**2. Embodied energy data: challenges and opportunities**

LCA studies are used to properly assess a product's or service's environmental impact. This strategy is largely data-driven, and is heavily reliant on the availability of precise, dependable, and high-quality data [21]. Gathering data with such qualities, on the other hand, has proven difficult for LCA end users and practitioners [22] due to a variety of issues, including manufacturer confidentiality requirements, the time and expertise required to generate reliable data, and inconsistent application of methodological approaches to data analysis [23, 24].

In theory, any LCA study in accordance with common PCRs should allow for reliable comparative analyses to take place for various building materials, products, and services. In practice however, the assumptions used in the LCA models including the service life of the product, maintenance requirements, in use operating energy, and varying system boundary options [1, 25] can significantly shift the results of the LCA models [26]. Several researchers have reported disparities between LCA results based on fundamentally different assumptions, such as functional units [27], system boundaries [28, 29],

LCI databases [21, 30], and End-of-Life (EoL) modelling scenarios [30]; Takano [31]. Clark [32] studied embodied equivalent carbon values for commercial buildings based on different methodologies and demonstrated results ranging from 300 to 1650 kgCO2eq/m2 . De Wolf et al. [22] comprehensively investigated discrepancies in the final results of LCA studies due to the quality of available data.

The other factor contributing to further discrepancies that has been studied comprehensively in the literature is the adoption of LCI techniques. The LCI techniques include process, input–output, and hybrid methods. There are fundamental differences between the way data is treated and analysed in these techniques with the process analysis formed around disintegrating the relevant life cycle stages into characteristic processes. The data associated with each stage is collected directly from relevant manufacturers or is provided by specialist data inventories including ecoinvent and GaBi. The Input–output technique is formulated around financial transaction matrices between engaged sectors. The embodied energy values are calculated using energy intensity values that have been assigned to each sector. Hybrid analysis in designed to benefit from advantages of the two techniques and at the same eliminate their shortcomings [15]. The most impactful shortcomings of the two techniques include the 'truncation error' which is believed to significantly underrepresent requirements for the process analysis [33–37] and also the 'aggregation error' for input–output analysis for allocating similar energy intensity measures to all products within a sector [38].

There are various studies that have highlighted the discrepancies in embodied energy results associated with adoption of different LCI techniques. Crawford [39], Stephan et al. [15] and Stephan and Stephan [40] have demonstrated in their studies of whole buildings that a hybrid LCI analysis can lead to embodied energy values of up to four times greater than those achieved using a process analysis. In a similar study Wiedmann et al. [41] explored the environmental impact of wind turbines and demonstrated twice as high environmental impacts for hybrid analysis compared with a process analysis. Bontinck et al. [42]. A hybrid LCI was used to explore structural insulated panel systems. The findings of the hybrid analysis were found to be 159 percent higher than a process analysis and 46 percent lower than an input-output analysis. Guan et al. [43] conducted a process study on a hybrid LCA of a building in China and found a 100 percent gap.

Drastic disparities of this nature highlight the need for a harmonised and standardised LCA to be adopted by building regulations allowing for an effective decision-making tool to assist in the early stages of building fabric design, or strategising future policies and product development for various stakeholders.

Gelowitz and McArthur [44] reviewed the published EPDs for building products and identified adoption of different LCI methodologies, high level of incomparability between EPDs using the same PCR, and poor verification practices as the main barriers in adopting the results in further analysis. Although conceding that the number of valid comparisons were substantially greater for EPD generated in compliance with EN 15804, Resalati et al. [1] argue that the EN 15804 harmonisation standard has not been totally effective.

Although several studies have investigated the LCA concept in detail and provided insight into how best these tools could be further optimised for decision making processes, their use is currently primarily limited to academic studies [30], and is not incorporated in the industrial ecosystems in enough depth [7]. This has been attributed to a series of factors in the literature including the lack of appropriate interoperability between LCA methodologies and high demand tools in the construction sector

#### *An Aggregated Embodied and Operational Energy Approach DOI: http://dx.doi.org/10.5772/intechopen.103073*

(Anand and Amor [30], Means and Guggemos [45]), the expertise required to carry out LCA studies reliably [45], and LCA priority for various industries at present in parallel to the confidentiality issues the manufacturers see as a barrier in publishing their LCA results [46]. As noted by Resalati et al. [1], such challenges may cause delays in the adoption of such technologies, implying that environmental policies and many of the assumptions on which current policies are founded may not accurately reflect energy and its consequent carbon investments. Several researchers such as Chastas et al. [47], Cellura et al. [48] and Moran et al. [49] have questioned whether our current energy efficiency measures with a focus on 'operational energy only', instead of a 'total energy' efficiency, are acceptable in the context of longer term strategic policy making.

This chapter, takes on an aggregated operational and embodied energy approach, aiming to demonstrate the impact of the uncertainties of embodied energy data when achieving low and zero energy buildings. The analyses aim to apply the aggregated approach on individual building elements and materials.

This chapter seeks to highlight the significance of considering the uncertainties of embodied energy data when LCA is used as decision making tool to inform the engaged stakeholder and other relevant end users. This will be carried out with a particular view of individual building components and materials, based on a total energy/carbon analysis.

This is illustrated by examining the sensitivity of optimal building insulation level to the deviations of embodied energy data. The assessments are shown in the context of residential buildings in the United Kingdom, although the methodology is not restricted to that and may be applied to a broader operational setting.
