters at 1.5 inch dept, securing it with 1x2s every six inches or so.
Heres a rough diagram of the ideas, you think these are viable ? the screen material is not air tight obviously, and may let alot of dust settle on the batt insulation ??? I am still looking into cheap materials.. the plastic mesh is very cheap in big rolls.
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Rifraf
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# Posted: 12 Apr 2012 01:28pm - Edited by: Rifraf
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I was on the phone when making this apparently running on auto pilot, what I really needed to do was add this to my other vent topic instead of start a fresh one.
sorry for that.
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soundandfurycabin
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# Posted: 12 Apr 2012 03:44pm
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I think a solid barrier between batts and vent space would probably be better. Otherwise on windy days there will be air blowing through the insulation, reducing its effectiveness.
In the other thread you said the manufactured vent baffles weren't going to work. I'm curious....why not?
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Rifraf
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# Posted: 12 Apr 2012 03:56pm
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Thanks for the input,
If i buy the ones that can bend and have one air channel they would work, the current ones I have contain two air channels making a W shape, my eve is only about 1.75 inches wide and the dip in that style would be impossible to connect to the eve without exposing holes to the finished side. I could make custom eve connections to use them but that is more trouble i think than finding another complete solution.
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MtnDon
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# Posted: 12 Apr 2012 09:31pm - Edited by: MtnDon
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I'm not sure an air impermeable barrier is needed between the fiberglass and the airspace. For example, in a 2x12 rafter roof using R38C (10 1/4" batt thickness) batts what faces up at the airspace is bare, uncovered fiberglass.
In a cold climate the thin impermeable layer of sheet foam would act as a vapr barrier, but not be thick enough to keep it warm. Condensation between foam and batt would then be likely.
In a hot and humid climate type the foam could be an advantage as it would act as a vapor barrier in the correct position for the climate. (Considering the interior to be cooled by refrigerated air much of the year and the exterior warmer than the inside.) So for that reason the thin foam might be a good idea, as long as it does not run into problems with the pressure from the compressed batt insulation. ???
Sure would be easier to have deeper rafters.....
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Rifraf
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# Posted: 13 Apr 2012 01:35am - Edited by: Rifraf
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I know MtnDon, I wish thicker rafters were an option for me 
I definately never want water of any kind up there.. so for that reason are you suggesting I not use foam ?
In that case MtnDon, is there a material you would recommend to lay between the insulation and the air path ?
Thanks
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Rifraf
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# Posted: 19 Apr 2012 04:55pm - Edited by: Rifraf
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Sorry to dig this up again,
was just brainstorming before I get to work on this saturday.. BUT
couldnt one flip the bats upside down so the paper faces the roof, and staple flaps against the joists leaving 1 to 1.5 inches above the paper facing for air flow ? wouldnt the paper face prevent winds from digging deep into the fiberglass ? or would that cause otehr moisture issues in winter when the warm side is inside the cabin ??
My default is still the foam boards with bats over them, but if i can cut out a step and save a few bucks, without causing issues for myself or the cabin, why not
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MtnDon
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# Posted: 19 Apr 2012 06:12pm
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The stapled paper may tend to tear when the insulation is compressed. ???
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Rifraf
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# Posted: 19 Apr 2012 07:19pm
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Yeah, I guess it would Thanks for being my logic.. getting my final supplies tomorrow.
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