If you don't build a strawbale house, there's always the option of an eco-treehouse. This could be something as simple as a perch in an oak tree like the Berkeley tree sitters who may have used their favored position to disrupt quarterback play. Those attending lofty heights often become philosophical or spiritual. Think Symeon Stylites or other anchorites.
A little more elaborate is this clear glass box, a showpiece of cubism, but also "green."