[yourgrandma]

I belive the idea with the rigid fiberglass is that it is denser than batting, thus absorbing more sound, rather than allowing it to pass through. If you have an air space anyway, I can't see any harm in it, but it would be a mess.

I'm thinking of building some corners while I'm off work, but its cold out and I dont feel like wasting a hundred pounds of LP heating my shop. I wonder if anyone has done corner traps with full squares, protruding into the room. I'm trying to envision how I'd cover them.