Hello Owen. Just wanted to share with you my plan:
Next year, I will build a large roundhouse in Hungary with raschel mesh tubes. I’ve got 7km of UV-stabilized raschel mesh from a Czech company called Juta. Since there are no volcanic rocks in Hungary, I might go with Ex-clay [expanded clay aggregates] for insulation. Ex-clay costs around 100 Euro/1m^3. Right now, I might go with a gravel foundation. The requirement given by my wife was 5 sleeping rooms (preferably in the lower floor, because Hungarian summers are quite hot).