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T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 5
T W E N T Y S E C O N D E D I T I O N
this carbon has been extracted from the
atmosphere through photosynthesis. The
carbon is stored in the timber and away from
the atmosphere until the end of the life of the
product. In fact, the carbon storage element
of timber means that it is storing more carbon
than was released to produce the timber
product. This often results in a large carbon
footprint benefit and partly explains why the
timber first principle works well.
Another good saving is the use of water-
based instead of solvent-based paints. A
water-based paint has a carbon footprint
around a third lower than a solvent-based
one. Paint has a high embodied carbon
value and is typically applied in multiple
coats. Therefore using fewer coats, where
possible, is another good way of reducing
its impact. Likewise, painting less often
has a large benefit. Repainting a room or
an object too often makes a considerable
difference to its whole life carbon footprint.
Bricks and mortar are high-carbon
items but have a long lifespan. The embodied
carbon of these products therefore needs
to be retained for as long as possible to gain
maximum value from them. One way of doing
this is to use a lime-based mortar, which has
less embodied carbon than cement. At the end
of the lime mortar’s lifespan the brickwork
can also be dismantled and reused more easily
than if a cement-based mortar had been used.
This gives the bricks a second lifetime, offering
significant embodied carbon savings.
There are naturally some instances
where embodied carbon doesn’t need to
be considered. For example, the embodied
carbon of additional insulation almost always
pays back through operational carbon savings.
Due to their composition and methods of
production some types of insulation have
lower embodied carbon but if this comes
at the expense of a considerably poorer
thermal performance, they are unlikely to
be an attractive whole-life carbon choice.
So far refurbishment has come out well,
but is it always best? Unfortunately not.
There are cases where it is better to replace
than to repair. For example, if single glazed
windows are upgraded to double glazed units,
the embodied carbon of the new windows
will be paid back by the operational carbon
savings and the occupants will experience
enhanced thermal comfort. For listed
buildings where single glazed windows are
common, this can be more difficult as the
replacement will affect the significance of
the building, and listed building consent will
be required. There may be occasions where
the original windows have been replaced
in the past, justifying a further change. In
other cases it may be possible to introduce
draught-stripping with secondary glazing and
thermal blinds, as these measures can achieve
a thermal performance equivalent to that
of double-glazing. Alterations such as these
offer compromises that we need to consider.
When it comes down to a choice between
refurbishing or replacing, embodied carbon
often becomes a useful ally. Arguments that
point to the reduced thermal performance
of refurbished buildings should be balanced
by a careful consideration of the additional
embodied carbon expense of the new build.
While there are cases where rebuilding
is the best option there are many more
where refurbishment is the better choice.
Furthermore, without refurbishment the UK
would lose much of the charm and character
of its older building stock.
Historic and traditional architecture
contributes to our enjoyment of the places
we live and work, and makes a significant
contribution to the UK economy, particularly
through tourism. Reducing the carbon foot
print of the UK’s building stock is without
doubt extremely important, but it is not the
only criterion that needs to be taken into
account when considering the future of our
historic buildings.
Further Information
Inventory of Carbon & Energy Database, an
embodied carbon database for materials,
www.circularecology.com/embodied-energy-and-carbon-footprint-database.html
Domestic Energy Fact File
, Department of
Energy and Climate Change, 2012
W Anderson and J Robinson,
Warmer Bath:
A Guide to Improving the Energy Efficiency
of Traditional Homes in the City of Bath
,
Centre for Sustainable Energy and Bath
Preservation Trust, 2011
CRAIG JONES
PhD is the founder of
Circular Ecology
(www.CircularEcology.com),
which offers a range of consultancy and
research services including life cycle
assessment, footprinting and resource
efficiency studies. He is the author of the
University of Bath’s Inventory of Carbon &
Energy Database, an embodied energy and
carbon database for building materials (see
Further Information).
A new terrace of traditionally detailed houses rises on the outskirts of Bath. The city was inscribed as a World Heritage Site in 1987 and opportunities for both
development and improvement are understandably limited. ‘Warmer Bath’, published by Bath Preservation Trust and the Centre for Sustainable Energy gives advice on
energy efficiency improvements for traditional homes in the city (see Further Information).
Like many historic features, cast iron windows
have inimitable character, but they do drain heat.
Secondary glazing and insulated blinds offer the only
practical solution. (Both photos: Jonathan Taylor)