Very good, although in the NE, it's common to vent the crawl and insulate the floors.
In any event, I'm thinking of trying what you're suggesting. I have a 30' x 15' x 3' crawl, with poured concrete and 3 vents. I'd like to insulate the inner walls with 'board insulation' (as well as the vents in winter only because some water gets in there in summer.) What do you recommend for insulation board on the inner walls?