homes’ carbon emissions and the impact building
had on the environment.
So, with a need to maintain an image of having
a positive attitude towards sustainability and
demonstrate a commitment to delivering carbon
neutral homes, what extra
steps can the sector take to
improve its sustainability?
Evaluating the options
One area that can
sometimes be overlooked
when seeking to improve
sustainability is the
individual materials that are
used in the build themselves. Yet this is something
that can make a significant difference to how
sustainable, and affordable, the build ultimately
ends up being.
Take for instance the material options for
windows and doors, which have been locked in
an on-going battle in the fenestration sector. For
many years, manufacturers of wood, aluminium
and PVC-U windows have been battling to win over
BUILDING PRODUCTS | NOVEMBER
both specifiers and the UK’s army of homeowners.
In the main, it appears subjective but as the
industry increasingly focuses on environmental
and sustainability issues, all that might be set to
change. And with factors such as energy efficiency
having more of an impact on public perceptions
of quality, it’s important to take a fresh look and
see how competing
materials fare in the
In terms of
performance, there’s little
distinction between the
main door and window
frame materials, with
no specific material
having an obvious advantage in the relevant
standard impact categories. Some will argue
that aluminium frames contribute to heat loss
more than wood or PVC-U frames because of the
inherent conductivity of metal for example, but in
general, there is little between each of them when
it comes to performance, with A and A+ ratings
largely the norm.
With the materials seemingly neck and neck,
if the social housing sector is to improve its
sustainability, it’s clear that they need a fresh
perspective on the issue if they are to achieve any
sort of marginal gains. And this ‘gain’ can be found
when evaluating the materials end of life, as this is
where the differences begin to emerge.
For instance, 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
More than 560,000 tonnes of what is referred
to as ‘post-consumer’ material is recycled across
Europe every year. 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. It actually gets stronger the first few
times it’s recycled, which means PVC-U can be
re-processed and used to make the same products
it came from or for high-value, ‘upstream’ recycling.
When it comes to aluminium, like PVC-U,
recycling rates are impressive, and it can also
be recycled and used to make new window and
door frames, again and again. However, the key
difference lies in the amount of energy consumed
(and emissions produced) to recycle each one.
PVC-U is reprocessed at a modest 160-220°C –
compared to the 700-750°C or more required to
melt down and recycle aluminium.
When evaluating the materials on this criteria,
it is timber that lags behind, as the fibres in wood
break down immediately when it’s recycled.
This means it can only be used to manufacture
chipboard and other low-grade timber products
or ‘downstream’ recycling. Although it can be
converted into biomass fuel and burned to produce
green energy, proportionately fewer wood frames
are sent for recycling – with an estimated 50%
ending up in landfill.
These small variances may seem trivial but as the
social housing sector looks to continually improve
its record on sustainability while boosting the UK’s
affordable housing stock, they have the potential to
make a very big difference.
By adopting some ‘outside the box’ thinking
the sector will see a world of possibilities exist for
improving its sustainability.
PVC-U is a very
easy material to
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