Which wall structure is meaningfully vapor-permeable?

And yes: new houses are practically airtight. But they are nice and cozy warm.

YES especially in midsummer :D

Mold also forms when a room is ventilated. Mold is possible where there is constant moisture. This occurs when warm and therefore quite humid air condenses in a joint, corner, angle, or niche because it is colder there due to defects in the thermal insulation, it also dries poorly there, and suddenly the enemy is there. I am also a fan of monolithic walls because no insulation errors can occur there since there is no insulation; the insulation is the thick Ytong stone itself, and it is uniformly built in everywhere. There is no plastic film in the wall; a cement and aerated concrete wall absorbs moisture and releases it if you do not block it from the inside with sealing wall coverings. Ventilation is still necessary, but our window rebate things are sufficient; when we return from vacation, there is no need to fear finding mold because all the windows were closed for two weeks.

Ventilation is still necessary, however, our window rebate things are sufficient,

= uncontrolled residential ventilation
Ventilation is key to prevent any issues. This is the only point the OP needs to keep in mind to have a good feeling.

Good morning,

I researched a bit more about the window rebate ventilations yesterday and I wonder why this is hardly ever offered in new buildings? I find the system very good and you don’t need a central unit. Or does this system only work with certain building structures?

I researched a bit about window rebate ventilations yesterday and I wonder why this is hardly or not at all offered in new buildings?

... because it is basically the small alternative to a permanently tilted window. Warm air is continuously exhausted outside and cold air is continuously brought into the house. Without control, without heat recovery. It is also not good for KfW calculations.

However, it is still an acceptable solution to always get fresh air into the house. Even if it is absurd to build an airtight house only to then have uncontrolled holes in the facade again.

= uncontrolled residential ventilation
Ventilation is the be-all and end-all to prevent anything from happening. This is the only point the OP must keep in mind to have a good feeling.

I add: proper ventilation is the be-all and end-all.
As an allergy sufferer, I prefer manual ventilation through windows – ventilation systems should be cleaned regularly, which is often overlooked.