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Clear glass again without a new window
A double pane window that looks cloudy, streaky or wet between the glass has a failed seal, and no amount of cleaning will clear it. GTS Windows & Doors has replaced sealed glass units in Kitchener-Waterloo homes and buildings since 1986, and in most cases we swap the glass alone and keep your existing frame. That usually costs a fraction of a new window and takes far less disruption.
Sealed unit replacement is specialist work that many window companies do not offer, because it means measuring glass to the millimetre, ordering custom insulated units and resetting them without damaging the sash. We handle it for homeowners, landlords, property managers and businesses across Kitchener, Waterloo, Cambridge, Guelph and the surrounding townships. It is also a chance to put better glass into a frame that still has plenty of life left.
We will also tell you honestly when a foggy unit is a sign that the whole window has reached the end of its service life, for example when fresh glass would go into a frame that is already rotting or cracked at the corners. Foggy glass is one of our core window repair services, alongside frame, hardware and seal repairs, and our crews are licensed, insured and WSIB covered.
A double pane unit is two sheets of glass held apart by a spacer around the edge and bonded with sealant. The spacer contains desiccant, a drying agent that soaks up the small amount of moisture that works into the gap over the years.
Daily heating and cooling makes the unit flex slightly, and eventually the edge seal breaks down. Once the desiccant is saturated, moisture condenses on the inner faces of the glass, first as occasional fog on cold mornings and later as a permanent white film or mineral streaks.
Early failures often trace back to water sitting against the bottom edge of the glass, blocked drainage in the frame, strong sun on dark frames, or the wrong sealant used in an earlier repair. Here is a quick test: if you can wipe the fog off from inside or outside, it is surface condensation caused by humidity, but if it cannot be wiped from either side, the seal has failed.
Replacing only the sealed unit makes sense when the frame and sash are sound, the hardware works, and the window is not leaking air around its edges. That describes many vinyl and fibreglass windows that have simply outlived their original glass seals.
A full window replacement is the better choice when most of the units in the house have failed, the frame is cracked, warped or rotting, or new glass would sit in a frame that still leaks. Our guide on when to replace windows covers the other warning signs.
| What we check | Replace the sealed unit | Replace the window |
|---|---|---|
| Frame condition | Solid, square, no rot | Cracked, warped or rotted |
| Failed units | One or a few | Most of the house |
| Air leakage | Minor, fixed with weatherstrip | Air leaks through the frame itself |
| Hardware | Works or is easy to replace | Worn out and discontinued |
The job takes two visits, one to measure and one to install. Between those visits your window stays in normal use, since a foggy unit still keeps out weather, and the install itself is usually quick once the new glass arrives.
We measure the glass itself rather than the frame, and confirm the unit's overall thickness, which on residential double panes commonly runs from about 16 mm to 25 mm. We also record the spacer type and colour, any grilles between the glass, and whether a corner stamp shows tempered glass or a spacer stamp shows the maker and date.
An insulated glass fabricator builds the new unit to your exact size and thickness. Standard units typically arrive in about one to three weeks, while tempered, laminated or oversized units can take longer. We confirm the glass specification with you before anything is ordered.
On site, we pry off the glazing stops, cut the old unit free from its tape or sealant, and lift it out. The new unit sits on setting blocks so its weight bears evenly and the drainage path stays open, then fresh glazing tape or sealant goes on and the stops snap back into place. Finally, we check that the sash opens, closes and locks properly.
A replacement unit does not have to copy the one that failed. Because it is made to order anyway, better glass usually adds only a modest amount to the price.
The one limit is thickness: the new unit has to fit the sash's glazing pocket, so moving from double to triple glazing in the same frame is rarely possible. Our triple pane glass replacement page explains why.
Below are typical installed prices for Waterloo Region in 2026. The main drivers are glass area, coating and gas options, tempering, the window's height and access, and how many units we replace in one visit.
Grilles between the glass and shaped units such as arches or trapezoids cost more than plain rectangles.
| Unit size | Typical installed price | Examples |
|---|---|---|
| Small (under 6 sq ft) | $250 to $450 | Basement windows, small casements |
| Medium (6 to 15 sq ft) | $400 to $750 | Bedroom casements, sliders, hung sashes |
| Large (15 to 30 sq ft) | $700 to $1,400 | Picture windows, patio door panels |
| Low-E and argon upgrade | Add $40 to $150 per unit | Depends on size and coating |
| Tempered glass | Add $75 to $250 per unit | Required in doors and some sidelights |
Two layers of coverage apply to a new sealed unit. The insulated glass fabricator warrants the seal against failure for a set term, which varies by supplier, and we name that term on your quote.
We stand behind our own installation work as well, and we put both the glass warranty and our workmanship coverage in writing before you approve the order. Full details of how our coverage works are on our warranty page.
Some companies offer defogging, which involves drilling small holes in the glass, cleaning the inside and fitting vents. It can improve the look for a while, but it does not restore the seal or the insulating gas, so the unit keeps losing heat. Replacing the sealed unit is the only permanent fix.
After we measure, a standard unit is typically ready in about one to three weeks, and tempered or specialty glass can take longer. Installing it usually takes well under an hour per unit, so a few windows can be done in a single morning.
It might be. Most window makers include a separate glass seal warranty, often 10 to 20 years and sometimes longer, and some cover the glass but not the labour to install it. Check your paperwork or look for the maker's name and date stamped on the spacer, and we can help you work out what is covered.
It is not a health hazard in itself. The real cost is lost insulating value, since the gas has escaped, plus mineral deposits that eventually leave the glass permanently cloudy. It is worth fixing before winter, when the heat loss matters most.
Send us a photo of the foggy glass and tell us roughly how many windows are affected. A close-up of any stamp on the spacer between the panes helps us identify the unit quickly.
Call or text226-806-0597