Double-pane windows: the basics

Unlike traditional windows, which are made of one pane of window glass, double-pane windows (or insulated windows) boast two panes, though it’s actually the space between them that does the work of keeping your home warm in the winter and cool in the summer.

The space between the panes is filled with air or dense gas (usually argon and krypton gases), whose molecules move slowly, keeping the air space at a consistent temperature. Consequently, the cold from outside moves more slowly through the window and into your home. Sometimes a desiccant material is added in the sealed space as well, as it can aid in moisture absorption, which prevents buildup of mold and mildew in the home.

Modern double-pane windows have two seals: the inner seal protects against moisture and corrosion while the outer seal holds the structure in place.

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What causes condensation on windows?

While insulated glass windows are known for working extremely well under a lot of strain (changes in temperature, inclement weather, etc.), age will eventually corrode the seals.

The heat from prolonged direct sun exposure can cause the panes to expand and contract, which eventually weakens the contact between the window glass and seal. Water retention in the frame, improper drainage, and saturation of the desiccant can also compromise the seal.

When window seals have been compromised, moisture sneaks into the airspace between the panes and condensation forms on the glass. You’ll notice a milky or foggy look.

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How to prevent condensation in double-pane windows

One way to prevent condensation is to increase indoor air circulation. Every time you cook or shower, remember to turn on the kitchen or bathroom fan for at least 15–20 minutes. Use ceiling fans as well, even in winter. Set them to rotate in a clockwise direction, which will push warm air downward.

It’s also important to keep humidity inside your home in check. If you notice a humidity problem in your home, try a dehumidifier, which takes in air, sucks out the moisture, and releases it back into your home.

You can prevent condensation by simply keeping the windows open when the weather allows, which will release the warm, moist air trapped in the house.

How to get rid of condensation in double-pane windows

Unfortunately there’s no easy DIY fix for condensation in your windows. Essentially, the moist air will need to be replaced with dry air, and for that you’re going to need to bring in the big guns— hire a professional.

That said, you do have two options. A professional can evaluate the right solution.

1. Replace the window (or pane)

Because the dry air between the panes has been compromised, replacement of the window may be necessary.

You can save a considerable amount of money by replacing a single window pane instead of the whole window, though in cases of rotting, it may be best to replace the whole thing. A professional can evaluate whether a single pane replacement will do the trick.

2. Professional cleaning

As a less-invasive alternative, a glass professional can clean the window. The process entails drilling small holes at the top and bottom corners, spraying a cleaning solution through the top hole, and sucking it out through the bottom. An expert will then seal the holes with vent plugs, allowing air, water, and vapor to escape the window cavity freely.

DIY or Hire?


  • Though you can save money by installing a new window yourself, those savings could be forfeited unless the window unit is properly installed to sit flush with the wall.


  • Because compromised air between panes will need to be replaced with dry gas, a professional is needed to perform the process with specialized equipment.
  • If the window needs to be replaced, House Method recommends hiring a professional for this home improvement task to ensure the window is installed correctly.

Our Recommendation – HIRE: If a seal has broken or been compromised, House Method recommends contacting a professional to repair or replace your double-pane windows.

Editorial Contributors

Thomas Boni

Thomas Boni is Today’s Homeowner Media's Digital Content Director. He is an award-winning multimedia journalist, having served as editor-in-chief of various Alabama and Florida newspapers from 2006-2018. Thomas earned more than 30 regional, state and national journalism awards and accolades during his news career. He has a passion for engaging, fact-based content and a keen eye for detail. He joined Today's Homeowner Media in 2018 and received recognition on the Marquis Who's Who list in 2023. He earned his Bachelor of Arts at Spring Hill College in 2005.

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Lora Novak

Senior Editor

Lora Novak meticulously proofreads and edits all commercial content for Today’s Homeowner to guarantee that it contains the most up-to-date information. Lora brings over 12 years of writing, editing, and digital marketing expertise. She’s worked on thousands of articles related to heating, air conditioning, ventilation, roofing, plumbing, lawn/garden, pest control, insurance, and other general homeownership topics.

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