We design a house from the inside out and engineer a house from the top down, but we build a house from the ground up. What are the most environmentally sensitive, durable materials? [Editor's note: Robert Riversong, a Vermont builder, continues his 10-part series of articles taking design and construction to what he sees as radical or "root" concerns. Enjoy--and please share your thoughts. – Tristan Roberts] 5. Foundations – it all starts here: how do we begin?