Kinda want to try making some of those portland cement/soapy water foam blocks.  Looks to be maybe better insulation than hay bales and looks smarter than a hay bale wall  as well.  Could do those for the outside and inside walls in my shop.  I think it might only be about 50 cents per cubic foot.  Would probably stucco the outside with a modern stucco to keep moisture out of it because I'd be afraid of freeze damage.  Would also need hollow top blocks and some with cores to throw rebar down and fill with real concrete for dealing with the 80mph winds that happen like every year here. 

 @2a51540c i was thinking similar- i want to make extruded hollow bricks from clay, then fill with aircrete