I hadn't considered geothermal, but there's a possibility the land owner would build a cluster of domes, then they could maybe share one unit to heat all of them. He also has his own digger so the cost of trenching would be minimal. I love the idea of using the earth to heat and cool the domes. Thanks for the suggestion! If you have time on your hands next November come on down to New Zealand for our workshop. We're just in the beginning stage of pulling it all together.