I've got a couple of estimates in for putting 2" of spray foam on the rim joists and floor joists of my crawl spaces, where currently there is NO insulation. Unfortunately, I've learned that I need a fire barrier/retardant on the foam, which can be a special paint (@.95/sq foot applied by the foam company) or 1/2 inch sheetrock, or rockwool applied OVER the foam so it's no longer exposed. Has anyone BTDT with this? What did you do? The house has chestnut floorboards so the building inspector laughed and wished me luck should we choose the sheetrock option. Plus the crawls are a little bit humid, I'm not excited about sheetrock down there. Also now that I'm looking into doing this people are coming out of the woodwork to tell me that insulating the crawlspace won't do nearly as much as insulatiing the walls. I am not redoing any walls so any insulation would have to be blown/injected through holes. Thoughts? Help?