Central ventilation system - is moisture recovery necessary?

Therefore nonsensical, because an enthalpy exchanger undeniably has advantages. The extent of these could be discussed. But since this is about savings of 300-500€ on an investment of +500-700k€, in my opinion it is nonsensical. One could also discuss whether windows are really necessary or maybe paint on the walls, as you can save significantly more there.

Well, for me the enthalpy exchanger costs over 1000€. I do think it’s worth considering whether you actually need it or not. If you approach every trade and all decisions like that, it adds up and for many the budget is blown in the end. If you don't have to worry about that, that’s nice. Comparing the sensibility of paint or windows to the question of whether moisture recovery is necessary… then there’s no need to discuss anything at all. I don’t deny that an enthalpy exchanger has advantages; there are plenty who manage without it and still have sufficient moisture in the house. That’s why I would recommend starting without one and see how it goes, and retrofit if needed.

Then see what it costs as ET and upgrade later

To properly adjust a system, you would have to control the rooms individually. Unfortunately, that’s not possible with all these single-family house controlled residential ventilation devices, very unfortunate that the manufacturers don’t offer anything there.

I really don’t understand that either. Basically, all you need are throttle valves per branch plus motor plus control. It shouldn’t actually be an insane extra cost. I adjusted our ventilation system a bit differently than the installers so that it runs more when we’re not home during the day. Overall, it now even runs higher than the standard intended. I’ve attached the CO2 levels of the children’s bedroom from the last two days. 400 ppm is ambient air; usually the room reaches that once a day. Interesting is the children’s bedtime with the door closed and 3 people in the room, and the increased speed from midnight. Humidity in the living room and children’s bedroom from the last 12 months is also attached. Currently, our humidity in the living room is actually just under 40%. But it will rise again soon and the air is still good. How do you calculate the air exchange rate? Do you have the volume flows, air masses in the rooms?

I think that's quite a lot, I have mine set so that it averages around 600-800 and ideally does not exceed 1000. In the bedroom, it's not completely possible, sometimes it goes a bit higher at night. Due to the aforementioned issue, the result is that at 3 a.m. in the bedroom where people lie around, I have 1000 ppm, and in the entire ground floor where no one is, 400... If living spaces were throttled at night and bedrooms during the day, average air exchange rates of 0.2-0.3 would probably suffice comfortably, but then at night you would have 4000 in the bedroom and the average at the system of 700 is all in the green zone.

Do you have any recommendations for measuring and logging? I don't really have the time to tinker myself.

Had bought a "Forever25 CO2 meter" back then, but it can only log when connected to a PC. If I had known it back then, I probably would have gotten a Netatmo.