How Long Does Double Glazing Last?

A double glazed window has a frame, one or more sealed glass units, rubber gaskets around the sash and the glass, and moving hardware such as hinges, handles and locks. The frame tends to outlast everything fitted to it. The sealed units, gaskets and hardware are the parts that wear, and each can usually be replaced individually.

A sealed unit is two or more panes held apart by a spacer, with an edge seal and a drying agent keeping the cavity dry. Sun, rain and the daily swing between warm and cold slowly work on that edge seal. When it fails, moist air enters and the glass turns cloudy between the panes.

Units facing full sun, those exposed to driving rain and those sitting in frames where water collects tend to fail sooner. A failed unit cannot be dried out, but it can be swapped while the frame stays in place, which is what our misted double glazing service does.

The rubber gaskets that seal the sash against the frame are squeezed every time the window closes and exposed to heat and cold all year. Over time they harden, shrink and crack, letting in draughts and rain. Renewing them is a modest job, covered by our window seal replacement service.

Friction stays, handles, gearboxes and locking cams are the moving parts, so they wear with use rather than with age alone. A window opened every day in a kitchen or bedroom will wear its hinges faster than one that rarely moves. Lack of lubrication and a sash that has dropped both shorten their life.

uPVC frames are low maintenance but can discolour and lose rigidity if neglected. Aluminium frames are strong and stable, though the parts that move in them still wear. Timber frames can last a very long time when the paint and putty are kept in good order, and local rot can often be repaired. In every case the frame material matters less to a window's life than how well its replaceable parts are looked after.

• Cloudiness or droplets between the panes
• Draughts or whistling with the window shut
• Water on the cill after heavy rain
• A sash that drops, catches or needs forcing closed
• A handle that is loose, stiff or spins without locking
• Rooms feeling colder near the window than they used to

Most of these signs point to one part rather than the whole window. Replacing a unit, a gasket or a hinge keeps a sound frame working, and our double glazing repairs cover all of those parts on uPVC, timber and aluminium windows. Replacement only becomes the better option when the frame itself has failed. Our guide on whether to repair or replace a window sets out how to make that call.