You’ve described the home we built 9 years ago...ICF, earth sheltered infloor geothermal heat/cooling.
I’ve never built or bought one but grew up in one, my folks were not exactly leftist but they did subscribe to Mother Earth News.
I did almost buy this one about ten years ago, custom architect designed passive solar. Wall of windows facing south, a sort of multistory atrium effect with masonry walls. Interior shutters to let heat into the residence when wanted, and out at night when not. Two high efficiency wood burning units, one soapstone stove below grade and one in a masonry fireplace with blowers and doors. The tall part on top is a small studio or retreat that serves as a heat chimney in hot weather, just open the windows up there, and open the windows in the basement, voila, cool air circulating. Sellers claimed it maintained 58 degrees in winter with no heat and 75 in summer with no air. The square footage on Zillow is wrong. It’s twice that size.
In some ways I regret that I didn’t buy it. But, it’s still substantially below selling price in 2005, so I’m probably better off.