Do you wake up to water beading on your windows? Maybe it drips onto the sill, or you see fog on the glass every winter morning.
In Raleigh, condensation is common, and it is not always a window problem. But where it shows up tells you a lot. Is it on the inside, the outside, or trapped between the panes?
Why Condensation Forms
Warm air holds more moisture than cold air. When warm, damp air touches a cold surface, it cools down and drops that moisture as water.
You see the same thing on a glass of iced tea on the porch in July. On a window, the cold surface is the glass.
Where Is the Water? That Is the Big Clue
| Where You See It | What It Usually Means | Should You Worry? |
|---|---|---|
| Inside the room, on the glass | Indoor humidity is high, the glass is cold, or both | Sometimes. Fix humidity first. |
| Outside the house, on the glass | Humid outdoor air is hitting cool glass. Common on summer mornings in NC. | No. It often means your glass insulates well. |
| Between the panes | The seal has failed and moist air got inside the glass unit | Yes. The glass or window needs to be replaced. |
Common Causes of Inside Condensation
- Cooking and showers without a vent fan running
- Lots of houseplants or an aquarium
- Drying clothes indoors
- A damp crawl space. Many Triangle homes sit over crawl spaces. Moisture there can rise into the house.
- A humidifier set too high in winter
- Old, cold windows. Single-pane glass and aluminum frames get much colder than modern windows, so water forms on them first.
How to Reduce Condensation
Start with the cheapest fixes first.
- Check your humidity. A simple hygrometer costs a few dollars. Many experts, including the EPA, suggest keeping indoor humidity between 30 and 50 percent.
- Run your fans. Use the bathroom fan during and after showers. Use the range hood when you cook.
- Move the air. Open blinds and curtains so warm room air can reach the glass. Ceiling fans help too.
- Check the crawl space. A vapor barrier on the ground and good drainage can cut moisture a lot.
- Use a dehumidifier in damp rooms or basements.
- Turn down the humidifier on cold nights.
When the Windows Are the Problem
If your humidity is under control and you still get heavy condensation, your windows may be too cold on the inside.
Better windows keep the inside glass warmer. That means less water. Look for:
- Insulated frames. Our Ascent windows have foam-filled frames and sashes, which the maker says greatly reduces condensation.
- Warm-edge spacers between the panes instead of cold metal ones
- Triple-pane or Heat Mirror glass, which keep the inner pane closer to room temperature
- A good condensation resistance rating on the window’s NFRC label. Higher is better.
Learn more about our energy-efficient window options.
Fog Between the Panes? That Is a Failed Seal
If you cannot wipe the fog away from either side, it is inside the glass. The seal around the glass unit has failed. The insulating gas has leaked out and damp air has leaked in.
Cleaning will not fix it. The glass unit or the whole window needs to be replaced. Not sure if it is time? Read how long windows last and when to replace them.
Why Raleigh Homes Get Condensation
Raleigh has a humid climate most of the year. On a cold January morning, all that moisture inside your home looks for the coldest surface it can find. Usually, that is the window glass.
Crawl spaces are a common cause around here. Many homes in older areas like Five Points, Mordecai, and downtown Garner sit over crawl spaces. Without a good vapor barrier, damp air from below can work its way up into the house.
Original windows add to the problem. Homes built from the 1950s through the 1980s often still have single-pane or aluminum windows. Those get much colder than modern windows, so they sweat first.
Frequently Asked Questions
Is condensation on the inside of windows bad?
A little on a cold morning is normal. Heavy condensation that runs down the glass every day can damage sills and trim and lead to mold. Lower your indoor humidity and check your windows.
Why do my windows sweat on the outside in summer?
In North Carolina, humid morning air hits glass that has been cooled by your AC. It is normal and usually a sign your windows insulate well. It burns off as the sun warms the glass.
Can you fix fog between window panes?
Not by cleaning. The seal has failed, so the glass unit or the window needs to be replaced.
What humidity should my house be?
Between 30 and 50 percent is a good target for most homes.
Still fighting wet windows? Call (919) 851-0060 or request a free estimate. We will help you figure out if it is the house or the windows.
About the Author
Harland Johnson is the owner of Harland Windows & Siding. He has run the company for over 40 years and has personally overseen window, siding, and sunroom projects throughout Wake County and the Triangle. Harland Windows & Siding is an A+ rated, BBB accredited business.