How To Eliminate Winter Window Condensation

Does condensation build up on the inside of your home’s windows during the heating season? If it does, you’re not alone. Winter window condensation can be a problem and there are ways you can deal with it.

As homes are sealed better against air leakage, natural ventilation to the outdoors is reduced. As a result, indoor air becomes much more likely to contain damaging levels of moisture during winter.

If your windows sweat enough during the heating season to require periodic wiping with a towel, then you have a problem. And this problem goes beyond ruined window-frame finishes and mould growth on windowsills. It includes the very real potential for decay within wall cavities and attics, too. Window condensation can also be a sign of low indoor-air quality which affects your health.

Where the water comes from

When warm, moist indoor air meets the cooler surfaces of windows during winter, condensation develops on the glass. It’s the same thing that happens on the outside of a drinking glass filled with a cold beverage on a hot summer day.

Breathing, cooking, showering and drying clothes all release huge amounts of moisture into the air. In the good old days, this moisture would make its way outside through all the cracks that were once common around windows and doors. That’s why old, leaky houses are often so dry during winter with no window condensation at all.

While today’s homes mean lower energy bills, they also demand that we consciously provide some sort of fresh air to vent off all that water vapour. Boosting home ventilation is the key to solving the window condensation problem.

Open windows a little

This approach is about as easy as they come. Yes, opening windows will cost you a bit more in heating, but it still may be the cheapest way to solve your moisture problem.

Use exhaust fans and proper venting

Installing a bathroom exhaust fan is important to remove moist air. Bathroom exhaust fans should be used during every shower or bath and for at least 15 minutes afterwards.

Installing an exhaust fan in high-moisture areas of your home can help if you continue having minor condensation problems even with your windows opened.

Dryers that vent indoors spew massive amounts of moisture into your home. Proper outdoor venting of your dryer could solve the whole problem.

Install a heat recovery ventilator (HRV)

Although this option will cost $2,000 to $2,500 installed, it will fix the problem once and for all. It will also retain most of the heat that you’d normally lose through open windows and out of exhaust fans. In fact, HRVs are so effective and energy efficient that they’re now required by code for new houses in some jurisdictions.

All HRVs direct a supply of fresh, outdoor air into your house while exhausting stale indoor air outside. This dual-flow system is the ventilation part of the equation. An HRV also reclaims most of the heat from stale air before shooting it outside.

If a home owner doesn’t want to purchase an HRV... Just open a window slightly and leave a bathroom fan running till the humidity is low enough for your windows to handle it. Might take a few hrs. Repeat as needed all winter.

Opt for better-insulated windows

The higher the R-value of a window, the better it can handle humidity and keep condensation from forming. Triple pane windows, for instance, are much less likely to form condensation than double-pane. In colder climates, triple pane windows will help your home be more energy efficient as well.

Replacing your windows with ones that have better sealing, but the same insulation value as the original ones, can actually increase window condensation because the new windows reduce air leakage and natural ventilation.

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