ᐅ Windows fogging up in the bedroom

Hello,

I have a major problem in my renovated farmhouse. Every morning, the bedroom windows are extremely wet on the inside of the glass, covering the entire surface.

Now, I need to find the cause.

The situation is as follows:
1. Windows are new, double-glazed
2. No compression tape on the outside and no silicone sealing (The window fitter did not do this?!)
3. Inside the house, everything was done: concrete, screed, walls, plaster—essentially a new build inside the old structure
4. There are pleated blinds on the windows for darkness, with a curtain in front of them (distance to the window about 35cm (14 inches), I have very deep window sills)
5. Exterior wall construction = facing brick / cavity / sand-lime brick / cavity / Ytong 17.5cm (7 inches)
6. Around the windows, the Ytong blocks were installed “around the corner” up to the window frame

I have had the underfloor heating running for two weeks now and air the rooms intensively in the morning and evening for about 30 minutes. Still, I cannot get rid of the moisture. I also noticed some minor mold in the corners of the skirting boards, which I managed to eliminate successfully.

Since I started the underfloor heating and intensive ventilation, no more mold has appeared, but the wet windows worry me...

The humidity level is between 50-65%... if I can trust the device.

I have been considering buying an electric dehumidifier... Maybe that would help.

Best regards,
Christian

Unusual masonry construction. However, it is better for moisture to condense on the glass than on the wall or any thermal bridges, such as your baseboard.

Without knowing the full details, I would recommend a decentralized ventilation system.

Since you basically have a new build within an old building, you need to ventilate regularly at first just like with a new build. There is still a lot of moisture inside the house, which will gradually disappear over time.

I agree with Koempy. Under these circumstances, ventilating twice a day by fully opening the windows is far too little.

I agree completely. If you are unable to ventilate frequently, I would recommend using an electric dehumidifier.