Window thermal panes are essential components for energy efficiency. They are made up of two or three panes of glass separated by a layer of insulating air or gas and sealed airtight. Their role is to limit heat loss, reduce condensation, and improve thermal comfort. However, over time, their performance can decline. Stay with us as we look with Charles-Vincent Trépanier, General Manager of Basco Portes & Fenêtres, at three signs that it’s time to replace your window thermal panes.

Did you know that in 2024 alone, the professionals at Basco Portes & Fenêtres saved more than 22,500 windows from ending up in the landfill? How? Thanks to their many clients who chose to replace the thermal panes instead of the entire window. And considering that the average PVC weight per window is around 7 kilograms, these clients helped divert nearly 157,000 kilograms of PVC frames from the trash! To put that into perspective, that’s roughly the equivalent of 39 million small plastic forks…

Fog or condensation between panes
The most obvious sign of a defective thermal pane is the presence of fog or condensation between the panes. This means that the seal has failed, allowing moisture to penetrate the cavity. Not only does this condensation reduce visibility, but it also indicates that the insulating gas has escaped, greatly reducing the window’s insulating capacity. In this case, replacing the thermal pane is highly recommended.

The age of your windows
The age of the window is another factor to consider. Sealed units generally have a lifespan of 15 to 25 years. So, if your windows are more than 20 years old, chances are they don’t feature the latest technologies, such as Low-E coatings, which reflect part of the sun’s infrared rays outward, helping keep interiors cooler in summer and warmer in winter.

The “E” in Low-E refers to emissivity, meaning the ability of a surface to absorb and emit radiant energy. In short, a window equipped with Low-E film significantly improves energy efficiency.

So, even if the thermal pane doesn’t seem damaged, replacing it could greatly enhance your home’s energy performance.

Drafts and air leaks
More subtle signs, such as feeling drafts, hearing increased outdoor noise, or noticing higher heating bills, may also indicate reduced glazing performance. Of course, before acting, it’s important to rule out other possible causes, such as insulation or sealing problems in the walls or attic.

A simple test is to hold a flame or just the back of your hand near the glass on a windy day. If the flame flickers or goes out, or if you feel air movement on your skin, it may be a sign that air is seeping through your windows…

In summary, if your glazing shows internal condensation, feels very cold to the touch, is several decades old, or affects your indoor comfort, replacing the thermal pane could be a cost-effective solution. Even better, replacing thermal panes and restoring windows also helps reduce your environmental footprint!

If you have questions about your windows or your home’s overall energy efficiency, contact us. Our evaluators and partners are here to help you make the best decisions for your needs.