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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)