16
BCD SPECIAL REPORT ON
HERITAGE RETROFIT
FIRST ANNUAL EDITION
has less challenging heat demand and
airtightness requirements. There are
many aspects of EnerPhit which are very
good such as mechanical heat recovery,
but the approach still relies on high levels
of insulation and airtightness and will
only work well if the relevant products
have been installed properly. Although
traditional buildings need to retain their
vapour permeability characteristics, the
high insulation levels which are required
(to achieve the specified U-values)
inevitably means solid wall insulation.
The technical feasibility of installing
solid wall insulation will depend on
the construction of the building and its
location, with due consideration paid to
UK weather exposure zones. This might
not be feasible in BRE zones three and
four (which includes most of Scotland,
Wales and Northern Ireland, and the
more westerly areas of England). The
impact on significance that such works
would make also needs to be assessed.
HOLISTIC ALTERNATIVES
While all these official and credible energy
and environmental assessment methods
provide tangible outputs, they are all
unreliable or potentially problematic
when it comes to traditional buildings.
The best way of achieving energy
efficiency in a sustainable way is to take
a holistic approach which considers all
aspects of the building. This, however,
doesn’t deliver any SAP points which are
of course needed for EPCs to improve the
official energy performance rating.
The STBA retrofit guidance wheel
(page 12) is an excellent tool for going
through the process of choosing retrofit
measures and there isn’t anything better
that does this. It takes one through all
the options, steering away from those
measures which are most risky and
less likely to work, and towards those
which are less risky and more likely to
work. It also advises on how measures
interact and therefore what they mean in
combination with each other. But again,
the wheel needs to be used with caution.
It is essential to understand the make-
up of the building and its condition, and
there is no substitute for a thorough
building survey which addresses the cause
of problems from a building pathology
perspective. In addition a heritage impact
assessment may well be required to
measure the impact of proposals on the
historic significance of a building.
There is much concern from the
well-informed about the approach we
take towards the energy efficiency and
sustainability of traditional buildings. One
problem is that standards and guidance
suitable for modern construction systems
are often incorrectly applied to traditional
structures, and there is clearly a lack of
specialist expertise in this area. However,
other forms of retrofit have had even
greater detrimental impact on traditional
buildings. For example, the retrofitting of
damp-proof courses and the associated
works (such as the use of impervious
plasters and cement renders, and often
the replacement of rotten timber floors
with concrete) have, just like many forms
of energy efficiency retrofit, resulted in
changing the hygrothermal performance
of traditional buildings. Dampness and
mould are common symptoms and both
suggest that any form of retrofit needs to
be well informed.
Several new courses are beginning to
address these problems. In particular the
new Level 3 SQA Award in the ‘energy
efficiency and retrofit of traditional
buildings’ had trained 200 people by the
end of 2016. However, there are some six
million traditional buildings in the UK,
and with an acknowledged deficiency
in the knowledge and skills of both the
professions and building contractors in
this area, thousands need to be trained
not hundreds.
JOHN EDWARDS
is a director of
Edwards Hart (www.edwardshart.
co.uk), a consultancy that specialises
in older buildings and heritage. He is
a conservation accredited surveyor
and chartered environmentalist
qualified to postgraduate level in
architectural building conservation.
Formerly assistant director at Cadw,
he was the lead author for
BS7913:
2013: Guide to the Conservation of
Historic Buildings
. He is a trustee of the
IHBC and Professor on Practice at the
University of Wales Trinity St David.
Above, draught-stripping sash windows at Clovelly, Devon as part of the programme of EPC improvement
measures and, top left, simple secondary glazing fitted to a casement window. (Photos: Jonathan Taylor)