For most homes, uPVC is all you need. Aluminium is the choice when uPVC can't cope: large glass, a slim frame, heavy sliding doors or a colour outside the standard range. Below are the differences in numbers — the decision is yours.
In short: when to choose which
- uPVC — detached houses, flats, replacing old windows. Anywhere warmth and budget matter and the windows are ordinary sizes.
- Aluminium — floor-to-ceiling glazing, post-free corners, lift-and-slide (HST) doors several metres wide, slim frames and any RAL colour.
Insulation: both meet the regulations
uPVC profiles with triple glazing go down to Uw 0.71–0.81 W/m²K, depending on the system. That comfortably meets the requirements for new buildings in the EU.
Aluminium itself conducts heat far better than uPVC. That is why a warm aluminium profile has a thermal break between its outer and inner parts. Aluprof MB-86 SI goes down to Uw 0.83, and the passive-house MB-104 HI to 0.73 — as good as the warmest uPVC. Only aluminium without a thermal break, such as MB-45, is cold. It is used for interior partitions and unheated conservatories.
Sizes and slimness
This is where aluminium clearly wins. It is stiff, so it doesn't bend under the weight of large glass units and doesn't move as much with temperature changes as uPVC. Fixed lights of several square metres and lift-and-slide doors several metres wide are the norm in aluminium. A single HST leaf can weigh up to 400 kg.
Stiffness also means slimness. For the same window size, an aluminium frame is narrower, so more of the opening is glass.
uPVC also makes large windows and lift-and-slide doors, but it reaches the manufacturer's limits sooner. In the configurator you see those limits straight away: enter the size and you'll find out whether the window works in a given system, and what it costs.
Colours
A uPVC window is a white profile, and the colour is a foil. You can choose woodgrain decors (golden oak, walnut, Winchester…), anthracites, greys and matt black — on the outside (white inside) or the same colour on both sides. The palette depends on the profile brand.
Aluminium is powder-coated, so the colour can be anything from the RAL palette — matt, gloss or textured. Aluminium windows are the same colour on both sides.
Price
For the same dimensions, aluminium costs more than uPVC. For ordinary house windows, uPVC is the more sensible buy. Aluminium starts to pay off where uPVC can't reach: very large glass, slim frames and unusual colours. To see the difference for your own windows, use the configurator — build the same project in both materials and compare the prices.
Durability and maintenance
Today's uPVC profiles don't yellow and never need painting. Wipe the seals and lubricate the hardware once a year and that's it. The powder coating on aluminium holds its colour for decades, without fading. With both materials, it is in practice the hardware and seals that decide how long a window lasts, not the frame itself.
uPVC with aluminium cladding
There is also a middle way: Kömmerling 76 MD and 88 MD with aluminium cladding (AluClip). Inside you have a uPVC profile, on the façade side aluminium. You get warmth and a price closer to uPVC, with a durable aluminium surface outside.
How many chambers does a good uPVC profile have, and does it matter?
The number of chambers in a uPVC profile affects insulation, but it is not the only factor — and more does not always mean proportionally better. Five-chamber profiles are today's standard and suit most homes. Six- and seven-chamber profiles add insulation that you will notice mainly in hard frosts or in a passive house.
Uw is decided by the whole construction: chambers, profile depth and glass together. A seller who gives you only the number of chambers, not the Uw of the whole window, is showing you half the information.
VEKA, Kömmerling, Gealan and Salamander in numbers
uPVC profiles have been getting deeper for years. Basic three-chamber profiles are about 60 mm; Kömmerling 88 MD is 88 mm with 7 chambers. In the comparison below, it has the lowest Uw.
- Gealan S 9000 — 82.5 mm, 6 chambers, Uw from 0.74 W/m²K. The system uses STV technology: the glass is bonded to the sash with double-sided tape instead of conventional glazing on plastic packers.
- Salamander bluEvolution 82 — 82 mm, 6 chambers, Uw from 0.75 W/m²K. On the market since 2013 and still among the leaders.
- VEKA 82 MD — 7 chambers, Uw from 0.75 W/m²K, a class A profile: the outer walls are a few tenths of a millimetre thicker than in class B. Nothing to the eye, but in a hailstorm or a break-in attempt those tenths decide whether the frame gives.
- Kömmerling 88 MD — 88 mm, 7 chambers, Uw from 0.73 W/m²K.
"Uw from" is the value for a 1230 × 1480 mm window with triple glazing and a warm-edge spacer. All four systems fall within 0.73–0.75 W/m²K, comfortably within the requirements for new buildings. They differ in small design details, not in one being worse than another.
How to choose in practice
Instead of asking "which material is best", answer four questions: how large is the glazing, are you building a new house or replacing windows, what colour do you want, and what is your budget. Then build the same window in uPVC and in aluminium in the configurator — you'll see the price of each version straight away. If you'd rather ask, write to us: we reply within 3 working days.