insulation recommendations

[handfab]

Hello,
I've been rebuilding a detached garage. See attached thread:
http://www.garagejournal.com/forum/showthread.php?p=2117138#post2117138

I haven't decided if I am going to insulate the ceiling. I know I'll loose heat if I don't. The rafters are 2x12" on 16" centers. I'd like to leave them exposed. I'd like to use rigid insulation board but the fire hazard of this type concerns me. Should I be? Is there a rigid foam board that is fire rated? I know the batting would be cost effective but I've seen exposed batting uinsulation that looks tattered after a few years.

Any suggestions would be appreciated.

 

[Falcon67]

Lay sheetrock on top of the rafters and screw it down from on top, then blow in insulation. More work but leaves the joists open. I know of no fire rated foam. By nature, it isn't.

 

[6768rogues]

http://building.dow.com/ap/en/tech/description.htm
I have used Dow products in the past. Their Styrofoam sheets contain a fire retardant but are still combustible. So is wood. Most codes require extruded foam to be covered with drywall or wood (plywood, osb, etc.). That said, I have two layers of Styrofoam on the ceiling of one of my buildings (14 feet up) and it is painted with latex paint. Foam boards shrink a little over time, so the two layers have their joints staggered.