Aluminium vs uPVC Windows

The aluminium vs uPVC question comes up in almost every window replacement conversation we have. Ten years ago, aluminium was mostly a commercial product (shopfronts, offices, high-end architect-designed homes). uPVC was the default for everything else. That has changed.

Aluminium has moved into mainstream residential in a serious way, particularly for extensions, modern properties and anywhere large glass panels are the priority. At the same time, uPVC has evolved beyond the chunky white frames people remember from the 1990s. Modern uPVC offers slim sightlines, foil-wrapped colours, flush casement styles and thermal performance that competes with anything on the market.

So in 2026, homeowners are genuinely choosing between the two, not defaulting to one. This guide covers what each frame type actually is, what it costs, how it performs, and which one suits which property.

uPVC windows

The workhorse of the UK residential window market, and still the frame material fitted to the majority of homes in Hampshire, Surrey and Berkshire. Modern uPVC is a very different product from the bulky white frames people associate with 1990s double glazing.

What uPVC windows actually are

uPVC stands for unplasticised polyvinyl chloride, a rigid plastic frame with multiple internal chambers (typically five to seven) providing insulation. Steel or solid uPVC reinforcement inside the profile chambers adds strength and reduces the chance of frame distortion. The result is a lightweight, thermally efficient frame that requires almost no maintenance.

At Cristal Windows we can specify high quality Rehau profiles as standard. Rehau is a German-engineered system with a strong track record on thermal performance, colour range and slim sightlines. As a Rehau Authorised Partner, we have access to the full Rehau range including flush casement styles that suit period properties. We can also offer alternative systems including Deceuninck, Epwin, Kommerling, Residence and Veka, with some of the latest corner joint options: ETL welds and timber welds for a traditional timber appearance, and the Graf weld system for a smooth joint finish, ideal on foiled products without the older grooved look.

Performance and cost

Fitted costs range from £400 to £1,000 per window depending on size, style and glazing. A typical whole-house replacement across 10 windows costs £4,500 to £9,500 fitted. U-values sit at 1.2 to 1.4 W/m²K with standard A-rated double glazing, dropping to 0.8 to 1.0 W/m²K with triple glazing. Lifespan is 20 to 25 years, with a 10-year warranty typical.

Colour options include white, foiled woodgrains, greys, blacks and dual-colour (one colour inside, another outside). Bespoke colours cost more and add a few weeks to lead time.

When uPVC works best

uPVC is the right choice for standard whole-house replacements, families upgrading from single glazing or older double glazing, and homeowners on a defined budget. It also works well on period and character properties, where flush casement uPVC in heritage colours replicates original timber windows at a fraction of timber’s cost.

The cost saving on a whole-house project versus aluminium is £4,500 to £8,000, which many homeowners redirect into other upgrades: triple glazing, integral blinds, a new front door, or a matching set of French doors.

Aluminium windows

The fastest-growing category in residential window replacement, particularly for extensions, new-builds and any project where slim sightlines and large glass areas are the priority. Aluminium windows have become the default choice for contemporary architecture.

What aluminium windows and doors actually are

An aluminium window frame is essentially two aluminium profiles (inside and outside) with an extruded polymer thermal break in the middle. The thermal break stops cold transferring through the metal from outside to inside. Modern thermally broken aluminium performs at levels that would have been impossible with older aluminium windows from the 1980s and 1990s.

Aluminium profiles are roughly one-third the thickness of uPVC while carrying more inbuilt strength features. That is why aluminium windows and doors can have slimmer sightlines, larger glass areas per window, and span bigger openings without needing extra mullions or supports. Aluminium is specified around 90 percent of the time for commercial and high-rise buildings, which reflects its structural credentials.

At Cristal Windows we work with two of the UK’s leading aluminium systems houses: AluK and Smart. Both offer precision-engineered profiles with state-of-the-art locking, thermal breaks and the full RAL colour palette. AluK is well established across the residential and commercial markets with a strong reputation for build quality. Smart offers highly versatile designs with standard, RAL and dual-colour options that give complete freedom on how the frames look, ideal where matching the property’s style matters. We specify whichever system fits the project best after the site survey.

Performance and cost

Fitted costs range from £800 to £1,800 per window depending on size, style and specification. A typical whole-house replacement across 10 windows costs £9,000 to £17,000 fitted. U-values sit at 1.3 to 1.6 W/m²K with A-rated double glazing, dropping to 0.9 to 1.1 W/m²K with triple glazing. Lifespan is 20 to 25 years or longer, with a typical 10-year warranty period.

Colour options cover the full RAL palette, over 200 colours in matt or gloss finishes, plus dual-colour options. This is where aluminium pulls away from uPVC on architectural specification.

When aluminium works best

Aluminium is the right choice for modern properties, contemporary extensions, and any project where you want maximum glass area per window or door. It handles very large spans structurally, which makes it the only realistic option for picture windows, wraparound corner glazing, or wall-to-wall glass on rear elevations. It is also ideal for bi-fold and patio sliding doors. Aluminium suits homeowners with a long-term horizon, since a properly installed frame comfortably reaches the 20 to 25 year plus mark.

Side-by-side comparison

Here is how the two frame types compare across the specifications that matter most.

Head-to-head analysis

The comparison table gives the numbers. This section looks at what actually matters when you are standing in front of a specification sheet trying to decide.

Thermal performance

Both frame types meet modern Building Regulations comfortably with A-rated double glazing. uPVC has a slight edge on raw U-value because plastic conducts less heat than metal, even with a thermal break. In practice, at the levels both products achieve today, the real-world energy performance difference is negligible for most homeowners. Where it does matter more is in extreme climates or Passive House builds, and in those cases uPVC still wins on paper.

Cost and value

uPVC costs roughly half as much per window as aluminium at point of purchase. Both frame types comfortably last 20 to 25 years, so the choice is less about longevity and more about what you get for the extra spend. Aluminium buys you slimmer sightlines, larger glass areas, a wider colour palette and the structural capability to handle bigger openings and door systems. For a straightforward like-for-like replacement, uPVC represents better value. For anything where design, glass area or large-span openings matter, aluminium earns its premium.

Aesthetics and style

Aluminium is the clear winner for modern design, especially where slim sightlines matter. On a Victorian terrace, contemporary aluminium can look out of place; flush casement uPVC blends better with the property’s character. On a modern rear extension with large glazed panels, uPVC’s chunkier frame profile can look dated next to the architecture. Match the frame to the building, not the other way around.

Structural capability

Aluminium handles larger openings structurally. If you are replacing a standard 1200mm by 900mm bedroom window, either material works. If you are glazing a rear elevation with a 4m by 3m picture window, aluminium is the only sensible choice. uPVC in that size would need multiple mullions and the frame area would visually swamp the glass.

Colour choice

uPVC covers most needs with standard whites, greys, blacks and foiled woodgrains. Aluminium opens up the full RAL palette. If you want a specific dark bronze, sage green, or bespoke satin finish to match architect drawings or planning conditions, aluminium is the route.

How to choose between them

Five scenarios cover most of the choices homeowners actually face.

You are doing a standard whole-house replacement

Go uPVC. On a typical three or four-bedroom home in Fleet, Aldershot or Basingstoke, replacing all windows in uPVC saves £5,000 to £8,000 versus aluminium with no meaningful performance downside. That saving typically funds other upgrades: triple glazing, integral blinds, or a new front door.

You are planning a modern extension or new-build

Go aluminium. Contemporary architecture is designed around slim sightlines and large glazed panels. uPVC on a new-build modern extension is usually a false economy, because the architecture and the frames will not visually match, and the resale value does not recover the saving.

You have a period or character property

Usually uPVC in flush casement style. Flush casement uPVC replicates original timber windows convincingly at a fraction of timber’s cost. Foiled woodgrain uPVC in heritage cream, agate grey or chartwell green sits well on brick and stone properties across Farnham, Petersfield and Winchester without looking modern or plastic.

You want the widest possible glass area

Go aluminium. Slim sightlines maximise glass area, which is what most homeowners actually want from a window replacement. Aluminium delivers up to 40 percent more visible glass per window compared to equivalent uPVC.

You are planning to sell within 10 years

For standard residential properties, uPVC. Aluminium does not return its premium in resale value for typical homes within that timeframe. For modern architect-designed properties, aluminium is expected and can support a higher resale figure.

What Cristal Windows recommends by property type

The theory above is useful; the practice is often clearer. Here is how the choice tends to play out on the ground across our catchment areas.

Standard 1970s to 1990s residential

Slim modern internally glazed uPVC in selected profiles, A-rated double glazing as standard, foiled colour or RAL palette painted finishes if the property colour scheme warrants it. This is by some distance the most common recommendation we make.

Contemporary new-builds and extensions

Aluminium in matt anthracite or matt black, AluK or Smart profiles, with larger picture-window and sliding door elements where the architecture allows. Ideal for internal slimline room dividers with the option of white or other colours on the internal surfaces.

Character properties in Farnham, Petersfield, Winchester and Windsor

Flush casement uPVC in period-appropriate colours (heritage cream, agate grey, chartwell green, painswick). Timber-effect foiling on the exterior with white or cream interior.

Rear extensions with large glazed panels

Aluminium every time. The structural capacity for spans of 3 metres and above makes it the only realistic choice for open-plan garden-facing elevations.

Bay windows on Edwardian and Victorian properties

Usually uPVC. The complexity of a bay window build-up favours the flexibility of uPVC construction, and period bay aesthetics work better in flush casement uPVC than in contemporary aluminium.

Two questions that keep coming up

Not quite FAQ material, but worth answering directly.

Can you mix aluminium and uPVC in the same house?

Yes, and it is a legitimate strategy. Some homeowners specify aluminium at the rear where they want large glazed panels facing the garden, and uPVC at the front where flush casement suits the property’s character. The two frame styles do not have to match if the design logic behind them is clear.

Isn’t aluminium always better because it is metal?

No. Both products are engineered for the same purpose and both meet modern performance standards. Aluminium is not automatically higher quality, and uPVC is not automatically lower quality. The right frame is the one that suits the property, the budget and the use case.

A note on cost

The cost figures in this guide are realistic for typical installations across Hampshire, Surrey and Berkshire on standard three and four-bedroom homes. Larger properties, bespoke shapes, triple glazing upgrades and integral blinds all add to the final number.

For a detailed cost breakdown for a standard three-bedroom home, including labour, glazing options, warranties and finance, see our guide to how much it costs to install double glazing in a 3-bed house.

Frequently asked questions

The questions we get asked most often by homeowners choosing between aluminium and uPVC.

Q. Are aluminium windows worth the extra cost over uPVC?

A. For modern properties, extensions, or large glazed openings, yes. For standard whole-house replacements on typical residential properties, uPVC delivers similar thermal performance at roughly half the cost, and the money saved is better spent on glazing upgrades or other home improvements.

Q. Which lasts longer, aluminium or uPVC?

A. Aluminium windows last 20 to 25 years plus. uPVC windows last 20 to 25 years. Both figures assume quality profiles from a reputable systems house and professional installation.

Q. Are aluminium windows colder than uPVC?

A. Marginally. Metal conducts more heat than plastic, even with a thermal break. In real-world use, the difference is small and often outweighed by other factors such as glass specification and installation quality.

Q. Can I get slim frames in uPVC?

A. Yes. Modern flush casement uPVC systems achieve slimmer sightlines than 1990s uPVC, though not quite as slim as aluminium. For a contemporary look at uPVC price, flush casement is worth considering.

Q. Are aluminium windows more secure than uPVC?

A. Both frame types meet PAS 24 security standards when properly installed with multi-point locking hardware. Structural strength differs between the two, but security in practice depends on locking hardware, glazing specification and installation quality, not frame material.

Q. Which is better for large glass panels?

A. Aluminium. Its structural strength allows larger unsupported spans, meaning bigger picture windows and wider sliding doors without extra mullions dividing the glass.

Q. Do aluminium windows suit period properties?

A. Usually not. Contemporary aluminium profiles look out of place on Victorian, Edwardian or Georgian homes. Flush casement uPVC or timber typically suits period properties better. That said, newer slimline aluminium profiles can now replicate the classic Crittall style, opening up an aluminium option for older and heritage properties.

Get a quote from a local installer

Cristal Windows is a family-run company based in Fleet, supplying and installing across Hampshire, Surrey and Berkshire. We have been members of the Glass and Glazing Federation for 34 years, we are FENSA registered and a Which? Trusted Trader, and we install a selection of six uPVC systems along with both AluK and Smart aluminium as core products.

If you would like to talk through which frame type makes sense for your home, request a free, no-obligation quote and we will arrange a site survey at a time that suits you.