Cross-ventilation - is it mandatory in apartments?

Cross-ventilation is the mumbo-jumbo euphemism for "ventilating chaotically and wasting energy." What really makes a difference is a central residential ventilation system with a heat exchanger – whether the neighbor is having a loud party or you're going on vacation, whether it’s bitterly cold or extremely hot outside: the air is perfectly exchanged, the heat or cold is retained, and the insects stay outside.

Cross-ventilation is just ventilation. If anything, then chimney ventilation, meaning open at the bottom and open at the top, that way there’s a real draft.

In general - "stable factory building" - the legal issues regarding rezoning and the Building Energy Act have surely all been clarified, right?

My first place was such an apartment, hallway in the middle and apartments on the right and left all only 2.5 rooms, one bathroom without a window, etc. It was very difficult to get air into the apartment, some neighbors even used the door to the hallway for ventilation..

I would try to avoid something like that but I don’t think there is a regulation for it.

Can confirm the experience, even in the corner apartment. Especially in summer, you can't get the air out in the evening due to lack of draft. I wouldn't move into something like that myself. It can be done for renting out, but only with forced ventilation to prevent mold.

Cannot confirm this here. Whether the apartment is in the middle or on the corner. There were never any problems with air exchange when ventilating normally. And what are 90% of all developers in the major cities of this republic supposed to say, where over 50% of the people live. It is completely normal for apartments to have only one side or at most two window surfaces. A detached house-building forum discussion and nothing more. Normal people live in such apartments without problems.

no problem.

You can see this from the fact that no one ever argues with their landlord about mold ;)

By the way, there is nothing pretentious about the observation that air exchange works orders of magnitude better with cross-ventilation than ventilating on just one side of a building. That is basic physics. In winter, you can still manage reasonably well, ideally with controlled residential ventilation. However, the necessary air exchange rates to cool down a house again in the summer evenings and nights cannot be achieved with controlled residential ventilation nor with one-sided ventilation.