Yes. Here in the UK there's a program called Grand Designs about people building beautiful or innovative bespoke homes. One such was an engineer building a home

Yes. Here in the UK there's a program called Grand Designs about people building beautiful or innovative bespoke homes. One such was an engineer building a home with insulated foundation walls as you describe, based on academic research done by his father in the 1970s & 80s. IIRC it took c. 18 months for the floor to reach equilibrium, but once there, virtually no other heating was required, winter or summer (in the UK).