Tips
Condensation on windows: What causes it and how to manage it
If you’re noticing condensation on your windows, you might be wondering whether or not you should be concerned. The short answer is: It depends. It depends on where the condensation is forming, i.e., inside, outside, or in between the glass. It also depends on the time of year and even the age of your home — condensation on windows in a newly built home is a common temporary occurrence.
Let’s explore what you need to know about condensation on your windows.
What is condensation? Why does it form on windows?
When warm air comes in contact with a cooler surface, condensation forms. The same way your glass of ice water “sweats” on a hot summer’s day, your window might fog up on a cold winter’s day.
Condensation happens because the air can only hold so much water vapor (moisture) before it changes into liquid water droplets. The amount of moisture the air can hold varies by temperature. Because cold air can hold less moisture than warm air, window condensation happens most often in the wintertime when your windows, warmed from the heat inside your house, meet the cold air outside.
Where the condensation forms is the key to understanding if it is a problem.
Condensation on the inside of your windows
When condensation forms on the inside of your windows, it can block your view, drip on the floor, or freeze on the glass. It can be annoying, and it can cause problems if left unchecked. The reason condensation forms inside the window is because the humidity level is too high indoors, not because there is something wrong with the window.
Humidity is the moisture in the air. It forms when we breathe, when we cook, when we shower, when we do laundry, and other everyday activities. It’s always present in air, and it’s not an inherently bad thing — as you’re probably aware if you’ve ever bought a humidifier. However, humidity can cause damage to your home if it’s too high for too long — for example: cracking, peeling or blistering paint; mildew and mold; and more.
If you’re noticing condensation on the inside of your windows in the winter, it’s a warning sign and you should take action.
How to prevent condensation on the inside of your windows
To help prevent condensation inside your windows, reduce indoor humidity. Here are a few ways to do that:
- Vent all gas appliances, clothes dryers, and exhaust fans to the outside. Your attic and crawl space should also be ventilated. Cover the earth in the crawl space with a good vapor barrier.
- When you cook, make sure to run the exhaust fans in the kitchen. When you bathe or shower, run the fans in the bathroom until your mirror is clear. Be careful not to overheat exhaust fans by running them too long.
- Open your drapes or shades during the day so warm air can reach your windows.
- Use ceiling fans to promote air movement.
- Avoid storing firewood in your house or basement.
- If you have a forced air furnace, make sure your home is properly ventilated by installing a fresh air intake. If your home is extremely “tight,” it may be helpful to install an air-to-air heat exchanger.
Tip: In the winter months, you should aim for 30 to 35 percent humidity in your home. Some thermostats measure humidity. If yours doesn’t, you can buy an inexpensive tool called a hygrometer to measure humidity.
