Want to be energy efficient, build your next home using straw bales as your major building material. Using natural resources that is considered waste, normally getting burnt up at the end of the season, strawbale built homes can be your best bet for living more efficiently. The fact is strawbales is actually betting insulating than any of todays commercial insulation.
Building a home from this type of renewable resource, strawbale homes not only would save on the CO2 from its normal burning at the end of the season, but also trees as well as all the oil and processing associated with milling of lumber.
It is very much possible that one could get off of the grid by building homes of straw while combining other alternative energies including geo thermal and wind power.