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8

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)