Window Condensation: Causes, Fixes, and Long-Term Solutions
Understanding Moisture and Window Performance
Why Do Windows Get Condensation in the Winter in Minnesota?
“I need new windows because mine are frosty!” or “There’s condensation on my windows!”—we hear it all the time from friends and family. And before you start thinking about spending thousands of dollars on replacements, let’s explore why condensation and frost appear, even on the most energy-efficient windows, and what you can do about it.
Think of your windows like a cold glass of water on a hot day. The cold glass attracts the warm, humid air, causing condensation. And basically, the same thing happens with your windows in the winter. The inside of your home is filled with warm, humid air, which interacts with your cold windows just like it will with a cold drink. The colder it gets outside, the more likely condensation and frost will form on your windows.
Condensation is an indication of excess humidity. Ask yourself these questions:
Have I checked the humidity in my home?
Common sources of indoor humidity are things like cooking, your furnace, drying clothes inside, or a damp basement. For example, boiling water for soups, pasta, etc., can add significant moisture to the air. If you have a vent above your stove, make sure to turn it on to help reduce moisture. If your basement tends to stay damp, consider investing in a dehumidifier that can run a hose to a floor drain.
Do I have a humidifier on my furnace?
- Many furnaces come with a built-in humidifier, and while it can help maintain comfortable indoor air during the dry winter months, it’s important to balance this with the outside temperature and the natural humidity levels in your home. Too much humidity can lead to condensation and frost, even on insulated windows.
- Are my blinds and drapes closed?
- Blinds and drapes can block airflow over window surfaces, which may encourage condensation and frost buildup. We learned this the hard way when we first moved into our home. We kept the blinds closed in the bedrooms, and soon enough, ice built up on the windows and damaged the paint on the sills. After adjusting our humidity and leaving the blinds open, we rarely see frost now.
Options for Older Homes:
If you live in an older home with single-pane windows but you do not want to sacrifice their charm, you have a few options:
- Install storm windows on the outside of your home.
- Put plastic over your windows to create an extra barrier.
- Replace the windows with more energy-efficient, insulated ones that are designed to be installed in listed or historic buildings.
Maintaining the Right Humidity Levels:
To help you manage indoor humidity and prevent condensation, here’s a handy table that shows the recommended relative humidity levels based on the outdoor temperature:
When the Outdoor Temperature Is: | This Relative Humidity Should Be Maintained: |
+40°F | 45% |
+30°F | 40% |
+20°F | 35% |
+10°F | 30% |
0°F | 25% |
-10°F | 20% |
-20°F | 15% |
The table provides a clear guideline for maintaining optimal indoor humidity levels based on the outdoor temperature. By adjusting your home’s humidity to match these recommendations, you can prevent condensation and frost from forming on your windows. For example, if the outdoor temperature is +20°F, you should aim to keep your indoor humidity at 35%. This balance helps ensure comfort while protecting your windows and home from moisture-related issues.
Ready to explore your options?
If you live in the southern part of Minnesota and are considering new windows, feel free to contact us for an in-home consultation. Windows are one of the most significant sources of heat loss in a home, so upgrading them can not only reduce condensation and frost but also save you money on your heating bills.
