Fiberglass insulation rolls for flooring?

[Seeria]

Is there any reason why fiberglass insulation rolls can't be used as flooring insulation? I noticed they're higher in R factor than insulation boards. I'm thinking of laying a barrier, laying a R13 or more rolls down with supports to hold flooring material and keep from smooshing the insulation.

Also noticed they're 3 1/2" or more thick. Would it ruin their R factor to compress them a bit? How much compression is too much?

[lornaschinske]

Don't compress more than 1/2 of their regular thickness (ie= 3" can be compressed down to 1.5" before you lose so much R value that you are wasting your time and money). Polyiso sheathing (foam board... NOT THAT STYRO FOAM BEAD CRAP) ) has a higher R-Value can hold up to getting wet without losing R Value and will not "shift" over time.

[Seeria]

Okay, you all win I'll stick to the boards *grumble grumble*