Now that is what we did. Used the land for insulation. We built our home to the back of a 40 acre sunflower field. Mostly because of the lay of the land and our aversion to water coming into the basement. Quasi-semi kinda sorta anyways. Our basement is dug in to a limestone ridge. Solid. (Note to self: find an insulation pic.)
Ours sits on limestone as well. We used Insulated Concrete Forms (ICF), 2-1/2" of styrofoam on each side of an 8" concrete wall with in-floor heat supplied by a ground loop geothermal system. We heat and cool two buildings and our garage, about 3500 sq, ft. total for under $700/year and that includes hot water. We're going into our 4th year since building and couldn't be more pleased. Here are a couple of more shots:
