My house is 3.5 feet off the ground; the crawlspace is open, except along the front of the house. It was built in 1919, and has hardwood floors, uninsulated (like many older houses here in New Orelans). BRRR! Baloon-framed, it looks like from underneath.
There's also a usually-damp area under the screened-in porch, so adding some soil or sand and grading it, then adding 6 mil. visquene (sp?) is probably in order.
Options I've looked into include: closed-cell spray foam (2 in.), open cell spray foam (2 in)., block off the crawlspace (with fiberglass panels, concrete bricks, panels of plywood).
Because the closed cell will crack and leave gaps as the temperature changes, that sounds unappealing.
Any suggestions about the best way to close off the crawlspace, or if that's even a good idea? I'd want to have a hatch of some sort for access, of course. And I'm concerned about ventilation being impeded if the area is closed up.
Cost is a huge issue, because I had to pay to have re-done what the seller's (unqualified) contractor did wrong (lesson: never buy a house in one city when you're living in a nother, unless you have someone watching the repairs--and don't count on your real estate agent for that!).
Your insulation requirements are different from what we use up here, but follow what is normal for your area. Installing plastic will reduce moisture, which is good. Not sure what type sprayed insulation is correct for you, but sprayed is likely a better choice. Fiberglass will soak up moisture in that climate. And you do not want a lot of moisture accumulating under the house.