Civil Engineering Reference
In-Depth Information
This type of statements, together with the difficulty in agreeing boundaries for
the analysis and for gathering life cycle information of building components and
systems, has resulted in life cycle energy evaluation not being widely applied in
practice and generally not being integrated into building energy assessment, or in
building regulations and standards.
On the other hand, in recent years, there has been an international effort to move
towards buildings approaching zero-energy use in operation, supported by building
regulations, policies and standards. It is of particular relevance to note that in this
context, while a life cycle energy perspective is still not addressed, it could be an
increasingly important factor. If in a refurbishment project we intend to diminish
the building energy use in operation, the 'embodied energy' (energy used during
other phases of the building life cycle) frequently increases as we add more and
more complex materials and systems and can represent a larger part of the life
cycle energy use. If the goal is to refurbish a building to 'zero-energy' use in
operation, the embodied energy of added products and processes is indeed the only
life cycle energy use.
This chapter introduces the concept of LCA in construction and presents a
building life cycle energy performance evaluation methodology which can be
integrated within the already established building energy assessment methods,
facilitating the consideration of a life cycle perspective in building refurbishment
as we move towards zero-energy buildings.
The concept of 'NER' is also introduced here as an indicator to support prac-
titioners in building life cycle energy optimization, particularly useful for building
refurbishment projects. The methodology is applied in a typical house in Ireland,
as a practical case study.
2 Life Cycle Assessment in the Construction Sector
Life cycle analysis or LCA originated in the late 1960s and early 1970s, firstly as
simple studies focusing on energy use and production of waste (Udo de Haes and
Heijungs
2007
). LCA progressively evolved to include a detailed analysis of a
wide range of environmental impacts, with a set of ISO standards detailing a
framework for LCA since 1990s. In ISO 14040 (ISO
2006a
), LCA is defined as a
'compilation and evaluation of the inputs, outputs and the potential environmental
impacts of a product system throughout its life cycle'. The life cycle inventory
(LCI) phase on an LCA quantifies inputs and outputs of the product life cycle, and
energy use continues to be a key aspect of the LCI.
There is an active process at international and European level to develop
standards for sustainability assessment of buildings, which follows an LCA
approach. Within the CEN Technical Committee 350—Sustainability of Con-
struction works, the standard EN 15978 'Sustainability of construction works—
