Fog between window panes: what it means
A haze inside the glass is a common problem with insulated windows. It looks unpleasant, but it is rarely an emergency.
The short answer
- Fog between the panes means the seal around the insulated glass has failed.
- Cleaning cannot remove it, because the moisture is trapped inside the sealed glass unit.
- A professional can often replace the glass unit and keep the existing frame.
Before
AfterThe problem
Fog that never wipes away
Homeowners notice a milky haze or tiny water droplets between the two panes. The fog usually looks worse on cold mornings.
The cause
A failed seal lets moisture inside
Insulated glass is two panes with a sealed space between them. Over many years, sunlight and temperature changes weaken the seal, and moist air leaks inside.
The fix
New glass, often in the original frame
When the frame is solid, a professional orders a new sealed glass unit in the exact size. When the frame is rotted, the entire window needs replacement.
What should you do first?
Fog in a window? Start here
Check both surfaces of the glass.
If the fog wipes away from either surface, it is ordinary condensation instead of a failed seal.
Write down which windows have fog.
A simple list helps a professional estimate the job and order the correct glass sizes.
Inspect the frame and the window sill.
Soft or discolored wood means the frame may need repair, in addition to the glass.
Request estimates for the glass alone and for a complete window.
Fog alone does not usually let in rain or cold air. Homeowners can schedule the repair for a convenient season.
Can you fix fog yourself?
A sealed glass unit must be manufactured to size in a workshop, so this repair belongs to a professional. Some kits promise to remove fog, but the broken seal remains.
Video coming soon
Read the transcript
A double-pane window has two sheets of glass with a sealed gap between them.
When the seal fails, damp air gets into the gap and fogs the glass from the inside.
Sources
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