Were incorrect windows installed?

Hello everyone,

we are currently building a KFW55 house (but less so in the amendment, as we switched from gas to a heat pump) with a ventilation system and heat recovery. We are at the stage where the screed will be laid next week or the week after. However, we have noticed that all the windows have a ventilation slot (about 10cm of sealing is missing on each window). That can’t be right, can it? Why have window ventilation when there is a ventilation system? We thought the house needs to be airtight, which will eventually be tested with the blower door test. Can this be correct? Are these the wrong windows?

Please help us. Thank you

What does the window manufacturer say? Window rebate ventilation with controlled residential ventilation makes no sense at all. But it is reversible with very little effort for me.

Same for me. Was also surprised. According to Febsterbauer, it is not a trickle vent but prevents moisture and the windows from fogging up. The blower door test afterwards also showed that the window is airtight. Would therefore inquire, but not worry too much.

According to Febsterbauer, not a trickle vent but prevents moisture and the fogging of the windows.

Can you explain that for a layperson? Which window fogs up – inside or outside? How does it work?

My windows also have this on the outermost of the three sealing levels. I also asked the manufacturer back then out of curiosity:

The recess is intentional. This ensures optimal pressure equalization, which makes the window tighter. At the same time, it is a specification from the profile manufacturer Veka.

With our Veka MD (middle seal), all three seals are intact. Nevertheless, the frame has openings on the outside for pressure equalization and water drainage.

how do the other seals look on your side?