Which central ventilation system?

One is generally more susceptible to certain illnesses even at low humidity. We have a Helios with humidity recovery and therefore maintain around 45%-50%. Otherwise, I am satisfied with the control system; in my case, the system does not always run at the same intensity but operates according to a weekly schedule with varying levels at certain times (e.g., stronger during times when cooking/showering).

Too humid air is also not good for the house...

What is better now, partially too dry with controlled residential ventilation or partially too humid without controlled residential ventilation?

Exactly right is best if you ask like that. You do so much with technology.. You could connect a humidity sensor to the Helios and also control it based on that, I think this is possible for many other controlled residential ventilation systems as well. Or consider your own solution, the Helios can be controlled via Modbus/LAN, the documentation is available. At least for us, the humidity value is quite optimal with the heat recovery.

Too moist air is also not good for the house...

What is better now, partially too dry with controlled residential ventilation or partially too moist without controlled residential ventilation?

Around 30% relative humidity I consider structurally uncritical.

For comfort, it is individual, I like 35-40%.
However, the humidifier easily achieves that......

Best regards
Thorsten

It should be noted that this low humidity is not present throughout the year. From around 5 degrees onwards, the humidity is already "normal" again – so almost the entire last winter here in the Niederrhein/Ruhrgebiet

It must be said that this low humidity is not present all year round. From about 5 degrees, the humidity is already "normal" again - so almost all the last winters here in the Lower Rhine/Ruhr area

Exactly right.