Sash windows costs UK 2026

The average cost to install sash windows in a UK home in 2026 is £2,400–£6,800 per window (including fitting and VAT)

Poorly performing single-glazed sash windows can account for up to 18% of a home’s total heat loss, according to 2026 GOV.UK Energy Price Guarantee data. Replacing them is one of the most effective ways to cut energy bills and improve comfort. For a standard-sized timber sash window (1,200 x 1,200 mm) installed in a semi-detached house, you should expect to pay between £2,400 and £6,800 per window, including fitting and VAT.

The final cost depends on three main factors: the material you choose (timber, uPVC, or aluminium), the glazing type (single, double, or triple), and whether you need a full replacement or a refurbishment of the existing frame. These figures are for a standard opening. If your windows are larger or non-standard shapes, such as bays or arches, you can expect the unit cost to rise by 30–60%.

Quick numbers cost breakdown by material and glazing for 2026

Lifespan data comes from DESNZ Energy Consumption in the UK 2026. Installation cost averages are based on MCS Register data. VAT at 0% on energy-saving materials applies under VAT Notice 708/6.

Timber sash windows cost the most upfront but last longest — expect £3,200–£6,800 per window in 2026

Timber is the traditional choice for sash windows and the most expensive option. Hardwood species like oak and mahogany push costs to the upper end of the range, while softwoods such as pine and spruce are cheaper. The Energy Saving Trust 2026 report states timber windows can last 40–60 years with proper maintenance, compared to 20–30 years for uPVC.

Adding double glazing to a timber sash adds roughly £600–£1,200 to the base cost. However, it significantly improves thermal performance, reducing U-values to 1.2–1.8 W/m²K, according to British Fenestration Rating Council 2026 data. Remember that timber requires repainting every 5–7 years, which adds £150–£300 per window over its lifetime.

uPVC sash windows are the cheapest option — £2,400–£4,200 per window in 2026

uPVC is the most common material for cost-conscious homeowners. A double-glazed uPVC sash window typically costs between £2,400 and £4,200 per window, including fitting and VAT. The Glass and Glazing Federation 2026 notes that uPVC is less durable than timber but requires no painting and is resistant to rot, with a lifespan of 20–30 years.

One trade-off is appearance. uPVC windows are less effective at replicating the slim sightlines of timber sashes, which can affect the look of period properties. On cost alone, a uPVC double-glazed sash is roughly 30% cheaper than an equivalent timber double-glazed sash.

Aluminium sash windows cost £3,000–£5,500 per window and offer the best thermal performance in 2026

Aluminium sash windows are strong, slim, and can achieve U-values as low as 1.0 W/m²K, according to the DESNZ Product Characteristics Database 2026. They sit between uPVC and high-end timber in price, costing £3,000–£5,500 per window installed, with a lifespan of 35–50 years and minimal maintenance.

Aluminium windows typically include a thermal break to reduce heat loss, and many models are fully recyclable. They are a good choice for modern homes or where a contemporary look is desired, but may not suit traditional period properties.

The direct answer what a sash window costs in the UK in 2026

The cost of a sash window in 2026 ranges from £2,400 to £6,800 per window, including fitting and VAT. The average homeowner spends around £4,000 on a double-glazed timber unit. The key factors are material, glazing type, and whether you need a full replacement or a refurbishment.

Refurbishment can be 40–50% cheaper, at £1,200–£3,000 per window. VAT is 0% on energy-saving materials, including double and triple glazing, until 2027 under the VAT Notice 708/6 scheme, which reduces the final cost by 20%. These figures are for a standard 1,200 x 1,200 mm window. Larger sashes or specialist designs, such as sliding bays, will increase costs by 50–100%.

double glazing grants and schemes 2026

How to verify your sash window installer and eligibility for grants in 2026

To qualify for the 0% VAT on energy-saving materials, you must use an MCS-certified installer, as required by GOV.UK VAT Notice 708/6. The Energy Company Obligation (ECO4) scheme can provide grants for low-income homeowners, covering up to 100% of replacement costs for inefficient single-glazed sashes. Eligibility is based on household income and property EPC rating, as outlined in Ofgem ECO4 Guidance 2026.

For timber windows, look for FENSA or CERTASS certification to ensure compliance with Building Regulations Part L, which covers the conservation of fuel and power. Always check the installer’s TrustMark registration for consumer protection, and obtain at least three quotes before proceeding.

When to repair rather than replace your sash windows — and what it costs

Refurbishment, which involves repairing existing timber sashes, costs £1,200–£3,000 per window and is often a better option for period properties in conservation areas. Historic England 2026 guidance shows that repairing sash windows can achieve U-values of 1.8–2.5 W/m²K if draught-proofed and secondary glazed, compared to 1.2–1.8 W/m²K for new double-glazed sashes.

Repair is only viable if the timber is structurally sound, meaning no rot deeper than 5 mm. Otherwise, replacement is necessary. Repair plus draught-proofing and secondary glazing is typically 30–50% cheaper than a full replacement, making it a cost-effective option for many homeowners.

sash window repair vs replacement guide