uPVC vs Timber vs Aluminium Windows Compared

The short answer

For most UK homes, uPVC remains the default choice on cost and low maintenance, aluminium wins where slim sightlines and large glazed areas matter (extensions, bifold-heavy elevations), and timber suits period properties or anyone prioritising a natural look over convenience. The right answer depends less on which material is "best" and more on your property, budget and how much upkeep you're willing to do.

uPVC windows

uPVC (unplasticised polyvinyl chloride) has been the standard replacement-window material in the UK for decades, and for good reason: it doesn't rot, doesn't need repainting, and is the cheapest of the three by a clear margin. A typical uPVC casement window supplied and fitted usually falls somewhere in the £350–£650 per window range, though larger or bay windows cost considerably more.

The trade-offs are mostly aesthetic and structural. uPVC frames are thicker than aluminium or timber to achieve the same strength, which means slightly less glass and slightly more visible frame. Colour options have improved a lot — foiled finishes in anthracite grey, black and woodgrain effects are now common — but a purist restoring a Victorian or Georgian property will usually find uPVC doesn't read as authentic close up, which matters in conservation areas where planning restrictions may apply anyway (see the point on conservation areas below).

Timber windows

Timber is the traditional choice and still the only real option where a property sits in a conservation area or is listed, since planning authorities frequently require a "like-for-like" material match. Modern engineered timber (rather than solid single-piece timber) resists warping far better than older timber windows did, and factory-applied microporous paint or stain finishes last 8–10 years between re-coats rather than the 2–3 years homeowners associate with old-fashioned timber windows.

Cost is the main barrier: expect to pay roughly £600–£1,200+ per window supplied and fitted, sometimes more for hardwood or bespoke joinery to match an existing property's proportions. Maintenance is real, if less onerous than it used to be — timber needs periodic repainting or re-staining, and any exposed end grain (especially at the bottom of the frame) needs to be checked for water ingress. In exchange, timber offers genuinely slim sightlines, a warmth uPVC and aluminium can't fully replicate, and — done well — it tends to add more to a period property's value than a uPVC swap would.

Aluminium windows

Aluminium is the newest of the three in mainstream UK residential use and has become the go-to choice for extensions, contemporary renovations and anywhere large expanses of glass are wanted. Because aluminium is much stronger than uPVC for a given thickness, frames can be significantly slimmer — which is why aluminium dominates bifold and large sliding door systems as well as windows.

It's also the most expensive option upfront, typically £500–£900+ per window, and thermal performance needs a closer look: aluminium conducts heat far more readily than uPVC or timber, so a genuinely well-performing aluminium window relies on a "thermal break" (an insulating strip inside the frame profile) to stop it becoming a cold bridge. Reputable suppliers all build this in as standard now, but it's worth confirming rather than assuming on a budget product. Maintenance is minimal — powder-coated aluminium doesn't rust and rarely needs anything beyond an occasional clean.

Thermal performance and U-values

All three materials can now hit strong U-values (a lower U-value means better insulation) when paired with modern double- or triple-glazed units, so material choice alone doesn't decide energy performance — the glazing unit does most of the work. Where material genuinely matters is cold-bridging at the frame edge, which is why an unbroken aluminium frame performs noticeably worse than a thermally broken one, and why uPVC's naturally low conductivity gives it a slight inherent advantage even before glazing is considered.

Conservation areas and listed buildings

If your property is listed or sits in a conservation area, check with your local planning authority before assuming you can fit uPVC or aluminium replacements — many authorities require timber (or timber-effect materials meeting specific profile requirements) to preserve the street scene, and unauthorised replacement can lead to enforcement action. This varies by council and by the specific conservation area's Article 4 Direction, so a quick call to the planning department before ordering windows is worth the ten minutes it takes.

Common mistakes

• Choosing purely on upfront price. A cheap uPVC window with a poor-quality gasket and hardware will need attention within a few years; a mid-range product from an established fitter with a solid warranty is usually better value over 10+ years.
• Ignoring the installer's FENSA registration. Whichever material you choose, using a FENSA-registered installer means the work is self-certified as meeting Building Regulations without you needing a separate council inspection — using an unregistered installer can leave you needing to sort this retrospectively.
• Assuming all aluminium is equally efficient. Ask specifically whether the frame has a thermal break, not just what the glazing U-value is.

Which should you choose?

If budget is the main driver and the property isn't in a conservation area, uPVC is still the sensible default for most homeowners. If you're doing a rear extension or want large glazed openings with slim frames, aluminium is usually worth the extra cost. If you own a period property — or one in a conservation area — timber may not just be preferable but required, and modern engineered timber makes the maintenance trade-off far more manageable than it once was.

Doors and other openings

Windows aren't the only opening worth thinking about as part of a wider doors and windows upgrade. If you're choosing between patio door styles, see our comparison of French doors vs sliding patio doors. If an existing window has started sticking or won't latch properly rather than needing full replacement, check why a window won't open or close properly before assuming a new one is needed. And if it's the garage door rather than the house windows that's due for replacement, our garage door replacement cost guide covers typical UK pricing.