High humidity despite decentralized ventilation system

This morning outside we had 12 degrees and 91 percent humidity. Inside 20.5 degrees and 64% humidity.

Ventilate or rather not??? :rolleyes:

The outside air warmed to 20.5 has a relative humidity of 54.5%, so 10% below your current indoor humidity -> ventilate!
In order to increase the indoor humidity (20.5 °C) over 64% with 12 degree cold outside air, the outside air would have to have 108% relative humidity (which is impossible).
At 70% relative humidity you can always ventilate below 15° ambient temperature, since the air always brings an improvement, no matter how humid it is.

The weather is currently actually too warm to achieve significantly lower humidity. Wait for the time with <5° in the morning and then tell us again if you still end up at 70%.

At the moment, the ventilation issue regarding construction-related problems (moisture/condensation or resulting mold) is also insignificant. With the high outside temperatures, at 20°C-21°C the surface temperature of the wall will be just below that. Condensation is therefore practically ruled out. Currently, ventilation is only necessary in the bathroom and kitchen areas. It can still be done for a better fresh air feeling, especially when working from home, but the humidity plays no role in this.

I'm a bit surprised by the debate. I currently (still) do not live in a new build apartment (although 6 years after construction/move-in the moisture should slowly be gone?), but in an old building from 193x (estimate), yet my measuring devices show 55-60% humidity in every room except the bathroom and kitchen. Even though we don’t heat and rarely ventilate. Which is not achievable at this time of year... that makes you think... in the bedroom, after airing out, I’ve also seen 4x% once, and that was rather in the morning, with 12°C outside...

Even in rainy weather, we haven’t had 70% humidity in the living rooms, although we quite like to ventilate when it rains... I like the pattering sound...

Could it be that apples are being compared with lemons?

You shouldn’t worry at the moment anyway, dertill has already explained that. Maybe turn off the decentralized ventilation and only ventilate by shock airing? The rest seems like hocus pocus to me...

Physics is physics, it should be the same in your world too ;) With certain changes to the parameters, of course, you get different values. If it is 10 degrees outside and 24 inside, then the air is much drier. In the current weather, this is quite sensitive to small changes in the parameters. Continuous ventilation through leaky windows is likely in an unsanitary old building

This morning outside we had 12 degrees and 91 percent humidity. Inside 20.5 degrees and 64% humidity. Ventilate or rather not??? :rolleyes:

An update.. outside it is now cold (night frost.. daytime below 10 degrees)… our indoor humidity is now at 50..53%..