PVCu, UPVC or PVC windows

You’ve probably heard of PVCu, UPVC and PVC windows, but do you know what each one means? And which you should select for your home?

What are PVC windows?

PVC, or polyvinyl chloride, is a plastic polymer. It was originally synthesized by German chemist Eugen Baumann in 1872 when he left a flask of vinyl chloride exposed to sunlight. It took until the 1920s for a form of PVC to be developed which was resilient enough for commercial applications.

How PVC is made

PVC is manufactured from vinyl chloride (H2C=CHCl), a chemical derived from petroleum, which is also known as vinyl chloride monomer (VCM).

The VCM is heated in a reactor along with a catalyst, which is a process called polymerisation. Heating to over 200°C combines the individual molecules (monomers) into long chains of molecules (polymers).


The resulting, unmodified, PVC then requires additives to be incorporated before it can be turned into a useful product. These give the PVC properties such as heat resistance, UV resistance, flame retardance and flexibility.

So, technically, PVC isn’t used to manufacture windows. Windows are only made from PVC plus additives to make it more rigid and durable – called PVCu.

What are PVCu windows?

PVCu windows are made from PVC which has been modified with additives to give it certain properties, such as resisting damage from sunlight, water and heat.

One additive which isn’t included in the ingredients list for PVCu is plasticisers. In many applications of PVC (eg flooring) these are added to make the product more flexible. But in window manufacturing no plasticisers are added, to keep the window frames rigid and strong. PVCu is sometimes known as RPVC: Rigid PVC.

It’s the lack of plasticisers which put the “u” into PVCu, it is unplasticised polyvinyl chloride.

What are UPVC windows?

Simple – UPVC the same as PVCu, just some people opt to put the u at the front instead of at the end!

How PVCu (or UPVC) windows are manufactured

Turning PVC into PVCu

PVC resin is mixed with the required additives, heated to combine the ingredients, then cooled, sieved and blended to give a smooth, consistent final product. The resulting PVCu is dried into a powder.

The powder PVCu is extruded to create the window frames. This means that it is heated up until it is molten, then forced through a die, forming the required shape for the window profile.

We use window frames which have been extruded by Liniar. This video shows the processes they use to create this strong, durable product:


Forming the PVCu window

The five or six metre lengths of extruded PVCu are then cut to size using precision machinery.

The sections of the frame are fixed by heating the edges and welding them together. Various processes follow, to add glazing, seals and fixtures to the windows.

You can see an example of PVCu windows being manufactured in this video from our partners, Platinum NRG:


Benefits of PVCu windows

The rigidity and durability of PVCu quickly made its stamp on the window and door market in the early 1980s. Customers recognised the advantages of this secure, low maintenance material. Unlike wooden window frames, PVCu won’t discolour, rot or warp. And they don’t need repainting every few years.

PVCu windows offer great thermal and sound insulation, lowering your heating costs and keeping noise at bay.

As time has gone on, PVCu windows have become more sophisticated. A huge range of styles are available, mimicking the appearance of old wooden or steel windows, but with all the advantages of this modern material.

PVCu windows from Window Wise

We fit a wide range of PVCu windows in styles to suit every home. Call our team of experts on 01444 45 71 45 for more information.