ᐅ Is that mold inside the window shutter box?

This is almost certainly an installation error. Ventilating four times a day is more than sufficient. Don’t let the construction manager downplay the need for more frequent ventilation.

The roller shutter boxes were opened, and everything inside is fine. Everything is dry, with no unusual stains or anything else. Even at the window where there was previously an issue with the wall, someone is now coming to take a closer look.

Our site manager suggested considering retrofitting window rebate vents since we do not have a mechanical ventilation system. What are your thoughts on this?

The absence of mechanical ventilation is already a deficiency in itself.

Lumpi_LE schrieb:
The absence of mechanical ventilation is already a defect in itself.

Just bar talk.

Technically, that is not correct.

Yes, they forgot the " ".
I still can’t understand how something like this can be overlooked in the planning, even if it’s just a window rebate ventilation.

It can also be incorrect ventilation caused by permanently tilted windows. The lintel/box cools down, and moist indoor air condenses exactly in that area.