# Floor joist insulation over basement.



## rjheard (Apr 21, 2011)

I have a two story house over a block wall basement with a two car garage. I'm going to insulate the 2x10 for noise and temp but am not sure it I need to use a vapor barrier. The first floor is mostly T&G wood over 3/4 plywood. I do plan to finish part of the basement eventually.


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## HomeSealed (Jan 3, 2008)

You basement is conditioned airspace. A vapor barrier in that app would not be appropriate, and you won't see any energy benefit either. If sound is your main concern, then go for it, just use a material that will be well-suited for that purpose. For energy-savings, you'll want to insulate the exterior walls of the basement. This is a very popular topic and there are a ton of threads, links, etc with good info. I'd also recommend www.buildingscience.com for some excellent info on the subject.


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## Gary in WA (Mar 11, 2009)

Use Roxul insulation rather than f.g. for sound. The 3/4" plywood has about the same moisture stopping abilities as the Kraft faced insulation. They probably already installed tar paper under the hardwood flooring for squeaks and moisture protection. Insulate the rim joists with foam board, air sealing afterward; http://www.buildingscience.com/docu...arriers/critical-seal-spray-foam-at-rim-joist

Gary


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