Best option is a partially in ground with properly reinforced CIP walls and continuous riding exterior insulation.

It's a three part solution: earth (insulator), CI (best manmade insulation solution), concrete (thermal mass and ballistic protection for you prepper types).

JYD #123 The great one formerly known as Architect.

I am now a fictional British television police officer (currently a Detective Sgt) at Thames Valley Station. My governor is Detective Inspector Fred Thursday and it’s 1969.