Residential ventilation KfW efficiency house 55

We are planning a KfW Efficiency House 55. Is it really the case that with this modern building method a residential ventilation system is always required?

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We are planning a KfW Efficiency House 55. Is it actually the case that you always need a mechanical ventilation system with this modern method of house construction?

No one is forcing you.
If you can properly ventilate by opening windows three times a day, then do it that way.
Others use forced ventilation (window rebate ventilation, etc.) to achieve at least some air exchange without manual effort.

KfW 55 is moreover not per se tighter than "just" the Energy Saving Ordinance. Airtightness initially has nothing to do with the thickness of the insulation or the system technology.

Is it really the case that one always needs a mechanical ventilation system with this modern house construction method?

No. For understanding, one should distinguish between fulfilling the KfW requirements and ensuring the necessary air exchange.

Just briefly: KfW: Which insulation and which building services technology are required for a certain "Effizienzhaus xy" standard can be primarily found in the KfW information sheets and clarified in detail with the energy consultant. General statements like "Gas always with solar thermal" are wrong.

Air exchange: Modern houses are airtight. To avoid "stuffy air" and mold, a minimum air exchange must be ensured. There are various technical solutions for this and also an organizational one (information sheet with ventilation instructions).