But install a controlled residential ventilation system?

It would be nice if a few people without [Kontrollierte-Wohnraumlüftung] could present their ventilation concept. Are there also those troubled by mold growth due to insufficient airing?

We have been living since August of last year in our (Massiv-)house without a ventilation system.

We air out twice a day. On weekends, some rooms are aired more frequently (e.g., children's room after an afternoon nap). In addition, the terrace door is sometimes left open or, depending on the weather, windows are tilted open. To reduce and then maintain the humidity in the house after construction, this was sufficient for us.
On the ground floor, we quickly achieved good values; on the upper floor, it took a little longer but it is now also in a good range. It is important at the beginning that unused rooms (e.g., guest room) and bedrooms are also heated. Only with warm air can you remove the moisture.
In our residential area, a builder reportedly had mold behind pictures. Therefore, we occasionally took the large pictures down.

I think that once the house has dried out reasonably well, it can also be left without ventilation for longer periods during vacations or business trips.
Where else besides the plants should all the moisture come from? Shortly after moving in, we did go on vacation for a week, but I was already a bit apprehensive about it.

In general, a new house also works without a ventilation system. Maybe not quite as comfortably, but it works.

We live in a four-year-old house without a ventilation system, both of us are out during the day. Ventilation is done if possible in the morning, and somewhat in the evening as well. On weekends, a window or door is sometimes left open for a longer time. Windows are (almost) never tilted open. Inside the house, we have relatively high humidity of well over 50%. We have no mold. However, I believe it would have been problematic to achieve the necessary ventilation in the first year. But we were not the owners then.

The question is always how airtight the house is, without special KfW Bank requirements and without [after measurements] you are also comparing apples and oranges (whether a house achieves 0.5 or 2.5 in the Blower Door test makes a big difference..). In my previous apartment, I never ventilated, but always had reasonable air. The required exchange was achieved through leaks. Some builders/prefabricated house providers install ventilation slots in window rebates without planned controlled residential ventilation, which may be very inconspicuous but are also sufficient against mold. For a comparison, more information would be needed.

The general contractor thinks that after the drying phase, one should ventilate about 2 times a day, that is enough. Since our bedroom only has about 12sqm of floor space, the good air would be used up quickly with the windows closed... Also for this reason, the idea with the [Kontrollierte-Wohnraumlüftung]...

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I can only warmly recommend installing a controlled residential ventilation system.

As self-proclaimed "window-open sleepers," we always had to struggle with stale air at night when we were forced to keep our bedroom window closed (in the old apartment) during bad weather.

Now, with the controlled residential ventilation system, we have both supply air (in the sleeping area) and exhaust air (in the dressing area) in one room and sleep much better even with the window closed.

I no longer want to do without our controlled residential ventilation system (purely as a comfort feature).

Greetings,

Dirk