New construction - Is high humidity still normal?

Good morning everyone,

We finally moved into our new building at the beginning of the month.
We are struggling with high humidity and I am unsure whether this is just the remaining construction moisture or if action is needed.

Here are some key data about the house:
- 113 m2 detached house without a slope and without a basement
- 30 cm aerated concrete blocks, drywall walls on top
- underfloor heating
- heat pump
- click vinyl in all rooms except the hallway on the ground floor (which still has no floor and will be done as soon as all the boxes are out of the hallway)
- no ventilation system (by now we know it was unwise, but during construction it was never mentioned, so we never thought about it)

In mid-August, we had a small water damage on the wall in the guest toilet on the ground floor. Luckily, the fault was found quickly and fixed immediately. Our plumber then turned on the underfloor heating on the ground floor for a week so that the moisture would evaporate faster.

At the moment I air the rooms 5-6 times a day.
The heat pump is still off as we still have over 22°C in all rooms.

Despite regular airing, the humidity remains constantly above 65%. At night it rises to 75%.
We bought an electric dehumidifier which stands in the hallway on the ground floor, but it only manages to lower the humidity to 60%. As soon as it is off, it rises immediately again.

My husband says I should be patient and that it is normal in a new building for the moisture not to go down. He says we should only worry if it does not improve next year.

However, I am worried that we have overlooked another water damage and soon will have mold in the house.

Is it worth looking for a cause or is this really the remaining construction moisture?
If it is normal, do we still have to do more against the humidity or is a winter with high humidity no problem as long as we continue airing regularly?

Many greetings
Sina

Despite regular ventilation, the humidity remains constantly above 65%

I have that too - renovated old building. That is currently normal.

At night it rises to 75%.

You breathe out a lot of moisture. The house does too (screed, plaster & co.). And you don’t ventilate at night.

So yes, currently no reason to worry.

No reason to worry, but also no reason to do nothing. In the past, the rich or investors were said to have given the houses to dry residents for 2 years so that they could dry out the place. Only after that were the houses rented out or used personally. Ventilate properly and thoroughly. Use shock ventilation, cross ventilation. Soon or already from now on, heat (very) well despite ventilating. Don’t be stingy about that.

In summer, we also always have around 65% humidity…. it's just damp, muggy air outside. As soon as it gets consistently cold, the indoor humidity drops significantly. We have been living in the new building for 7 years… everything is fine, no mold.

Thank you for the answers, that reassures me a lot ^^ Then I will continue airing and turn on the heating this week

Don't you have a ventilation system installed? We already had an average of only 55% shortly after moving in. Now, a year later, it's below 45% on average during the day. In midsummer, it was never over 60%. However, we also had a 9-month delay before moving in. Without knowing how severe the water damage really was, it's hard to say if "one week of underfloor heating" is enough to dry it out. Did the water get into/under the screed? Hopefully, cement screed is installed in the bathroom?! Who "assessed" the damage and decided what to do? The person responsible? To me, it sounds like you should trust your gut feeling and take a closer look again.