Mold inside a 3-year-old house wall/ceiling corner

Oh yes... the good old heating/ventilation debate.

Those who understand the connections immediately... recommend more heating and ventilation.

The others look for problems in the wall structure, etc.

The problem is, as always, a thermal/cold bridge. You can call it whatever you want. The fact is the wall is colder (and possibly more humid) than the rest, and for this reason, the air moisture condenses here.

Air humidity of just under 70% is not "healthy"; airing out is possible, but either with a forced ventilation system or with the well-known shock ventilation behavior. Well, or in leaky houses (old buildings, etc.) but that apparently does not apply here.

However, for this, you have to increase the moisture absorption of the air in the room. Because in order to be able to air out large amounts of moisture in a short time (shock ventilation), you must also have these amounts available for transport.

To put it exaggeratedly, without higher temperatures, you can keep the window open all day and nothing will change.



The house is only 3 years old. If little ventilation and heating have always been done and the thermal bridge has always been there, then possibly the construction moisture is still there at that spot and the occupant is only ventilating out the additionally introduced moisture. Result: the wall never dries.

Thank you for all the answers. I see I need to air out more often, heat more (the room was below 20 degrees - only used as a bedroom).

By the way, the room is on the 1st floor, south/west corner.

What still surprises me: the wall itself is dry everywhere (measured by professionals - "34" whatever that means). Only at the top corner is it really wet ("136" whatever that means) and 2.5 degrees cooler. Is this therefore a thermal bridge? Can something be done about it or do you live with it and make the best of it?

Best regards

Roof insulated? Insulate floor ceiling?

The corner of the exterior wall is always cooler. You can also put a dryer in there and run it. It just costs electricity, you have to calculate what is cheaper for you, often ventilate and heat properly, or put a small dryer in the corner.

Yes, it is a thermal bridge. As soon as you have dried out the wall, it should improve.

live with it and make the best of it?

YOU can also paint over it every 3 months so you don’t see it.

Our completely renovated apartment always had problems with mold stains in the corners of the living room and bedroom toward autumn/winter (whether ETICS really plays a role or not, no idea?!). We never managed to get it under control in the corners. Which was really annoying. Since we had our own front door back then, we could also easily ventilate by shock airing. So it couldn’t be due to ventilation. We painted over it every 6 months because nothing else helped!