Underfloor heating in the children's room? Some rooms planned without underfloor heating? Air-to-water heat pump removed?

The ERR, which is required by the energy saving ordinance for a surface heating system, but is unnecessary due to the low supply temperatures and the well-insulated massive houses (thanks to the self-regulating effect): I just tell the heating engineer that I don’t want to install an ERR despite the regulation and hope that he accepts it without saying "We have to install it, otherwise as a company we would be violating regulations"... what are the experiences with this? If he absolutely wants to work according to the energy saving ordinance, do I have to find another heating engineer?

There is probably the possibility of an exemption. I cannot tell you how this is done formally. Or you have them installed and keep them open without power.

As far as I know, you have to apply for the exemption. Google it, there are some very informative sites.

You cannot effectively cool with controlled residential ventilation; it only heats up more slowly if you can keep the windows closed during the day. The underfloor heating can also only cool a few degrees over a large area. I don't know how well that would work with the air shaft, but every measure helps.

If this is very important to you in summer, then plan for an air conditioning system.

For us, the bedroom is the coolest room in winter (18°). We don't get the adjacent bathroom above 21°, which we planned that way. Everything is great.

In midsummer, unfortunately, our bedroom on the north side is 1-2° warmer than other rooms. It is small, has relatively much supply air from the controlled residential ventilation (heat recovery losses), but mostly it's due to body heat, which would almost be enough to heat the room even in deep winter.

No, cooled (such as by air conditioning) rooms are not that important to us. But of course I want to avoid the rooms reaching around 27 °C in the summer. In this case, shading is the right solution.

And we are also aware that in modern houses all rooms inside the envelope with surface heating have approximately the same room temperature (unlike in old buildings, where one room can be 24°C and the neighboring room 15°C).

But we are aware of the possibility of cooling via controlled residential ventilation by mixing in cold air from an air well and/or cooling via the ring trench collector brine heat pump and will discuss this with our architect.

yes, that could be done. but that's stupid and nobody does that. if you need temperature differences of 7 degrees in different rooms to be happy, then an old building is the only option for you. the colleagues here in the forum have hinted at it, but exceptionally, I'll be the direct one. that won't work and is nonsense.

To pick this up again. I have a two-story detached house with a basement, where the basement is also supposed to be included in the envelope (meaning it is insulated accordingly from the outside). Now I want to set up a room in the basement as a pantry / wine cellar, and it should have the lowest possible room temperature and be the coldest room in the house.

Insulating this one room "pantry/wine cellar" on the inside with XPS or EPS against the "warmth" of the surrounding rooms and completely omitting the surface heating there would be nonsense? Why?