I'm adding a room onto my house using ICFs for the crawlspace stemwall. Since the ICF walls are already insulated I'm planning on insulating the rimjoist area and pouring a concrete floor over 2" foam so that the crawl is somewhat conditioned area. Access will be through a small hatch to the conditioned basement.

I think I need to cover the ICF walls on the inside of the crawl for fire protection. Drywall seems like a bad idea. What is normally used to cover ICFs in crawl areas? 

Drywall can have issues if exposed to moisture, mold can form. Densglass is another product available, it will prevent the growth of mold, meets and exceeds fire code, but is not pretty, meaning it can't be finished nice, but it's a crawl space so it should not be an issue

Why do you say that? If you're conditioning the crawl space moisture shouldn't be a problem and the drywall ought to be in the same enivironment as the rest of the house.

For the house I'm building I'm planning on using exterior drywall in the crawl space, which is also sealed and conditioned with a concrete slab over 3/4" blue board. The only reason I'm using exterior drywall is I plan to install it as soon as the ledger board is hung and while everything is clear and open so it may see some weather before the floor is in place.

Are you planning on insulating the entire crawl floor, or just around the perimeter? Whichever, take a read here http://www.greenbuildingtalk.com/Forums/tabid/53/view/topic/forumid/12/postid/32800/Default.aspx. I discuss my analysis of the payback of insulating the crawl space floor. You don't need 2" except around the perimeter in a cold climate.

I was concerned about the drywall because, although the crawl will be within the building envelope, I have no plans to heat/cool or otherwise actively ventilate the crawl area except for the incidental conditioning that will occur with it being not tightly sealed off from the conditioned basement area. I was concerned about incidental moisture issues that might occur with drywall in contact or very close to the slab/exterior wall junction in an area that will largely be unobserved for long periods of time (I hope). I definitely want to avoid any potential for mold.

I really do expect the crawl to remain quite dry though as it is essentially identical in construction to my basement - just shorter. I was not aware of exterior grade drywall. I will investigate it and the densglass. The addition is fairly small and very little of it is not within 4' of the perimeter so I have 2" foam for the whole thing.