Understanding Window Condensation in London, Ontario

Condensation is the light fog or film of water droplets that appear on your window and door glass during the cold weather in London, Ontario. Windows that are more efficiently made will show condensation more readily simply because they are more airtight than your original windows.


What causes condensation?

Window condensation forms as a result of humidity in your home. The glass provides a cold surface on which humidity can visibly condense, similar to the condensation that forms on a cold drink glass.

Condensation usually occurs on windows first because glass surfaces have the lowest temperature of any interior surfaces in the house. 

When condensation occurs on your windows and doors, it is a sign that you should reduce the indoor humidity level. Along with the minor annoyances we listed above, it can cause severe problems in extreme cases. Mildew, mould, damaged paint surfaces, rotting wood, and moisture spots can occur if your home’s humidity levels are excessive for too long.


Why is there condensation on new windows?

It is common for homeowners who replace windows to start having condensation on the inside suddenly. It’s usually because you now have airtight windows, making it difficult for excess humidity to escape.

In most cases, adjusting your home’s humidity will be enough to prevent or significantly reduce your window condensation, a common occurrence that you should not be concerned about.

Older windows are usually draughty, allowing excess humidity to escape through the cracks. Moreover, the previous windows may not have been made with energy-efficient materials. Natural Resources Canada offers more details on the causes of condensation.

Condensation should not occur between the panes of window glass and could be due to a faulty window seal that’s allowing moisture in. Please contact us at Forest City Window & Door Ltd. and we will assess the situation for a solution.



It is crucial that you open your windows even in the winter to prevent Carbon Monoxide (CO) buildup in your home.

Opening your windows is the best way to refresh the air quality of your home and push out some of its humidity. The Canadian government website describes a de-pressurized home (one that does not have natural airflow) as pulling required air, often down through chimneys or appliances that may be storing a buildup of pressurized gasses.


Other ways to reduce condensation on your windows.

There are a few steps you can take to reduce condensation on your home’s windows like opening windows to maintain healthy air, circulating the indoor air with fans, adjusting your humidifier, installing a Heat Recovery Ventilator (HRV) system, or in extreme cases, using a dehumidifier.

Improve air circulation near your windows

Constant airflow across glass surfaces helps keep them warmer. That’s why vents and electric baseboards are typically located beneath windows.

Furniture, drapes and blinds can block airflow and allow cool air to collect near windows. Keeping these further away can help reduce condensation. Another option is adding a rotating fan in the room to help circulate air thoroughly.


Adjust your humidifier

If your furnace has a humidifier, adjust it to be lower. Doing this will reduce humidity levels throughout your home. You may need to make more than one readjustment to reach your desired level.


Use a dehumidifier

Another great option is purchasing a dehumidifier. It could be ideal if you only have excess humidity in one area of your home, like the basement. They remove moisture from the air but must remain away from walls and objects for proper airflow.


Invest in a Heat Recovery Ventilator (HRV) system

These are ideal for homes in colder climates, like London, Ontario. An HRV system continuously removes indoor air and supplies fresh air from the outside. The air brought into your home is warmed to make your home more comfortable.




Check to ensure the condensation isn’t accumulating between the window panes. If that occurs, please contact Forest City Window & Door Ltd at the number below. We will assess the situation and guide you through a solution.

For more information about windows and doors, check out our website’s blog page. We have a wide variety of articles about windows and doors to help you.