Two layers of faced insulation in attic - remove one or both?
EDIT: I mean insulation, not drywall, obviously...I'm an idiot on Mondays...
I have (you guessed it) two layers of kraft-faced fiberglass insulation in my attic. I understand this is bad (two vapor barriers), but I'm not sure exactly how best to deal with it. I'm thinking I want to add blown-in cellulose, anyway, since it performs better than fiberglass in cold weather (I'm in Minnesota).
Should I remove both layers of fiberglass and then add the cellulose? Or would that just waste perfectly good insulation? The bottom layer is, unfortunately, the worse of the two. It seems to have all but disintegrated over the years. I don't see mold, that I can tell, but I know that doesn't mean it isn't there.
In terms of insulation performance, since cellulose does better than fiberglass at lower temperatures, wouldn't it be better to go entirely with cellulose? Or at least not have fiberglass as the bottom layer?