Semi-detached new build, which technology to install?

You are right, the air-to-water heat pump operates well on its own and automatically when it is well adjusted. However, one should not save on individual room control/sensors for single rooms. This can easily be done via BUS systems. WHY? If I ventilate/heat/cool each individual room according to demand and necessity, the overall system works much more efficiently. If there are no sensors, energy is supplied that was neither requested nor needed, for example, for heating the master bedroom or ventilating the children's room. That means the supplied energy is then "wasted" unnecessarily and worsens the overall energy balance of the building services. And thus, the whole system causes a higher energy demand for the heat pump. This is actually the case in many projects where savings were made at this, and thus wrong, point. It has been proven that the annual performance factor calculated and forecast in the planning stage is more likely to be achieved or even exceeded when the above-mentioned issue is taken into consideration.

Ok, and how can I implement that? Every room has a thermostat where I can control the temperature. And since the underfloor heating is so slow to respond, it doesn't help if I turn the regulator down when airing the room, does it?

Unfortunately, I don't quite understand that.

You understand correctly that an ERR with a heat pump and underfloor heating makes no sense at all. No matter how you adjust it, especially cooling down in the morning, in the evening it will be cold, but at noon rather not. In other words, exactly when you come home from work and want the rooms to be warm, they are cold.

However, the statement by Denk_Mal19 applies very well to existing buildings with radiators or air heaters or even underfloor heating in dry systems. Here, the system reacts quickly and the heat can be distributed according to demand. This way, it is not “unnecessarily” heated/cooled.

In a modern low-energy building (according to [Energieeinsparverordnung] or better) with that heat pump (but also with gas) with a heat demand in the single-digit kW range, possibly also with a [Kontrollierte-Wohnraumlüftung], it is simply not possible to achieve larger temperature differences and reaction times of under 2-3 hours (if it is to run efficiently). Night setbacks are also counterproductive.

A perfectly thermally balanced system therefore does not need an ERR and can still provide a spread of air temperatures in the rooms of a few degrees. The desired temperatures are simply set via the flow, and the valves remain permanently open at that setting.

Empty conduits and deep flush-mounted boxes (at least at the light switches).

The question also remains how much time the electrician has for your property. We were a bit shocked because there was about a 1-week gap between the meeting on site for discussion and the start of work...

I also spent quite a lot of time on this and came to the conclusion that a KNX installation through the electrician from the general contractor will not be implemented optimally. The general contractor rushes the electrician from site to site and the time window is very tight. Although we settled directly with the electrician, he was still more obligated to the general contractor than to us, the builders.

I always assume that in modern and newly built houses the heat pump is combined with ventilation. It makes sense here, for example, to combine temperature sensors with CO2 sensors in the bedroom/children’s room. For this, only one CAT5/CAT7 cable needs to be run once through the house. Rooms that are only heated as needed (guest/work/hobby rooms, among others) are then switched on accordingly by T-sensors when required. During this time, they are ventilated with the minimum volume flow according to DIN 1946-6:2019-12. Otherwise, I can set them to a lower temperature. This works best via a home control unit/TOUCH display rather than going through and adjusting all rooms. This also makes the room values quickly and easily visible and, for example, stuck valves and the like become noticeable more quickly.

that in modern and newly built houses the heat pump is combined with ventilation.

Unfortunately, this is still not the case.

Rooms that are only heated as needed (guest / work / hobby room etc.) are then switched on accordingly via T-sensor when required.

Here lies a fundamental error in the understanding of thermodynamics. All rooms within the same thermal envelope strive for a state of equilibrium. Thus, the rooms that are turned off are heated by the surrounding rooms. This results in the heat demand of the surrounding rooms increasing, and thus energy is still consumed even if room X has apparently been decoupled from the system.