Foggy Window Repair. Clear Glass, Same Window.
Cloudy or misty double-pane glass means the seal has failed. We replace the sealed glass unit and keep your frame and sash — for up to 75% less than a new window.
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Why Windows Fog Between the Panes — and Why Wiping Won't Help
If your double-pane windows have turned cloudy, hazy, or misty and no amount of cleaning makes a difference, the problem isn't on the surface — it's sealed inside the glass.
Modern windows use an insulated glass unit (IGU): two or three panes of glass sealed together with a layer of insulating gas and a moisture-absorbing spacer around the edge. That sealed pocket is what makes the window energy-efficient.
When the seal around it fails, outside air and humidity leak in, the moisture-absorbing spacer becomes saturated, and water vapor condenses on the inside surfaces of the glass — exactly where you can't reach it.
The result is the permanent foggy, cloudy, or streaky appearance that gets worse over time and often changes with the weather — heavier on humid days, sometimes clearing partially on dry ones, but never truly going away. It is not dirt, and it is not a cleaning problem. The sealed unit has failed and needs to be addressed.
What a failed seal actually costs you
A foggy window isn't only a cosmetic annoyance. Once the seal fails and the insulating gas escapes, the window stops insulating the way it was designed to — letting heat out in winter and in during summer. That means higher energy bills and a colder, draftier room alongside the cloudy view. Restoring the sealed unit fixes both problems at once.
You may hear it called a broken window seal, a failed thermal seal, a fogged thermopane or condensation between the panes — it's all the same problem. Double- and triple-pane glass is one sealed insulated glass unit (IGU).
Once its seal fails, moisture between the window panes leaves you with cloudy windows — streaked or milky glass that no amount of cleaning will clear. The lasting window seal repair is thermopane replacement: a new sealed unit made to fit your existing frame.
Foggy windows are one of the most common repairs we do. Because the fog sits between the panes, cleaning won't help — but double pane window repair doesn't mean a new window either.
Glass unit replacement restores clear glass in the frame you already have, and the cost to fix foggy windows is usually a fraction of replacement (see prices below).
Not sure this is your problem? Use our window triage guide — pick the symptom and see the likely cause and cost. Related reading: Why windows fog up in Illinois winters · Repair or replace? Decision flowchart
Cloudy or hazy glass
A milky or foggy film between the panes that won't wipe away from either side.
Visible moisture or droplets
Condensation, water beads, or even trickles trapped inside the sealed glass.
Fog that changes with weather
Haze that worsens on humid or cold days and partly clears on dry ones — a hallmark of seal failure.
Rising energy bills
A drafty, harder-to-heat room and creeping bills as the lost gas stops insulating.
- On the inside surface — indoor humidity condensing on cold glass. It wipes off from inside — lower the humidity. No repair needed.
- On the outside surface — dew on efficient glass on cool mornings. It wipes off from outside and burns off. Completely normal.
- Between the panes — the seal has failed. It won't wipe off from either side. The glass unit needs replacing — not the window.
Only number 3 needs a repair.
- Two glass panes — the window's glass, sealed together as one unit.
- Spacer with desiccant — keeps the panes apart and absorbs trace moisture.
- Edge seal — the airtight seal around the whole unit.
- Insulating gas — dry air or argon that slows heat loss.
- Broken seal — after years of heating and cooling, a gap opens and humid air leaks in.
- Fog between the panes — moisture condenses inside the unit, where it can't be wiped off.
The fix: replace the sealed glass unit — the frame and sash stay.
Foggy Window Repair: We Replace the Glass Unit, Not the Window
Free Assessment
We confirm the seal has failed, rule out other causes, and measure the unit precisely. You'll know the expected cost before anything is ordered.
Custom Glass Unit Made
A new insulated glass unit is manufactured to your window's exact dimensions and specification — matched to the original pane count and thickness.
Installed in Your Frame
We fit the new sealed unit into your existing sash and frame — usually in a single visit — and confirm a clean, weathertight seal.
Clear View Restored
You get back a crystal-clear window with its insulating performance restored — backed by our warranty.
Every Window Type & Material
We replace glass in every kind of window: vinyl, wood, clad and aluminum frames; double-hung, casement, awning, sliding and fixed picture windows; bay and bow windows; and patio doors. Failed seals are especially common in the vinyl and clad windows of 1990s–2000s homes. The frame stays — only the glass is new.
Foggy Window Repair Cost vs. a New Window
Typical prices
Per window · typical local prices| Insulated glass unit — standard size | $300 – $800 |
| Insulated glass unit — large or custom shape | $500 – $1,500 |
| Sash repair while the glass is out (if needed) | $400 – $700 |
When homeowners see foggy glass, they often assume they're facing the price of brand-new windows — and replacement companies rarely correct that assumption. But foggy-window repair addresses only the failed component: the sealed glass unit. Your frame, sash, hardware, and trim stay exactly where they are.
The exact price depends on the size of the unit, the number of panes, and any specialty glass (low-E coatings, tempered, or decorative). What stays consistent is the value: replacing an insulated glass unit costs a small fraction of replacing the entire window, and it restores both clarity and energy efficiency.
We give you an estimate after a free assessment, so you know the number before any work begins — no surprises, no pressure to replace what doesn't need replacing.
Why so many McHenry County windows fog up
Northern Illinois puts every sealed glass unit through wide seasonal temperature swings and repeated freeze-thaw cycles, and each cycle flexes the seal a little. Homes near Crystal Lake, the Fox River and the Chain O'Lakes add constant humidity on top of that. Many 1990s–2000s subdivisions in Lake in the Hills, Algonquin and Huntley still have their original glass units — now 20 to 30 years old — past the 15 to 25 years that seals typically last.
Broken Window Seal: What You Can Check Yourself
Safe to do yourself
- Rule out ordinary condensation: if the fog wipes off the inside or outside surface, it isn't a failed seal.
- If the fog is on the room side, lower indoor humidity — run bath and kitchen fans, and avoid drying laundry indoors.
- Photograph the window on a cool morning, when seal failure shows most clearly, and text us the photo.
- Look for a stamp on the metal spacer between the panes — it often shows the glass maker and date, which helps us order.
Call a pro
- Drill-and-dry 'defogging' kits — they can hide fog for a while but don't restore the seal or the insulating gas.
- Removing a sealed unit from the sash — it is easy to crack the glass or break the glazing stops.
- Large patio units or upper-floor windows — the weight and height make it a two-person job.
- Tempered safety glass near doors, stairs and tubs — it must be replaced with the same safety rating.
Warranty on Replacement Glass Units
Parts we don't make (cranks, balances, locks) carry only their supplier's warranty. Leaks from roofs, flashing or siding aren't window defects. Full warranty terms → · Read our reviews
Got a quote to replace these windows?
Send it to us before you sign. We'll tell you — free — whether a repair would solve it for less.
Foggy Window & Broken Seal Questions
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Foggy Window Repair in these towns and more
Based in Lake in the Hills, serving homes within about 40 miles.
Foggy Glass? Keep the Window.
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