I've been thinking about home heating a lot actually. My first step will be to move the home under ground where it is a constant 52 degree F. Second step will be to build a geothermal greenhouse above the home with a clay wall facing the south and pipes inside the wall. My third step will be to run those pipes into the house and use solar power to pull warm air from that heat bank wall. I will report my findings here when I finally get around to doing this.