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Maintenance and Repair


It is often claimed that uPVC windows require no maintenance. Whilst it would be lovely if this were true, unfortunately it is not: there is no such thing as a ‘Maintenance-Free Material’.


uPVC can be discoloured by dirt and stains; this damage is difficult to reverse, as it is not a layer of paint that has lost its colour, but the material itself. The standard solution to this problem is to apply an acidic ‘cleaner’ to the windows, which does not actually clean the dirt, but instead melts away the stained layers of plastic, therefore structurally damaging the unit in the process (!)

This problem is further compounded when you realise that you cannot replace a section of a uPVC window. Small damage, such as hairline cracks caused by extreme exposure to sunlight, or impact damage in cold weather is irreparable; you must either leave the damage and allow it to weaken the integrity of the unit, or you must pay for an entirely new replacement unit. It is apt to think of a uPVC unit much like a car with the bonnet welded shut; you may be aware of the issue, but you are unable to do anything about it.

However, this is not true of timber units; the advantage of working with a natural material is that sections can be cut out and replaced with new timber / wood filler (of course, though, we would expect this to never be needed, as often timber windows live longer than their owners!). Continuing the car analogy from earlier, once the bonnet is not welded shut, and you have full access to the engine, it is a simple task for a trained professional to replace faulty components and extend the service life of the existing unit. 

In addition, the Teknos micro-porous paint that we use as standard at Core Sash Windows allows the timber joinery to breathe. When this is combined with our modern design techniques, which minimise water retention, our high-performance Engineered Redwood double glazed windows actually require very little maintenance.



As previously mentioned, uPVC windows are not painted. The white coating is the actual material, and therefore, any degradation of this exposed layer results in degradation of the unit itself. This is an important distinction, as with timber windows, it is only ever the paint layers that are exposed to the elements. Resultantly, providing that a weatherseal paint is used, the timber unit is protected and only the paint should need replacement or repairing.

In the case of our Core Sash Windows products, our factory-finished windows can expect to see 8 years without requiring paint replacement, after which the average repainting cycle is around 1 – 2 years, but potentially longer depending on exposure to the elements. Additionally, our factory-finished products enjoy full micro-porous coating at all points of the joinery; even areas that would be missed by hand or not visible when installed. As a result, this factory finishing can further help to increase the longevity of the frame by providing all-round protection.


The dangers of uPVC windows

The production and disposal of uPVC windows can lead to the release of chemicals that are known to be highly toxic to humans. 

A small sample of the noxious chemicals involved in uPVC production / disposal is as follows:

  • Cadmium – As an additive during production.
  • Chlorine – A key component of PVC (Poly Vinyl Chloride) that is also released during incineration.
  • Dioxin (2,3,7,8 TCDD) – released during disposal, and one of the most toxic synthetic compounds know to mankind
  • Lead – As an additive during production
  • Mercury – A key component during the production of uPVC.


The detrimental health impacts of these chemicals include, but are not limited to:

  • Cadmium – Kidney failure, respiratory issues such as emphysema, and a potential link to lung cancer.
  • Chlorine – Eye and throat irritation, skin burns, respiratory disorders such as bronchitis. Please note that chlorine gas was used as a chemical weapon during WW1.
  • Dioxin (2,3,7,8 TCDD) – Hair loss, loss of body weight and a weakening of the immune system.
  • Lead – Neurological damage, nerve damage, severe fatigue.
  • Mercury – Kidney failure, Central Nervous System damage, reduced cognitive function, muscle tremors, headaches and memory loss.


Disposal of uPVC

Whilst it is obvious how these chemicals can enter the atmosphere via incineration, they may also contaminate the local water tables if uPVC is landfilled. This means that neither incineration, nor conventional disposal, is a viable or safe long-term option with regards to uPVC windows.

To make matters worse, burning uPVC releases Hydrochloric Acid. This is obviously extremely harmful, and thus neutralising salts must be added to counteract the dangerous acid. This proves to be a problem in and of itself, as for every tonne of uPVC that is incinerated, over 2 tonnes of contaminated waste is produced. This waste must, in turn, be landfilled, thereby further contaminating the environment.

This situation would therefore lend itself to recycling; it seems like an obvious solution as it both prevents the disposal of uPVC and negates the need to produce more. Unfortunately, uPVC degrades when recycled, which means that this is an exceptionally limited solution. In addition, uPVC recyclate is of a lower quality that virgin uPVC, but is more expensive due to the intensity of the recycling process. This makes ‘green’ uPVC windows both lower quality, and more expensive than their ‘virgin’ counterparts.


So why don’t we offer uPVC?

Whilst we hope that we have provided you with enough facts to make your own decision, allow us here at Core Sash Windows to establish our own viewpoint:

We believe uPVC to be an inferior material. 

With regards to the level of maintenance that is required, our Engineered Redwood windows and doors are by no means more time consuming or demanding than uPVC, thereby fully negating this apparent ‘advantage’ of uPVC in place of timber.

We are also certain of the longevity of our Engineered Redwood windows and doors. We are so certain, in fact, that we give a 10 Year Guarantee on any new joinery that we provide. This matches the 10 Year Guarantees offered by national companies such as Everest and Crystal on their uPVC windows and doors. If uPVC truly had such a great life-span by comparison to timber, surely you could expect to receive a either a much longer guarantee for uPVC or a shorter guarantee for timber? 

Finally, we consider ourselves an environmentally-conscious company. The environmental impact of the production and disposal of uPVC is staggering, and we feel that we have adequately outlined the perils of this toxic material above. Timber, however, is a sustainable resource that can be recycled or repurposed with great ease. Additionally, all of the timber that we use comes from responsibly-sourced, sustainable European forests, so we even go so far as to minimise any long-term impacts that our lumber requirements could have.


To conclude

  1. uPVC does not hold any advantages with regards to longevity or maintenance  when compared to our Engineered Redwood.
  2. uPVC is an environmental hazard, which cannot be adequately recycled.
  3. Any attempt to source recycled-uPVC windows will result in inferior quality and increased costs.


Enjoy being warm and comfortable!

call us: 020 3302 2060 or email: [email protected]

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