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Old 05-28-2010, 07:18 PM   #1
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Unfaced insulation above garage


I have a garage that has only attic space above it... I want to insulate the ceiling, mainly for sound reduction... the walls are already insulated R-19 but the ceiling has nothing (not even a vapor barrier) just drywalled and painted.... a lot of sound comes in from the attic from the road about 20 ft away... is there any problems with insulating it with R-30 unfaced insulation? I can't seem to find faced R-30 anywhere around me... lowes and the local building supply stores dont carry it... just unfaced R-30... this will never be a living space, just an attic with a plywood decking on it...

so my plan was to have it like this

1)Drwall ceiling in garage.. (already there
2) R-30 unfaced insulation stuffed into the 2x10 ceiling joists cavaties
3) 23/35 OSB or plywood decking so we can store some stuff up there

any problems you guys see with this? or do I absoulty need to get a vapor barrier in there?

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Old 05-28-2010, 08:16 PM   #2
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Unfaced insulation above garage


Along with proper attic ventilation the vapor barrier helps to keep the insulation dry. Damp insulation doesn't insulate as well as dry insulation. e.g. when your clothing gets wet in the winter you get cold pretty quick and the damp clothing wicks away the body heat. So in your situation where you are not conditioning the garage space and you are likely not generating moisture (no showering, cooking or house plants, just some breathing) in the garage, I think you can go with the unfaced insulation. good luck with the project.

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Old 05-29-2010, 03:39 PM   #3
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Unfaced insulation above garage


For a 2x10, you should put in R-25 as it's made for the joist size. Compressing an R-30 has no advantage. If you want a vapor barrier, lay a 6 mil plastic in the joist bays before you install the batts.
Ron
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Old 05-29-2010, 03:43 PM   #4
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Unfaced insulation above garage


R30 is also made for 2x10 joists - 9.5"
R38 is for 2x12 joist

R25 I see listed as 2x8 - 8" thick ?
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Old 05-29-2010, 08:30 PM   #5
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Unfaced insulation above garage


Quote:
Originally Posted by Ron6519 View Post
For a 2x10, you should put in R-25 as it's made for the joist size. Compressing an R-30 has no advantage. If you want a vapor barrier, lay a 6 mil plastic in the joist bays before you install the batts.
Ron
The John Mansville insulation at lowes here says R-30 is for 2x10 joists... says its 9 inches thick... must be higher density then R-25 at the same height
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Old 05-29-2010, 08:31 PM   #6
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Unfaced insulation above garage


Quote:
Originally Posted by Scuba_Dave View Post
R30 is also made for 2x10 joists - 9.5"
R38 is for 2x12 joist

R25 I see listed as 2x8 - 8" thick ?

I can get R-38 faced, but yeah, that is way to thick for this application since it would be compressed....


which brings up the question, does anyone make a faced R-30?
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Old 05-29-2010, 08:34 PM   #7
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Unfaced insulation above garage


I installed R30C faced for a cathedral ceiling
I have an insulation store about 2 miles from the house
Its all they do
They can get just about anything made

Big box may be able to order it
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Old 05-29-2010, 08:36 PM   #8
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Unfaced insulation above garage


Quote:
Originally Posted by Scuba_Dave View Post
I installed R30C faced for a cathedral ceiling
I have an insulation store about 2 miles from the house
Its all they do
They can get just about anything made

Big box may be able to order it
Was yours from a specific mfg like owens or johns? or some other company? just wondering who made what you got to see if any of the local people can order in what I want
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Old 05-29-2010, 08:44 PM   #9
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Unfaced insulation above garage


Owens Corning - I bought it at HD actually
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Old 05-31-2010, 03:30 PM   #10
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Unfaced insulation above garage


Well I was able to find R-30 batts that are Kraft faced... wish we had rolls since they are generally 25 ft long at R-30 and that would of been a perfect length, but I guess batts will do also

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