The ventilation system is loud and disturbing

Rather the other way around. If the same amount of air has to pass through a smaller opening, it gets louder. Maybe it will even start to whistle eventually, like with drafty front doors and windows.

Or like that, yes :D
We adjusted everything individually back then as well.

Good morning, thank you for your interest.

The system is located in the attic. It hangs on the wall there. Normal door. Sound dampers are probably installed. The system itself makes almost no noise. It is the flow noise at the valves inside the rooms. Especially at the suction points (bathroom, kitchen) but also at the blowing points (all other rooms) at the highest level.

The system runs on the lower of two levels. I cannot say more myself. If the humidity rises above 70%, it should automatically switch to the higher level, and then it is no longer acceptable.

I cannot open the valves further, then the disks would fall out. That is why we have removed them in some places.

The pipes are located in the walls. I believe they are within the insulation.

I wonder what the throughput of such a system should be for 2 people in ~130 m². On the web I have found very different information about this. From 30-70 m³/h per person up to ~300 m³/h just for the living room.

In the kitchen, I measured just under 50 dB in the middle of the room with my phone.

Even if I assume a measurement error of 10%, that is unacceptable. It means that the volume flow at the valves is too high. So incorrectly adjusted, possibly the threshold for humidity is set too low. I thought for KfW40 there has to be a protocol on the regulation of the controlled residential ventilation? I may be wrong.

We have also wondered whether an official acceptance would still have to take place ...

I wonder what the throughput of such a system should be for 2 people in ~130 m². On the web, I have found very different figures on this. From 30-70 m³/h per person up to ~300 m³/h just for the living room.

As a rule, one says 0.5 air changes per hour as the nominal ventilation. For 130 sqm, that would roughly be around 160 cubic meters. For two people and the area, I would also find half of that sufficient.

Even if I assume a measurement error of 10%, that is unacceptable.

It means that the volume flow at the valves is too high. So wrongly adjusted, possibly the threshold for humidity is too low.

I thought that for KfW40 there has to be a protocol for the regulation of the controlled residential ventilation? I might be wrong.

Hi, we built KfW40+ with controlled residential ventilation. The system was of course calculated and partially adjusted by ourselves. A device for that (anemometer) was lent to us by the plumber. However, there was apparently no obligation to adjust (at least I did not read about it anywhere or was informed about it.) In 2 out of 4 residential units, the system was then later measured by the plumber. However, not in my two units (because it was already fine as I had adjusted it). I "somewhat" programmed the system myself, meaning times when it should be quiet (level 1) and times when it is allowed to run louder. Of course, the system ramps up in the morning after showering.

I would definitely check the filters (especially the exhaust valves should be checked every 6 months and replaced if necessary. Unit price for good "3rd party replicas" is 1-2 euros if they are the approx. 8cm round white Helios standard filters)