Floor joist insulation help

Drewkernovich

Hi,
I'm doing a small Reno on my unfinished basement, I had a bunch of left over 5.5 inch r22 insulation that I am going to stick in the joist spaces. The joists themselves are 2x12.

My question is does it matter where the insulation sits in the joist space, as in can it be pushed all the way against the subfloor, or should it be flush with the bottom of the joists? There will be a vapor barrier as well enclosing the basement.
The insulation is to dampen the sound and protect against heat exchange from one floor to another.

Thanks for your help

cbaur88

You want the insulation flush against the subfloor eliminating any air space between the insulation and the subfloor. Press it snugly in there but not to much or the compression will reduce the r-value of the fiberglass which is I am assuming your using.

What kinda of vapor barrier will be enclosing the basement and also is the fiberglass your using faced or unfaced?

Windows on Wash

Between conditioned spaces, the insulation should have zero theoretic impact unless you are planing on keeping the basement much colder than the upstairs floor.

Insulation will have only modest impact on noise (I was under the wrong impression previously) but should be tight to the underside of the floor if treated as and insulator.

Sound control is another discussion altogether if that is what you are ultimately after.

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Drewkernovich

I will be using a 6 mil poly, and it is unfaced insulation. I know that insulation isn't the best for noise transfer, but it is leftover and non- returnable so it is definitely better than nothing. Thanks for your advice