Understanding Window Condensation in Ontario

Condensation is the light fog or coating of water droplets that appear on the glass of windows and doors in cold Canadian weather. If you own a home, you’re probably very familiar with it. We understand condensation can be annoying to deal with regularly.


It can obstruct your view, drip on the floor, and freeze on glass. It is common to blame the new windows, but you shouldn’t. It’s very rarely the fault of your new windows. We’ve created this article to help you understand condensation and why it occurs in your home. We’ll also review a few options for reducing condensation in your home.

What Causes Condensation?

Window condensation forms as a result of excess 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.


Condensation on New Windows

It is common for homeowners who replace windows to start having condensation on the inside suddenly. It’s usually because they now have airtight windows, making it difficult for excess humidity to escape. As mentioned above, condensation indicates that you have excess moisture in your home.

Old windows are often 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.

If condensation occurs between the panes of window glass, then you have a problem. This is uncommon but could be due to a faulty window seal that’s allowing moisture in. Contact us, and we will assess the situation for a solution.

Reducing Condensation

There are a few steps you can take to decrease humidity and reduce condensation on your home’s windows.

1) Improved Air Circulation Near Windows

Constant airflow across glass surfaces help 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.


2) 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.


3) Invest in 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.


4) Invest in a Heat Recovery Ventilator System (HRV)

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.



In summary, condensation with new windows is very common. In the majority of instances, it’s not a cause for panic. 

In most cases, adjusting your home’s humidity will be enough to prevent or significantly reduce your window condensation.

To be on the safe side, we recommend checking to ensure the condensation isn’t accumulating between the window panes. If that occurs, please contact us. 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 and other homeowners.


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