C O N T E X T 9 9 : M A Y 2 0 0 7



The envIronmental impact of a BuIlding

Throughout its lIfetime (harris, 99)

Input

Stage

Output

Energy

(Earthmoving)

site preparation Carbon dioxide

dirt

Noise

loss of amenity

loss of trees

loss of wildlife

Energy

Components

raw materials

Construction Carbon dioxide

dirt

Noise

Waste materials

Energy

Materials

(Maintenance and

refurbishment)

use

Carbon dioxide

Indoor effects

(asthma, sick

building syndrome)

Energy

demolition

Carbon dioxide

dirt

Waste material

DAVID DREWE

Embodied energy: new build v refurbishment

When considering the energy cost of development, it should not be assumed that a new

energy-efficient building will always be the best option.

Embodied energy is the energy tied up in materials as

a result of extraction, manufacture, production and

delivery. The embodied energy in buildings is that

used to produce building materials, to transport them

to site and to build with them.

The idea of embodied energy ha s been the subject

of research for many years. It has been proposed that

energy, including that embodied in materials, could be

used as an indicator of environmental impacts.

Ted Kesik (2002) quotes typical embodied energy

values of some common building materials as 5,170

MJ/m

3

for brick;139 MJ/m

3

for rockwool; 37,550

MJ/m

3

for float glass; 1,380MJ/m

3

for timber; and

3,770MJ/m

3

for fibreboard.

One of the arguments put forward for not demolishing

buildings is the loss of the embodied energy contained

in the existing stock. So lifetime energy should include

the embodied energy of the initial constr uction,

energy required for its operation, any improvements

and finally the energy for demolition.

Should the embodied energy contained within the

materials of existing buildings be included in any

assessment of total energy? While embodied energy

has no doubt been used to constr uct the existing

housing stock, it is in effect a sunken energy cost. The

energy and the materials have already been consumed.

They can now only be offset in part if the materials

can be recycled, recovered or reused.

When undertaking comparison calculations, the

embodied energy in the original property is cancelled

out, so it can be discounted. It is suggested therefore

that the embodied energy of exis ting buildings is not

part of any total energy comparison calculations.

Is the existing dwelling favoured by ignoring its

embodied energy? In the case of demolition and new

build, the consequences of the demolition are the loss

of the embodied energy and the resources conta ined

in the existing property. This energy cos t has to be

considered as part of the price paid for under taking

the new build.

For refurbishment, the total energy used is the

embodied energy of exis ting materia ls, plus the

embodied energy of materia ls used in refurbishment,

plus the operating energy, plus the energy for

demolition.

For new build, the total energy used is the (loss

of) embodied energy of existing materials (of the

demolished house), plus the embodied energy of the

new build materials, plus the operating energy, plus

the energy for demolition.

Embodied energy can be used as an indicator of

environmenta l impacts. Buildings should have the

lowest total lifetime energy use possible, indicating the

lowest possible environmental impacts.

The move towards sustaina ble development has

required c onsideration of the wider social a nd

economic impacts, as well as environmental ones.

Energy use would appear to be able to be used

as a good indicator for economic issues. Potential

shortages as the result of conflicts, natural disasters

or politica l unrest can lead to a direct impact on our

economy.

Energy can also be linked to a number of social

issues. Pollution, as a result of the production and

use of energy, can cause health problems and pla ce

increased demands on society to care for or treat

those affected. Fuel pover ty can add to these health

problems, and results in some people experiencing a

lower standard of living and financial hardship.

The big impact of energy use is on climate change.

Predicted increased flooding, higher extremes of

summer temperature and water shortages will all

affect society. The relationship between carbon dioxide

emissions and energy makes energy a good indicator

of potential climate damage.

One of the most important issues to consider is

that an energy-efficient building may use more energy

over its lifetime then a less efficient building with a

higher operating energy. The energy -efficient building

would require not only more energy to construct

but also more for maintenance of both its fabric and

equipment. It should not therefore be assumed that a

new energy-efficient building will always be the best

option.

References

Harris, dJ (1998) ‘A

quantitative approach

to the ass es sment of

the envi ronmental

impact of building

materials’, Building and

Environment, 34

Kesik, T (2002)

‘Perspectives on

sustai nability’,

Architectural Science

Forum, January 2002,

www.canadianarchitect.

com/asf/perspectives _

sustai nability/index _

frameset.htm

David Drewe is head

of the building services

engineering and safety

team at English Herit age,

and coordinator for

the English Heritage

Sustainable Development

Board .