Ahhh.. the age old problem. Has been discussed many a time! .. LOL
I also have the craftsman 12".. love it. So I NEVER cut fiber glass with it. I have a Ryobi 9" bandsaw with a beater rip blade I use to cut the fiberglass. Blades are only 8 bucks and I can get two bows out of them. The 12" only cuts wood. You can use an old blade as well on the 12", I just hate changing out blades all the time.
Someone mentioned that carbide blades will do it, but I have a hard time spending 70 plus bucks on a blade