Guide
How to Fix a Foggy Double Pane Window
What causes fog between the panes and the right fix that actually lasts in coastal San Diego.
Why double-pane windows fog
Fog between the panes means the insulated glass seal has failed. Moisture enters the air gap and condenses on the inside surface. Cleaning the outside cannot fix it.
The real fix
The failed insulated glass unit must be replaced. A glass shop removes the old unit, measures precisely, and installs a new sealed unit. In San Diego this usually costs $150–$450 per pane.
When to act
Replace a failed IGU before winter to prevent condensation, mold risk, and rising energy bills from the lost insulating gas between the panes.