Pattern through insulation panels on house wall

Hello,

on the exterior walls of our house (built in 2007), a pattern is becoming more and more visible. Where the insulation boards meet, black lines can be seen.

This is especially noticeable on the north side. On the south side not at all, on the other sides somewhere in between.

We have completely "normal" white exterior plaster.

The general contractor now claims that it is because of the "damp" north side and that "he can't do anything about it."

Does anyone have a good tip for us?

Regards
Christian

In my opinion, these are classic thermal bridges because the insulation was applied sloppily! You can also often see the fastening dowels protruding through the facade after a few years if they were not properly recessed, or if a cheap variant was chosen...