Now there's an open-ended question!
Any particular grade of glasswool? E-glass?
Needle-mat or molded? With organic or innorganic filler?
New, or after it's broken down and blown out of a silencer?
Seriously, though: I'd recommend you contact a major supplier of fibreglas, like Owens-Corning, and ask them.
You might have to tell them a little about your intended application.
Best,
Robert