Insulating the floor was my first instinct too, but I was immediately told by our contractor that doing this, and therefore heating the floor from above, is a waste of heat. Hence, his suggestion to insulate around the sides of the crawlspace and then heat it (to 40 degrees or so). This also seems like a waste of energy (& money!) to me, especially with an electric heater. I'm just trying to figure out which technique is more commonly accepted, if either. Thanks again!