Caution on vapor barrier at the floor with insulation below that. There are several reports of condensation collecting at the vapor barrier above the insulation during the cooling season. This rots the top of the joist and grows mold. Better chioce may be to seal and insulate the walls with foam board. Most experts suggest closing vents and allow the crawlspace to dry to the house. Track the %RH with a good meter and dehumidify if the %RH exceeds 60%.