1. Install 15 mil polyethylene sheet on the crawlspace floor and mechanically fasten or tape it to the exterior walls and all other upturns at the floor and seal laps on the floor.
2. Install rigid foam board between floor joists at the rim joist. Size them to fit snugly between floor joists.
3. Install spray foam around all joints at the rim joist and seal to the wall.
4. Install batt insulation in each joist space and secure it in place with insulation supports.

Note

All mechanical ducts, water lines and other services running in the vented crawlspace and through the ceiling should be made airtight and insulated.