Windows fog up, high humidity with mold on the windowsills

We have a problem with the windows in our single-family house. Since the cold season began, every morning our windows are completely fogged up. These are quite "normal" double-glazed plastic windows. We ventilate and heat regularly, a measurement of the humidity yielded values between 45 and 55%. The room temperatures fluctuate between 19 and 22 degrees. In my assessment, these are quite normal values. What can I do to prevent the fogging of the panes? It is sometimes so severe that water drips from the panes and mold forms in the corners of the windowsills.

Hello Konstantin, there might be an error in the construction of the windows, the heat conduction seems too high. However, warmer air condenses on cooler surfaces; at very low outside temperatures this can also happen on the inside of ISO windows – but not at normal winter temperatures. Please get the window installer and show him the fogged windows, ask him what he thinks about it.

I had similar problems in my old house. Maybe you had your walls re-insulated but left the "old" windows in place? Humidity always condenses at the coldest spot in the room. You might have to replace your windows and choose triple-glazed models. How often have you measured the humidity? 45% to 55% is really not much, but perhaps your humidity rises sharply overnight. You should check that. I know it's annoying to hear this over and over, but if the building fabric is dry and in good condition, the only help is more ventilation and heating.

Hello, I am a window builder. The topic was window replacement. There is a solution also without it. In double glazing, aluminum spacers were certainly used. You can change the panes, stay with double glazing but use a TGI spacer. It is made of plastic with a noble metal insert. Usually, a switch to triple glazing is difficult because the shallow installation depth of the old windows does not allow the glazing bead to accommodate the triple glazing. There are also soundproof ventilators. Information about them:::: Moisture-controlled supply air Fully automatic without electrical wiring Option to set off, on, or automatic mode. In automatic mode, the air volume flow is regulated according to the room humidity with a moisture sensor (polyamide fiber tape). 30 years guarantee on hygrostatic regulation. Supply air element with 41 dB Application for all types of windows + on window frame extensions and roller shutter boxes

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The solution my predecessor writes is exactly the right one, because with it you can achieve very good results, even without replacing the windows. But one should still consider whether other damages can occur, because somehow the dew point has been displaced here.