The architect told me that I don't need to ventilate, because with this weather you would only unnecessarily bring in more moisture, those were his words
I want to describe this in a layman's way. Imagine you are in a snugly warm heated bathroom, running water into the tub, lying down in it, and what happens? The mirror fogs up, where you want to style yourself after a long bath, what do you do? Wipe the mirror, or briefly tilt the window or open it? Observe what happens.
I had insisted on that, was rejected by the architect, I have now sent him the defect in writing so that he finds a solution with the drywall installers.
Without heating, ventilating currently does little/nothing. At 10 °C outside and 99% relative humidity, you need about 20°C inside to get below 55% relative humidity (or similar - just Google relative humidity) The principle is air exchange; warm moist air ideally against dry cold air.
the architect told me that I don’t need to ventilate, because in this weather you would only unnecessarily bring in more moisture, those were his words
I see it a bit differently; in the first 1.5 weeks of February, temperatures in NRW were still around ±12°. Here, a shock ventilation would certainly have been beneficial, but afterwards, technical drying should have been done until the heating program begins.
The more interesting question, however, is: do you have the architect’s statement regarding the unnecessary ventilation/drying of the new building in writing? Otherwise, it will surely become interesting when it comes to the question of cost coverage.