Properly insulating the crawl space is very important to the energy efficiency of a conditioned crawl space. Insulation in the floor joists cavity is no longer needed if the crawl space is conditioned. Insulation in the floor joists would trap the heat in the crawl space and would only accomplish heating the crawl space. In order to allow the heat to pass through the floors they need to be kept open. There for the only place that insulation is needed is around the perimeter of the crawl space. The rim (band) joist is a critical area of heat loss because there is only 1 ½ inches of wood between the inside and the outside. This is also and area that will have small opening or cracks in the wood. I recommend R-19 or higher fiberglass insulation. Close cell spray foam insulation comes up often when discussing crawl space insulation. I do not believe this product is good for the crawl space. When it is sprayed it eliminates the ability to inspect the structure for water or insect damage and would make the repair very difficult and more expensive. When selling a home the spray foam can hinder a sale due to the inability to properly inspect the structure. I just don’t believe that the one advantage it has over fiberglass is worth the potential problems it could cause. Insulation on the foundation walls is going to be guided mainly by the local energy code of where the home is located. Every climate will have a different take on the requirement if foundation wall insulation. This information can be found fairly easily on the internet at any of the states websites or at the local building department.