Ladies and Gentlemen, how y'all doing?? Have a question about insulation. Many of you use solid board insulation for walls, etc. After researching costs involved, fiberglas come in tons cheaper and has a better R value. Plus it bends well and can be fitted easily on curved surfaces. Granted, there isn't a lot of depth in the space it needs to go. Now, Question: If a roll of R13 fiberglass is 6 inches thick, if it is compressed down to 2 inches, does it retain its R13 rating and if not how much does it lose?? In my mind, it has many desirable properties, but there must be a reason so many use the board. Thanks. Regards, J.D.