🏠 Free Assessment: Get a written exterior renovation quote — no obligation!
Kitchener • Waterloo • Cambridge • Guelph & Waterloo Region
(519) 502-3905 Mon–Sat 7AM–6PM

Insulated Window Seal Failure: Repair Options Explained

Foggy windows are a sign of seal failure. Here's what your repair and replacement options are.

Window and Door Replacement

Fogging between window panes occurs when the seal of an insulated glass unit (IGU) fails, allowing atmospheric moisture to enter the sealed space. The moisture condenses and evaporates on the glass surfaces, leaving mineral deposits and obscuring the view.

The proper repair is IGU replacement — not window replacement. In many cases, the window sash and frame are structurally sound; only the glass unit needs replacement. An IGU replacement is significantly less expensive than replacing the entire window.

Energy Efficiency and Style

Sash replacement is the next level of repair. If the sash itself is damaged, warped, or deteriorated, replacing the sash unit (the moving frame that holds the glass) restores function without replacing the frame installed in the wall.

Full window replacement is appropriate when the frame is damaged, the window style needs updating, or when energy performance requirements have changed since original installation. Full replacement is more disruptive and expensive than IGU or sash replacement.

Getting a Free Estimate

Drilling and dehumidifying is a temporary repair method. Small holes drilled in the spacer bar allow the IGU interior to be dehumidified with desiccant, temporarily clearing the fogging. This doesn't restore the IGU seal and typically requires repeating.

DIY IGU replacement is technically possible but challenging. IGU units must be measured precisely, ordered from a glass supplier, and installed correctly to seal. Errors result in a unit that fogs again quickly.

When getting quotes for seal repair, ask explicitly whether the quote is for IGU replacement, sash replacement, or full window replacement. Ensuring you're comparing equivalent scope is essential to making an informed decision.