I too find low tech answers fascinating and sometimes feasible, but high tech answers more often than not more practical. If you are attracted to the idea of straightforward, high R-value building technique, I suggest looking into Structural Insulated Panels (SIP's). They require more up-front engineering and design time, but go up quickly and easily and result in a very strong, tight building that can save you money on both the installation and future energy spending fronts.