New building with underfloor heating, residential ventilation, and air conditioning

If you want really efficient cooling performance, you hardly can avoid separate air conditioning units. Therefore, I assume that every window will get an external shading. In my opinion, the cooling capacity is sufficient if you get a split air conditioning solution for the bedroom and the office. Unless you also want to have your 18° in the living room. Unfortunately, I lack knowledge about ventilation systems with integrated air conditioning and split modules. But that would be my approach and in my opinion it would work excellently in a new building.

If you want really efficient cooling performance, you can hardly avoid separate air conditioning units. Therefore, I assume that every window will get an external shading. In my opinion, the cooling capacity is sufficient if you get a split air conditioning system for the bedroom and office. Unless you also want your 18° in the living room. Unfortunately, I lack knowledge about ventilation systems with integrated air conditioning and split modules. But that would be my approach and in my opinion, it would work excellently in a new building.

The living area would probably be air-conditioned as well, but in the end it also depends on our floor plan and the overall size. A solution that reaches every room via the ceiling similar to controlled residential ventilation would be optimal, but whether the rooms can still be individually temperature-adjusted then? I need to look more closely at the manufacturers for that…

The living area would probably also be air-conditioned, but in the end it also depends on what our floor plan and the overall size look like. A solution that supplies every room through the ceiling similar to controlled residential ventilation would be optimal, but would the rooms still be individually adjustable in temperature then? I need to look more closely at the manufacturers for that…

This can certainly be well dimensioned during construction with the calculation of ventilation flows depending on the expected summer overheating. It's great, in any case, that you have recognized that summer thermal protection is much more important nowadays than just keeping the house warm in winter. I have built solidly with KS blocks (inside + outside) and concrete ceilings and can say that the inertia of the mass greatly contributes to climatic comfort.

I have now discovered a "4-way ceiling cassette SLZ-M" from Mitsubishi, where you can apparently connect fresh air… it would now be interesting to know if that can replace a controlled residential ventilation system :D

No, the cassette cannot replace controlled residential ventilation. Because then you would need one in every room.

Climate+underfloor heating+controlled residential ventilation+photovoltaics is a sensible combination. However, none of the devices can really take over the function of the others. Of course, the house can also be planned and built as much as possible through various measures with an eye on maximum shading, etc. But here it also depends on the area and the plot of land. These measures are not always sufficient and often the costs of passive cooling far exceed the investment in active cooling.

Furthermore, a modern house not only requires little heating power in winter. It works just as well the other way around. The required cooling capacity is equally manageable.

Another "problem" with modern houses is that insulation doesn't only work in winter. Passive cooling via shading etc. carries the problem that it is difficult to get the heat out of the house once it is inside. In summer, it is enough to forget to shade a window exposed to sunlight for one day, to leave a door open too long, and so on. In my experience, you simply cannot open all the windows long enough at night to get the heat out of the house once it is inside. With passive measures, you therefore have to be meticulously careful to ensure everything is always optimal. Or you automate shading, but that also costs a considerable amount of money. Our air conditioning cost about €5000, all in.