I've been "investing" in home improvements before I retire. It was always damp and moldy under the house, so I had a vapor barrier installed, all the foundation windows shut and insulated (not the high end option). Even when the temperature dropped to 20°F (cold for us!) it was 45° under the house last winter, no more frozen pipes!If you had insulation under there attached to that skirt the rising earth temperatures would help from freezing. Helps if the floor is insulated too. Just don't do like the idiots here do and put hay bales around your house. Swear people move out here to be stupider if that's possible, no wait it is possible. Got one that is building a house from hay bales covered in "cob" I mean half arse cob.