Mold due to residual construction moisture or insulation problem?

Hello everyone,

we have now been living in our new build for a little over a year. As is well known with all new builds, there is residual moisture in the walls during the first 1-2 years. This can sometimes mean that mold forms behind a wardrobe or picture due to the lack of circulation. This is a known issue that can occur.

We have a side gable on the house. The walk-in closet is located in the upper floor within this. Above the ceiling is the insulation, and the attic is cold. Yesterday we wanted to run cables along the wardrobe for new lighting in the closet above the wardrobe and discovered mold in one spot above the wardrobe. At first, we thought, okay - classic residual moisture problem, the mold must have formed behind the wardrobe and has now spread at one spot above the wardrobe. But when we pushed the wardrobe elements aside, a different picture emerged. The walls themselves are not really affected. The origin point is at the junction between ceiling and wall, from where some moisture and mold then migrate downwards. I hope the photos show this well.

This surprised us because we would have thought that circulation still takes place in the area above the wardrobe (about 6 cm to the ceiling) and would have expected the mold behind the wardrobes, where there is little circulation. It is the other way around. Therefore, we are uncertain whether the cause is the classic residual moisture or if it indicates a problem with the insulation. What is noticeable is that the most severely affected spot is roughly where the gable protrudes from the roof. And on the opposite wall, we also found mold at about the same height above the wardrobes. We haven’t been able to move the wardrobes there yet for a closer look because we first need to treat the other side. After removing the mold with cleaner, we also saw that at the heavily affected spot, the transition between wall and ceiling had slight "bubbles" (photo after). We believe this was not there when we moved in.

What do you think is the cause? Normal residual moisture or something with the insulation?

Best regards
Ubibubi

I am not on site and therefore cannot really help.

What does surprise me, however, is that it looks as if liquid has really "run down" - you can see real "tracks"...

Yes, the thing with the rails also confused us. Meanwhile, we have also exposed the opposite wall. Similar symptoms. What is strange is that there is a crack running in a kind of special pattern there.

Please get an expert from the IHK to take a look at it … doesn’t cost much and is a first assessment of what the cause might be … What is your house made of? We have pictures on the exterior walls and cabinets standing against them, I don’t know about residual moisture, not after such a long time!

It has nothing to do with residual moisture.

You might be heating with a heat pump? Is the room being heated or was it heated? Exterior wall?