Polyisocyanurate foam insulation for exterior foundation walls

When I put it on I just backfilled it without any screws but I was working small areas at a time, if its to hold it until you back fill one tapcon and a washer or some liqued nails should do. Above grade I painted it. What is Tuff R value, if I remember right the regular foil faced Polyisocyanurate is 1/2-1R better in insulation value. I used I think Owens Corning and the TUFF R has fiberglass in it and is a nightmare to work with, the big glass shards get into your hands and clothes real easy and are a hurting bad experiance so I wont use or even touch that stuff anymore. The foilfaced starts at R 7.2 and settles to about R 6.5. I hate the Tuff R so much I junked the last sheets from the glass getting into my hands.