Getting a straight answer on double glazing costs is genuinely hard. Every company quotes differently, the “half price today” deals cloud the real figures, and the exact same window can cost hundreds of pounds more depending on your postcode. So here’s the honest version, with real numbers you can actually plan around.
The average UK double glazing job costs around £4,500. A single uPVC casement window comes to about £650 fitted. And doing a whole average semi lands somewhere between £4,000 and £10,000, driven mostly by how many windows you replace and which frame material you choose.
This guide covers everything – prices by material, by style and by house size, plus what installation adds, how much you’ll save, and the grants worth knowing about. But it goes further than most. You’ll get the true 25-year cost once maintenance is in the mix, the cheap glass upgrade almost nobody mentions, why national quotes run 15-30% high, and what new windows do to your EPC rating, which matters more from 2026 than it ever has. Every figure here is indicative, so confirm it with a proper survey – but you’ll know roughly what you should pay before anyone knocks on your door.
- The average job costs around £4,500, but a whole semi ranges from £4,000 to £10,000 depending on frames and window count.
- uPVC is the value pick at roughly £650 per window fitted, while timber can more than double that at £900 to £1,800.
- Installation is 20-40% of your bill, with fitting labour alone at £200 to £400 per window.
- Only about 15% of households qualify for any grant, so most people pay for the work themselves.
- Doing every window at once is cheaper per window, because you share the survey, scaffolding and disposal costs across one job.
All prices below are fully fitted and indicative for 2026. Confirm with a survey and live quotes, as figures shift by supplier, region and season.
Cost per window by frame material
The frame you pick is one of the two biggest things that move your bill. The other is simply how many windows you’re doing. Here’s how the materials compare for a standard casement, fully fitted.
| Frame material | Per window (fitted) | Compared to uPVC |
|---|---|---|
| Fixed (non-opening) | £200 – £400 | Cheapest |
| uPVC casement | £400 – £1,000 (~£650 avg) | Baseline |
| Aluminium | £700 – £1,400 | +25% to +40% |
| Composite | Around timber level | Premium |
| Timber | £900 – £1,800 | +50% to +110% |
uPVC is the sensible default for most homes. It’s the cheapest framed option that still opens, it needs almost no upkeep, and at around £650 a window it keeps a whole-house project affordable. The downside is looks – the frames are chunkier than aluminium, and some people find them less characterful than real wood.
Aluminium costs 25-40% more. For that you get slim frames and more glass, which suits modern extensions and big openings where you want light flooding in. It’s tough, it won’t rot, and it barely needs a thought once fitted.
Timber is the priciest, sometimes more than double uPVC, and it needs repainting or re-staining to keep the weather out. But it lasts longest and looks right on period and listed homes. As a rough guide, a timber casement at 600x900mm comes in around £925 supplied and fitted.
Composite sits at the premium end too, roughly at timber level. It marries a low-maintenance outer skin with a timber-effect finish – the look of wood without the endless repainting. Prefer to think in area? Standard uPVC works out at roughly £150 to £300 per square metre installed.
Cost per window by style
Style matters nearly as much as material. A plain casement is the cheapest thing to make and hang. Anything with a sliding mechanism, a bigger footprint or more moving parts costs more.
| Window style | Fitted price | Notes |
|---|---|---|
| Fixed (non-opening) | £200 – £400 | No moving parts, cheapest |
| Casement (uPVC) | £400 – £950 | Most common UK style |
| Sash (uPVC) | £900 – £1,500 | Sliding mechanism adds cost |
| Aluminium (any style) | £800 – £1,600 | Slim frames, modern look |
| Timber (any style) | £1,200 – £2,000+ | Period and heritage homes |
| Bay or bow | Quoted as full assembly | Always priced higher |
Casement windows are the standard and the cheapest. They hinge at the side or top and swing outwards, and they suit almost any property. Sash windows cost more because of the sliding mechanism and counterbalance system inside them. A uPVC sash that mimics a traditional timber one runs £900 to £1,500 – a big step up on a casement, but far cheaper than the real timber version.
Bay and bow windows aren’t priced per pane. They’re built as one large angled assembly, so they sit well above a standard window – and if your bay carries any structural load, expect more on top.
Add-ons that change the price
A handful of extras appear on most quotes, and they stack up fast.
- Heritage sash or Georgian astragal bars (the bars that split glass into smaller panes): +£100 to £300 per window.
- Coloured or woodgrain foil – Anthracite Grey is the runaway favourite in 2026: +10-20%.
- Double to triple glazing: +£150 to £300 per window, roughly a 15-25% uplift.
That triple upgrade buys you about 20% better heat retention than standard double glazing. It’s a real improvement, but the money for it usually comes from your own pocket.
Whole-house double glazing costs
Most people don’t buy one window. They do the lot. Here’s what a full replacement looks like, fully fitted, by property size.
| Property | uPVC | Aluminium or mixed |
|---|---|---|
| 2-bed | From ~£5,320 | Higher |
| 3-bed semi (8-10 windows) | £4,000 – £6,000 (up to £8,000) | £7,000 – £10,000 |
| 4-bed | ~£11,000 | Higher |
Across all materials, a three-bedroom home can land anywhere from £4,000 to £16,000. That huge spread is exactly why your material and style choices matter so much – a uPVC semi and a timber-sash semi are two completely different bills. A typical home with 8-10 windows usually falls in the £4,000 to £12,000+ bracket.
The 3-bed semi in detail
A three-bed semi is the most common UK home, and it usually has 8-10 windows. In uPVC, budget £4,000 to £6,000 for the full house – a mix of bedroom casements, living-room windows, and maybe a bigger picture window or bay downstairs. You’ll hit the top of that range if you’ve got more openings or larger-than-average glass. Switch to aluminium and you’re at £7,000 to £10,000. Go full timber sash and you can sail past £16,000.
The money-saving point most people miss
Doing every window in one go is cheaper per window than replacing them piecemeal. You pay once for the survey, once for the scaffolding, and once for waste disposal, and those costs spread across the whole job instead of hitting you on every single window. Replace four now and four next year, and you’ll typically pay several hundred pounds more overall – plus you risk callout fees and minimum-order surcharges each time. If your windows are all a similar age and heading towards the end of their life, one big project wins comfortably.
What installation actually costs
Installation isn’t a hidden extra. It’s baked into the fitted prices above. But it helps to know how much of the bill it represents. Fitting is roughly 20-40% of the total, charged per window. A proper fitted price includes:
- The window unit itself.
- Fitting labour, at around £200 to £400 per window depending on size, access and complexity.
- Removal and disposal of your old windows.
- Sealing and finishing.
- Your FENSA or CERTASS certificate (more on that shortly).
Scaffolding, access gear and disposal usually spread across the whole job rather than landing on each window – another reason a single larger project is better value. Upper-floor windows that need scaffolding always cost more to reach than ground-floor ones.
Is it “supply and fit” or “supply only”? Supply-only prices look far cheaper, but you’ll then have to find your own fitter and handle building regulations yourself. For most people, supply and fit is the sensible route.
Regional price variation
Where you live moves the price more than you’d think, and it comes down to local labour rates and demand.
- London and the South East: typically 15-25% above the national average.
- The North, and parts of Wales and Scotland: usually below it.
So the same three-bed semi that costs £5,000 in the North East could push past £6,000 in the South East for identical windows. Get quotes from a few local, FENSA-registered installers rather than assuming a national headline applies to your street.
The argon gas upgrade: the cheap win almost everyone skips
Here’s a genuine money-saver that rarely makes the sales pitch. Standard double glazing is two panes of glass with a gap between them. Fill that gap with argon gas instead of plain air and you cut heat loss noticeably – argon is denser than air, so heat struggles to move through it.
The clever bit is the price. Argon adds only a small amount per window, yet it lifts a window’s thermal performance enough to nudge it into a better energy band. Most reputable A-rated windows now include it as standard, but not every quote does.
Check whether your quote specifies argon-filled units. If it says air-filled, ask why. It’s one of the cheapest performance gains going – a few pounds per window that cuts heat loss through the glazing by over 30% – and skipping it to save a little is a false economy across the 20-plus years you’ll own the glass.
Energy savings and payback
New windows do more than smarten up the front of your house. They cut your bills and your draughts. But be realistic, because your savings hinge on what you’re replacing. If you’re upgrading from single glazing, the Energy Saving Trust puts the yearly savings at:
- Semi-detached: around £140 a year.
- Detached: around £235 a year.
Another 2026 estimate lands at roughly £195 a year for a typical semi at current price caps. On top of the cash, you’ll get around a 40% cut in outside noise and save roughly 330kg of carbon a year – a real win for comfort and for the planet.
Now the honest caveat. If you’re replacing old double glazing rather than single, the bill savings shrink a lot. The bigger benefits then come from killing draughts, clearing that misted-up look of failed seals, and quieter rooms – genuine quality-of-life gains, just not headline cash. On pure energy savings, a full uPVC job on a semi can take a couple of decades to pay for itself. So treat windows as an investment in warmth, quiet and home value as much as a bill-cutter. The money side is a bonus, not the whole story.
Total cost of ownership: uPVC vs timber over 25 years
Most guides stop at the upfront price, and that’s a mistake, because the sticker cost and the true cost aren’t the same once you factor in maintenance and lifespan. Let’s do the sum properly.
Costs less upfront and asks for almost nothing over its life – the odd wipe-down and a squirt of hinge lubricant. Budget near £0 in maintenance. It lasts 20-25 years, then you replace it.
Costs far more upfront and needs repainting or re-staining every 3-5 years to fend off rot. In return it lasts 30-60 years – two to three times longer than uPVC.
Here’s the interesting part. Spread everything – purchase plus upkeep – across the full lifespan, and the gap between uPVC and timber narrows far more than the upfront prices suggest. Timber’s longer life partly cancels out its higher cost and maintenance.
So which wins? For most people staying 10-15 years, uPVC is the clear value choice – lower cost, zero hassle, done. But if you’re in a period home you’ll keep for decades, and you’ll actually do the maintenance, timber’s total cost of ownership is more competitive than it looks, and it’ll likely still be standing long after a uPVC set needs ripping out. Choose on how long you’re staying and whether you’ll keep up the upkeep, not on the upfront number alone.
How long double glazing lasts
Windows are a long-term buy, and lifespan varies a lot by material. This is where paying more upfront can genuinely pay off.
- uPVC: 20-25 years.
- Aluminium: 25-30+ years.
- Timber: 30-60 years (with regular maintenance).
One thing worth flagging: the sealed glass units can fail after 15-20 years even when the frames are perfectly fine. You’ll spot it as misting or condensation between the panes. The good news is you don’t always need whole new windows – which brings us neatly to repair versus replacement.
Material lifespans and sealed-unit repair costs fact-checked 28 Jun 2026Sealed unit repair vs full window replacement
If your double glazing has failed – condensation between the panes, blown seals, or draughts round the edges – you don’t automatically need to bin the whole window.
Just the glass, kept in your existing frame. Makes sense when the frames are still sound – no warping, cracking or discolouration – and the only problem is misted glass.
The right call when the frames are damaged, you want a different style, or you’re jumping to modern A-rated performance. New glass alone won’t improve an old frame, and some won’t accept high-spec units.
A handy rule of thumb: if more than half your windows need new sealed units, it’s often cheaper to replace all the windows at once. You get a bulk discount, a consistent finish, and a single warranty across the lot.
Signs you need new windows
Not every problem means a full replacement. Knowing which faults are repairable and which spell the end saves you spending thousands you didn’t need to – or dragging your feet on a replacement that’s quietly costing you in wasted heat.
- Condensation between the panes – the sealed unit has failed and the gas has leaked. Not repairable; needs a new unit (£70-£150) or a new window if the frame is also going.
- Draughts you can feel with a hand near the edge – often failed seals (£20-£40 to swap) or a warped frame.
- Stiff opening, closing or locking – usually worn hinges (£30-£50) or a warped frame.
- Rising energy bills with no other cause – your windows may be leaking heat.
- More outside noise than there used to be – the insulation is dropping off.
- Visible damage – cracks in uPVC, rot in timber, pitting on aluminium.
- You don’t know how old they are – if they’re 20+ years, they’re likely due.
Double vs triple vs secondary glazing
If you’ve decided to upgrade, you’ve got three routes. Here’s the plain-English version of each.
Double glazing
Two panes with an insulating gap, usually argon-filled. It’s the UK standard, and rightly so – it hits the sweet spot of cost and performance. For most homes, A-rated double glazing with argon is the best-value choice, full stop.
Triple glazing
Three panes, two gaps, better insulation. It costs £150 to £300 more per window than double for roughly 20% better heat retention. The honest catch is that the extra energy saving is small – often only £20 to £40 a year across a whole house – so the payback on the upgrade alone stretches past 20 years. It earns its place on new builds (where the marginal cost is lower), very exposed properties, or rooms where noise is the enemy. For a standard retrofit, double glazing with argon usually makes more sense.
Secondary glazing
This adds a second pane inside your existing window rather than replacing it. It costs £100 to £300 per window and is the go-to for listed buildings and conservation areas where modern double glazing isn’t allowed. It’s less efficient than proper double glazing, and the extra pane can slightly dull the light and complicate ventilation. But it’s cheaper, it rarely needs planning permission, and on noise it can actually beat some double glazing. For period homes where your hands are tied, it’s a genuinely useful option.
Your EPC rating, mortgages and rental rules
This is the angle most price guides skip, and it’s fast becoming one of the most important. Your EPC (Energy Performance Certificate) rates your home’s efficiency from A (best) to G (worst), and windows feed straight into that score. Upgrading tired glazing can lift your EPC by several points, and that matters for three real reasons in 2026.
- Selling. Buyers and surveyors increasingly look at the EPC. A better rating helps your home show well and can support the asking price.
- Mortgages. More lenders now offer “green mortgage” deals with sharper rates for efficient homes, and they use the EPC to decide. A higher band widens your options.
- Renting it out. If you’re a landlord, minimum EPC standards for rented homes are tightening. Efficient windows help you clear the bar and keep the property lettable.
The practical takeaway: if you plan to sell, remortgage or let within a few years, factor the EPC uplift into your decision. New windows aren’t only about warmth and bills – they help protect the value and lettability of your biggest asset.
Does double glazing add value to your home?
In short, yes. New double glazing typically adds 5-10% to a home’s value, with the biggest gains where you’re replacing failing single glazing or units over 20 years old. The value comes from three things buyers notice: a better EPC, the reassurance they won’t face replacement costs soon, and plain kerb appeal – homes with fresh, quiet, draught-free windows show better at viewings, especially on busy roads. The one place the return shrinks is upgrading already-decent 10-year-old double glazing to triple, where the resale bump rarely covers the cost.
FENSA and CERTASS explained
You’ll see these two names on every reputable quote, so here’s what they mean. FENSA and CERTASS are the government-approved schemes that let a window installer self-certify that their work meets building regulations.
Use a registered installer and you get a certificate proving the work is compliant, with no separate council inspection needed. Use an unregistered fitter and you’ll have to arrange building control sign-off yourself (£200-£400), and a missing certificate comes back to bite you when you sell – buyers’ solicitors ask for it, and getting one after the fact is a hassle and a cost. The rule is simple: only use a FENSA or CERTASS registered installer. Ask for proof, and check their registration before you sign anything.
VAT on double glazing: you pay the full 20%
Here’s one that catches people out. You may have heard energy-saving home improvements get 0% VAT. That’s true for solar panels, insulation and heat pumps – but it does not apply to double glazing.
Windows are standard-rated at the full 20% VAT. Every price in this guide already includes it, which is exactly what you’ll pay on a normal residential job. So if an installer hints they can supply your windows VAT-free, they’re not applying the rules correctly. On a £5,000 job, that VAT is £1,000, and it’s a legitimate, unavoidable part of the bill.
Grants for double glazing in 2026
Let’s be straight, because there’s a lot of confusion here. Only around 15% of households qualify for any funding at all, so most people pay for their windows themselves. Grants are means-tested and follow a “fabric-first” rule – your home usually needs proper insulation before windows get funded, since glazing counts as a secondary measure. Here’s the 2026 landscape. Verify all of this live before relying on it, as the schemes have shifted a lot.
- Warm Homes: Local Grant (England) – the main scheme to know. Up to £30,000 combined for fabric and heating, including up to £15,000 for fabric measures such as glazing. You’ll need a household income under £36,000 and an EPC of D to G. It’s delivered by councils and open until 2028.
- Warm Homes Plan – a £6.6bn national push aiming to upgrade 5 million homes.
- ECO4 – the status is genuinely unclear right now. Some sources say it closed on 31 March 2026, others say it’s been extended to 31 December 2026 with no successor. Check the current position before assuming anything.
- Scotland – Home Energy Scotland offers an interest-free loan (not a grant) up to £8,000, or £9,500 in rural areas, but for single-glazing upgrades only.
- Wales – the Nest scheme provides free improvements for eligible low-income homes.
- Northern Ireland – Affordable Warmth offered up to £7,500 for incomes under £23,000, but it closed at the end of March 2026.
Because grant rules change so often, treat this as a starting point, not gospel. Check your local council’s website and the official scheme pages for the live picture – and do it before you commit to a quote, since a successful application could reshape your whole budget.
Why national brand quotes are often inflated
Here’s something the big names won’t tell you, and it’s worth real money. National installers frequently quote 15-30% more than local FENSA-registered firms for what is essentially the same window. That premium covers heavy advertising, branded products and big-company overheads. It also leaves deliberate room to “discount.” You’ve probably heard the routine: a high opening price, a phone call to “the manager,” then a dramatic “today only” offer if you sign on the spot. Here’s how to use that knowledge.
- Never sign on the day. A legitimate discount will still be there next week. The pressure exists purely to stop you shopping around.
- Get the local comparison first. Local installers using the same glass and hardware often come in far cheaper for identical performance.
- Treat the “manager discount” as the real number, and assume there’s still room below it.
None of this means national brands are bad – some people value their aftercare and insurance-backed guarantees, which have genuine worth. But you should never pay the first number a national salesperson shows you.
How to compare quotes properly
The single most effective way to cut your cost is to get at least three quotes for the exact same specification. Prices for identical work vary by 30-50% between companies, so this one step can save you hundreds or thousands. To compare fairly, make sure every quote spells out:
- Frame material, glass type (including argon fill), and energy rating.
- The exact number, size and style of windows.
- Installation labour, and whether scaffolding is included.
- Removal and disposal of the old windows.
- Any “making good” – the plastering and finishing around the new frames.
- The FENSA or CERTASS certificate.
- The warranty length and whether it’s insurance-backed.
A vague quote is a red flag. If a company won’t itemise, they’re leaving room for surprise add-ons once the work starts. A few extra ways to save:
- Time it right. Installers are quietest in late autumn and winter. Booking off-peak can shave 10-15% as firms compete to fill their diaries.
- Bundle doors with windows. Ordering both together from one installer often saves 5-10% and gives you a matching finish.
- Haggle on the whole-house job. On a big order, installers expect to negotiate. Once you’ve got three quotes, tell your preferred firm the lowest and ask them to match it – many will come within 5-10% to win the work.
How to pay: cash, personal loan or installer finance
If you’re not paying cash, how you borrow makes a real difference to the final cost. Let’s compare honestly.
Installer finance is convenient – it’s offered right there in your living room, sometimes with a tempting “0% for 12 months” or “buy now, pay later” hook. But read the rate carefully. Once any interest-free period ends, installer finance rates commonly sit around 12-16% a year, which is expensive money. The 0% deals can genuinely be worth it if you’ll clear the balance inside the offer window – but only then.
A personal loan from a bank usually undercuts installer finance comfortably, often around 6-7% a year. If you need to spread the cost, this is nearly always the cheaper route. Paying in cash beats both – no interest, and often more room to haggle the headline price down.
So the order of preference is clear: pay cash if you can; if not, a personal loan usually beats installer finance; and only take a 0% installer deal if you’re certain you’ll clear it before the interest kicks in. Whatever you do, don’t let a “great finance offer” distract you from the price of the windows – a cheap loan on an overpriced job is still a bad deal.
Frequently asked questions
How much does double glazing cost for a 3-bed house?
A three-bed semi with 8-10 windows costs £4,000 to £6,000 in uPVC, or £7,000 to £10,000 in aluminium. Prices include supply, fitting and 20% VAT. A three-bed detached costs more, thanks to extra windows and more exposed wall space.
What’s the cheapest type of double glazing?
uPVC casement windows are the cheapest at £400 to £950 fitted. Fixed, non-opening uPVC windows are cheaper still at £200 to £400, but most rooms need at least one opening window for ventilation.
Is triple glazing worth the extra cost?
For most homes, no. It costs 20-40% more than double glazing but saves only about £20 to £40 a year on energy, so the payback runs past 20 years. It makes sense for new builds, very exposed homes, or rooms where noise is the priority. A-rated double glazing with argon is the best value for most people.
Can I get free double glazing?
Possibly, through the Warm Homes: Local Grant in England (up to £30,000 combined, with no household contribution). You’ll need an income under £36,000 and an EPC of D to G. Wales, Scotland and Northern Ireland run separate schemes with different rules. Only around 15% of households qualify for any funding.
How long does double glazing last?
uPVC lasts 20-25 years, aluminium 25-30+ years, and timber 30-60 years with maintenance. The sealed glass units can fail after 15-20 years even if the frames are fine, and replacing just the glass costs £70 to £150 per window.
Do I pay VAT on double glazing?
Yes, the full 20%. Windows don’t qualify for the 0% energy-saving-materials rate that covers solar panels, insulation and heat pumps. All prices in this guide include VAT.
Do I need to replace all my windows at once?
No, you can phase it. But bulk orders attract a discount and share the survey, scaffolding and disposal costs, so doing the lot together is cheaper per window. If more than half your windows are failing, it’s usually the smarter move.
Does double glazing add value to my home?
Typically 5-10%, with the biggest gains where you’re replacing failing single glazing or units over 20 years old. A better EPC, the promise of no imminent replacement costs, and stronger kerb appeal all help at viewings.
How do I know if I need new windows or just new glass?
If the frames are sound and only the glass is misted, replacing the sealed unit (£70-£150) is enough. If the frames are warped, cracked or rotten, or you want a new style or better efficiency, go for full replacement.
Should I use a national brand or a local installer?
Local FENSA or CERTASS registered firms often quote 15-30% less than national brands for the same window. National brands may offer stronger aftercare and insurance-backed guarantees, so weigh both – but always get at least one local quote to compare.
Double glazing in 2026 is a sizeable investment, but the numbers are easy to plan for once you know the levers. Budget around £650 per window for uPVC, or £4,000 to £10,000 for a full semi, and remember that the frame material and window count drive most of the difference.
uPVC is the value pick for the vast majority of homes, with aluminium worth the premium for slim frames and big glass, and timber reserved for period homes you’ll keep for decades. Whatever you choose, get three like-for-like quotes from local FENSA or CERTASS registered installers, check the glass is argon-filled, and never sign on the day – the “today only” discount will still be there next week.
This guide was fact-checked on 28 June 2026. Verified against multiple current UK sources: the per-window and whole-house cost ranges by material, style and property size; that double glazing is standard-rated at 20% VAT and excluded from the 0% energy-saving-materials relief (GOV.UK VAT Notice 708/6); the FENSA/CERTASS self-certification role; material lifespans and sealed-unit repair costs; and the 2026 grant landscape, including the Warm Homes: Local Grant and the genuinely unsettled status of ECO4.
Prices, grant rules and energy-saving figures change frequently and vary by home – always get at least three like-for-like quotes and confirm current figures before relying on any number here.
