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6
BCD SPECIAL REPORT ON
HERITAGE RETROFIT
FIRST ANNUAL EDITION
RETROFIT IN
HERITAGE BUILDINGS
Understanding the risks
IAIN McCAIG
I
T IS a widely held view that older
buildings are not energy efficient and
must be radically upgraded in order
to improve their performance. In reality
the situation is more complicated and
assumptions about poor performance
are not always justified. For example,
as Dennis Rodwell points out in his
article on heritage and sustainability
(see page 3), when HM Courts Service
analysed their records of energy use they
found that ‘…buildings from the early
part of the 20th century and before tend
to use less energy than the equivalent
more recent buildings’. Nevertheless,
opportunities exist to improve the
energy and carbon performance of many
heritage buildings, thereby helping them
to remain viable and useful now and in
the future.
The challenges in striking the right
balance between benefit and harm
can, however, be considerable. The
unintended consequences of getting
energy efficiency measures wrong
(or doing them badly) include:
• harm to heritage significance
altered appearance
loss of features
• harm to human health and
building fabric
poor indoor air quality
condensation and mould growth
decay of building fabric
• failure to achieve the predicted
savings or reductions in
environmental impact.
Getting the balance right is best achieved
through a systematic ‘whole building’
approach. This is a logical process based
on conservation planning principles
that uses the understanding of a
heritage asset, its context, significance
and all the factors that affect energy
use (not least, the people inhabiting
it) as the starting point for devising
strategies for energy efficiency.
Strategies may vary depending on
whether the main aim is to mitigate
carbon emissions, cut fuel bills or
comply with legislation such as the
Building Regulations. Compromises
are inevitable, but the whole building
approach enables informed decisions to
be taken and ensures that improvements
are suitable, well-integrated, properly
coordinated, effective, cost-efficient
and sustainable. It also provides an
effective framework for communication
between all parties involved in the
process, including assessors, designers,
installers and the people who will
use and manage the building.
A ‘Mean, Lean, Green’ philosophy
has evolved for the design, construction
and use of new buildings. This is based
on a hierarchy that begins with the
siting, orientation, form, materials and
construction of the building to optimise
the efficient use of energy and other
resources (‘Mean’). Next comes the
design, management and control of
engineering systems to ensure they can
Shrewsbury Flaxmill Maltings (Grade I, 1797), where Historic England is assessing the effects of internal
wall insulation on the hygrothermal behaviour of brickwork (Photo: Jonathan Taylor, all other images:
Iain McCaig/Historic England)