visibilityHow to check
- Wipe the inside face of the glass with a dry cloth. If the fog wipes clean, it's surface condensation from indoor humidity — work that instead (see the windows condensation page); it isn't a seal failure.
- Wipe the outside face too. On a cool morning, dew or light frost sits out there on an efficient window and clears as the day warms — also not a seal failure.
- If a haze, droplets, mineral streaks, or a milky film stays put no matter which face you wipe — often worst in the middle of the pane — the moisture is sealed BETWEEN the panes. That confirms a failed insulated glass unit in that window.
- Note which windows are affected and roughly measure each pane (width, height, and the glass thickness/spacer if you can see the edge). A glass shop will need those numbers, and it tells you the scope before you call.
buildAucun outil schedule5 min
handymanHow to fix it
warning Large glass is heavy and sharp — know when to hand it offA sealed glass unit is a heavy slab of glass with sharp edges, and getting the measurement, setting blocks, and re-seal right is what keeps the new unit from fogging next winter. Swapping a small, accessible, stopped-in unit at ground level is a reasonable careful-DIY job with gloves and a helper. Anything large, high up, on an upper floor, or held in with structural glazing tape belongs to a glass shop — they do this every day, usually for a few hundred dollars per window, and the frame stays put. There's no urgency: a fogged unit is cosmetic, not a safety issue.
Have the sealed glass unit measured and replaced — the frame and sash usually stay. A glass shop can re-glaze in place or take just the sash; a careful DIYer can swap an accessible, stopped-in unit. Until then the fog is only cosmetic and slightly less efficient, so there's no rush.
- Measure the sealed unit carefully — width, height, overall thickness, and pane count — or, easier and safer, remove the sash and take the whole thing to a glass shop to measure and match (including any low-e coating and argon fill).
- Order the replacement sealed unit. This is the part with the lead time; the window stays usable and only cosmetically fogged while you wait.
- If you're doing it yourself on a stopped-in unit: pry off the glazing stops or beads carefully, note their order, and lift the old unit out onto a padded surface — sealed units are heavy and the edges are sharp.
- Set the new unit on the same setting blocks, re-fit the stops, and seal per the manufacturer's instructions. If the unit is large, high up, or held in with structural glazing tape, stop and let a glass shop do it — it's a routine job for them.
schedule120 min savings$120–400
Replacement insulated glass unit (sealed unit)Match width, height, overall thickness, pane count, any low-e coating, and gas fill; a glass shop will size it from the old unit or the sash
gavel Vérifiez d’abord votre province AB: permis au propriétaire · BC: permis au propriétaire · ON: permis au propriétaire · PE: permis au propriétaire · QC: permis au propriétaire
Replacing a sealed glass unit (the glass only, frame in place) is homeowner-or-contractor work across Canada. Note separately: replacing the whole window, changing the opening size, or a bedroom egress window may require a building permit and a contractor — verify the municipal/provincial rule before that scope of work.
Replacing a sealed glass unit (the glass only, frame in place) is homeowner-or-contractor work across Canada. Note separately: replacing the whole window, changing the opening size, or a bedroom egress window may require a building permit and a contractor — verify the municipal/provincial rule before that scope of work.