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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
ENVIRONMENTAL
IMPACTS
TO RESTORE OR TO REPLACE?
CRAIG JONES
A
S WELL
as the 600,000 or so listed
buildings, it is estimated that almost
6 million dwellings in the UK were
built before 1919. There comes a time in
the life of every building when extensive
refurbishment is required, and for some
developers this raises the question of whether
it might be better to start again. Many would
argue that refurbishment cannot bring old
buildings up to modern energy efficiency
standards, and these days demolition and
replacement is all too often the favoured
option. Conservationists, who inevitably
favour repair and refurbishment, counter
this by pointing to the energy used to make
new buildings. But what does environmental
analysis show? Does it support refurbishment,
or replacement? When making the argument
for conserving traditionally constructed
buildings, conservationists need to be aware
of the facts and avoid suppositions. This article
explores the issues.
Traditional buildings were constructed
with materials and details that conduct heat
from the interior to the exterior. During
refurbishment it is possible to introduce
insulation into many elements, making
substantial improvements to their energy
use. However, some traditional details often
prevent energy performance levels to equal
those of modern construction. For example,
the appearance of fine brick or stone may
prevent the use of insulation on solid masonry
walls externally, while a finely plastered
interior may prevent insulation of the inside
face, and the need for permeability and vapour
movement can cause problems for insulation
in any case. Ground floors and cross walls
provide thermal bridges that also need to be
addressed.
In addition to considering the energy used
to heat a building, any analysis also needs to
consider the ‘embodied carbon’ of building
materials. This is the amount of carbon
released during the production and processing
of materials. It mainly comes from the
consumption of fossil fuel energy throughout
the production supply chain. Environmental
analysis therefore considers consumption
at all stages, such as material extraction,
refining, transportation, processing, assembly
and fabrication.
While it is true that many older buildings
cannot be refurbished to the same energy
standards as modern construction, the
additional impact of new materials must be
considered. Refurbishment requires fewer
materials and therefore less embodied carbon.
But is this enough of a carbon swing to sway
the argument in favour of refurbishment?
To answer this question, embodied and
operational carbon need to be considered side
by side, which is called the whole-life carbon
footprint. Let’s start by looking at embodied
carbon. Embodied carbon is all too easily
forgotten because it is largely concealed from
view – most people are unaware of the high
environmental impact associated with the
production of the goods they consume.
New-build houses in the UK (which
are among the smallest in Europe) release
on average around 45 tonnes CO
2
e (carbon
dioxide equivalent) during construction.
This is enough carbon to power a light bulb
continuously for over 450 years, or to power a
television for two hours a day for almost 1,440
years. It’s also enough carbon to drive to the
moon. The embodied carbon levels are, of
course, far higher for non-domestic buildings
and larger domestic estates.
To place these figures into further
perspective we need to compare them with
the operational carbon of houses. Operational
carbon varies widely but the average UK
household emits in the region of 3,300 kg of
CO
2
to heat their home. This value includes
space and hot water heating, but not the
energy for lighting or appliances, which have
their own embodied versus operational carbon
balance. In contrast, the heating carbon of
a new-build UK house is around 2,000 kg of
CO
2
per year. This means that rebuilding a
new house saves about 1,300 kg of operational
carbon every year. However, it comes at the
expense of the additional embodied carbon
emissions of the new construction.
To rebuild the house, 45,000 kg of carbon
dioxide is required. It therefore takes 34 years
before the savings in operational carbon
have matched the extra embodied carbon
that has been spent to rebuild the house.
This is particularly significant, because if
Thermographic image showing heat loss from traditionally constructed terraced houses
(Photo: Mitifo, iStock.com)