20% humidity in KFW 40+ new construction

Since I am no longer allowed to edit: You explicitly ask on the first page about incorrect settings in the controlled residential ventilation. What air exchange rates/volume flows are currently set? Maybe the levels are set too high.

The controlled residential ventilation runs on automatic. What exactly that means: I do not know..

Due to the recent move + severe cold, we have not yet had the time, energy, or inclination to deal with the controlled residential ventilation settings. We thought: automatic is fine.

Are you sure that your measuring device is working correctly?

The controlled residential ventilation runs on automatic. What exactly that means: I don't know..

Automatic usually means that a time program for runtime or stages is active. The rest (temperature, possibly air volume) always runs automatically. So if you were to set it to manual, usually only the runtime or the speed changes (if it is supposed to change at different times).

Without EWT you won’t really be able to raise the humidity in winter. Any moisture is removed again by the air exchange. On the other hand, an EWT can only retain what is already there.

My suggestion:
- Bite the bullet and buy a German piece of engineering (EWT) at pharmacy prices. There are often no-name replicas that are considerably cheaper, though still borderline usurious.

- Get a CO2 meter. For example, I have one from Netatmo. Use it to adjust the volume flow so that ventilation runs only as much as necessary. I have mine set so that 1000 ppm is never exceeded.

- Produce moisture. Hang laundry inside, ventilate the house toward the outside after showering, cook, plants, etc. etc.

There were really many and varied hints and tips, thank you very much for that :-)

It makes sense to me that a house, especially a passive house, must first be lived in when warm – that’s what our heating engineer said as well. The same probably applies to the air. Many new pieces of furniture have moved into the house, also new blankets, pillows, towels, etc. It may take some time for everything in the house to acclimate.

We actually only have one hygrometer and cannot make a second reference measurement. But regardless of whether the 30% figure is correct or not: it doesn’t feel good. So action is needed, at least in the bedroom. The humidifier has been running all day there today, and we have already had over 50%.

Sooner or later, an EWT will have to be installed in the house. Here, only the overheard information that it brings a maximum of 5% improvement discouraged us. But I think this ‘info’ is simply wrong. We will still have a conversation with Zehnder and/or our plumber about this.

Certainly, we will also work with plants, but with the goal of emphasizing livability and not to save the air. Honestly, all the watering would annoy us too much.

Running the controlled residential ventilation at minimum so that you just have an appropriate CO2 value we exclude personally. We were really looking forward to the controlled residential ventilation and the permanently fresh air it provides.

To sum it up: The humidifier in the bedroom will remain our friend for a long time and we will wait a year and probably buy an EWT next spring.

Thanks again to everyone, it really became a constructive thread :-)