How to Fix a Window That Has Condensation Between Panes

Condensation between window panes — water droplets or streaks trapped inside the sealed glass unit — is a clear sign of a failed window seal. Here's what it means, what you can do, and how to prevent it on your other windows.

Condensation Between Panes vs. On the Glass Surface

It's important to distinguish between two different problems:

• Condensation between the panes: Moisture is trapped inside the sealed glass unit — this means the IGU seal has failed and the glass unit needs replacement
• Condensation on the interior glass surface: Normal in cold weather when indoor humidity is high — this is not a window failure, just physics
• Condensation on the exterior glass surface: Also normal on cool mornings — not a problem

If you can't wipe the condensation off with a cloth, it's between the panes and the seal has failed.

Why Does the Seal Fail?

• Age — most IGU seals last 10–20 years
• Thermal stress from repeated heating and cooling cycles
• UV degradation of the sealant material
• Physical damage to the frame allowing water to reach the seal
• Improper installation with inadequate drainage

Fix Option 1: Replace the Insulated Glass Unit (IGU)

The only permanent fix. A glazier removes the failed glass unit from the existing frame and installs a new sealed unit. This is much cheaper than replacing the entire window and restores full performance.

Fix Option 2: Defogging Service (Temporary)

A defogging service drills small holes, cleans the interior surfaces, and installs one-way vents. This can clear the condensation temporarily but doesn't restore the seal or the insulating gas. Expect the problem to return within 1–3 years.

Fix Option 3: Replace the Entire Window

If the frame is also damaged or the window is very old, full replacement makes more sense economically.

Reducing Interior Condensation (On the Glass Surface)

If your condensation is on the interior surface (not between panes), reduce indoor humidity:

• Use exhaust fans in bathrooms and kitchens
• Run a dehumidifier in winter
• Ensure adequate ventilation throughout the home
• Keep indoor humidity between 30–50% in winter

Protect Other Windows While You Wait

Seal the exterior frame joints on all windows to slow future seal failure.

• GE Advanced Silicone Caulk Window & Door Clear — seal exterior frame joints to protect IGU seals from moisture infiltration

How to Check All Your Windows

On a cold morning, check each window. Interior surface condensation that wipes off is normal. Condensation that doesn't wipe off, or that appears between the panes, indicates seal failure. Make a list of affected windows and prioritize replacement by severity.