You can simply peel off the paper from the kraft faced insulation on the R13. You can also purchase R19 unfaced and peel it in half.If you have concerns about airborne fiberglass. You can go to a commercial insulation supplier, or HVAC supplier in your area. Get 1" high density fiberglass "duct liner" The 1" high density has the same accoustical properties as 3" insulation.
Duct liner in inside almost all commercial air conditioning ducts. Lots of people breathing it all day long. Dont know if that makes it better!
Bill