Decentralized ventilation only in individual rooms in new construction KfW 55?

Yes or then at least decentralized in the bathroom, even if 11ant upstairs gives understandable reasons, when it comes to money then better none and certainly not in the sleeping room unless one doesn't care and sleeps like a log .... In the bathroom it is practical though, because you can simply turn on the device in the morning and leave the room and everything is fine ... I am also in favor of no device rather than decentralized.

Yes, or at least decentralize it in the bathroom, even if 11ant gives understandable reasons above

Where did I give reasons to do at least one in the bathroom? If it is purely about spatially separating an active component, that does not necessarily imply a central system.

you didn't and I didn't write/mean that either ... You say all or nothing and list reasons and I meant instead of nothing at all at least one in the bathroom

So we also bought our house completely without a ventilation system because a central residential ventilation system causes permanent costs.

[...]A central residential ventilation system is expensive to maintain because it must be serviced continuously, which causes ongoing costs. [...]

No.

So we also bought our house completely without a ventilation system because a centralized residential ventilation permanently incurs costs.

And what costs are those supposed to be? A ventilation system doesn't even require maintenance.