Double Up R12 to Get to R24?


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Old 03-27-21, 10:07 PM
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Double Up R12 to Get to R24?

Maybe a dumb question:
If I have some R12 batt insulation, can I just double up the R12 insulation in my 2x6 walls to achieve R24?

Thanks.

Wayne
 
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Old 03-28-21, 01:19 AM
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In theory yes, but if your compressing the insulation you will loose some value, dont put that first with vapor retarder (paper faced) inside the wall!
 
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Old 03-28-21, 05:23 AM
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Dont put that first with vapor retarder (paper faced) inside the wall!
Not sure I follow. Could you please elaborate?

Thanks.

Wayne
 
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Old 03-28-21, 05:51 AM
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Insulation is most effective when its fluffy and you have/maintain the optimum air space. Compress it and it loses R value.

So, if your R12 is made for a 2x4 wall it is meant to expand to be 3 1/2" thick. A 2x6 is only 5 1/2" thick. So if you put 2 layers of R12 into a 2x6 wall it will squeeze the insulation. And anytime insulation is compressed, you lose r value. So 2 layers of compressed R12 would not equal 24. It would likely equal R19-21 which is what most 5 1/2" thick insulation is rated to be.

If your insulation is Kraft faced, and you want to use 2 layers of the same insulation,, you should rip the Kraft facing off the first layer. You should only have one vapor retarder within the wall cavity, not two. The vapor retarder faces the warm conditioned side of the wall.
 
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