How to Eliminate Condensation on Windows

Do your interior windows sweat in winter?

I know, sweating in winter sounds odd but it actually makes perfect sense.

When there is an extreme difference in temperature and humidity between inside air (warm and moist) and outside air (cold and dry), condensation can form on the interior of your windows.

What happens is some of the water vapour that can no longer be held by the cooled air in a room is deposited on the glass. The resulting condensation can fog up your windows and blur out the view, drip on the floor, create mould problems and even freeze on the glass.

To prevent window condensation, you generally want a humidity level of 30% inside your home. If your home thermostat doesn’t have a humidity meter built-in then you should consider picking up a small, inexpensive hygrometer from your local home improvement or big-box store to track humidity levels.

Once you know how humid it is inside, you can take measures to bring the levels down. This includes opening window treatments. Window coverings can exacerbate the problem if they are tightly closed since this traps the humid air between the window and drapes and/or shades. Blinds should be raised three inches and California shutters left slightly open to allow for airflow.

Turning on a ceiling fan or pedestal floor fan is another measure that can be taken. This will circulate the air and take an edge off the humidity. Also, consider temporarily turning down or off your humidifier, whether stand-alone or part of your furnace, until the relative humidity decreases. And make sure you always use exhaust fans when cooking or showering.

While these methods will alleviate the problem room-side, you should expect some condensation along the bottom of your windows on extremely cold days.

The best way to remove condensation is to use absorbent paper towel or a microfibre cloth. If you can’t easily remove the condensation by wiping the glass, the moisture is between the panes. This is generally an indication of glass seal failure. Either the window pane will need to be replaced or a whole window replacement will be required.