Foggy window repair
Foggy window repair, weighed evenly: defog, new sealed unit or new window
A foggy window has one of two problems. If the moisture wipes off, it's on the surface. If it sits between the panes and won't budge, the seal around the glass has failed. That kind won't clear on its own, but it rarely means a new window. Usually the sealed unit, the glass part, can be replaced in the frame you have. We set out every option here without a side to take, then pass your request to a local glass pro who swaps sealed units.
- Defog, reseal or replace, set out evenly
- A new sealed unit in your existing frame
- Photos first, then a written quote
What you're seeing
What fog between the panes actually means
Inside the sash, the glass is one sealed unit: two or three panes, a spacer bar between them, and a seal around the edge. Owners of older homes may still call it a thermopane. Dry air inside keeps it clear. Once the edge seal lets moisture in, the unit fogs, and it can't be sealed back to factory condition.
Droplets or haze that come and go
Early failure. The fog thickens on cool mornings and fades in the afternoon sun as moisture moves past the seal.
A white film that never clears
Later, minerals dry onto the inside faces of the glass. If several same-age windows are doing this, weigh new glass against new windows.
Check first
Condensation or a failed seal? A quick check before you call
Run a dry cloth across the misty patch, on the room side and then outside. If it smears or wipes clear, the moisture is on the surface. If the haze stays whichever side you wipe, it's between the panes.
Foggy in the morning: room-side fog at dawn, often on bedroom and bathroom windows, is overnight humidity meeting cold glass. It says nothing about the seal.
Foggy when it rains: mist outside the glass on a damp day is normal, especially on well-insulated windows whose outer pane stays cool.
Foggy from humidity all day: the house holds more moisture than the glass can handle. That's a ventilation job.
The usual fix
Replacing the sealed unit: what the pro measures and orders
When the frame is sound, this is the standard repair: two visits, with a wait in between while the glass is built.
Measure and check the frame
The pro takes the exact glass size, notes how the unit is held in and checks that the sash and frame are worth keeping. If a new unit is the wrong answer, you'll hear it now.
Choose the spacer, coating and gas
You choose the spacer around the edge (warm-edge types are a common pick), a low-e coating that reflects heat back indoors, and argon between the panes. Ask what the warranty covers.
Tempered glass where code calls for it
Ontario's Building Code calls for safety glass in sliding patio doors, storm doors and some sidelights, so those units are ordered tempered. For a fogged patio door, see sliding door repair.
Install, then take away the old unit
The foggy unit stays in until the new one arrives, so the window is never left open. Ask whether removal of the old unit is quoted.
All four options
Defogging services versus a new sealed unit: what each can and can't do
Defogging means drilling small holes in the glass, drying and cleaning the space inside, then plugging the holes. It can clear the view. It doesn't rebuild the seal or replace lost gas. No option suits every window:
| Option | Suits | Falls short when |
|---|---|---|
| Defogging | A unit you'd keep a while, fogged but not etched | The glass is etched, or you want the seal back |
| Resealing from outside | Cracked caulking around the frame, which is a draft fix | The fog is between the panes, where outside sealant can't reach |
| New sealed unit | A sound frame and sash with one or several fogged units | The frame is soft, split or leaking air |
| New window | Frames past saving, most units failing, or a move to ENERGY STAR certified windows | Only the glass has failed in a sound frame |
Look past the glass
When the frame, not the sealed unit, is what's failing
New glass in a failing frame is money spent twice. Before ordering, the pro should check a wood sash for soft corners, a vinyl frame for split welds, and the sill for water held against the glass. A unit sitting in water will fog again, whatever glass goes in.
If the frame is past saving, see replacement windows. A stiff crank or a draft is a hardware and weatherstripping repair, not a reason to replace. Other faults are on the windows overview.
Pricing a sealed unit
What drives the price: size, glass package, shape, access, how many units
Every sealed unit is built to order. These move the price:
- Size, from a small casement pane to a picture window
- The glass package: double or triple pane, low-e, gas fill, spacer type
- Shape: arched, round-top or angled units take more work
- Access: upper storeys, units behind storms, awkward bays
- How many same-age units are done on one visit
- Tempered glass where code calls for it
A photo with a tape measure across the glass helps the pro quote.
The local picture
Why so many Durham windows are fogging now
A good share of Oshawa's homes went up between the '80s and the 2000s, and in Whitby, Ajax and Clarington that era is most of the housing; Courtice grew from a village into subdivisions from the mid-1980s on. Many of those houses still have their original sealed units or same-era vinyl retrofits. Oshawa's winters swing above and below freezing often, and each thaw and refreeze strains the edge seal a little more.
In older and rented homes, the question is when to replace a fogged unit, not whether. It still keeps wind and rain out, so it's seldom urgent; for landlords, turnover is a practical time.
Rebates
Rebates: why glass-only swaps don't qualify
Ontario's Home Renovation Savings Program pays back per rough opening when a whole ENERGY STAR certified window or door goes in, and it generally expects an energy assessment and at least one other upgrade. New glass or a new sash in the old frame is excluded. So a new sealed unit is the practical fix for one or two foggy windows, but earns nothing back. If most of the house is fogging and the frames are tired, price whole windows side by side, and check the program page for current rules.
Durham Greener Homes lists upgrades such as insulation, air sealing and heat pumps; ask its coach whether windows qualify.
Questions
Foggy window questions
Explore your options
If it's more than the glass
Pros replace sealed units across Oshawa and the Durham subdivisions, including Whitby, Brooklin, Courtice, Bowmanville and Ajax.
Photograph the foggy unit and its spacer bar
Include the whole window, a close-up of the corner where the spacer bar and any label sit, and a rough size. The pro who picks it up can price the glass on its own and flag anything the frame needs.