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When the end is nigh for old windows and doors...

How does it affect the environment?

If you want to start a fight at a double glazing convention, the easiest way is to claim PVC-U is a better all-round material than wood and aluminium. Or that aluminium is better than wood and PVC-U. Or that wood is… well, you get the picture.

For decades, manufacturers of PVC-U, wood and aluminium windows have been locked in a battle to win over the hearts and minds of homeowners.

The fact that PVC-U has for many years enjoyed by far the largest share of the replacement window and door market suggests it’s winning the battle, if not yet the war, and speaks volumes for its economy, flexibility, strength, security and all round appeal.

But with energy efficiency and sustainability featuring more and more in people’s purchase decisions, how do competing materials line up when it comes to their environmental credentials?

Just as importantly, how do they compare in their impact on the environment when it comes to recycling frames or disposing of them at the end of their useful life?

Getting the measure of environmental impact

As with so many other discussions around the environment, the short answer is ’it depends who you ask.’

Over time, the way industry bodies and independent regulators measure the environmental impact of building products has changed significantly.

For many years, the BRE (British Research Establishment) Green Guide was the bible for anyone seeking information on the performance of all sorts of items, giving us the familiar ‘A+ to G’ energy rating guide we see on so many products and appliances nowadays.

More recently, The Environmental Profiles Certification Scheme and Environmental Product Declarations (EPDs) have been introduced to furnish more in-depth information.

Regardless of how environmental performance is measured, however, those looking for a clear indication of a winner between the three main door and window frame materials will be disappointed.

While some might say aluminium frames contribute to heat loss more than wood or PVC-U frames because of the inherent conductivity of metal, for instance, across the board there is little to choose between each of them, with A and A+ ratings largely the norm.

Indeed, in the words of one report*: ‘It can be concluded that none of the acknowledged studies nominated a “winner” in terms of a preferable material. Most of the studies conclude that none of the materials have overall advantages in the related standard impact categories.’

But start to examine the environmental impact of each material when it comes to being scrapped or recycled at the end of its life, and some marked differences begin to emerge.

Different materials, different endings.

PVC-U is a very easy material to recycle and re-use, and the replacement window and door industry has an impressive record for recycling old frames and using them to make new ones.

Over 560,000 tonnes of what the industry refers to as ‘post-consumer’ material are recycled across Europe every year, aided by companies like Eurocell, who operate an advanced ‘close loop’ system for the recovery, recycling and reuse of PVC-U frames.

In contrast, recycling rates for timber window frames are much lower, and it’s easy to see why.

Each time PVC-U is recycled, the proportion of additives such as impact modifiers in the mixture can be adjusted to ensure it keeps its strength. Indeed, PVC-U actually gets stronger the first few times it’s recycled. Which means it can be re-processed and used to make the same products it came from, or for high-value ‘upstream’ recycling.

But the fibres in wood...

But the fibres in wood break down immediately when it’s recycled, meaning it can only be used to manufacture chipboard and other low-grade timber products or ‘downstream’ recycling. Alternatively, it can be converted into biomass fuel and burned to produce green energy.

Not that a great deal of wood frames are sent for recycling. It’s estimated up to **50% of the timber windows removed from refurbishment projects in the UK end up as landfill.

This is partly because the timber frame manufacturers have nothing like the advanced pathways for returning and recycling old frames that the PVC-U industry has, and partly because the paint, stains and preservatives in treated wood make it much harder to recycle - not mention more toxic to the environment when it begins to break down in landfill.

And aluminium?

So much for wood. Now how do aluminium window frames fare when they reach the end of their life?  

Like PVC-U, recycling rates for aluminium are impressive, reaching 90% across Europe for the construction and vehicle industries***. And, like PVC-U, aluminium can be recycled and used to make new window and door frames many times over.

The difference lies in the amount of energy consumed - and therefore emissions produced - to recycle each one.

PVC-U is reprocessed at a modest 160-220 degrees centigrade, compared to the 700-750 degrees centigrade or more required to melt down and recycle aluminium.

While aluminium companies will maintain recycling their product uses a fraction of the energy required to make it in the first place, everything is relative; aluminium production is an extremely energy hungry process, requiring huge amounts of power to extract the metal from its ore. So even the small proportion used in recycling still adds up to a hefty fossil fuel footprint.

In conclusion...

Of course, advances in manufacturing, materials technology and recycling techniques will continue to change the relative merits of ‘the big three’. And who’s to say what other miracle material will come along to challenge them in the next few decades?

One thing is certain though: PVC-U is not the poor relation regarding sustainability and recycling that it’s sometimes assumed to be. And when it comes to PVC-U, wood or aluminium, end of life will never be the end of the argument.

*Life Cycle Assessment of PVC and of competing materials. European Commission Publication

**https://www.bre.co.uk/filelibrary/pdf/rpts/BeAware_Timber_Windows_Sector_Report_02Mar09.pdf

***https://european-aluminium.eu/media/1712/ea_recycling-brochure-2016.pdf

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