ᐅ Central ventilation system – is humidity recovery necessary?

Lumpi_LE schrieb:

That’s why it doesn’t make sense, because a enthalpy exchanger clearly has advantages. The exact extent can be debated. But since this is about saving 300–500€ on an investment of over 500,000–700,000€ in my opinion it’s pointless. You could also argue whether windows are really necessary or maybe paint on the walls, where you can save much more.

Well, for me the enthalpy exchanger costs over 1,000€ (about 1,100 USD).
I do think it’s worth considering whether you actually need it or not. If you approach every trade and every decision like that, the costs add up and for many people the budget ends up being exceeded. Of course, if you don’t have to watch that, it’s great.
Comparing the usefulness of paint or windows to the question of whether moisture recovery is necessary... then there really is no point in discussing anything at all.
I’m not denying that an enthalpy exchanger has advantages; there are also plenty who manage without one and still have sufficient humidity in the house.
That’s why I would recommend starting without it, see how it goes, and retrofit if needed.

Then check the price of the equipment and upgrade later.

Lumpi_LE schrieb:

To properly adjust a system, you would need to control the rooms individually. Unfortunately, that’s not possible with all these residential mechanical ventilation units for single-family homes. It’s a real shame that manufacturers don’t offer that.

I honestly don’t understand that either. Basically, you only need dampers per duct plus a motor and control unit. That shouldn’t be an extremely expensive addition.

I have set up our ventilation system a bit differently than the installers did, so it runs more when we are not home during the day. Overall, it now runs even more than the standard setup intended.
I’ve attached the CO2 levels of the children’s bedroom over the last two days. 400 ppm is outdoor air; usually, the room reaches that level once per day. What’s interesting is the kids’ bedtime with the door closed and three people in the room, followed by the increased fan speed from midnight.
Humidity data for the living room and children’s bedroom over the last 12 months are also attached. Currently, our humidity in the living room is just below 40%. But it will rise again soon and the air quality is still good.

How do you calculate the air exchange rate? Do you have the volume flow rates or air masses in the rooms?

I think that’s quite a lot. I’ve set it so that it averages around 600-800 and ideally doesn’t exceed 1000. That’s not entirely possible in the bedroom, where it sometimes goes higher at night. Due to the issue mentioned above, this results in having 1000 ppm at 3 a.m. in the bedroom where you’re lying down, while the entire ground floor, where nobody is, measures 400 ppm.

If it were possible to reduce ventilation in living areas at night and in the bedroom during the day, average air exchange rates of 0.2-0.3 would probably be sufficient. However, that would mean reaching 4000 ppm in the bedroom at night, and an average of 700 at the system level is well within the safe range.

Do you have any recommendations for measuring and logging?
I don’t really have the time to DIY.

I bought a "Forever25 CO2 meter" back then, but it can only log data when connected to a PC. If I had known about it at the time, I probably would have chosen a Netatmo instead.