Low humidity in the new building?

Hello everyone,

We have now been living for about 4 months in our KfW 55 new build with heat pump and underfloor heating built on Poroton (36.5cm monolithic), but without a ventilation system. During the approximately 10-month construction phase from January to November, we always ventilated properly, usually opening the windows for a longer time 3-4 times a day in the mornings and evenings.

From stories and many experience reports, we were quite afraid of mold in the new building, hence our urge to ventilate. However, since moving in, we have had stable 40-60% humidity in every room, even in unheated cellar rooms. We still continue to ventilate diligently, but we are somewhat perplexed because we have often heard that new buildings contain construction moisture for months and sometimes years.

Have I stored the information about residual moisture incorrectly and we basically already have an ideal indoor climate, or do the hygrometers simply measure the air humidity in the room, but not, for example, in the masonry?

Hi,

stable 40-60% humidity in every room since moving in,

That's quite humid already. It's winter, so you can expect more like 25-40%. It takes a while. But up to 60% is not critical.

Best regards,

Andreas

Don't air out for a week, then you'll know how much moisture is still in your new build.
That was of course a joke. Keep airing out diligently. However, I wouldn't describe 40-60% as "quite humid." That is the optimal humidity for living in the house. At 25% humidity, I would be very reluctant to live...
Since you built over the summer, there is surely still a good amount of residual moisture in the house. Starting construction in January probably means you got screed in July/August and then heated it up? At that time of year, even with windows open 24/7 for ventilation, you can hardly get moisture out of the house.
Air out, air out, air out.