8 min read · Updated 2026-08-02
The short answer: vinyl windows last 20 to 30 years, wood windows 30 or more with maintenance, aluminum 15 to 20, and fiberglass 30 to 50.
But those numbers describe the frame. The part that almost always fails first is the insulated glass unit — the sealed sandwich of two or three panes with gas between them. That seal typically fails between year 10 and year 20, well before the frame is worn out. Most people who think their windows “lasted 15 years” are describing a seal failure, not a frame failure.
Understanding that difference is what saves money: a failed seal in a sound frame is often a glass-only repair at a fraction of full replacement cost.
| Material | Typical lifespan | Fails because |
|---|---|---|
| Vinyl (uPVC) | 20–30 years | Frame warps or becomes brittle from UV; welded corners split |
| Wood | 30+ years, longer if maintained | Rot at the sill and lower rail where water sits |
| Aluminum | 15–20 years | Thermal bridging causes condensation, then corrosion |
| Fiberglass | 30–50 years | Rarely fails structurally; the glass unit goes first |
| Composite | 30–40 years | Similar to fiberglass, hardware wears before the frame |
These are service-life ranges under normal residential conditions, not warranty terms. Manufacturer warranties are usually shorter and cover specific defects rather than general wear.
Sun exposure. A south or west-facing wall gets dramatically more UV and heat cycling than a north wall. On the same house, installed the same day, south-facing windows commonly fail five to ten years before north-facing ones. If your south side is fogging and your north side is fine, that is normal — not a defect.
Temperature swing. Insulated glass units are sealed with a gas fill. Every heating and cooling cycle expands and contracts that gas, flexing the edge seal. Climates with large annual swings fatigue seals faster than mild ones. In Michigan, a January night at -10°F and an August afternoon at 90°F is a 100-degree annual range working on every seal in the house.
Installation quality. This is the most underrated factor. A window installed out of square, shimmed unevenly, or foamed with high-expansion product will bind and stress the frame every time the sash moves. Poor installation can cut a 25-year window down to 12.
Water management. If the sill was never flashed and there is no pan under the window, water that gets past the exterior seal has nowhere to go but into the wall and the bottom of the frame. This is what rots wood windows and corrodes aluminum ones.
Hardware use. Balance springs, crank operators, and locks are mechanical parts with their own life. A window you open daily wears its hardware in a decade; one that stays shut can go thirty years. Hardware is usually replaceable without touching the frame.
This is the definitive one. If you can see condensation or a hazy film between the glass layers — not on the inside surface you can wipe — the seal has failed permanently. The gas fill has escaped and moisture has entered. It cannot be cleaned, resealed, or dried out. Any product claiming to “defog” a window is treating the symptom by drilling and venting the unit, which removes what little insulation value remains.
Once the seal fails, the window has lost most of its energy performance. It still keeps rain out, so there is no urgency measured in days — but it is no longer doing the job you paid for.
Run your hand around the perimeter of a closed window on a windy day. Air movement at the sash means worn weatherstripping, which is a cheap fix. Air movement at the frame-to-wall junction means the rough opening was never properly insulated — a more involved repair, and a strong argument for full-frame replacement.
A double-hung sash that slides shut on its own has failed balance springs. On most windows made after 1990 this is a $30 part and a 20-minute repair. It is not, by itself, a reason to replace the window — and a contractor who quotes full replacement for this alone is not doing you a favor.
Soft wood you can press a screwdriver into, vinyl that has become chalky and brittle, corner welds that have separated, or aluminum with white powdery oxidation. Frame damage is the one category where repair rarely makes sense.
Windows that are 25 years old, seal-intact, operating smoothly, and not drafty are working windows. There is no benefit to replacing them on a schedule. Replacement makes financial sense when a specific failure exists, not when a birthday passes.
The exception is single-pane glass. A single-pane window is not a failed window — it never had an insulated unit to fail — but its thermal performance is so far below current standards that replacement usually pays back on energy cost alone in a way that replacing functional double-pane windows does not.
| Symptom | Repair | Replace |
|---|---|---|
| Fogged glass, sound frame | Glass-only replacement | Only if frame is also failing |
| Broken pane | Glass replacement | No |
| Sash won’t stay up | Balance springs | No |
| Draft at sash | Weatherstripping | No |
| Draft at frame perimeter | Sometimes re-insulate | Usually yes |
| Rot, warping, split welds | No | Yes |
| Single-pane throughout | No | Usually yes |
Glass-only replacement typically runs a fraction of full-frame cost. It is the right call more often than the industry admits, because it is the smaller job.
Walk the house once with two things in mind: which windows fog, and which ones you can feel air at. Those two observations separate the openings that need work from the ones that do not, and they are the entire basis of a sensible quote.
If you are in the Canton area, our free in-home estimate documents every opening and tells you plainly which ones are repairs and which are replacements — including the ones where we recommend doing nothing.
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