Ventilation system - Noise level dependent on which factors?

This is the necessary construction service description

All right, I will address it as already mentioned, I think a closer installation should not be a problem, but if it is written down, it is written down... I myself am curious how this will proceed. My preferred home builder does not come from the region where I want to build...

My fear is that these units get louder as they age, just like any refrigerator does.

Possible. Such a bearing is not made to last forever. But unlike a refrigerator, where the compressor is the culprit, the repair should be manageable.
I've already opened our Zehnder for a "major inspection" (which is ultimately a visual check and cleaning, anyone can do it), you can see the fans, the connection. It shouldn't be rocket science to replace it.

My preferred homebuilder is not from

That would be a reason for me not to build with him.
Because that either means subcontractors who basically only come for assembly, which in case of scheduling difficulties causes a domino effect of the highest order, or regional ones that he probably no longer chooses and in the worst case only selected according to the cheapest offer price.
Do you also have regional companies in your selection and is architect and self-contracting an option or if not - for what reason?

Overall, we had contact with 19 home builders (i.e., personal conversations), including prefabricated house manufacturers as well as some solid house builders. Self-contracting was never an option for us, as we are not very knowledgeable with architects and never wanted to have much to do with the construction itself due to lack of time.

The issue with the region was clear to us from the beginning, yet we always thought that this is basically the case for everyone, since very few prefabricated house manufacturers are nearby. Of course, there are some in the region (around Stuttgart) who actually are based here, but unfortunately all of them are out (for various reasons).
But even if he is not from here, it is not the first time he is building here and he probably already knows one or two subcontractors (at least we hope so for now), but this will still be asked, it’s already on the list.

We went through the topic very thoroughly, not just by gut feeling, and narrowed down the circle more and more. Our favorite has stood out from the competition in every respect from day one, yet as far as possible we have been as objective as possible. We have a good feeling and all the others would basically just be compromises. However, we are not so rigidly fixed that we want to work with him at any cost; if something seemed strange to us, we would not take the risk. On Friday, the next conversation will take place with another list of questions from us, and after that we will also give the contract and the service description to the "Fertighausexperten" for review.

Still, I am curious what the answer regarding the subcontractors will be...

What is Bauleistungsbeschreibung?

In this case, the "particularly mild ground temperature" ... ;)

regional which he probably no longer

Should not mean knows.

since we are not very knowledgeable with architects and we never wanted to have much to do with the construction itself due to lack of time

The important thing is not that you are knowledgeable about the architect (what does that even mean), but that he is knowledgeable about all phases of a construction. Then he helps much more with the second part of your idea than a general contractor who primarily puts his own interests first.