Civil Engineering Reference
In-Depth Information
Understanding and properly evaluating energy performance of buildings is a key
preliminary step to define an approach towards reducing building energy use.
Energy performance evaluation methods have already been the focus of much
research since the 1970s, when efforts to reduced energy use were sparked by the
oil crisis. Through the building process, project teams nowadays employ a variety
of assessment methods and indicators, which provide information about building
energy performance as a project advances. This information, depending on
building size and complexity, ranges from building energy benchmarks, guided by
regulation and standards, to hourly or subhourly dynamic analysis of building
performance. Hundreds of sophisticated methodologies and tools have been
developed over the last decades which have been shown to provide accurate and
detailed data to evaluate energy performance of buildings and their components
and systems.
However, one aspect that is frequently not considered in the building energy
evaluation process is that energy used does not correspond solely to the operational
phase. Buildings are complex systems comprising of a multitude of materials and
components, each of which goes through a different life cycle phase, from material
extraction, transport, production, etc., until disposal. The term 'embodied energy'
is used by different authors to describe the sum of the energy use through all or
some of those phases (Dixit et al.
2010
) and can be calculated through different
methods as process-based analysis, input-output analysis or a mixture of the two
(hybrid analysis).
In some research studies performed since the late 1970s, the embodied energy
of building products and the construction process has been analysed. As one of the
first examples, Hannon et al. (
1978
) calculated the embodied energy of building
construction, based on an input-output model for energy flows through the US
economy in 1967 and concluded that embodied energy was already a very sig-
nificant factor that needs to be considered in detail for the construction sector.
Many other relevant studies have been carried out in the last decades (Cole and
Kernan
1996
; Adalberth
1997a
,
b
; Treloar et al.
2001
) describing embodied energy
calculations for buildings and comparing the results with energy use in operation,
providing a life cycle energy evaluation of buildings. Some reviews have been
compiled with studies (Sartori and Hestnes
2007
) and tools (Haapio and Viitani-
emi
2008
) for building life cycle energy and environmental assessment. Although
all these previous studies acknowledge the potential for reducing energy use of
buildings by considering a life cycle perspective, the majority still indicate that the
operational phase of the buildings is the main factor of the life cycle energy use.
For example, in a review of life cycle assessments (LCA) for buildings by Sharma
et al. (
2010
), it is concluded:
all the life cycle phases were found to have significant environmental aspects but oper-
ational phase has the highest percentage (80-85 %) of energy consumption in the life
cycle of a building
