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Old 12-07-2009, 07:40 PM   #1
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Fiberglass Insulation + Reflective Insulation Q?

I have 2x4 exterior walls in my home and I'm wanting to get some more insulation besides what R-13 can give. Has anyone ever put the reflective barrier insulation up with it before? Below is the link to the instructions on how to install it and what it looks like. How well does this work as a vapor barrier? I have 4 mil plastic up right now. Also, it says unfaced but I have kraft faced up right now with a vapor barrier on top.. Is this a big problem? I know, two vapor barriers against each other, but does that faced stuff even work that well? Can I just take off the facing?


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Old 12-08-2009, 12:21 AM   #2
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The insulation has a vapor retarder, the other is a vapor barrier: You would be compressing the insulation by 3/4" for the radiant barrier which would lose R-value. The gap in front would create a convective air loop that would do more harm than good: This on attic radiant barriers: Gives you an idea anyway.....

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Old 12-08-2009, 01:12 AM   #3
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Thanks for the links. I thought it was odd that r 13 plus their r 3.4 or whatever equaling 14 was odd. What do you think about it in place of where a vapor barrier usually goes? Think it might be more effective?
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Old 12-08-2009, 06:18 AM   #4
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In order for a radiant barrier to work it has to have air in front of it -- it stops radiant heat, not conductive heat. If it's in contact with something then the heat will transfer through conduction. If you want it to do something in the summer and the winter, then it needs air on both sides.

If you want to get more insulation consider R-matte rigid insulation. It takes up a 1/2 inch, so you have to shim out the insides of your studs 1/2 inch.
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