Alternative to central/decentralized ventilation

Not at all. Exhaust air to the street might be more sensible to have somewhat cleaner filters and thus slightly extend the replacement intervals.

Cleaner filters would be an argument to consider. Additionally, I was thinking about the outside temperatures, which on warmer days might be more pleasant on the north side to use as supply air?
Presumably, the small difference (north/west) probably does not matter much in this regard.

A nice north/west wind at strength 7 really hits the pipes well.
I wouldn't necessarily place the inlet/outlet directly in the main wind direction.

Unfortunately, we have no choice there anymore, so it is only about swapping the positions of supply and exhaust air. I therefore hope that the neighboring houses will somewhat curb the wind strength 7.... :)

One more question to the controlled ventilation experts now regarding the positioning of the supply air elements in the ceilings.

I have often read that distances of at least 50 cm, sometimes 75 cm or even 1-1.5 m from the walls must be maintained. Unfortunately, these are very different specifications, the relevance of which I cannot assess in practice.

In my current design planning, the distance of the supply air elements (ceiling) is only 25-30 cm and therefore feels too small, right?

Plays only a minor role and as long as the airflow of the room is ensured, it is practically irrelevant whether it is 1m or 20cm away from the wall. More interesting/more important is the design of the valve and the associated flow characteristics.

As for the airflow, I am honestly quite relaxed, especially after reading the research report "Air movements in freely ventilated living spaces"...

However, the (reasonable) distances to the walls etc. were unfortunately not addressed in it. Therefore, the question arises from practical experience: what distances have been used by whom? :)

Keyword here: "Air turbulence" at the walls/room corners?

Sorry - just a quick question again, which doesn't 100% fit this thread - but I think and hope that can help me out:

We were just at our heating engineer and decided on a complete indoor installation of the air-water heat pump with a separate controlled residential ventilation system (wall unit).

The air-water heat pump is located in the basement in the technical room
The ventilation system is located in the basement in the laundry room

The devices are therefore about 5m apart. He said that he can arrange the piping etc. better in the laundry room, since he then comes up through the wall via the study and not through the kitchen. As I said – I don't really care and it doesn't bother me that the ventilation system is then located in the laundry room. If it helps with the installation? Then go for it.

However, he said that the devices cannot and do not have to communicate with each other. He doesn’t even know what we mean by that, since the devices are independent of each other. One device heats and the other ventilates...

But the BAFA subsidy only allows funding of the ventilation system in combination with the air-water heat pump and an appropriate connection.

Luckily, we had that noted in our contract with the general contractor (communication via KNX or similar). How do you proceed best here? How do you connect the two devices? These are two single devices from Tecalor. I somehow have no trust in the communication between our general contractor and the heating engineer... I somehow feel that it will go wrong and in the end we won't get the full subsidy... I would like to "help" there.

ohoh, apparently the HB has no idea (about the funding conditions of BAFA). Discussing the sensibility of this joint regulation with the HB is not purposeful. It is solely about creating circumstances for BAFA that lead to fulfilling the funding conditions. This can be a BUS (but it would have to be provided in the models that they also "communicate" with each other. Via KNX or possibly even a Raspberry PI with some generic actuators or according to the report in the other forum, a timer switch (which I find quite absurd).