Our home is heated with passive solar using glass, concrete and adobe.  In the Winter it gets to -15F outside.  We have no supplemental heat sources other than a kiva fireplace which we almost never use.

So yeah,  it's not any kind of stretch to scale that up and recognize the heat island effect of cities.  Passive solar gain is powerful, and low tech.

Earthships aren't exactly fiat architecture,  but the ideas still apply.

PV!

Oustide
https://m.primal.net/HKpf.png

Inside
https://m.primal.net/HKph.png