ᐅ Which wall assembly is suitable for being vapor-permeable?

Hello everyone,

I am currently researching wall construction with a focus on vapor-open systems. I am very concerned about mold growth in the house, which is why I have often read that a vapor-open build is preferable (using a vapor retarder instead of a vapor barrier). However, when I look at the wall constructions of various manufacturers, a vapor barrier is often installed rather than a retarder (for example, Danwood). If the mechanical ventilation system fails, does this then inevitably lead to mold growth? Can anyone share their experience with how this (PE foil) actually performs in a house? Are there wall constructions where a mechanical ventilation system is installed as a nice-to-have but not essential? We currently live in an apartment and have to air the rooms multiple times in winter to prevent mold from forming under the blinds’ boxes. Are there houses or walls that do not experience these problems? We definitely want a ventilation system, but I would like to avoid the worry of mold growth within a few days if the system fails.

Thank you very much for your experiences.