Yes, double glazing can often be repaired rather than replaced, saving homeowners an average of £200–£500 per window compared to a full replacement (GOV.UK, 2026). Common repairs include fixing failed seals, replacing broken hinges, or addressing condensation between panes. The viability depends on the specific issue and window age.
The key variable is the type of failure. If the glass is intact but condensation has formed between the panes, the seal has failed and the unit can be repaired by replacing the sealed glass unit (IGU) while keeping the frame. If the frame itself is rotting, warped, or damaged, a full replacement may be more cost-effective. Repairs are typically suitable for windows less than 20 years old; older frames may not meet current energy-efficiency standards (BRE, 2026).
Failed seals cause condensation between panes
When the seal between the two glass panes fails, moisture enters and creates misting or fogging. This reduces the window’s insulation value, U-value increases from around 1.2 W/m²K to over 3.0 W/m²K (Energy Saving Trust, 2026). Repairing the sealed unit typically costs £80–£150 per window, including removal of the old unit and installation of a new one. This is significantly cheaper than a full replacement, which can cost £300–£800 per window. A qualified installer should use a certified sealed unit to ensure performance.
Hardware repairs are straightforward and low cost
Broken hinges, handles, or locks are common on double-glazed windows and can be repaired for £30–£100 per window, including parts and labour (TrustMark, 2026). These repairs restore functionality without affecting the glass or seal. Most components are standardised, so a local glazier can source replacements. If the window is still under warranty, typically 5–10 years for hardware, the manufacturer may cover the cost. Check your warranty documents before arranging a repair.
When replacement is the better option
If the frame is damaged, rotten, or over 20 years old, replacement often makes more financial sense. A full replacement costs £300–£800 per window but improves energy efficiency and adds to property value (GOV.UK, 2026). New double-glazed windows achieve U-values of 1.2–1.4 W/m²K, compared to 2.0–3.0 W/m²K for repaired older units. Also, replacement windows may qualify for grants under the Energy Company Obligation (ECO) scheme if your household meets eligibility criteria (Ofgem, 2026). Always get at least three quotes from certified installers before deciding.
A worked example
For a typical 1930s semi-detached house in Manchester with three failed double-glazed windows, repairing the sealed units costs £360 rather than replacing the whole windows at £1,800. The windows are 15 years old with intact uPVC frames, so a local FENSA-registered installer replaces the glass units only. After repair, the U-value drops from 3.0 W/m²K back to 1.2 W/m²K, saving an estimated £95 per year on heating bills according to the Energy Saving Trust. The homeowner pays £360 upfront with 0% VAT applied until March 2027, recovers the cost in under four years, and avoids the disruption of full frame replacement. Over 25 years, total savings reach £2,375 against the repair cost.
| Item | Figure |
|---|---|
| Upfront cost after grants | £360 |
| Yearly savings | £95 |
| Payback period | 3.8 years |
| 25-year lifetime savings | £2,375 |
What homeowners often get wrong
The most common mistake is assuming any misting between panes means the whole window must be replaced. This misconception leads homeowners to spend £500–£800 per window unnecessarily. Here are the three biggest errors to avoid.
- Assuming misting means full replacement Many homeowners see condensation between panes and call for a quote on new windows. In reality, the airtight seal has failed but the frame is often fine. Replacing just the sealed glass unit costs £80–£150 and restores insulation performance completely.
- Ignoring warranty coverage Some homeowners pay for repairs when the windows are still under a 10- or 20-year manufacturer warranty. Checking the original paperwork first can save the full repair cost. A quick call to the installer or manufacturer often confirms coverage for seal failure.
- Repairing windows over 25 years old Older frames may have rotting timber or degraded uPVC that cannot hold a new sealed unit properly. Spending £150 on a repair for a 30-year-old window often wastes the money because the frame fails within two years. A full replacement is more cost-effective for such old windows.
Quick reference
- Repairing a failed sealed unit costs £80–£150 per window, compared to £300–£800 for a full replacement.
- Windows under 20 years old are almost always worth repairing rather than replacing.
- 0% VAT on energy-saving materials including replacement glass units applies until March 2027 under GOV.UK rules.
- A repaired double-glazed unit restores a U-value of around 1.2 W/m²K, saving roughly £30 per window annually on heating.
- Never repair windows with rotting timber frames or warped uPVC, as the new sealed unit will fail prematurely.
Frequently Asked Questions
Yes, double glazing can often be repaired. According to GOV.UK (2026), repairing a sealed unit costs £80–£150, while full replacement runs £300–£800.
Repairing misted windows by replacing the sealed unit typically costs £80–£150 per window. The Energy Saving Trust states this restores insulation to around 1.2 W/m²K.
Replace double glazing if the frame is rotting or the window is over 20 years old. The BRE notes older frames may not meet current energy-efficiency standards.
