A window is three components with three different lifespans, and treating it as one object is why people either replace too early or wait until a sill has rotted.
The sealed glass unit: 20 to 25 years
This is usually what fails first. The perimeter seal holding the argon between the panes degrades with thermal cycling, and Canadian shoulder seasons are hard on it — it is the repeated crossings of 0 °C in March and November that do the work, not the January minimum. When the seal goes you get permanent fog between the panes and most of the insulating value is gone.
Units on south and west elevations tend to fail first, because they take the most UV and the widest daily temperature swing.
The frame: 25 to 50 years, depending on material
- Vinyl (PVC) — 25 to 40 years. Good welded corners last well; cheap extrusions get brittle and chalk on sun-facing walls.
- Fibreglass — 40 to 50 years. It expands at nearly the same rate as glass, which is a real advantage across a 70-degree annual swing.
- Wood — 30 years or a century, entirely depending on whether water was kept out of the sill and whether it was maintained.
- Aluminum — the metal outlives everything, but a frame with no thermal break is functionally obsolete long before it falls apart.
Hardware: 10 to 20 years
Cranks, hinges, balances and locks are the cheapest part to replace and the most common reason a window feels finished when it is not. A casement that will not pull tight is often a $60 operator, not a $1,200 window. Ask before you accept a replacement quote.
What warranties actually cover
Read for three things: how long the sealed unit is covered against fogging (often 15 to 20 years, sometimes prorated after year 10), whether hardware is included and for how long, and whether labour is covered or only the part. A twenty-year warranty that ships you a free glass unit but bills $400 to install it is a different product from one that covers the visit.
Transferability matters if you might sell. Some warranties survive a change of owner once; others end at the sale.
Tired, or finished?
Signs it is genuinely time: fog between the panes on several units, frames that have gone brittle or cracked at the corners, rot in a wood sill, or sashes that no longer close square because the opening has moved. In much of the prairies that last one is soil movement rather than the window — our Regina page covers how expansive clay racks openings out of square.
Signs it is not: a draft that turns out to be failed weatherstripping, a stiff crank, or condensation you can wipe off. The first two are cheap repairs; the third is usually indoor humidity, covered in our condensation guide.
If you do decide to replace, vinyl versus fibreglass compares the two frame materials most Canadian homeowners choose between, and our cost guide sets expectations before the first quote arrives.