uPVC vs Aluminium Windows: An Honest Comparison

Straight away: 313 Glass fits uPVC windows only. We use aluminium where it is at its best, on bi-fold and sliding doors. This comparison explains why, so you can judge the choice for yourself whoever you buy from.

The frame material is only one part of the price. Size, number of openers, glass specification, colour finish and the condition of the opening all move a quote. Like for like, aluminium frames generally cost more than uPVC because the profile, thermal break and powder-coat finish are more expensive to make. For a whole house of standard openings, that difference adds up, which is one reason uPVC remains the usual choice for replacement windows.

uPVC is a poor conductor of heat, and its multi-chamber profile traps air inside the frame. Aluminium conducts heat readily, so modern aluminium frames rely on a thermal break, an insulating barrier between the inner and outer parts of the frame, to stop heat escaping. A good thermally broken frame performs well, but for an ordinary window the insulating advantage starts with uPVC. In both cases the glass does much of the work: low-emissivity glass such as Planibel A, a warm-edge spacer and a gas-filled sealed unit matter as much as the frame.

Aluminium is stiff, so the frame can be slimmer for the same size of glass. That is exactly why it suits large, heavy panels on bi-fold and sliding doors, where slim frames maximise the glass. On a typical window, the gap is far smaller, and uPVC offers chamfered or sculptured profiles, flush sash options and woodgrain or colour foils, including greys and anthracite, that suit both period and modern houses.

Neither material rots or needs painting. uPVC needs an occasional wipe with soapy water and a little lubricant on the hinges and locking points. Aluminium's powder-coated finish is similarly low maintenance. In practice the lifespan of either window depends heavily on the quality of the hardware and, above all, the fitting: a well-installed frame, sealed properly to the wall, lasts far longer than a good frame fitted badly.

For most replacement windows, uPVC gives the best balance of insulation, appearance options and cost, which is why it is what we fit. Where the opening is wide and the panels are large, such as bi-fold and sliding doors, aluminium's strength and slim frames make it the better material, and that is where we use it. Everything we install is fitted by FENSA and CERTASS registered fitters, starting with a free survey.