Why Foggy Windows Happen & How to Fix Them

You notice a cloudy haze on your window — but no matter how many times you clean it, it won't wipe away. That's because the fog isn't on the surface. It's trapped inside the window, between the two panes of glass, where you can't reach it. This is one of the most common window problems in GTA homes, and the good news is it's almost always fixable without replacing the entire window. Here's everything you need to know about foggy windows — what causes them, what your options are, and what it realistically costs to fix in Brampton and the GTA in 2026. Understanding Window Fogging Modern residential windows are double-pane or triple-pane units. Two or three sheets of glass are sealed together with a space between them filled with air or argon gas. This sealed unit — called an insulated glass unit or IGU — is what gives your window its insulating power. The seal around the IGU is made of rubber and a desiccant material designed to absorb any moisture that gets in. Over time, this seal degrades. When it fails, outside air and humidity enter the space between the panes. When temperatures change, that moisture condenses — and you get the fog you can see but cannot touch. This is called seal failure. It is not a cleaning problem. It cannot be fixed by wiping the glass. Why Window Seals Fail Seal failure is normal. Most IGU seals have a functional lifespan of 15 to 25 years. In Toronto and the GTA, our extreme climate accelerates this process. Temperature cycling is the main cause. GTA temperatures swing from -25°C in winter to +35°C in summer — a 60-degree range that causes constant expansion and contraction in the glass and seal. South-facing windows experience the most thermal stress and typically fail sooner than north-facing ones. UV exposure gradually breaks down the rubber seal material. Water pooling on window sills can work its way into the frame and accelerate degradation. Poor original installation creates weak points in the seal from the beginning. The impact on your home's energy efficiency is real. A failed IGU has lost most of its insulating value — the gas between the panes is gone, and you're essentially heating and cooling through a single pane of glass. This can increase energy loss through that window by 50 percent or more. How to Tell If Your Seal Has Failed The clearest sign is condensation or fogging between the panes that you cannot wipe away from either side. Other signs include a rainbow or oily haze effect on the glass, white mineral deposits or streaks inside the glass, or a window that looks dirty even after a thorough cleaning. A simple test: press gently on the centre of the glass pane. If you see the fog shift or move slightly, the seal has failed and moisture is trapped inside. Can You Prevent Foggy Windows Once a seal has failed, you cannot repair it through maintenance. But you can slow seal degradation on healthy windows with a few simple habits. Keep window sills clean and dry. Water pooling against the frame is one of the fastest ways to shorten seal life. Ensure proper ventilation in your home to reduce interior humidity. Avoid placing heat sources like baseboard heaters directly under windows — the additional thermal stress accelerates seal degradation. Regular inspection helps too. Catching a small gap or crack in the exterior caulking early prevents water infiltration that can damage the seal. Your Repair Options You have three realistic options when you have a foggy window: Option 1: Do nothing. The fogging does not make the window structurally unsafe, but it continues to worsen over time. Your energy efficiency suffers, and the aesthetics are poor. Not recommended. Option 2: Window defogging service. A technician drills small holes in the glass, injects a cleaning solution to remove moisture and debris, then dries and seals the holes. This costs $100 to $200 per window. It is a temporary solution — the seal has still failed and moisture will return, typically within 2 to 5 years. Suitable if budget is very tight. Option 3: IGU replacement (recommended). The glass unit is replaced entirely while the window frame stays in place. This is a permanent repair that restores full insulating performance. Costs $150 to $350 per window for standard-sized units. Lasts 15 to 25 years — same as the original. In most cases, IGU replacement is the right choice. It costs 60 to 80 percent less than full window replacement and delivers the same result. What Full Window Replacement Actually Costs Full window replacement — removing the existing frame and installing a complete new window — costs $800 to $1,500 per window in the GTA in 2026. It is only necessary when the window frame itself is rotted, warped, or structurally compromised. If your frame is sound and only the glass has failed, IGU replacement saves you thousands of dollars across a typical home. Our Professional Process When you contact Window Fix GTA for foggy window repair, here is what happens: We inspect the window to confirm seal failure and check the frame condition. We measure the existing IGU precisely — size, thickness, glass type, and any coatings. We order the replacement IGU if not in stock, or proceed same-day if we have the right unit available. We remove the old glass unit, clean the frame, and install the new IGU with professional-grade sealant. Total time: typically 1 to 2 hours per window. Most homeowners see immediate improvement — the fog is gone and the view is clear. Energy Savings from Fixing Foggy Windows Replacing a failed IGU restores your window to its original thermal performance. For homes with multiple foggy windows, this translates to measurable savings on heating and cooling. A 2026 study of Canadian homes found that replacing old failed IGUs with energy-efficient double-pane units reduced heating costs by up to 15 to 20 percent per replaced window. For a home with 4 to 6 foggy windows, the energy savings over a Canadian heating season can be $200 to $500 per year — often recovering the cost of repairs within 2 to 3 years. Frequently Asked Questions Can I wipe away the fog? No. The moisture is trapped between the panes inside the sealed unit. It cannot be reached from either surface. The only fix is replacing the glass unit or the full window. Do I need to replace the entire window? In most cases, no. If the frame is structurally sound, only the glass unit needs replacing. This is called an IGU replacement and costs significantly less than full window replacement. How long does new glass last after IGU replacement? A properly installed IGU lasts 15 to 25 years under normal conditions. Will fixing foggy windows lower my energy bill? Yes. A failed IGU has lost most of its insulating value. Replacing it restores thermal performance and reduces heat loss — typically saving $50 to $150 per window per heating season in Toronto. Is it worth fixing foggy windows in older homes? Yes, as long as the frames are in good condition. IGU replacement is cost-effective even in older homes because you preserve the original frame and just replace the glass. Do you offer a warranty on IGU replacement? Yes — we provide a full 1-year warranty on all labour and materials. Get a Free Assessment If your windows are foggy, call Window Fix GTA at (647) 961-8637 for a free inspection. We serve Brampton, Mississauga, Toronto, Oakville, and the surrounding GTA — often with same-day availability.