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6

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)