Double glazing doesn't last forever. Modern units typically last 20-30 years; older 1980s and 90s installations are often well past their useful life. Catching failures early can save you thousands — full window replacement is often unnecessary if the frames are sound.
Sign 1: Condensation between panes
This is the classic sign of failed double glazing. Condensation inside the sealed unit means the perimeter seal has failed and moisture has entered the cavity. Once this happens, the unit's insulating gas (argon or krypton) has escaped and thermal performance has dropped significantly. The fix: replace the sealed unit (not the whole window). Typical cost: £80-£180 per pane.
Sign 2: Draughts around the frame
Cold draughts you can feel near the window edges suggest frame seals or gaskets have perished. Modern uPVC and aluminium gaskets are replaceable — typical refurbishment costs £30-£80 per window.
Sign 3: Difficulty operating the window
Stiff handles, doors that don't latch, sashes that drag on the frame — these are usually hinge, gearbox or friction-stay issues, not full-frame failures. Hardware replacement typically costs £45-£120 per window.
Sign 4: Visible damage to the frame
Cracked uPVC, peeling powder coating on aluminium, rotten timber sills — these are structural problems that may require full replacement. If the frame itself is failing, repairing glass units is wasted money.
Sign 5: Steamy or wet internal panes
Internal condensation on the room-side of glass usually indicates ventilation issues rather than glazing failure — but it can also signal poor U-value performance forcing internal warm air to condense on cold glass surfaces. Upgrading to A-rated glass typically solves both problems.
When to repair vs replace
If frames are sound (under 20 years old, no cracking, sashes operating well), repair individual sealed units and hardware as needed. If frames are over 25 years old and showing structural fatigue, full replacement makes more economic sense — modern A++ rated windows will pay back the difference within 10-12 years in energy savings.
Get a free assessment
We offer free assessments for any property in the UK — we'll tell you honestly whether you need repairs, partial replacement or a full re-glaze. Call 0800 088 6341.
Need help with your glazing project? S&K Glazing offers free surveys and fixed-price quotes across the UK. Call 0800 088 6341, message us on WhatsApp at 07830 175306, or request a quote online.