Why Are My Windows Foggy Between the Panes?
The physical reason behind foggy double-pane glass, and why it can't be cleaned or repaired.
Foggy or hazy glass between the panes means the seal on your insulated glass unit has failed. Modern double- and triple-pane windows are built with the space between panes filled with dry air or insulating gas (argon or krypton), sealed by an edge spacer. When that seal fails — from age, manufacturing defect, or physical stress on the frame — outside humidity enters the gap.
Why it can't be cleaned
The moisture is trapped between two sealed panes of glass, not on an accessible surface. No amount of exterior or interior cleaning reaches it. Once you see this haze, it means the insulating gas has also likely escaped, so the window has lost meaningful insulation performance even beyond the visible fog.
What can be done
Some companies offer insulated-glass-unit-only replacement — swapping just the glass, not the whole window — if the frame itself is in good shape. This is worth asking about as a lower-cost alternative to full window replacement, though it's not offered by every installer.
Is it a health or safety issue?
No — a failed seal is a performance and cosmetic issue, not a safety concern. It simply means the window has lost its insulating capability.
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