There are two completely different problems people call "foggy windows," and the fix for one has nothing to do with the other. Work out which you have first.
Which fog do you have?
Wipe the inside of the glass. If the moisture comes off, it is indoor condensation. Your window is fine.
Wipe the outside. If it comes off there, it is dew or morning humidity. Also fine, and usually a sign the glass is insulating well.
If you wipe both surfaces and the haze is still there, the moisture is between the panes. The seal has failed. That is the problem this guide is about.
Failed seals often look less like fog and more like a permanent milky film, or a white or rainbow coloured mineral stain that grows from the bottom corners upward. That staining is the residue left behind after moisture has been evaporating and condensing inside the unit for a few seasons.
What actually failed
A double glazed window is two panes of glass separated by a spacer bar, sealed around the perimeter, with dry air or argon in the cavity. Inside the spacer is a desiccant that absorbs any small amount of moisture that gets in.
The unit spends its life expanding and contracting. In Ontario that means going from minus 25 in January to plus 35 in August, over and over. Eventually the perimeter seal fatigues and lets outside air in. The desiccant absorbs the moisture until it is saturated, and after that the water has nowhere to go. It condenses on the inside of the glass every time the temperature drops.
Nothing about that process is reversible.
Why you cannot fix it
You will find services offering to drill the unit, dry it out and reseal it. It does clear the visible fog. What it does not do is restore the seal, the desiccant or the argon fill, which means the insulating value stays gone and the moisture comes back, usually within a season or two. You are also left with holes in a unit that used to be sealed.
The sealed unit is a manufactured component. When it fails, it gets replaced.
What it costs
| Situation | Cost |
|---|---|
| Standard sealed unit | $350 to $650 installed |
| Large picture window or tempered | $650 to $900+ |
| Low-E with argon | add roughly 15 to 20 percent |
| Arched or specialty shape | higher, plus longer lead time |
The frame stays where it is. There is no drywall, no trim removal, no exterior work. We measure on the first visit, the unit is manufactured to that exact opening, and the install itself usually takes under an hour once the glass arrives, typically three to seven business days later.
How long a sealed unit should last
Twenty to twenty five years is normal. Better units with warm edge spacers and a good perimeter seal go longer. Cheap builder grade units with aluminum spacers fail sooner, sometimes in ten to fifteen years.
This is why fogging arrives in waves by neighbourhood. Glen Abbey and River Oaks in Oakville were built out through the late 1970s to early 1990s, so an entire generation of glazing there is failing at once. The same pattern shows up in 1970s Bramalea, in Scarborough's postwar bungalows and in the 1980s subdivisions across Mississauga. If your neighbours are dealing with it, you probably will be soon.
What makes it happen faster
- South and west facing walls. More sun, more heat cycling, shorter seal life.
- Lake exposure. Wind and temperature swing off Lake Ontario are hard on seals. We see more failures in Stoney Creek, Winona and the Hamilton lakeshore than a few kilometres inland.
- Large units. More glass area means more expansion force on the same perimeter seal.
- Poor drainage. If water sits in the frame's drainage channels, the bottom seal stays wet. Clearing weep holes helps.
- Pressure washing directly at the seal. Worth avoiding.
Does a foggy window actually cost you anything?
Yes, but modestly. Once the argon has escaped and the cavity is full of moist air, the unit's insulating value drops toward that of ordinary double glazing, and in a badly failed unit closer to single glazing at the affected area. You will feel it as a cold spot near the window in January.
The bigger practical costs are that you cannot see out of it and it looks bad on the front of the house. Most people fix it for those reasons, not the energy bill.
The other fog: condensation on the inside
If moisture wipes off the interior surface, your windows are working and your indoor humidity is too high for the outdoor temperature. That is a house problem, not a glass problem. Running bathroom and kitchen fans, keeping humidifiers under about 35 percent in winter, and improving air circulation near the windows all help. Persistent heavy condensation on the interior is worth taking seriously, since it leads to mould on sills and frames.
Caulking gaps around the frame, $75 to $150 per window, reduces cold spots at the perimeter and helps here too.
Getting yours replaced
Measure the visible glass, note whether the haze is between the panes, and call. We will give you a range on the phone. Same day across Hamilton, with no travel fee.