Do I need to have insulation between the floor joists in my crawl space?

No, not unless it’s required by code. The best method of insulating the crawl space is to use a closed crawl space system with insulation on the inside of the foundation walls. Studies by Advanced Energy have shown savings of up to 18% on new structures using closed crawl spaces and wall insulation. (Be sure to check your state and local building codes for type of insulation required and R values.)