PVC vs aluminium windows: which should you choose?

PVC and aluminium are today the two most widely fitted window materials. Both are durable, high-performing and available with double or triple glazing: the choice isn't really about which material is "better", but about your building, your openings and the look you're after. Here's how to decide with confidence.

The key differences at a glance

• PVC is naturally an excellent insulator: the material itself slows down heat transfer.
• Aluminium is a metal: structurally stronger, but a natural conductor of heat, which is why modern profiles include a thermal break.
• PVC needs wider frames to stay rigid; aluminium allows slimmer sightlines and lets in more light.
• Aluminium is available in almost any RAL colour, in matt, satin or textured finishes, including two-tone options (different colours inside and out).
• Both materials require very little maintenance: routine cleaning is enough.

Appearance: slimness of the frames and colours

This is often the deciding factor. Aluminium allows noticeably slimmer frames, a contemporary look and deep colours that age well. PVC has come a long way — woodgrain foils, anthracite grey, textured finishes — but its frames remain a little thicker, which is most noticeable on large glazed surfaces.

In Brussels, this also comes down to the façade itself: in some neighbourhoods and for some buildings, the appearance of front-facing windows is subject to planning rules. We check this with you before any order is placed.

Thermal and acoustic insulation

For equivalent glazing, PVC naturally delivers excellent thermal performance at a reasonable cost. Aluminium with a thermal break now reaches comparable levels, provided you choose a serious system. In both cases, it's really the glazing, the quality of the installation and the airtightness around the frame that make the real difference to your comfort and your energy use.

Acoustically, the frame material plays a secondary role: it's the make-up of the glazing (asymmetric thicknesses, acoustic laminated glass) that cuts down noise from a busy street.

Maintenance and longevity

• PVC: clean with soapy water, no painting required. Darker colours need a little extra attention in strongly exposed spots.
• Aluminium: the powder-coated finish is very stable over time, even on exposed façades.
• In both cases, hardware and seals should be checked periodically: that's what really determines the lifespan of a window.

Large openings and architectural possibilities

As soon as you're talking about a sliding door, a large fixed window or heavy glazing, aluminium has the edge: its rigidity allows for dimensions and weights that PVC simply can't match without making the frames much thicker. For a living room opening onto the garden, a glazed extension or a façade with large bays, it's generally the right choice.

For windows of standard size — bedrooms, kitchen, the rear façade of a Brussels house — PVC does the job perfectly well.

Renovation: what really changes

In a renovation, everything depends on the condition of the building and how the replacement is carried out: full removal or fitting onto the existing frame. Full removal restores proper airtightness and preserves the glazed area. Aluminium's slim frames also help avoid losing daylight when part of the old frame is kept in place.

On-site measurements are essential: an older Brussels building is rarely perfectly square, and an approximate survey shows up later as a poor finish.

Budget: how to think about it sensibly

For equivalent performance, aluminium is generally more expensive than PVC: that's the cost of slimmer frames, greater strength and a free choice of colour. But comparing two quotes on material alone doesn't tell the whole story. Look instead at the glazing on offer, the profile range, the hardware, the type of installation, the interior and exterior finishes, and the removal of the old frame. We always break these items down so you can compare properly.

Pros and cons

PVC windows

• Pros: excellent insulation for the cost, minimal maintenance, wide range of colours and foils.
• Cons: wider frames, limits on very large dimensions, a less contemporary look than aluminium.

Aluminium windows

• Pros: slim frames, large openings possible, RAL colours and two-tone options, excellent long-term durability.
• Cons: higher budget, thermal performance depends on the thermal break and the range chosen.

Which material suits your project?

• Replacing standard windows with comfort and budget as priorities → PVC.
• Contemporary façade, bold colours, discreet frames → aluminium.
• Sliding door, large glazed surface, heavy glazing → aluminium.
• Renovating a Brussels building with planning constraints → this needs an on-site judgement call, as the front and rear façades can sometimes take different materials.

It's actually quite common to combine both within the same building: PVC at the back and in the bedrooms, aluminium for the living room's glazed opening or the visible façade. That's often the most sensible balance.

In summary

PVC is the most sensible choice for standard openings when insulation and budget come first. Aluminium comes into its own when you're after large glazed surfaces, slim frames or a specific colour. The best guide remains your own building: bring your dimensions and photos, and we'll compare the two options in concrete terms.