So, we don't have any heat in the south-facing rooms. They all have triple-glazed windows and the south side is also insulated in a passive house style (I started with the south, I'm doing the facade myself). No roof overhang, no shutters. The south-facing rooms are just as warm/cold as everywhere else. We now have a split air conditioning unit in one of the rooms, powered by photovoltaics. Since all the rooms are open (without doors), the little unit can heat and cool the entire floor. Very pleasant in summer, I suppose. It was only installed in October, so I'm now curious about the summer. It didn't even cost 900 euros with complete installation and commissioning, and I wouldn't want to do without it anymore.