Vapor Barrier Vs. Vapor Retarder - Building & Construction - DIY Chatroom Home Improvement Forum

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Old 12-11-2010, 05:49 PM   #1
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vapor barrier vs. vapor retarder

What's the difference, and which should I use? I'm Looking to put something between drywall and blown in cellulose. I live in SE Ohio. Thanks in advance.


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Old 12-12-2010, 08:05 AM   #2
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It's a question of degree of permeance; a 'vpour barrier' lets no vapour through it, a 'vapour retarder' does, to varying degrees. I also thin that nowadays we speak of vapour retarders more than vapour barriers, as we now know lots more about permeance of vapour through different materials. E.g: a coat of paint can be a vapour barrier of sorts...

A combination of vapour retarders can = a vapour barrier, too. In cold climates like yours, the idea is to control (perhaps even 'prevent') air from carrying moisture from warm to cold temperatures and thereby prevent excessive condensation. You do that, partially, by sealing gaps and by using vapour retarders on the warm side - in your climate.


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Old 12-12-2010, 11:35 PM   #3
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carlisle pretty well hit it. if curious, search on the for the ADA, and/or vapor barrier, etc. then read for a few hours and you'll know everything you need to. true vapor barriers are generally discouraged in all but zones 7 and 8 (very cold), esp if you air condition. one of the articles on the gba site had a story about a cat in southern(?) ohio that went boobs up because of using a vapor barrier in his new homes that had air conditioning. real bummer. j
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Old 12-14-2010, 08:12 PM   #4
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Old 12-14-2010, 09:01 PM   #5
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also read up at
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