Vinyl vs. Fiberglass Windows: Which One Lasts Longer?

Both are sold as lifetime windows. Only one actually behaves like one in a cold climate.

Vinyl windows dominate the replacement market because they are cheap to manufacture and cheap to install. Fiberglass is roughly 30 to 50% more expensive at every tier. So why would you spend more?

Thermal expansion. Vinyl moves about 7 times more than glass when temperatures swing. In climates that go from -10°F to 95°F, the seal between the vinyl frame and the glass unit gets worked harder every year. Fiberglass expands at almost exactly the rate of glass, which is why high-end manufacturers use it.

If you live somewhere mild, vinyl is fine. If you live somewhere that freezes and thaws, fiberglass is the better long-term call.