Civil Engineering Reference
In-Depth Information
building elements. Housing renovation should reduce the environmental impact
(e.g. energy and resource consumption, emission of air and water pollutants, waste
generation, and noise), increase the indoor comfort and improve the architectural
appearance of the building facades.
2 Literature Review
Energy use in building operation accounts for 70-90 % of energy used during its
life cycle (Chen et al.
2001
; Zimmermann et al.
2005
; Cole and Kernan
1996
; Fay
et al.
2000
; Suzuki et al.
1998
; Nemry et al.
2008
; Ortiz et al.
2009
). Some
literature studies on LCA carried out on low-energy houses focused on minimising
the final energy use or the purchased energy in the operation phase, while the
energy consumption in other phases is often neglected.
All of the cited studies reach the conclusions that moving toward low-energy
building and to nearly Net ZEBs involves a decrease in the relative share of energy
use related to building operation.
An interesting Swiss study, based on a life-cycle approach, estimated that the
construction sector is responsible for about 50 % of the life-cycle primary energy
consumption in Switzerland (Zimmermann et al.
2005
). Such consumption is
mostly due the single-family dwellings, followed by the multi-family dwellings.
The highest contributions are given by the energy use for heating and hot water
supply (50-70 % of the global consumption), while embodied energy of the
building materials accounts for 10-20 %.
Another life-cycle study was carried out within the EU Building Project
'Environmental Improvement Potentials of Residential Buildings'. It assessed the
environmental improvement potentials of residential buildings, including all rel-
evant types of existing and new buildings used as household dwellings in the
EU-25 (Nemry et al.
2008
). Such a study took into account the residential building
stock in the EU 25, divided in single-family houses, multi-family houses and high-
rise buildings. The operation and the end-of-life phases were included in the
existing building analyses, and the construction phase was added in the new ones.
The results showed a common trend both for new buildings and existing buildings:
the high-rise buildings involved the lowest life-cycle impacts, while, on average,
single-family houses have the highest impacts (i.e. a primary energy requirement
of 1,000-1,500 MJ/(m
2
y), and a GWP of about 70-80 kgCO
2eq
/(m
2
y)). This trend
depends on the effects of the climatic conditions, the building shape and the shell
insulation on the internal thermal loads. For new buildings, the use phase domi-
nates the total environmental impacts at EU level, but the construction phase also
accounts for a large rate of the impacts (8.3-34.3 % of the environmental impacts).
Another interesting comparative study among different residential buildings
was presented in (Ortiz et al.
2009
). Six semi-detached house typologies, common
in the central Europe, with living surfaces ranging from 176 m
2
to 185 m
2
and an
average useful life of 80 years were analysed. The houses differed in the energy
