I have always felt we would be better off building homes underground and this is one example. I would also like to find a way to capture the heat of summer to supplement the heat needed for winter using some sort of giant black(absorbs radient heat) heat sink that could be raised during the summer and then lowered into the ground where the ground would insulate it (store the heat) to be used when needed.
Inside A $1.5 Million Cave House - Yahoo! Real Estate