Condensation on our Windows

November 5th 2002

Question from Jeff in Winnipeg, Manitoba -----

Hi Shell,

Sorry if I am repeating myself. We are in a 40-year-old house. Our bedroom window faces south with a heat vent underneath the window. We have a cold air duct behind our dresser which is moved about 12" inches from the wall to let air flow. As the temperature is getting colder we find a little condensation on the window. The window is aluminum sliders and it is double pane. We leave the blinds up a little so that air can flow during the night. When we wake up in the morning a little condensation is dripping. At this point it does not appear to be that much but as the temperature drops we are afraid that more condensation will appear. What is your suggestion to help solve this dripping problem because the condensation is dripping onto the wood frame? Hoping to hear from you.

Thank you,



Hi Jeff,

It sounds like you might not be controlling the moisture levels in your home by using your bathroom exhaust fan.

Consider installing a dehumidistat to control the on/off feature of your bathroom fan. Set your dehumidistat as follows:

50 - 55% Relative Humidity when outside temperature is +0 to +10C

40 - 45% Relative Humidity when outside temperature is -0 to -12C

35 40% Relative Humidity when outside temperature is -13 to -25C

It's Just That Easy!