Window Installation Costs UK — UPVC, Aluminium, Timber and Sash Window Replacement Pricing Guide (2026)

Window replacement is one of the most consistent streams of domestic work in the UK trade sector. Energy costs have pushed homeowners to upgrade single-glazed and ageing double-glazed units, while changing tastes have created demand for aluminium and timber frames that would have been considered premium-only a decade ago. For window installers, understanding the full cost landscape — frame material, glazing specification, certification, and regional variation — is the foundation of quoting accurately and winning work at the right margin.

This guide covers every major window type, the factors that move prices up and down, what building regulations require, and how to structure a quote that wins on value rather than racing to the bottom on price.

Window Installation Costs at a Glance (2026)

All prices below are supply-and-fit for a typical domestic opening (approximately 1,000 × 1,200 mm) at ground or first floor level with standard access.

UPVC Window Costs

UPVC casement windows remain the most installed frame type in the UK, accounting for the majority of domestic replacements. They are the most affordable option, require minimal maintenance beyond an occasional wipe-down, and are available in a wide range of profile depths and hardware grades.

A standard UPVC casement window costs £300–£700 per window installed. The lower end reflects a mid-range 70 mm profile with a standard 4/16/4 double-glazed unit and white finish. The upper end reflects a premium 76 mm multi-chambered profile, argon-filled warm-edge units, A++ energy rating, and upgraded shootbolt locking hardware.

What drives the price within the UPVC range

• Profile depth and chamber count: A 70 mm six-chamber profile outperforms a basic 60 mm three-chamber system on thermal efficiency and rigidity. Premium profiles add £40–£100 per window in materials cost.
• Glazing unit specification: Standard 4/16/4 air-filled double glazing achieves roughly 2.8 W/m²K. Upgrading to 4/20/4 argon-filled with a warm-edge spacer bar and low-E coating brings that down to around 1.2–1.4 W/m²K. That upgrade typically adds £30–£80 per unit.
• Colour finish: White UPVC is the baseline. Coloured UPVC — anthracite grey, cream, black, and dual-colour (white inside, colour outside) — adds 10–25% to the frame cost. A window priced at £400 in white might be £440–£500 in a standard colour.
• Hardware grade: Budget friction stays and a single-point espagnolette lock are standard at the lower end. Upgraded multipoint shootbolt systems with stainless hardware add £30–£60 per window.

Full-house UPVC replacement on a typical three-bedroom semi-detached (8–12 windows, including a front door) sits at £3,000–£10,000 depending on the above variables and whether the job includes any structural making-good or lintel/cill replacement.

Aluminium Window Costs

Aluminium has taken significant market share from UPVC over the past decade, particularly for contemporary extensions, new builds, and commercial refurbishments. Slimmer sightlines, greater rigidity for large openings, and superior longevity make it the premium domestic choice. Aluminium windows are also standard on most commercial and educational projects.

A thermally broken aluminium casement window costs £400–£1,000 per window installed. Non-thermally-broken aluminium (rarely specified for habitable spaces now) sits at the lower end; high-specification slim-profile systems with triple glazing sit at the top.

Aluminium colour and RAL costs

All aluminium windows are powder-coated to a RAL or BS colour. Standard RAL colours (RAL 7016 anthracite, RAL 9005 black, RAL 9010 white) are typically included in the base price. Special or non-standard RAL colours — including dual-colour frames (different inside and out) — add 20–40% to the frame cost. A window that would be £600 in standard anthracite might be £720–£840 in a bespoke dual-colour finish.

A full aluminium house replacement (8–12 windows) costs £5,000–£15,000 installed. The wide range reflects system choice, glazing specification, and whether the job involves large or complex openings.

Timber Window Costs

Timber is the preferred material for period properties, conservation areas, and listed buildings. It carries a higher purchase price and requires more maintenance than UPVC or aluminium, but planning authorities often require it — or a like-for-like timber replacement — in sensitive areas.

• Softwood casement (supply and fit): £500–£900 per window. Redwood pine and Douglas fir are the common choices. They need painting or staining every five to seven years to prevent rot.
• Hardwood casement (supply and fit): £750–£1,200 per window. Accoya (modified radiata pine), oak, and iroko are dimensionally stable and carry longer manufacturer warranties — typically 30–60 years on Accoya.
• Modified timber (e.g., Accoya) with aluminium cladding: £900–£1,400 per window. The external aluminium cladding eliminates virtually all external maintenance while retaining a timber reveal internally. Popular for homeowners who want a timber look without the upkeep.

Lead times for timber windows

Lead times are a critical differentiator between frame materials. UPVC windows are typically available within 2–4 weeks of order from most fabricators. Timber windows — particularly bespoke or hardwood units — carry lead times of 6–12 weeks, and sometimes longer for unusual profiles or conservation-spec units. Set customer expectations at survey stage, not after the order is placed.

Sash Window Costs: Restoration vs Replacement

Sash windows are a distinct product and service category. Many homeowners in Victorian and Edwardian properties have the option to restore their existing sashes rather than replace them — often a more cost-effective route and one that planning authorities frequently prefer.

Sash window restoration

A full sash window restoration costs £400–£800 per window. This typically includes: removing both sashes, stripping and re-priming, re-cording or fitting spring balances, installing brush draught seals to the box frame and meeting rail, re-glazing any broken or cracked panes with safety or heritage glass, and re-hanging. Decorating (external painting) is usually priced separately.

Draught-proofing alone — without full re-cording or re-glazing — sits at £200–£400 per window. It is a quick win for customers who want to improve heat retention without the cost of full restoration.

Sash window replacement

Full sash window replacement costs £700–£2,000 per window installed, depending on whether the frame is UPVC, aluminium, or timber, and the glazing specification. UPVC sliding sash is the cheapest option. Timber sash — particularly in a conservation-spec profile with slim double or secondary glazing — sits at the top of the range.

Bay Window Costs

Bay windows are significantly more complex to price than standard casements. The cost varies with the bay geometry (square, canted, or curved), the number of lights, the frame material, and whether the structural cill and roof are in good condition.

• UPVC square or canted bay (supply and fit): £1,500–£2,800. This assumes a three-light bay with one or two opening sashes and a serviceable timber or brick cill. If the cill needs replacing, add £300–£600.
• Aluminium bay (supply and fit): £2,000–£4,000. Aluminium is increasingly specified for front-elevation bays on contemporary refurbishments. The structural weight and precision fabrication push the cost up versus UPVC.
• Curved or oriel bay: £2,500–£4,000 or more, depending on the curve radius and number of sections.

Bay windows take longer to survey than standard openings — always check whether the bay pole and flat/pitched roof are sound, and whether the structural lintel is in good condition before committing to a fixed price.

Double vs Triple Glazing: Is It Worth It?

Triple glazing adds an extra pane and cavity, improving the centre-of-glass U-value from around 1.1 W/m²K (double) to around 0.5–0.7 W/m²K (triple). In practice, a high-specification double-glazed unit with argon fill and low-E coating performs well in most UK climates; triple glazing delivers the greatest benefit in north-facing rooms and properties in colder regions.

The premium for triple glazing over equivalent double glazing is typically £80–£200 more per window, depending on unit size. On a full-house replacement of 10 windows, that is an additional £800–£2,000. Estimated energy savings from upgrading a full house from single to double glazing run to £150–£250 per year; the further step from double to triple is smaller, typically £40–£80 per year for most UK homes.

The honest advice for most customers: spend the triple-glazing budget on better frame insulation and warm-edge spacer bars first. Triple glazing makes more sense for Passivhaus-standard builds, rooms with high heat loss, and customers who also want better noise reduction.

Window Energy Ratings: A++, A+, A Explained

The British Fenestration Rating Council (BFRC) rates windows on a scale from A++ (most efficient) to E (least efficient), similar to the energy labels on white goods. The rating combines three factors: heat loss through the frame and glass (U-value), solar gain (how much free heat the window lets in from the sun), and air leakage.

• A++: The highest rating. Typically triple-glazed or premium thermally broken aluminium with argon or krypton fill. Whole-window U-value typically below 0.8 W/m²K.
• A+: High-specification double glazing with warm-edge spacer, argon fill, and good-quality thermally broken frame. Whole-window U-value around 1.0–1.2 W/m²K.
• A: The Building Regulations minimum for most replacement windows. Whole-window U-value at or below 1.4 W/m²K.

For domestic replacement work, specifying at least A-rated windows is a Building Regulations requirement (Approved Document L). A-rated windows are the baseline; quoting A+ or A++ as standard signals quality and differentiates your business from those quoting the bare minimum.

Acoustic Glass and Noise Reduction

For customers on busy roads, near railways, or in urban areas, noise reduction is often as important as thermal performance. Standard double glazing with two equal-thickness panes (e.g., 4/16/4) gives limited acoustic benefit. Acoustic glazing uses panes of unequal thickness or laminated glass to break up the resonant frequency, reducing noise transmission significantly.

Acoustic glass upgrades cost £100–£200 extra per windowover standard double glazing. Common specifications are 6.4 mm laminated glass on the outer pane with a standard 4 mm inner pane, or 6.4/6.4 laminated units for maximum noise reduction. The difference in practice: standard double glazing achieves around 28–32 dB reduction; an acoustic unit can achieve 35–42 dB.

Acoustic glazing is worth proactively quoting for front-elevation windows on main roads. Many homeowners do not know it exists; presenting it as an option positions you as the expert and can increase the job value by £1,000–£2,000 on a full-house replacement.

Building Regulations: FENSA, CERTASS and Building Control

Window replacement in England and Wales falls under Building Regulations, specifically Approved Document L (energy efficiency), Approved Document N (glazing safety in critical locations), and Approved Document F (ventilation). You have two routes to compliance:

• Competent person self-certification (FENSA or CERTASS): Registered installers can self-certify their installations without notifying the local authority building control. FENSA (Fenestration Self-Assessment Scheme) and CERTASS are the two main approved schemes. Both carry equal weight for conveyancing. FENSA membership costs approximately £200–£500 per year plus a per-job registration fee of around £15–£35, which is typically passed to the customer. The FENSA certificate is issued to the homeowner and is required documentation when the property is sold.
• Local authority building control notification: Non-registered installers must notify the local authority before starting work. The authority will inspect on completion and issue a certificate. This route adds cost and delay — and leaves the customer with the administrative burden of chasing the certificate.

Why unregistered windows cause problems at sale

A window replaced without a FENSA or CERTASS certificate — or without a building control sign-off — is a non-compliant installation. Conveyancers routinely flag missing window certificates on property searches. The homeowner either has to obtain indemnity insurance (typically £200–£400) or, in serious cases, have the window replaced by a registered installer. For your customers, this is a genuine financial risk that appears years after the job is done. FENSA registration is not a bureaucratic nicety — it is protection your customer needs and a selling point you should name in every quote.

The Window Fitting Process

Most replacement windows take 1–2 hours per window for an experienced two-person crew, from removal of the old unit to finishing and cleaning down. A full-house replacement of 10 windows typically takes 2–3 days. The process for each opening is:

1. Remove existing window frame and sashes, taking care with the reveal if decoration is to be retained.
2. Prepare the opening: clean out mortar residue, check the lintel is sound, apply DPC tape or mastic to the back of the new frame.
3. Offer up and fix the new frame level, plumb and square using frame fixings or frame ties, checking diagonals.
4. Fit the glazing units, packers, and gaskets.
5. Apply expanding foam or mineral wool insulation around the frame perimeter, then internal and external mastic seals.
6. Making good: fill, sand, and prime internal and external reveals to the agreed standard.
7. Fit handles, restrictor stays, and any trickle vents required by Approved Document F.
8. Clean glass, check all sashes open and close correctly, issue FENSA certificate.

The making-good and decoration allowance is the most common source of disputes. Be explicit in your quote about what is included — filling and priming only, or full decoration? Internal or external only? Ceramic tile upstands in kitchen and bathroom? Setting these out clearly prevents margin erosion and callback disputes.

Quoting Guide for Window Installers

Survey checklist

• Measure each opening at three heights (top, middle, bottom) and three widths (left, centre, right) — use the smallest dimension for the frame order to allow for reveal depth.
• Check reveal depth: standard reveals are 70–90 mm; shallow reveals under 60 mm may require a sub-frame or packers.
• Assess lintel and cill condition. A failing lintel is a structural issue that must be scoped separately — do not include remedial structural work in your glazing price without a contingency allowance.
• Note floor level and access: upper-floor windows may need scaffolding or a scaffold tower (price this separately).
• Identify conservation area or listed building status before quoting frame material — do not quote aluminium for a listed building without first checking planning.
• Confirm whether the customer wants making-good only or full decoration, inside and out.
• Confirm FENSA registration is required (standard for all domestic replacement work in England and Wales).

What to include on the quote

• Line itemise each window: frame material, colour, glazing specification, energy rating.
• Separate lines for scaffold or access equipment if required.
• Decoration allowance: state explicitly what is and is not included.
• FENSA/CERTASS registration fee (or state it is included).
• Removal and disposal of old frames — specify whether glass is included in the waste removal price.
• Lead time: confirm expected installation week, not just a delivery date.
• Payment terms: a 30–40% deposit on order, remainder on installation completion is the standard for this sector.

Red flags to warn customers about

The window industry has a long history of high-pressure sales tactics. If a customer mentions any of the following, advise them to get a second quote:

• A salesperson quoting a dramatically lower price that is “only available today.”
• Pressure to sign the contract on the same day as the survey visit.
• Discounts that disappear if the customer asks to think overnight.
• Vague or absent detail on frame profile, glazing specification, and energy rating.
• No mention of FENSA certification.

Positioning yourself as the transparent, professional alternative — with a written quote that names the profile system, the glass specification, the FENSA registration, and the payment terms — is the most effective way to win against high-pressure competitors.