Mold due to residual construction moisture or insulation problem?

Are you possibly heating with a heat pump? Is the room being heated or was it heated? Exterior wall?

The room was heated and yes, heat pump with underfloor heating.

What is your house made of? We have pictures on the exterior walls and cabinets standing there; I don't know the issue of residual moisture, not after such a long time!

The house is solidly built, Ytong and clad with bricks, gable roof with a side gable, in which the dressing room is located.

So we also had moisture meters in all rooms since moving in, and for the first half to three quarters of a year, it was still over 70% with closed windows. Meanwhile, it is on average under 60%. We believe that the mold only developed after November because we had already put things above the cabinets before and had not noticed anything there.

the room was heated and yes heat pump with underfloor heating

That is probably your problem. No convective heat and too low room temperature. It is completely normal for moisture to accumulate in the corners of the room at a possible thermal bridge. And quite a lot can add up there.

Maybe you should just heat the room properly with an oil radiator for 2–3 days so that the moisture can escape. It is possible that moisture has accumulated in the masonry that has nowhere to go.

There are many possibilities here. I would investigate whether the moisture is in the masonry or only superficial room moisture.

As said, first heat and ventilate, then observe what happens.

Thank you for the recommendation, but we must consider that heating here only addresses the symptom and not the cause. If a thermal bridge is present, it is ultimately crucial to identify and eliminate it, isn't it?

A quick interim update from me:

The carpenters were here and checked the insulation at the gable from the attic. However, there was apparently sufficient insulation material everywhere, the foil was well sealed, and no moisture could be felt.

If the cause is not coming from above, then it must be from the side. Probably somewhere in the marked area?



The search is definitely continuing..