Aluminium vs uPVC windows

Where aluminium genuinely wins

• Frame slimnessAround 55mm against 70mm+. That is 15–20% more glass through the same hole in the wall — the difference you actually notice.
• Large spansuPVC needs steel reinforcement inside the profile to carry big panes, and the profile gets fatter. Aluminium is the material, and stays slim.
• Lifespan30–50 years versus 20–25. Aluminium does not go brittle or yellow in UV.
• ColourAny RAL, powder coated through the surface, 25-year guarantee. uPVC colour is a foil laminate that can lift and cannot be recoated.
• Conservation areasA slim aluminium heritage profile is routinely accepted where a uPVC profile is refused.

Where uPVC genuinely wins

• Price25–50% cheaper. If the budget is the constraint, this is a real answer, not a compromise to be talked out of.
• Raw thermal performanceuPVC is a poor conductor, so a uPVC frame will usually beat an aluminium frame of the same depth on the frame U-value alone. Modern thermal breaks close most of the gap, but not all of it.
• Rental and resale propertyIf the window needs to work, be warm and cost as little as possible, uPVC is the rational choice.

The honest verdict

If you are staying, and the look of the house matters to you, aluminium. If you are letting, flipping, or the budget is tight, uPVC — and anyone who tells you otherwise is selling.

The one situation where it is not close: a conservation area, a steel-window house, or any elevation where the frame has to be slim to look right. There, aluminium is not a preference, it is the only option that works.