Are cold corners in new buildings still contemporary?

Thank you very much for the very detailed contribution!!

The wall material also consists of aerated concrete with a thickness of 36.5 cm. But of course, I don't want to ask for a remote diagnosis now. That needs to be looked at again on site.

In short: In EVERY new building, your "cold corners" problem should not exist. If mold appears, it is due to incorrect ventilation habits, but not because the corners are too cold.