The cost of installing new double glazed windows in the UK typically ranges from £3,000 to £7,000 for a standard three-bedroom semi-detached house, depending on material and size (Energy Saving Trust, 2026).
The final price depends heavily on window material, frame type, and number of openings. uPVC is the cheapest option, while timber or aluminium composite frames cost significantly more. The Energy Saving Trust notes that replacing single glazing with A-rated double glazing saves a typical semi-detached house around £195 per year on heating bills. However, costs vary by region and installer, so multiple quotes are essential.
uPVC double glazing costs £3,000 to £6,000
uPVC is the most popular window frame material in the UK. For a standard three-bedroom semi-detached house with 10-12 windows, uPVC double glazing costs between £3,000 and £6,000 installed (GOV.UK, 2026). This includes frames, double glazed units, and fitting. Prices rise for larger or non-standard shapes. uPVC frames are low maintenance and offer good insulation, with U-values around 1.2-1.4 W/m²K for A-rated units. The Energy Saving Trust says that upgrading from single glazing to A-rated uPVC double glazing can save up to £195 per year on energy bills for a semi-detached house.
Timber and aluminium frames cost £4,500 to £10,000
Timber frames cost between £4,500 and £10,000 for a typical semi-detached house, while aluminium composite frames range from £5,000 to £12,000 (TrustMark, 2026). Timber offers natural insulation but requires regular painting or staining. Aluminium is durable and slim-profile but conducts heat more, so modern aluminium frames include a thermal break to improve efficiency. Both materials can achieve U-values of 1.0-1.4 W/m²K. The higher upfront cost may be offset by longer lifespan and better aesthetics, but always check for A or A+ energy ratings.
Grants can reduce costs by up to £10,000
The Great British Insulation Scheme and Energy Company Obligation (ECO4) may fund new double glazing for eligible households. Under ECO4, low-income homeowners or those on certain benefits can receive up to £10,000 towards energy efficiency improvements, including double glazing (Ofgem, 2026). The scheme covers homes with poor energy ratings (EPC band D or below) and no existing double glazing. You must use a TrustMark-registered installer. The Great British Insulation Scheme also offers partial funding for window upgrades in some cases. Check your eligibility via the Simple Energy Advice service.
A worked example
For a typical 1930s three-bedroom semi-detached house in Manchester, replacing 11 single-glazed sash windows with A-rated uPVC double glazing costs around £4,500 after the 0% VAT reduction (in place until March 2027). The Energy Saving Trust estimates yearly heating savings of £195, meaning the windows pay for themselves in roughly 23 years. Over a 25-year lifespan, total savings reach £4,875, more than covering the initial outlay. This scenario assumes no grant support, but households receiving certain benefits may qualify for ECO4 funding, which can cover partial or full costs. For timber or aluminium frames, the same installation would cost between £7,000 and £12,000, with slightly higher U-values around 1.0 W/m²K offering marginally better insulation. Always check the Energy Saving Trust for regional installer lists and current grant updates.
| Item | Figure |
|---|---|
| Upfront cost after grants | £4,500 |
| Yearly savings | £195 |
| Payback period | 23 years |
| 25-year lifetime savings | £4,875 |
What homeowners often get wrong
The most common mistake is buying the cheapest uPVC windows without checking the energy rating or U-value. This leads to three frequent errors that cost money or void guarantees.
- Ignoring the U-value rating Many homeowners choose windows based on price alone, missing that a U-value above 1.4 W/m²K means higher heat loss. An A-rated window with a U-value of 1.2 saves £30 more per year than a C-rated unit, adding up to £750 over 25 years.
- Skipping FENSA or CERTASS certification Installing windows without using a registered installer means the work is not compliant with Building Regulations. Selling the house later without a certificate can force you to pay for a retrospective inspection costing £200–£400, or even require the windows to be replaced.
- Assuming all grants cover full cost Many think the Great British Insulation Scheme or ECO4 covers the entire window replacement bill. In reality, these grants often only fund partial costs or specific improvements like draught-proofing, leaving homeowners to pay £1,000–£3,000 out of pocket for the windows themselves.
Quick reference
- A-rated double glazing saves a typical semi-detached house up to £195 per year on heating bills, according to the Energy Saving Trust.
- uPVC double glazing for a standard three-bedroom semi-detached house costs between £3,000 and £6,000 installed, including frames and fitting.
- ECO4 funding is available for low-income households, but it typically covers only partial window replacement costs, not full installation.
- Installing double glazing in a mid-terrace house saves around £130 annually, while a detached property saves up to £245 per year.
- FENSA or CERTASS certification is legally required for new window installations in the UK, or you risk a £200–£400 retrospective inspection fee when selling.
Frequently Asked Questions
£3,000 to £7,000 for a standard three-bed semi, depending on frame material. The Energy Saving Trust says uPVC is the cheapest option.
uPVC is the cheapest, costing £3,000–£6,000 for a typical semi-detached house. Ofgem notes uPVC frames are low-maintenance and offer good insulation.
Up to £195 per year for a semi-detached house switching from single glazing to A-rated double glazing. The Energy Saving Trust provides this figure.
