This project was built by J.W Construction in Saugerties N.Y. We used the Performance Building Systems method and basic steel frame. All other materials were sourced locally. You can find them at EarthShelter.com. They are a great company to work with, very knowledgeable and friendly.  The result is a highly energy efficient house, able to withstand any natural calamity,  it is surprisingly light and airy on the interior, and costs about the same as a stick built home. If a south facing slope is available on your lot, I would consider this type of structure.