ᐅ Were the wrong windows installed?

Hello everyone,

we are currently building a KFW55 house (actually less since 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 installed either next week or the week after. However, we noticed that all the windows have a ventilation slot (about 10cm (4 inches) of sealing is missing on each window). This can’t be right, can it? Why would there be window ventilation with a ventilation system? We thought the house needs to be airtight, which will eventually be checked 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 combined with controlled mechanical ventilation doesn't make much sense. However, it is relatively easy for me to reverse.

It’s the same for me.
I was also surprised.
According to Febsterbauer, it’s not a trickle vent but prevents moisture and window condensation.

The blower door test afterwards also showed that the window is airtight.

I would ask about it, but I wouldn’t worry too much.

Martial.white schrieb:

According to Febsterbauer, it is not a rebate vent but prevents moisture and window condensation.

Could you explain this in simple terms? Which side of the window gets condensation – inside or outside? How does it work?

My windows have the same issue on the outermost of the three sealing layers.
At the time, I also asked the manufacturer out of curiosity:

The recess is intentional. It ensures optimal pressure equalization, which makes the window more airtight. At the same time, this is a requirement from the profile manufacturer Veka.

In our Veka MD (central sealing) system, all three seals are intact.
However, the frame has openings on the outside for pressure equalization and water drainage.

@DierkW79 how do the other seals look in your case?