My husband and I are interested in a subterranean home using a greenhouse on the south side, possibly solar colectors to heat water, and a wind mill for energy. We still are in the day dreaming stage. We have considered having a large fireplace and colored bottles of water absorb heat as well as tiled floors, and we hoped that simple ceiling fans could help with the comfort level as well. Did you find a solution to your problem. Do you have pictures of your home that you share over the internet? What did you surface the inside of your walls with? I lived in a partially underground home before with a lot of exposed stone, and I always felt like I was loosing radiant heat to it. Do you have your own well and septic system or are you on a community line? Ever have any problem with dampness getting into your home? I hope your problem is solved by now. I visited "Gas World" today and saw they now have Mexican style chimneys as well as heaters that look like the pretty old freestanding wood heaters that are now ventless and 99% efficient. Something like that might work for you as you can use bottled gas. I doubt you would burn much of it.