Aluminium vs uPVC Windows

Where people go wrong is assuming one material is universally superior. Aluminium is not automatically "better" than uPVC; it is a different set of trade-offs, at a different price point, suited to different buildings.

Aluminium windows use a powder-coated extruded aluminium frame with a thermal break, a strip of insulating polyamide bonded between the inner and outer sections of the extrusion, that stops heat conducting straight through the metal. This construction is what allows a slim, strong frame while still meeting current thermal regulations.

uPVC windows are built from multi-chambered PVC-U profile. Modern Residence Collection systems bond a foil finish over the profile to replicate painted timber, and use flush sculpted horns and a wider sightline than aluminium to achieve strength without steel reinforcement in most cases (heavier openers still take internal steel).

This is usually the deciding factor once cost has been discussed. Aluminium's strength allows narrower frames and larger glass areas for the same opening, which reads as a cleaner, more architectural look. It suits contemporary extensions, barn conversions and new builds where large panes and flush glazing are part of the design.

The Residence Collection was developed specifically to answer the opposite brief: a genuinely convincing timber look, complete with sculpted horns, ovolo details and deep woodgrain foils, for houses where a flat aluminium frame would look wrong. On a stone Lakeland cottage or a Victorian terrace, a well-specified R9 window in wood-grain white or cream can be difficult to distinguish from painted timber at ten paces.

• Choose aluminium if the brief is large glass, minimal frame, and a flat, modern colour like Anthracite Grey or Jet Black.
• Choose uPVC if the brief is a traditional sash or casement look, woodgrain finish, or you are matching neighbouring timber windows.
• Both are available in the same RAL colour ranges, so colour alone is rarely the deciding factor.

Both materials can comfortably meet the Part L requirement of 1.4 W/m²K whole-window U-value for replacement windows. In practice, modern aluminium systems achieve around 1.2-1.4 W/m²K double glazed and 0.9-1.1 W/m²K triple glazed, and the Residence Collection sits in a very similar 1.2-1.4 W/m²K double, around 0.9 W/m²K triple. Neither material has a meaningful thermal advantage once glazed to a comparable specification; the glass and spacer bar do most of the thermal work.

Where aluminium has a genuine edge is on exposed, weather-beaten elevations. It does not expand and contract with temperature to the same degree as uPVC, holds its shape over very long spans, and its powder coat does not fade or chalk in the way some cheaper uPVC foils can after many years of strong western sun and driving rain.

Aluminium U-value (double)

1.2-1.4 W/m²K

Aluminium U-value (triple)

0.9-1.1 W/m²K

Residence U-value (double)

1.2-1.4 W/m²K

Residence U-value (triple)

around 0.9 W/m²K

Part L minimum

1.4 W/m²K whole-window

This is where the two materials separate clearly. A Residence Collection uPVC window supplied and installed typically runs £950-£1,700 depending on size, opening style and glazing. Aluminium casement windows typically run £1,400-£2,600 per window for the same job. Across a whole house that difference adds up quickly: on a fifteen-window project the gap between the two materials can be £7,000-£13,500.

Both materials are low maintenance compared with timber, needing no repainting. Aluminium's powder coating typically carries a longer guaranteed life against fading and generally continues performing well past 35-40 years, with the frame itself effectively lasting the life of the building. uPVC frames are generally guaranteed for around 10 years on the profile and typically perform well for 25-35 years before hardware wear or foil degradation makes replacement worthwhile.

In practice, hardware, hinges and seals are usually what fail first on either material, and both are readily serviceable. Neither needs sanding, painting or the ongoing care that timber demands.

Being blunt about the weaknesses is more useful than another list of benefits.

• Aluminium is the wrong choice if budget is tight and you need to replace every window in the house in one go: the price premium can push a whole-house project out of reach for no real performance gain on a standard semi-detached elevation.
• Aluminium on a small period cottage with fussy glazing bar patterns can look thin and slightly clinical if the wrong profile is chosen, undermining the character the house should keep.
• uPVC is the wrong choice on very large openings, wide sliding doors or where you want minimal visible frame: it simply cannot match aluminium's structural spans or sightlines.
• Cheaper uPVC foils on strongly south or west-facing elevations in exposed locations can, over many years, show colour change before an equivalent powder-coated aluminium frame would.

If your house is a cottage, terrace or traditional semi and you want the maximum number of windows replaced within a set budget, the Residence Collection is very likely the right call, and there is no meaningful performance penalty for choosing it.

If you are extending, building new, or replacing large openings and want the frame to disappear as much as possible, aluminium earns its higher price. It is also the more sensible long-term choice on very exposed elevations where you plan to stay in the house for decades.

Many of our Cumbrian projects use both: aluminium on a rear extension's large glazing, and Residence Collection uPVC on the original part of the house where sightlines matter less and budget needs to stretch further. That mixed approach is common and nothing to be embarrassed about.