Foggy Window Repair in the Capital Region
Fog between the panes is one of the most misunderstood window problems. It is not dirt, it is not condensation you can wipe away, and it is not a sign that the whole window has to come out. It is a seal failure in the insulated glass unit.
Fog between the panes means the insulated glass seal has failed and the argon fill has escaped. It cannot be repaired, but the glass unit can be replaced while keeping your existing frame and hardware, typically for $150 to $600 per sash.
Here is the mechanism. A modern window has two panes held apart by a spacer, with the gap filled with argon and sealed at the perimeter. A desiccant inside the spacer absorbs any residual moisture. Over years of thermal cycling, and our climate delivers a lot of it, the seal eventually breaks down. Argon leaks out, humid outside air leaks in, the desiccant saturates, and then every time the glass gets cold you get condensation inside the sealed space with no way to dry out.
Once it starts you have lost most of the insulating value of that window even on days when it looks clear. The good news is the fix is glass, not a whole new window.
How to know it is a seal failure
- Haze or moisture that will not wipe off from either side
- Fog that appears in the morning and partially clears by afternoon
- A permanent cloudy or milky patch, usually starting at the bottom edge
- Visible water droplets or running water between the panes
- White mineral streaking etched into the interior glass surface
- One window fogging, then others in the same age group following
Three kinds of window condensation, three different fixes
Where the moisture sits tells you exactly what the problem is.
| Where the fog is | What it means | What to do |
|---|---|---|
| Inside surface, room side | Indoor humidity too high for the glass temperature | Lower humidity, improve glass, run bath and kitchen fans |
| Outside surface, exterior | Glass is well insulated and colder than the dew point | Nothing, this is a sign the window is working |
| Between the panes | Sealed unit has failed | Replace the insulated glass unit |
| Around the frame edges only | Cold bridging at the perimeter or a bad air seal | Check the perimeter insulation and weatherstripping |
Is defogging a real fix?
There are companies that drill a small hole in the glass, flush the interior surface, insert a one-way vent, and seal it. It does clear the visible fog and it costs less than a new unit. What it does not do is restore the argon fill or re-seal the unit, so the insulating performance stays degraded, and because the unit is now vented to the outside, humid air continues to cycle through it. For a window you are replacing next year anyway it is a reasonable cosmetic stopgap. For a window you intend to keep for a decade, replacing the glass unit is the real repair and the difference in cost is not large.
Ranges reflect typical Capital Region projects and are for planning only. Every Sundog quote is written, itemized, and free.
How the project runs
- 1
Confirm it is the seal
Interior surface condensation is a humidity problem. Exterior surface condensation is normal on efficient windows. Between the panes is a seal failure. We confirm which one you have.
- 2
Remove and measure the unit
The sash comes out and we measure the glass unit exactly, including overall thickness and spacer depth.
- 3
Match or upgrade the glass
We can match the original spec or upgrade to low-E with argon for a modest additional cost, since the labor is the same.
- 4
Install the new unit
New unit set on blocks, glazed, stops reinstalled, sash rehung and tested.
Why the seal fails in our climate
- Thermal cycling, over a hundred freeze-thaw crossings each winter
- Large temperature differential between inside and outside glass surfaces
- UV degradation of the perimeter sealant, worst on south and west elevations
- Poor original spacer design, common in units built before the mid 1990s
- Water sitting at the sill, which attacks the seal from the bottom edge first
- Installation twist that stressed the unit from day one
- Age, since most insulated units are designed for a fifteen to twenty-five year service life
Where we do this work
We handle foggy window repair across Albany, Rensselaer, Schenectady and Saratoga counties from our Troy office. These are the markets we are in most often.
Frequently asked questions
Can foggy windows be fixed?
The seal itself cannot be repaired, but the insulated glass unit can be replaced while keeping your existing frame, sash and hardware. That runs $150 to $600 per sash depending on size and glass package, compared to $450 to $1,400 for a full window replacement.
How long does a window seal last?
Most insulated glass units are designed for fifteen to twenty-five years. In our climate, with roughly a hundred freeze-thaw cycles a winter, the lower end of that range is common, especially on south and west facing windows that also take UV exposure. Many manufacturers warranty the seal for ten to twenty years, so check whether yours is still covered before paying for a replacement.
Does a foggy window still insulate?
Poorly. The argon fill has escaped and been replaced by ordinary air carrying moisture, which conducts heat better than argon. You lose a meaningful portion of the unit's insulating value even on days when the glass looks clear. It is not just cosmetic.
Why did all my windows fog up around the same time?
Because they were all installed at the same time and the seals have the same service life. When one goes in a house where everything is the same vintage, the rest are usually within a few years behind it. That is the situation where replacing the windows makes more sense than replacing one glass unit at a time.
Is the foggy window still under warranty?
Possibly. Many manufacturers cover seal failure for ten to twenty years, and some warranties transfer to a new owner. If you can find a label etched in the corner of the glass or stamped on the sash, we can usually identify the manufacturer and the approximate date, which tells you whether it is worth filing a claim before paying out of pocket.
Can I prevent seal failure on my other windows?
Somewhat. Keep water from sitting at the sill by clearing weep holes and maintaining the exterior caulk joint. Keep indoor humidity reasonable in winter. On south and west elevations, exterior shading helps reduce the thermal cycling and UV load. Beyond that, seals are a wear item with a finite life.
Related services
Worth reading before you decide
Get a written quote for foggy window repair
Free measure, itemized pricing, and an honest recommendation on whether this is the right scope for your house.