ᐅ Condensation on Roof Windows

Created on: 7 Feb 2012 16:17
J
JonnYWeeD
Hello everyone,

I’m having the usual problem this time of year with a lot of condensation forming on the lower and side edges of the roof window.
Outside temperature is about -15°C (5°F), inside about 22°C (72°F) with 43% humidity. The house was completed two years ago. The window reveal is designed to allow warm air to flow upward along the window. The heat comes from underfloor heating. We ventilate about 4 times a day for around 5 minutes each time, opening windows diagonally. Sometimes only 3 minutes during such cold weather. The humidity then drops to about 33%, almost too low. Still, condensation forms on the glass in the evening and then overnight.
Does anyone have any ideas on how to prevent this? Besides ventilating a lot—which we do and I believe do correctly.

Is there a foil or film that can raise the surface temperature of the glass?
Could the roof windows be defective? They have been installed for two years with insulation frames. But this problem occurs with all the windows, so it would be strange if they were all faulty. Roto sent me new seals which didn’t help either.

I would appreciate any responses.

Best regards,
JonnY
B
Bauexperte
14 Feb 2012 20:51
Hello,
JonnYWeeD schrieb:
Roof windows were not available; in fact, they didn’t exist at that time.

I don’t like to sound pedantic, but in my opinion this statement is incorrect. For example, Velux has offered these better-insulated windows for many years. There are also no issues with Velux products.

Addendum:
JonnYWeeD schrieb:
Because I didn’t want a dirt blower inside the house. I have maintained ventilation systems and know what lives in the ducts after 2 to 3 years.

If that is your job, then to be fair, I would have expected you to mention that unwanted inhabitants are only found where maintenance intervals or filter replacements are neglected!

Kind regards
S
Steffi33
19 Jan 2017 17:41
We also have a roof window that always fogs up when the outside temperature is freezing. I use a small, almost silent fan that runs continuously and blows air directly onto the glass. That works really well. Best regards, Steffi33.
S
Steffi33
19 Jan 2017 18:38
Here is a picture of the fan. It is sufficient.


Wood window frame inside with cables, bracket, and small blue component.