Ventilation in summer

Hello dear forum!

I just don’t understand... maybe someone can enlighten me?

We moved in a week ago and I am currently dealing a lot with the topic of ventilation and mold. Nevertheless, a few questions remain:

Why shouldn’t I open the windows and doors for several hours at a time when the weather is good?
The humidity outside is currently quite low, the sun is shining.
So far, I have kept the windows and doors open for several hours during the day.
As a result, the humidity (which usually was around 80) sometimes dropped down to 40 percent.
But that’s good, isn’t it?
I always read that this kind of ventilation behavior would bring moisture into the house.
Where should that come from if it’s dry outside?
The air would condense on the cold walls. What exactly is meant by "cold"?
Why should one always close the windows again when ventilating? What does that achieve?
And is it sensible to keep the heating running during the first summer?

Thanks in advance for answers :)

Hello,

....we moved in a week ago and I am currently dealing a lot with the topic of ventilation and mold...

That should be done before, not afterwards!

....Where should it come from if it is dry outside?..

Dry is always relative, just like the relative humidity!
What matters is always the absolute humidity!
Summer AT conditions are generally not suitable to deal with internal drying matters, especially not in basements (Mollier-h,x diagram)!

Best regards.

So I really tried to write as unassailable as possible.... guess it didn't work. Who says I never dealt with it before? The previous ventilation method unfortunately didn't help. ...Mollier-h,x diagram... why didn't I think of that :D :D

....Who says that I have never dealt with it before?...

Apparently completely insufficient, otherwise you would not have asked for help here! :-)

best regards

I am unfortunately unable to help you. I think many builders are overwhelmed with this topic.

It's a pity that those who are familiar with it don't write anything.

It's a pity that those who are knowledgeable about it don't write anything.

This is probably more due to time constraints than unwillingness; moreover, the topic in question is one of the "Jehovah topics" – ask 10 experts and you get 12 different opinions ;)

"Cold wall" should not be understood as a wall being "cold" in the sense of refrigerator temperatures, but merely a few degrees cooler than the air temperature. Humidity (and also the described "dry" summer air still carries moisture) always settles at the "coldest" spot; anyone can experience this effect in the bathroom, provided they have a closed shower cabin – simply close it and take a really hot shower for 10 minutes in the warm bathroom. Then open the shower cabin and pay attention to the bathroom mirror...

I think, without being able to prove it scientifically, that it is better to first let the room air absorb the existing moisture and THEN exchange this now more humid air for "new" drier outside air by briefly airing the room forcibly.

Regards
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