Wet glass, foggy corners and a sill that’s always damp are part of winter for a lot of homes in Milwaukee and Waukesha. Condensation on your windows usually isn’t an emergency, but it is a clue. Work through the four steps below, and you’ll know whether you’re dealing with a humidity problem, a window problem or a little of both.
What’s Happening on Your Glass
Indoor air always carries some moisture. When that air hits a surface colder than its dew point, the moisture turns into water droplets. Window glass is usually the coldest surface in a room during winter, so that’s where condensation shows up first. The colder the glass and the more humid the air, the more water you’ll see.
Step 1: Find Where the Moisture Is
- Room side of the glass: The most common winter scenario. Humidity is high for the temperature, the glass is cold, or both.
- Outside of the glass: Usually nothing to worry about. Exterior condensation on cool mornings often means your windows are holding heat in.
- Between the panes: The seal on the insulated glass has failed. No amount of wiping or dehumidifying will fix this one, and the window has lost much of its insulating value.
Step 2: Check Your Indoor Humidity
Pick up a hygrometer and take a reading in a few rooms. The EPA suggests keeping indoor relative humidity below 60 percent and ideally between 30 and 50 percent. In a Southeast Wisconsin cold snap, you’ll want to sit toward the low end. Common moisture sources include:
- Long, hot showers without the exhaust fan on
- Boiling pots and the dishwasher
- Whole-house or room humidifiers are set too high
- Drying laundry indoors or a dryer that isn’t vented outside
- A damp basement or crawl space
Step 3: Try These Quick Fixes
- Run exhaust fans for 15 to 20 minutes after showering or cooking.
- Lower your humidifier setting when outdoor temperatures drop.
- Move furniture and rugs off heat registers so warm air can flow along exterior walls.
- Use a ceiling fan on low to keep air moving.
- Open blinds and shades during the day.
That last one surprises people. Research from Pacific Northwest National Laboratory for the U.S. Department of Energy found that window coverings can limit how much warm room air reaches the glass, which lowers the glass temperature and can increase condensation. Closed shades help with heat loss at night, so open them up in the morning and let the glass warm and dry.
Step 4: Look Closely at the Windows Themselves
If humidity is in a healthy range and you still find water or ice on the same windows every morning, the windows are likely running too cold. That’s common in older homes around Milwaukee and Wauwatosa that still have original single-pane sashes, aluminum frames or tired weatherstripping. Watch for:
- Frost or ice is building up on the frame and sash, not just the glass
- Peeling paint, dark spots or soft wood on sills and trim
- Drafts or whistling on windy days
- Fogging between panes that never clears
Moisture that sits on wood trim week after week can lead to rot and mold, so it’s worth acting on before spring.
How Replacement Windows Help
Better insulating windows keep the inside surface of the glass warmer, which raises the bar for condensation to form. Renewal by Andersen windows pair insulating glass with Fibrex® composite frames built to resist heat transfer and hold up to Wisconsin’s swings in temperature. Read more about energy efficiency or browse our window FAQs.
FAQ
Why do I have condensation on new windows?
New windows seal out drafts, which also means moisture that used to leak out with warm air now stays inside. A little condensation in a tighter home is often a humidity signal, not a window defect. Lower your indoor humidity first and see if it clears.
Can condensation on windows cause mold?
It can. Water that collects on sills and trim gives mold the moisture it needs. Wipe it up, keep humidity in check and look into windows that stay wet.
Should I be worried about ice on the inside of my windows?
Occasional frost on a subzero morning is common. Thick ice that builds up daily usually means high humidity, a cold window or air leaks around the frame.
Does a dehumidifier help?
It can in damp basements or during humid months. In winter, ventilation and lowering humidifier settings usually make a bigger difference upstairs.
Talk to a Local Window Expert
From Mequon and Menomonee Falls to Racine, Kenosha and West Bend, Renewal by Andersen of Milwaukee helps homeowners figure out what’s behind wet, icy windows and what it takes to fix it. Schedule your in-home consultation today.
