I’d be surprised if they’re not planning to use heat pumps and underground heat-exchange grids. Some neighbors (a couple miles from here, out in The Boonies) has had that since they built their home, heating and cooling, and they get just the one bill. :^) Even in Michigan, its temperature-stable starting about eight foot down.
Yup. We have an underground well house. It’s amazing how stable the temp is down there.
The goal was to not pay for heating a small building to house the pressure tanks and water softener. I got the idea from working in underground defense facilities where I noticed it never got cold enough to freeze down there in the winter, nor did it get hot in the summer.