London · Q2 2026
uPVC vs Aluminium Windows
Aluminium isn't better. It's different.
Marketing pretends aluminium is the premium upgrade and uPVC is the budget compromise. The reality is more useful than that. On published figures, aluminium wins on the size and weight of sash it can carry, on how little frame it shows, on acoustic performance and on the sliding and bifold systems that have no uPVC equivalent. uPVC wins on cost and on the traditional casement, sash and bay configurations, and modern uPVC is thermally excellent, our tilt & turn is published from 0.85 W/m²K. Plenty of London projects use both: uPVC at the front, aluminium at the rear extension.
The full comparison
Side by side on the figures each manufacturer actually publishes. uPVC figures are from the Apex uPVC ranges; aluminium figures are from the APX aluminium ranges, Cortizo COR and Schüco AWS. Where a manufacturer does not publish a figure, this table says so rather than estimating one.
| Spec | uPVC | Aluminium |
|---|---|---|
| Frame depth | 70 mm | 70 mm (APX Casement, APX70, AWS 70.HI) |
| Narrowest visible section published | Not published in mm | 66 mm (APX70), 51 mm frame face width (AWS 70.HI) |
| Whole-window Uw, casement | From 1.2 W/m²K | From 0.9 W/m²K (APX Casement) |
| Whole-window Uw, tilt & turn | From 0.85 W/m²K | From 0.84 W/m²K (APX70) |
| Best published casement Uw | From 0.85 W/m²K | From 0.76 W/m²K (Cortizo COR 70 Industrial TB) |
| Max sash, casement | 800 × 1500 mm | 950 × 1300 mm side-hung, 1800 × 1800 mm projecting |
| Max sash weight | 40 kg | 42 kg side-hung, 100 kg projecting, 160 kg on APX70 |
| Max sash, tilt & turn | 800 × 1500 mm | 1300 × 2400 mm, 1200 × 3500 mm heavy duty |
| Glazing thickness | Up to 36-40 mm | Up to 44 mm (APX Casement), up to 62 mm (AWS 70.HI) |
| Acoustic Rw, up to | 37 dB (tilt & turn, acoustic glass) | 45-48 dB depending on system |
| Energy rating | Up to A++ | Up to A |
| Security | PAS 24 available | PAS 24 available, up to RC3 on AWS 70.HI |
| Guarantee | 10 yr | 10 yr |
| Colour range | 30+ colours and woodgrain foils | Any RAL colour, dual colour, anodised |
| Best for | Casement, sash, bay and bow, budget | Slim sections, large sashes, steel-look, big sliding doors |
Sources: Apex uPVC and APX aluminium product data sheets, Cortizo published system data and Schüco AWS 70 system documentation. Note that "70mm" on a uPVC window is the frame depth, not a sightline, and it is often quoted as though it were one. uPVC manufacturers, including REHAU and Liniar, generally do not publish a sightline figure in millimetres at all.
What each one costs
Aluminium costs more than uPVC for the same opening. How much more depends on the system, the size, the opening type, the glass specification, the finish and site access, so we price it after a survey rather than publishing a table that would be wrong for most houses. Every Apex quote includes the frame, glazing, fitting, removal of the old window, FENSA self-certification under Reg 40373 and our 10-year guarantee, on both materials.
When uPVC wins
For these scenarios, uPVC is the right answer and resisting the upsell to aluminium costs you nothing real. Honest installer-side advice.
| Standard semi-detached or terrace casement upgrade |
| Traditional sliding sash window replacement (uPVC heritage range now excellent) |
| Bay and bow window replacement on Edwardian and Victorian properties |
| Conservation-area front elevations where heritage uPVC is approved but aluminium isn't |
| Flush-sash heritage replacement where the look is the brief |
| Buy-to-let, HMO and short-hold investment properties |
| Whole-house replacement where the budget is the binding constraint |
| Sashes inside 800 × 1500mm and 40kg, which covers most standard openings |
| French doors and standard patio doors where the slim sightline doesn't matter |
When aluminium wins
For these scenarios, aluminium is genuinely the only credible answer. uPVC physically can't replicate the slim sightline or carry the structural span.
| Steel-look casement replacement (Cortizo COR 70 Industrial TB) |
| Sections uPVC cannot reach, the APX70 tilt & turn shows just 66mm of aluminium |
| Large sashes, APX Casement takes a projecting sash to 1800 × 1800mm at 100kg against uPVC's 800 × 1500mm at 40kg |
| Corner glazing, a 90° structural corner without a corner mullion |
| Passivhaus-certified windows (Schüco AWS 90.SI+ at Uw 0.79 W/m²K) |
| Slim sliding doors (APX20 Ultra Slim, APX20 Plus, Schüco ASE, no uPVC equivalent) |
| Bifold doors across a wide opening (Schüco AS FD 75 runs 7 leaves across 10.5m) |
| Architect-specified contemporary new-builds where the brief names aluminium |
| Any RAL colour, dual-tone inside and out, or anodised finishes |
The mixed-property approach
A pattern we fit regularly: uPVC at the front, where the brief is period accuracy and conservation-area approval, and aluminium at the rear, where the brief is a slim section and a large opening. Done properly the property reads as coherent, because each material is in the context it suits.
| Location | Material | Why |
|---|---|---|
| Front elevation (Victorian terrace) | uPVC heritage sash | Period detailing, conservation-area approval, lower cost |
| Side bay window | uPVC casement | Matches the front, no slim-section benefit to be had |
| Rear extension (kitchen-diner) | Aluminium picture window | APX Casement takes a projecting sash to 1800 × 1800mm at 100kg |
| Rear extension door | Aluminium slim slider (APX20 range) | 20 or 25mm central junction, contemporary brief |
| First floor rear bedroom | Aluminium tilt-and-turn (APX70) | 66mm visible section, Uw from 0.84 W/m²K, cleans from inside |
Frequently asked
Are aluminium windows better than uPVC?
Aluminium isn't "better", it's different. On published figures aluminium wins on sash size and weight, our APX Casement takes a projecting sash to 1800 × 1800mm at 100kg against uPVC's 800 × 1500mm at 40kg, on how little frame it shows, on acoustic performance up to 45-48 dB Rw against 37 dB, and on the sliding and bifold systems that have no uPVC equivalent. uPVC wins on cost and on traditional casement, sash and bay configurations. Thermally they are now very close.
How much do aluminium windows cost vs uPVC?
Aluminium costs more than uPVC for the same opening, and how much more depends on the system, the size, the opening type, the glass specification, the finish and site access. We price after a survey rather than from a table, because a table would be wrong for most houses. What we will tell you honestly at survey is when the aluminium upgrade buys you nothing your opening can actually use.
Are aluminium windows worth the extra money?
For contemporary builds, large sashes, slim sections and steel-look replacement, yes, uPVC genuinely cannot deliver the look or carry the sash. For traditional casement and sash configurations on a typical semi, often not: modern uPVC is published from 1.2 W/m²K on a casement and from 0.85 W/m²K on a tilt & turn, which is essentially level with aluminium. The honest test is whether the difference would show on the finished elevation. On a sash window, rarely. On a steel-look screen, instantly.
Which lasts longer, uPVC or aluminium?
Aluminium generally has the longer service life, but we won't put a specific number of years on either, because it depends on exposure, orientation, installation quality and maintenance, and nobody publishes a tested figure. What we can tell you is what is covered: both materials come with our 10-year guarantee on the frame and 5 years on the sealed glass units, and powder-coated aluminium is finished to BS EN 12206-1.
Are uPVC windows still allowed in conservation areas?
Often, but it is a decision for the local conservation officer rather than a rule we can promise you. Heritage uPVC ranges with authentic Georgian or astragal bar options and a flush-closing sash are regularly accepted on period properties, and we fit them across London. Front elevations of listed buildings usually require timber. Always get the position in writing from the conservation officer before ordering, and we can help with that at survey.
What is the slimmest section available?
Be careful with this question, because uPVC systems, including REHAU and Liniar, generally do not publish a sightline figure in millimetres at all. The "70mm" you see quoted on a uPVC window is the frame depth, not the sightline. On aluminium, our APX70 Tilt & Turn publishes a visible aluminium section of 66mm because the sash is concealed behind the frame, and Schüco publishes a frame face width from 51mm on the AWS 70.HI. Cortizo publishes frame and sash depths for its COR casements but not a face width.
Can uPVC windows replace Crittall steel-frame?
Not convincingly. Steel-look replacement is what systems like Cortizo COR 70 Industrial TB and Smart's Alitherm Heritage exist for, and Smart publishes a 59mm sightline on Alitherm Heritage. uPVC's proportions read as a different product entirely. Note that Crittall itself does not publish a sightline figure in millimetres, so treat any "Crittall is 20mm" claim you see quoted as third-party rather than manufacturer data.
Which is more thermally efficient, uPVC or aluminium?
They are now within a fraction of each other. Our uPVC casement is published from 1.2 W/m²K and our uPVC tilt & turn from 0.85 W/m²K with an A++ energy rating. On aluminium, APX Casement is published from 0.9 W/m²K, APX70 Tilt & Turn from 0.84 W/m²K, and Cortizo COR 70 Industrial TB from 0.76 W/m²K. All are inside the Approved Document L limit of 1.4 W/m²K for a replacement window. The thermal gap aluminium had in the 1990s no longer exists.
Should I mix uPVC and aluminium on the same property?
Yes, frequently. Many London projects use uPVC sash at the front, where the brief is period accuracy and conservation approval, and aluminium sliding or bifold doors at the rear, where the brief is a slim section and a large opening. Mixing within a single elevation usually looks awkward. Mixing across elevations, front uPVC and rear aluminium, is a common and well-judged specification.
