ᐅ Condensation on windows, mold, thermal bridging. Are the windows poorly insulated?

Hello everyone,

There are periods, especially in winter when it’s really cold, when our windows sweat heavily from the inside. Additionally, despite airing out and sufficient heating, mold develops on the exterior wall where there is a thermal bridge.

On one hand, this obviously happens because the radiators are located far from the exterior wall. On the other hand, I would like to know how well—or of course how poorly—the wall is insulated, or if it is unacceptably poorly insulated. The only thing I was able to do is the lighter test. Please have a look at the linked video.

Thank you!

You have already received quite a bit of feedback in your other thread, haven't you?
https://www.hausbau-forum.de/threads/suche-nach-der-ursache-des-schimmels.42395/

The problem in your case is surely the dew point. Heat more, ventilate more. Possibly use a dehumidifier.

Well, how much more heating and how much more ventilation... The room temperature fluctuations are already within the healthy range (18-21°C (64-70°F)) and the indoor humidity levels as well (40-57%).

As long as the windows are sweating or the walls are damp, both the room temperature and the absolute humidity are outside the healthy range.

This is simply due to the fact that the room temperature drops below the dew point -> moisture condenses on the coldest surfaces. This is a relatively straightforward principle. If you keep the room temperature above certain values (which always vary depending on the room conditions) and ventilate to remove excess moisture, condensation will no longer occur.

karambol schrieb:

Well, how much more heating and how much more ventilation…
The room temperature already stays within the healthy range (18–21°C (64–70°F)) and the indoor humidity is also within a good range (40–57%).

You can easily calculate that yourself.

Just search online for "dew point calculator" and use the first result.

Benutzer200 schrieb:

You can simply calculate that yourself.

Google "dew point online calculator" and use the first result.

When I took the measurement, the room temperature was 20°C (68°F) and the indoor humidity was 49%. This is approximately the average for us. According to the online calculator, the dew point is around 9°C (48°F). So what am I doing wrong?