The Short Answer
On our estimates, a replacement uPVC double-glazed casement window costs £450 to £900 supplied and fitted, so a typical semi with 9 windows is about £4,050 to £8,100. Aluminium is £800 to £1,600 a window and timber £900 to £1,800. Sash and bay windows cost more. Expect one to three days for a typical house.
Whoever fits them, the windows have to meet the building regulations, and you should get a certificate to prove it. The easy route is an installer registered with a competent person scheme (FENSA, CERTASS, Assure, Blue Flame, Certsure or NAPIT): they register the job and the certificate comes to you.
New windows cost calculator
Prices a whole house of replacement windows by count, frame and style. Pick your house for a typical count, then adjust.
Estimated total
£4,050 to £8,100
| 9 casement windows, uPVC | £4,050 to £8,100 |
Window prices by frame and house
| Frame | Per window, fitted | Semi (9 windows) | Detached (12 windows) |
|---|---|---|---|
| uPVC | £450 to £900 | £4,050 to £8,100 | £5,400 to £10,800 |
| Aluminium | £800 to £1,600 | £7,200 to £14,400 | £9,600 to £19,200 |
| Timber | £900 to £1,800 | £8,100 to £16,200 | £10,800 to £21,600 |
| Alu-clad timber or composite | £1,100 to £2,000 | £9,900 to £18,000 | £13,200 to £24,000 |
| Style | Price compared with a casement | uPVC, per window |
|---|---|---|
| Casement | Baseline | £450 to £900 |
| Tilt and turn | 1.1 to 1.25 times | £500 to £1,150 |
| Sliding sash | 1.4 to 1.6 times | £630 to £1,450 |
| Bay (3 to 5 sections) | 2.5 to 3.5 times | £1,150 to £3,150 |
uPVC, aluminium, timber or composite?
| Frame | Per window, fitted | What the Energy Saving Trust says |
|---|---|---|
| uPVC | £450 to £900 | Tends to be the cheapest; no regular maintenance; can be recycled |
| Aluminium | £800 to £1,600 | Slim and long lasting; can be recycled |
| Timber | £900 to £1,800 | More sustainable, and with maintenance can last far longer than uPVC; often used in conservation areas |
| Alu-clad timber or composite | £1,100 to £2,000 | An inner timber frame covered in aluminium or plastic |
The frame material matters less to warmth than you'd think: the Energy Saving Trust says high-performing windows come in all of them. Compare the energy rating instead. Windows are rated A++ to E under the British Fenestration Rating Council scheme, which rates the whole window for heat loss, draughts and solar gain. A U-value on its own isn't the whole story.
Building regulations for replacement windows
Replacing a whole window, frame and all, is controlled work in England. The new window must:
- Meet the energy standard: a U-value of 1.4 W/m²K or better, or a Window Energy Rating of band B or better (Approved Document L, Table 4.2).
- Keep the ventilation: if the old windows had trickle vents, the new ones need them, no smaller. If they didn't, new airtight windows can make the house stuffier, so Approved Document F asks for trickle vents of 8,000mm² in living rooms, bedrooms and kitchens and 4,000mm² in bathrooms, unless the house has other ventilation.
- Keep escape routes: a window big enough to serve as a fire escape must stay at least as good when it's replaced. An escape window needs an opening of at least 0.33m², at least 450mm high and wide, with the bottom no more than 1,100mm above the floor (Approved Document B).
- Use safety glass where people could fall into it: glazing below 800mm from the floor, and in doors and side panels below 1,500mm (Approved Document K).
Replacing only the glass in an existing frame isn't covered by these energy rules: see misted glass replacement.
Do you need planning permission?
- Not usually for windows of similar appearance to the house (Planning Portal). A new bay window is treated as an extension.
- New upper-floor windows in a side wall must be obscure glazed and either fixed or opening only above 1.7m from the floor.
- In a conservation area, the council may have removed these rights with an Article 4 direction; check before changing timber to uPVC.
- Listed buildings need listed building consent. See sash windows for the repair-first approach and secondary glazing.
- Flats: ask the freeholder or managing agent first.
Getting quotes and paying
- Get at least three quotes (the Energy Saving Trust's advice), each for the same count, styles, opening sashes and glass.
- Ask what's included: removing the old windows, making good inside and out, sills, trickle vents and the certificate.
- Get the energy rating in writing.
- Expect a deposit. Windows are made to measure, and the Glass and Glazing Federation says around 20% upfront is typical. Citizens Advice says not to agree to more than 25%, and to pay by credit card: for work costing £100.01 to £30,000, section 75 gives you a claim against the card company if it goes wrong.
- Know where to complain. Glass and Glazing Federation members follow a consumer code with a free dispute service.
- Ignore the pressure. I'd walk away from any "today only" discount; a fair price doesn't need one.
Only want warmer glass in good frames? Read is double glazing worth it first.
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Frequently asked questions
How much on average do new windows cost?
On our estimates, £450 to £900 each for a standard uPVC casement, fitted, so about £4,050 to £8,100 for a semi's 9 windows.
How much do new windows cost for a 3-bed house?
About £4,050 to £8,100 for 9 uPVC windows on a typical semi, fitted, on our estimates. Aluminium and timber cost more.
How much to replace all windows in a 4 bed house?
For a typical detached house with 12 windows, about £5,400 to £10,800 in uPVC, on our estimates.
How much does it cost to replace one window in the UK?
£450 to £900 for a standard uPVC casement, fitted, £800 to £1,600 in aluminium and £900 to £1,800 in timber, on our estimates. A single window can cost more per window than a whole house's worth.
How much would 7 windows and 2 doors cost?
In uPVC, about £4,550 to £8,900 on our estimates, using our uPVC door prices. Composite doors cost more.
Do replacement windows need building regulations approval?
Yes. Use an installer registered with a competent person scheme (FENSA, CERTASS, Assure, Blue Flame, Certsure or NAPIT), who certifies the work, or apply to building control. You should get a certificate.
Do new windows need trickle vents?
If the old ones had them, yes, no smaller. If they didn't, Approved Document F asks for trickle vents (8,000mm² in habitable rooms) unless the house is ventilated another way.
How long does it take to replace windows?
Usually one to three days for a typical house.
How we priced thisView sources (11, 7 official)
Rules come from the legislation and official guidance, read at source. Prices are our estimates: we check them against trade price data, retailer shelf prices and specialists' price lists, then build them up from their parts so the totals add up. Below are the sources behind the page; the trade price guides we only compare against aren’t listed. Where sources disagreed, we've said so. More on our method.
- OfficialApproved Document L: Conservation of fuel and power, Volume 1 Dwellings (2021 edition incorporating 2023 amendments), GOV.UK. Checked 16 Oct 2026.
- OfficialApproved Document F: Ventilation, Volume 1 Dwellings (2021 edition; 2026 edition from 24 March 2027), GOV.UK. Checked 14 Oct 2026.
- OfficialApproved Document B: Fire safety, Volume 1 Dwellings (2019 edition incorporating 2020 to 2026 amendments), paras 2.10, 2.16 and 2.18 to 2.20, GOV.UK. Checked 16 Oct 2026.
- OfficialApproved Document K: Protection from falling, collision and impact (2013 edition), Section 5, GOV.UK. Checked 15 Oct 2026.
- OfficialThe Building Regulations 2010, Schedule 3: self-certification schemes (para 16, roof coverings), legislation.gov.uk. Checked 15 Oct 2026.
- OfficialDoors and windows: planning permission and building regulations, Planning Portal. Checked 15 Oct 2026.
- IndustryEnergy efficient windows and doors (updated 20 May 2026), Energy Saving Trust. Checked 15 Oct 2026.
- IndustryPaying for your home improvement (15 May 2020), Glass and Glazing Federation. Checked 15 Oct 2026.
- OfficialBefore you get work done on your home (England), Citizens Advice. Checked 15 Oct 2026.
- IndustryHow much do new windows cost?, Everest. Checked 15 Oct 2026.
- Trade guideNew windows cost guide and calculator, Checkatrade. Checked 15 Oct 2026.
