Moisture in the laundry room - ventilation or dehumidifier?

Cool tips are back here…

: what does your fresh screed even matter here…?

cool tips again here…

: what does your Fischer screed matter here…?

Do you actually read what others write or do you just complain? A neighbor like you and one might as well look for a new house...

I said that right now it is difficult to ventilate when it is colder outside because we have very high temperatures. And I discussed this with the specialist who set up the construction dryers. He said that normal shock ventilation is enough for us and theory is theory and practice is practice.

By the way, your "Brain Bug" post has certainly contributed a lot....

Where does the moisture come from for you? From inside or outside? If you cool 30-degree warm air down to cellar temperature, the relative humidity rises sharply. Ventilation then does not help. Even airing in the morning doesn’t help much because morning air has a high relative humidity and is probably still warmer than your cellar at current temperatures. If you hang laundry down there or the dryer blows moist air into the cellar, I would address that.

Don't even bother with granules. The solution would be an automatic dehumidifier, you can get one for 100-200 EUR. You set the desired humidity (e.g., 55%) and it runs as soon as this is exceeded. Which dryer do you have? Probably a condenser dryer? Ours used to release a lot of moisture outside. With the heat pump dryer it was much better, and after installing the drain hose directly into the drain (instead of the collection container) it was no longer a problem and always dry. So you can consider whether to invest money in a dehumidifier (with corresponding running costs) or perhaps get a newer/more efficient dryer with a drain hose right away. Of course, only if my assumption about the condenser dryer is correct :)

Is the rule generally valid that you should only ventilate the basement when it is cooler outside than inside the basement? What if it is warmer outside but the air is drier than in the basement? Currently, it is 28 degrees outside during the day with about 40% relative humidity. The basement has 19 degrees and about 60% relative humidity.

It depends on the absolute humidity. In your example, the relative humidity of the cooled outside air is 66%, so by ventilating you are introducing moisture.