Roller shutter system moist all the time...!

We are now living through the second winter in our beautiful new house, but we have problems with moisture concerning one roller shutter. The roller shutter is permanently wet on the inside, which leads to it sometimes freezing during frost and then barely being able to move. They are mini blinds made of aluminum, which are foam-filled. The roller shutter box was installed completely with the window and is therefore located behind the facade insulation. (House KS with 15cm Styrofoam on the outside). Above the rooms, there is a roof terrace with a masonry parapet. There are basically no moisture problems or similar issues on the ceiling or walls of the rooms, so we assume that the terrace is probably watertight.
Where does the moisture on the roller shutter come from all the time?
If any information or anything else about the building materials used is missing, I can gladly provide it.

Regards

Hello

Of course, it's difficult to make a concrete diagnosis from a distance without an inspection. According to your descriptions, this is probably a condensation problem. With roller shutter boxes, there is the risk of thermal bridges. Therefore, they are mostly installed made of polystyrene rigid foam with additional thermal insulation. For example, if the insulation on the outward and upward-facing side is damaged or missing, a thermal bridge forms there, leading to condensation. Another common issue is often the tightness of the wall and ceiling connections of the roller shutter boxes. Due to convection etc., the component temperature drops, causing condensation. So it should be checked whether the connection joints are airtight, because then there is no draft. Was a so-called blower door test carried out by the builder before handover? And how is the thermal insulation of the roof terrace executed at the top?

However, the problem could simultaneously have several such causes. For example, there is the possibility that on the front side of the reinforced concrete slab of the roof terrace, besides inadequate thermal insulation in the roller shutter box, condensation also occurs due to insufficient insulation of the reinforced concrete slab of the facade.

Have a nice evening