I have crawlspace with an earth floor. it is approx. 24" from the ground to the floor joist. I have 6 mil poly on the ground. I have vents that will be opened in the summer and closed during the winter. There are no heating or a/c ductwork in the crawlspace and the water lines are insulated to keep condensation from being a problem. What is the thought on installing insulation between the joist and if so what is the best type of insulation to use to keep it from keep insulation from hanging down over a period of time.
When I've done this in the past, I've put in fiberglass between the floor joists, and then covered it with sheets of extruded polystyrene insulation board (XPS) to add a bit more R value and keep it in place. If you're worried about critters chewing around, you can do the same thing with thin plywood or fiberglass reinforced plastic panels.