Why is there water and ice on my windows?

I am getting a lot of questions about the amount of water, and sometimes ice, forming on the inside of windows. With the winter temperatures plummeting to the lowest of the season, this is going to happen and there is something you can do to help.

Normally, I am telling you to increase the humidity levels in your home, which have become low because of your winter heating. Well, at this time, it is important to reduce your humidity level in order to reduce the amount of condensation on your windows. This humidity level chart will help you to determine the best home humidity level.

Home Humidity Level Chart

Outdoor TemperatureIndoor Humidity Levels
over 50˚Fshouldn’t exceed 50%
over 20˚Fshouldn’t exceed 40%
between 10˚F and 20˚Fshouldn’t exceed 35%
between 0˚F and 10˚Fshouldn’t exceed 30%
between -10˚F and 0˚Fshouldn’t exceed 25%
between -20˚F and -10˚Fshouldn’t exceed 20%
at -20˚F or lowershouldn’t exceed 15%
Water on windows
Ice on window

What happens is the cold outside air is trying to freeze your house from Ice on windows the outside in. The colder the air is outside the further the cold makes it into your home. This makes the dew point, the place where water wants to condensate, close to the inside of your home. This causes an excess of condensation, and maybe a little ice on that single-pane window. So, during these cold times, you may have to turn the humidity down to reduce the window condensation.