Foggy Double Pane Windows — What Are Your Options
Understand why double pane windows get foggy and what you can do about it. Seal failure explained.
Time Estimate
⏱️ N/A (professional repair)
DIY Cost
💰 $100-150 defogging / $300-800 glass replacement / $500-1500 full window
That hazy, foggy look between your window panes isn’t condensation you can wipe away — it’s trapped inside the sealed unit. Here’s what’s happening and what you can do.
What’s Causing It
Double and triple pane windows (insulated glass units or IGUs) have a sealed space between panes filled with air or argon gas. This provides insulation.
When the seal fails:
- Moisture-laden air enters the space
- It condenses inside when temperatures change
- The fog is trapped — you can’t wipe it away
- Over time, it may leave mineral deposits even when dry
Can You Fix It?
Option 1: Defogging Service ($100-150 per window)
Some companies drill small holes, remove moisture, and reseal. This is the cheapest option but:
- Results vary
- May not last long-term
- Doesn’t restore lost insulating gas
- Not all windows are candidates
Option 2: Glass-Only Replacement ($300-800)
Replace just the insulated glass unit (IGU) while keeping the existing frame:
- More affordable than full window replacement
- Works if the frame is in good shape
- Professional installation recommended
- Restores insulation performance
Option 3: Full Window Replacement ($500-1500+)
Replace the entire window unit:
- Best option if frames are also damaged or dated
- Opportunity to upgrade efficiency
- Most expensive but most thorough
- May be required for some window types
DIY Options
There’s no real DIY fix for foggy sealed units. The seal has failed, and repairing it properly requires equipment and expertise.
What you can do:
- Clean the exterior surfaces (won’t fix the fog but helps appearance)
- Check if windows are under warranty (many have 10-20 year seal warranties)
When to Act
Foggy windows are cosmetic first, functional second:
- They look bad
- They’ve lost some insulating value
- They won’t get worse quickly
You don’t need emergency repair, but don’t ignore them forever.
Prevention
- Buy quality windows with good warranties
- Proper installation matters for seal longevity
- Avoid pressure washing directly at seals
- Normal aging will eventually cause seal failure (15-25 years typical)
The Bottom Line
Foggy double pane windows mean the seal has failed. Your options are defogging (cheap but temporary), glass replacement (moderate cost, good fix), or full window replacement (expensive but comprehensive). Check your warranty first — seal failures are often covered.