Why it’s there and what you can do to minimize it
If you’ve just replaced old, leaky windows with new, more energy-efficient windows, you may notice something new when cold weather hits; condensation. Rather than being a defect, condensation actually means that your new windows are protecting your home more than your old ones were. But there are ways to minimize it if it is a concern.
If condensation continues after taking these smaller steps, consider purchasing a dehumidifier and using it either as part of your central heating system or in the areas affected most by condensation. Excess humidity in the home doesn’t just take a toll on your windows - it can encourage mold and other indoor air pollutants, so you should fix it if you notice it. Both Health Canada and the Canadian Mortgage and Housing Corporation recommend a 30% relative humidity level inside during the winter, and 50% during the summer. If you find 30% too dry, you can go up to 50%, but monitor the amount of condensation on your windows and be prepared to wipe it up if you get more. You should also check that ventilation fans in your bathroom and kitchen are being ventilated to the outside, and not to an attic space where mold can become a problem.
Extremely cold weather will bring on condensation even if your home has perfect humidity. If you just notice condensation on extremely cold days, don’t worry about it as it is a short-term problem that will only occur when it is way past the point where you want to go outside. If you want to reduce the risk of condensation when the exterior temperature dips below -25 Celsius, reduce the humidity in your home to between 20-25%. Give the bottom of your windows a quick wipe on extremely cold days to prevent mold from forming.