I have an old wood home raised several feet off the ground on brick pillars. At this point you can see the ground through some of the floors. I'm wondering if it would be effective to insulate the floor by putting foam panels across the joists to create an insulated air space (not looking for great insulation, just an improvement). Would there be a moisture concern? It is a waterfront home (on a bay, mildly salty). Am also considering skirting to enclose the area.
That's one approach, but you might do better from a thermal standpoint to use fiberglass batts and housewrap. You could then lay 3/8" plywood over it all and not have to skirt it.
If you use foam, I'd tape the seams to create a better air/moisture barrier.