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Old 03-23-2011, 08:18 PM   #1
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Vapor barrier ?????


Plz help, no one seems to have the right answer. I framed out my Garage ceiling. I drop the ceiling about 2 ft from the bottom of original joist with 2x4's. my garage is 24x45 1080 sqft. I want to heat garage in winter there is about a foot & 1/2 space now btwn the roof and new framing (now there is attic space) I'm using R 30 unfaced Insulation & 3/8 drywall ((((( My QUESTION IS, IS 6 MIL PLASTIC NEEDEDFOR VAPOR BARRIER ????? )))) I will more likely have to Install 2 to 4 roof vents but is 6 mil plastic needed as a vapor barrier. I don't want to trap moisture btwn the insulation and roof plz help don't want condensation build up ???

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Old 03-23-2011, 08:26 PM   #2
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Vapor barrier ?????


Quote:
Originally Posted by M.A.M
Plz help, no one seems to have the right answer. I framed out my Garage ceiling. I drop the ceiling about 2 ft from the bottom of original joist with 2x4's. my garage is 24x45 1080 sqft. I want to heat garage in winter there is about a foot & 1/2 space now btwn the roof and new framing (now there is attic space) I'm using R 30 unfaced Insulation & 3/8 drywall ((((( My QUESTION IS, IS 6 MIL PLASTIC NEEDEDFOR VAPOR BARRIER ????? )))) I will more likely have to Install 2 to 4 roof vents but is 6 mil plastic needed as a vapor barrier. I don't want to trap moisture btwn the insulation and roof plz help don't want condensation build up ???
Use double bubble foil.Hope this helps.

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Old 03-24-2011, 12:38 AM   #3
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Vapor barrier ?????


Welcome to the forum!

Location, location, .....

If in a heating climate, your local Building Department may require one..... The air venting may be reduced when using a vapor barrier. Read this, and hit the links at the bottom of the page; http://www.buildingscience.com/docum...ecommendations

Gary
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Old 03-24-2011, 01:42 AM   #4
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Vapor barrier ?????


And, be sure to READ the code. Some officials will tell you "6 mil poly" because that is all they know. If the code says "1 perm or less", there are other options that are likely far better than poly. Read on the bs site that Gary gave you. And, air seal like a maniac. That is far more important than a vb, which may be harmful.
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Old 03-24-2011, 10:01 AM   #5
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Vapor barrier ?????


Yes I would definately put a vapor barrier, especially if you get any amount of snow in the winter. Ice dams are no fun. 6 mil is what I've used in the past for similar projects, like they said though, if you want to be sure whats necessary for your area, you will want to check local building codes.
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Old 03-24-2011, 12:42 PM   #6
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And now to throw more confusion into this:

http://www.greenbuildingadvisor.com/...ilding-advisor

It is never as cut and dry as we want it to be. Sigh!
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Old 03-24-2011, 01:40 PM   #7
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Vapor barrier ?????


I don't see the confusion. I read there all the time. Drop the VB. There is a very good builder up here who does not use them, and I won't in my new house. I put one in in '80 (everybody did; that was "the thing") and have no problems, but we are likely colder than you. Air seal. No vb against concrete.

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