How Much Does Secondary Glazing Cost in the UK? The Cheaper Way to Beat Winter Heat Loss
The short answer
Secondary glazing cost: typically £300 to £500 per window installed in the UK, according to Checkatrade’s 2026 price guide. For a typical three-bedroom semi-detached house, a whole-project quote averages around £2,314. That is substantially less than full double glazing replacement, which runs £500 to £1,250 per uPVC window and £8,000 to £15,000 for a whole house. Research by Historic England shows secondary glazing can cut window heat loss by over 60 percent and match double glazing for thermal performance when low-emissivity glass is used, with the added bonus of better noise reduction. With gas unit rates around 27 percent higher year on year under the October 2026 price cap, it is one of the fastest ways to cut draughts and heat loss before winter.
What is secondary glazing?
Secondary glazing is a second pane of glass (or clear acrylic) fitted on the room side of your existing window, inside a slim secondary frame. It creates a sealed air gap between the old window and the new pane, usually around 100mm wide. That gap is what does the work: still air is a poor conductor of heat, so the extra layer slows the escape of warmth through the glass and cuts the draughts that whistle through old frames.
Unlike double glazing, the original window stays exactly where it is. Nothing is ripped out, the frame is untouched, and the work can usually be done room by room with minimal disruption. It is also reversible: the secondary units can be removed without damaging the original window, which matters a great deal in period homes, as we will see.
How much does secondary glazing cost in the UK?
Installed secondary glazing costs £300 to £500 per window including labour, according to Checkatrade’s 2026 secondary glazing price guide. The final figure depends on the size of the window, how many you are doing, and which system you choose: simple fixed panels are cheapest, while sliding or hinged units that open for cleaning and ventilation cost more. Fitters typically charge a day rate of £120 to £160 on top of the materials for the job.
For a sense of a full-house project, Checkatrade’s regional trade data cites whole-project ranges of roughly £1,477 to £3,617, with an average installer-quoted job of around £2,314. That compares with a typical three-bedroom house needing 8 to 12 replacement double-glazed windows at £8,000 to £15,000.
There is also a DIY route. Magnetic or clip-on secondary glazing kits can be fitted to smaller windows with no installation cost, though prices vary widely and we found no reliable current UK price survey for kits, so get quotes rather than trusting a round number from an old blog post.
Secondary glazing vs double glazing: the cost head to head
Here is the honest comparison, all figures from sources verified this week.
| Consideration | Secondary glazing | Double glazing (uPVC replacement) |
|---|---|---|
| Cost per window | £300 to £500 fitted (Checkatrade, 2026) | £500 to £1,250 fitted (Checkatrade, 2026) |
| Whole 3-bed house | Around £2,314 average project | £8,000 to £15,000 (8 to 12 windows) |
| Heat loss cut | Over 60% (Historic England research) | Similar; whole-window U-value 1.2 to 1.6 W/m2K |
| Noise reduction | Better than double glazing (Historic England) | Good, but smaller air gap |
| Listed buildings | Generally no consent needed | Consent usually required |
| Lifespan | 60 to 100+ years with maintenance | Around 25 years for slim-profile units |
| Disruption | Low; original window untouched | High; full removal and refit |
The per-window saving is real but the whole-house picture is what matters. A full set of replacement windows for a semi can cost four to six times a secondary glazing project. Checkatrade’s own guide describes full window replacement as a much larger installation project at a much higher overall cost, and calls secondary glazing the standard solution for listed buildings.
How well does secondary glazing cut heat loss and draughts?
The physics is straightforward. A single-glazed steel window has a U-value of about 5.7 W/m2K; a timber-framed one is around 4.7. Adding a secondary pane with standard glass brings that down to about 2.9, and specifying hard-coat low-emissivity glass pushes it below 2. That is roughly a 60 percent reduction in the heat escaping through the glass, and it lines up with Historic England’s research finding that secondary glazing can reduce window heat loss by over 60 percent and perform as effectively as double glazing, particularly with low-e glass.
On noise, secondary glazing has a genuine edge. The wide air gap, typically 100mm, makes it particularly effective at soundproofing, and Historic England’s research concludes it is even better than double glazing at reducing noise. If you live on a busy road, that is a benefit double glazing struggles to match without specialist acoustic glass.
What will it save on energy bills?
Here is where honesty matters, because no one publishes a neat savings figure for secondary glazing alone. The Energy Saving Trust publishes two nearby figures: draught-proofing around windows, floors and doors could save around £55 a year in Great Britain, and installing A-rated double glazing in an entirely single-glazed semi could save around £85 a year. Secondary glazing sits between those two measures in effect, but the Trust has not published a dedicated figure for it, so treat any website quoting one as guessing.
What is not guesswork is the price of the heat you are losing. Ofgem’s October 2026 price cap put gas unit rates at around 8p per kWh, up from 6.29p last winter, which the End Fuel Poverty Coalition reports as around 27 percent higher year on year and the highest level since early 2023. Every unit of heat kept inside the house this winter is worth more than it was last winter, which is exactly why low-cost heat-loss measures are the highest-urgency October upgrade.
When is double glazing still the better choice?
Secondary glazing is not the answer for every window. Be straight with yourself about these cases.
Your frames are failing. Secondary glazing insulates the glass, not the frame. If your timber frames are rotten or your old uPVC units have blown seals and failing locks, fitting a second pane inside a broken window is polishing a problem. Replacement is the honest fix.
You want the deepest possible thermal upgrade. The best modern double glazing reaches whole-window U-values of 1.2 to 1.6 W/m2K, and Building Regulations cap replacement windows at 1.6. Secondary glazing with low-e glass gets below 2 but rarely beats the best double units. If you are doing a whole-house deep retrofit and the budget stretches, new windows win on pure performance.
You are selling soon and buyers expect it. Estate agents will tell you that buyers notice new windows and rarely notice secondary glazing. That is a market reality, not a physics one, but it affects the payback maths if a sale is on the horizon.
Ventilation still matters. Whichever route you take, remember that a better-sealed home needs controlled ventilation. If condensation is already appearing on cold mornings, read our guide to stopping condensation on windows before you seal anything up.
The listed building and conservation area advantage
This is where secondary glazing goes from being the cheaper option to being the only practical option. Replacing historic windows with double or triple glazing will always require listed building consent, and even inserting double glazing into historic frames usually requires it. Installing reversible secondary glazing, by contrast, does not generally need listed building consent, because the original window is untouched and the work can be undone. The Energy Saving Trust describes it as a non-intrusive way of insulating historic windows from the inside.
The longevity figures favour it too. Historic England notes that secondary glazing can last 60 to 100 years or more with good maintenance, against around 25 years for slim-profile double-glazed units. In a Georgian sash or a Victorian bay, that is a strong argument on its own.
Getting secondary glazing fitted before winter
October is a sensible time to act: installers get booked up as the cold bites, and every week of delay is another week of heat escaping at this winter’s gas prices. A practical sequence:
- Get three quotes. Prices vary by system type and region, so treat the £300 to £500 per-window guide as a starting point and compare like with like: fixed, sliding, hinged and lift-out systems are priced differently.
- Ask about low-e glass. The jump from standard to low-emissivity glass is what takes performance from good to near-double-glazing levels. Confirm the specification in writing.
- Check ventilation. A good installer will ask about trickle vents and extractor fans. If they do not, that is a warning sign.
- Use an accredited installer. Check the company against TrustMark and confirm any guarantees in writing before work starts.
- Mind the grants. Secondary glazing can appear in council-delivered schemes: the Warm Homes: Local Grant lists draught-proofing and double glazing among eligible measures, so it is worth asking your council whether secondary glazing qualifies under its local offer. Our guide to free insulation grants maps the live schemes.
For the wider fabric-first picture, see our breakdown of home insulation savings, which puts window upgrades alongside the measures that cut heat loss fastest.
Frequently asked questions
How much does secondary glazing cost per window in the UK?
Between £300 and £500 per window installed, according to Checkatrade’s 2026 price guide. Simpler fixed panels sit at the lower end; sliding, hinged or lift-out systems that open for cleaning and ventilation cost more. A whole-house project for a typical three-bedroom semi averages around £2,314.
Is secondary glazing as good as double glazing for cutting heat loss?
Close to it, and sometimes effectively equal. Historic England’s research shows secondary glazing can cut window heat loss by over 60 percent and match double glazing when low-emissivity glass is used. The best modern double glazing still wins on pure U-value (1.2 to 1.6 W/m2K whole-window against below 2 for low-e secondary glazing), but the gap is small relative to the price difference.
Does secondary glazing stop draughts?
Yes, noticeably. The sealed secondary frame cuts the air leakage around old sashes and casements, which is often where the worst draughts come from. For the full picture on draught-proofing, the Energy Saving Trust estimates draught-proofing windows, floors and doors saves around £55 a year in Great Britain.
Will secondary glazing cause condensation?
It can move it. Warm moist indoor air that used to condense on the cold single pane may instead condense on the original window now hidden behind the secondary pane, where you cannot wipe it. This is manageable with ventilation: trickle vents, extractor fans in kitchens and bathrooms, and not drying laundry on radiators without ventilation. Our condensation guide covers the room-by-room plan.
Do I need planning permission for secondary glazing in a listed building?
Generally no. Historic England advises that installing reversible secondary glazing does not generally need listed building consent, because the historic window is untouched. Replacing historic windows with double glazing, by contrast, will always require consent. If the work would damage the frame, panelling or shutters, check with your conservation officer first.
Can I fit secondary glazing myself?
For simple magnetic or clip-on kits on smaller windows, yes, and there is no installation cost. For hinged, sliding or lift-out systems, and for any window in a listed building or conservation area, professional fitting is the safer route. Poorly fitted units can trap moisture and underperform.
How long does secondary glazing last?
A long time. Historic England notes secondary glazing can last 60 to 100 years or more with good maintenance, compared with around 25 years for slim-profile double-glazed units. The moving parts and seals need occasional attention, but the glass itself effectively lasts indefinitely.
Sources
- Checkatrade, Secondary Glazing Costs 2026 UK Price Guide (updated July 2026): https://www.checkatrade.com/blog/cost-guides/secondary-glazing-cost/
- Checkatrade, Double Glazing Costs in the UK in 2026 (updated May 2026): https://www.checkatrade.com/blog/cost-guides/double-glazing-cost/
- Building magazine CPD, Specifying secondary windows (U-values): https://www.building.co.uk/cpd/cpd-9-2016-specifying-secondary-windows/5081177.article
- Historic England, Modifying historic windows as part of retrofitting energy-saving measures: https://historicengland.org.uk/advice/technical-advice/retrofit-and-energy-efficiency-in-historic-buildings/modifying-windows-and-doors-in-historic-buildings/modifying-historic-windows-as-part-of-retrofitting-energy-saving-measures/
- Energy Saving Trust, Draught-proofing: https://energysavingtrust.org.uk/advice/draught-proofing/
- Energy Saving Trust, Windows and doors: https://energysavingtrust.org.uk/advice/windows-and-doors/
- End Fuel Poverty Coalition, Ofgem confirms soaring gas prices will hit bills in winter 2026: https://www.endfuelpoverty.org.uk/ofgem-confirms-soaring-gas-prices-will-hit-bills-in-winter-2026/
