super thanks for your answers.
Is there something in between, so between 400 euros extra charge and the normal doors?
I don’t quite understand the ventilation system yet. There are also systems that mix cold air from outside with warm air from inside.
I’d like to search the forum myself, but what should I look for?
House fees is a good topic. The total additional costs are calculated here at 0.25 per square meter. It will probably be closer to 0.50.
Usually your developer has samples or a craftsman (e.g., wood specialist dealer) where he sends you for sampling. You choose and get told the extra cost.
An example: For us, the extra charges were really reasonable (interior door with groove, glass door in the living room). We had everything done through the developer for an extra charge.
A colleague lives in FFM and worked with an apothecary developer. It blew my mind what extra charges they came up with around the corner. It went so far that they assigned the glass door elsewhere because it was cheaper than the extra charge.
The motto is always to sample beforehand if possible or express your wishes and ask about the extra charge. Don’t be surprised by a big price shock after the ink on the purchase contract dries.