Decentralized ventilation system that is hardly visible on the exterior facade

Zentral has much quieter operating noise,

Quieter, but not much.

no holes in your exterior walls (noise from outside),

Can be installed almost invisibly in the window reveal. Outdoor noise is only an issue in loud environments.

easier to keep clean (only regular filter changes),

Ditto for decentralized.

much better ventilation performance

The ventilation performance is correctly calculated for both variants and is identical.

heat recovery

... of over 90% in decentralized.

It's just a bad low budget solution. I would rather leave it and ventilate manually.

Nonsense!

We had decentralized from Meltem, which are supposed to be not the worst. We actually never used them again because they were very loud, drafty, and not centrally controllable. Now central, it is a world of difference.

I-Tec from Internorm meets almost all your wishes, unfortunately priced at the higher end. With an integrated heat exchanger, a heat recovery of up to 93% is supposedly possible.

I-Tec from Internorm fulfills almost all your wishes, unfortunately priced at the higher end With integrated heat exchanger, a heat recovery of up to 93% is supposedly possible.

:D just googled reviews about it. Devastating. Loud buzzing already at the lowest level, at level 3 it's unbearable in the room. Who installs something like that??

:D just googled experiences on that. Devastating. Already loud humming on the lowest level, at level 3 it's unbearable in the room. Who installs something like that??

That was not a recommendation from me either, by the way! I just held back comments on decentralized ventilation since the OP explicitly did not want a central one. So here's my opinion on it after all to avoid a wrong impression: Who does such nonsense? Do it properly - finished.

We had decentralized units from Meltem, they are supposed to not be the worst. We actually never had them on anymore because they were very loud, caused drafts, and could not be centrally controlled. Now central, it is a world of difference.

We also have decentralized units from Meltem – one in the living/dining/kitchen area and one in the bathroom. In the new building, it will definitely be central in every room.