Civil Engineering Reference
In-Depth Information
allow the client to understand the yield from the investment in
a sustainable building and encourages client participation. (For
more information see www.usgbc.org.)
Sustainable houses have been built by and large from mate-
rials sourced locally and/or materials whose thermal behaviour
is appropriate to the site and climate. They may even include
materials that absorb CO
2
. Materials which have low-embodied
carbon (i.e. those requiring only a small amount of energy to
process, transport and manufacture them) are used where pos-
sible and are chosen primarily for their thermal performance as
required by the local climate and site. The building is designed
to be flexible enough so that daytime solar heating is maxim-
ised and night-time heat losses are minimised. An example of
this technique would be to use Trombe walls which, due to the
material's specific heat capacity, absorb and effectively store
heat releasing it slowly back into the building during evening
hours.
Figure 4.4
shows how the Trombe Wall theory can be
adapted for roofs.
Water consumption can be reduced through the use of a grey-
water system and solid waste can be fed back into the nitrogen
cycle. The whole design of the building is focused around avoid-
ing the need for significant heating, lighting, ventilation and
water requirements. The building is also adaptable and flexible
for all seasons using design features implicit within the building
envelope. As the thermal envelope of buildings become more
airtight and thermally efficient, the internal air quality will have
to be maintained through increased and adaptable natural ven-
tilation and possibly through the use of hygroscopic materials
which absorb excess humidity and improve air quality.
4.3.11
Green Star
Green Star has been set up by the Australian Green Building
Council to address the carbon emissions from the built environ-
ment. Green Star was launched in 2002 to tackle commer-
cial buildings which account for 8.8% of Australia's national
greenhouse emissions. The assessment method has developed
from BREEAM and LEED and follows the same principles
shown in
Table 4.1
. (For more information see www.gbcaus.
org.au.)
4.3.12
Code for Sustainable Homes (CSH)
The building of domestic properties constitutes a major por-
tion of UK construction sector activity, and as such was seen
as one of the main targets for improvement.
The BRE's EcoHomes guide (Rao
et al
., 2003) was estab-
lished in 1990 to provide guidance on how to build homes in
a sustainable way. The guide was superseded by the CSH for
new domestic properties in October 2007.
The CSH (DCLG, 2008) is a design guide produced with the
aim of helping UK housing developers to achieve zero carbon
emission levels by 2016 (HM Government, 2008, 2009). In
terms of energy performance, a 'Level 1' home corresponds to
basic UK Building Regulations Part L compliance, 'Level 4'
is a Passivhaus standard and 'Level 6' represents a zero carbon
development.
Currently, use of the CSH is compulsory in the design of
social housing, which must achieve a minimum of code Level
3 or 4 by 2010, Level 5 by 2013 and Level 6/zero carbon by
2016. The CSH has stipulated that the energy and water credits
are mandatory, and the code level can only be achieved if the
energy and water credits comply with the corresponding per-
formance targets.
To promote the winning of credits engineers should consider
The Green Guide for Specification
(Anderson
et al
., 2002)
which rates the proposed construction thermally and ecologic-
ally at the structural design concept stage.
The CSH approach is being adopted in the Code for Non-
domestic Buildings which will become future practice.
4.4.1.1 Case Study: Hockerton Housing, Nottinghamshire
Passively designed buildings such as the Hockerton Housing
Project have been designed to use solar energy to heat the build-
ing. The project to build five homes was completed in October
1998, with each home costing £90 000 to construct (costs were
driven down by it being a self-build project). One of the pas-
sive techniques adopted included the use of south-facing sun-
spaces to harness the heating capacity of solar energy. The heat
is absorbed into exposed masonry walls and released when the
HEAT GAIN
REDUCED
INSULATION
REMOVED
INSULATION 'COVER'
WATER
WATER COOLS
METAL SKIN
SUMMER DAY
4.4 Implementing an integrated design approach
4.4.1 What is a sustainable building?
A sustainable building is something that goes beyond the
targets and asks how the building responds to its site, geo-
graphically, climatically, socially and economically: ques-
tions that, when answered, will lead to the beginnings of a
sustainable building. A sustainable lifestyle is a further step
that will lead to self-sufficiency and energy autonomy. It
is perhaps useful to describe here what a truly sustainable
building would be like.
INSULAT ION
ADDED
WATER
EXPOSED
(SOLAR COLLECTOR)
HEAT RETAINED
WINTER DAY
WINTER NIGHT
Figure 4.4
Trombe wall theory adapted for use on a roof
