Civil Engineering Reference
In-Depth Information
3 Simplified Methodology for Life Cycle Energy
Performance Evaluation in Building Refurbishment
Projects
The advantage of the proposed simplified methodology is that it can facilitate life
cycle energy performance evaluation, through the combination of embodied
energy data for products with energy assessment tools already applied for the use
stage of the buildings, such as national tools for building regulation compliance
and building energy ratings. The embodied energy of the products is in this chapter
considered from 'cradle to gate', which means including all energy inputs to a
product, expressed in primary energy, from extraction to manufacturing, until the
product leaves the factory gate. This approach is proposed as the basis for this
methodology as it is the most commonly used value referenced in embodied
energy studies (Hammond and Jones
2008
). It has to be noted, however, that a full
life cycle energy performance evaluation would also include transport to the
building site, construction processes and the 'end of life' part of the life cycle,
considering demolition and recycling potential or landfill. These additional life
cycle stages have not been considered in this chapter, partly because of lack of
relevant data and partly because the energy use on those stages have been reported
in various studies as being below 1 % of the total life cycle energy (Sartori and
Hestnes
2007
). However, it is acknowledged that these aspects could have a
potentially high impact in some situations, as discussed by various authors (Itard
and Klunder
2007
; Thormark
2006
; McCall and McNeil
2007
), and it is suggested
that an extended life cycle should be used if reliable embodied energy data are
available. More research is needed in a detailed quantification for these life cycle
phases for future inclusion in the analysis, particularly as they gain increasing
relative importance as the building use stage decreases towards zero-energy use.
For the life cycle energy performance evaluation method presented here, the
embodied energy of construction products and systems used in the refurbishment
project, calculated up to the product factory gate, is added to the annual opera-
tional energy use, so the influence of the different building options can be com-
pared. The embodied energy values presented in this chapter can therefore be
considered slightly underestimated as transport to site, construction and end of life
stage have not been considered.
The representation of embodied energy in an annualized form (divided by the
expected lifetime of the product) will allow representation of life cycle energy
performance in a common indicator, for example, kWh/m
2
*year, which is an
indicator already used for regulations and building energy rating in some EU
countries. This is a way of simplifying the understanding and application of life
cycle energy performance evaluation by architects and other design team members
on a refurbishment project.
The following sections will deal with the different steps included in the life
cycle energy performance evaluation and will introduce the concept of 'NER', as
