Depending on how homes are constructed and insulated in your area, a crawl space could be way too warm in the winter or way too cold. A lot more information is needed to make that decision. Does your area insulate the foundation walls, or the furnace duct work, or floor, or vents, or ground cover, or a combination of those? I like the initial thought of using the crawl space but think more thought needs to be put into it. JMO