Graham Treloar

Extracting Embodied Energy Paths from Input–Output Tables: Towards an Input–Output-based Hybrid Energy Analysis Method

Embodied energy is defined as the energy consumed in all activities necessary to support a process, including upstream processes. The Leontief inverse input-output (IO) matrix gives results that are practically complete, because of the aggregation of direct and indirect requirements, but which are also unreliable, because of inherent assumptions. Although accurate for the system boundary considered, process analysis results are incomplete relative to the pure IO system boundary. Attempts to combine process and IO analysis tend to be based on process analysis data. The system boundary is still significantly incomplete—although not as incomplete as for pure process analysis. An IO-based hybrid analysis technique that requires the extraction of particular paths from the direct IO matrix has been developed. The potential for embodied energy paths to be used as the basis for a hybrid analysis of the Australian residential building sector is discussed. The results indicate that less than three-quarters of the total embodied energy of this sector is likely to be able to be validated, because of the complexity of the embodied energy paths.

Using national input-output data for embodied energy analysis of individual residential buildings

Embodied energy (EE) analysis has become an important area of energy research, in attempting to trace the direct and indirect energy requirements of products and services throughout their supply chain. Typically, input-output (I-O) models have been used to calculate EE because they are considered to be comprehensive in their analysis. However, a major deficiency of using I-O models is that they have inherent errors and therefore cannot be reliably applied to individual cases. Thus, there is a need for the ability to disaggregate an I-O model into its most important ‘energy paths’, for the purpose of integrating case-specific data. This paper presents a new hybrid method for conducting EE analyses for individual buildings, which retains the completeness of the I-O model. This new method is demonstrated by application to an Australian residential building. Only 52% of the energy paths derived from the I-O model were substituted using case-specific data. This indicates that previous system boundaries for EE studies of individual residential buildings are less than optimal. It is envisaged that the proposed method will provide construction professionals with more accurate and reliable data for conducting life cycle energy analysis of buildings. Furthermore, by analysing the unmodified energy paths, further data collection can be prioritized effectively.

A hybrid life cycle assessment method for construction

Life cycle assessments (LCAs) are used to evaluate the environmental impacts attributable to products and processes. For construction projects, LCAs can be used to assess the pollution associated with the manufacture of building materials for the construction process. Despite the reliability of traditional LCA data, many upstream processes are excluded, which adversely affects overall reliability. Input-output analysis is systemically complete, but is subject to inherent errors when applied to the LCA of specific products. Analysis of an input-output LCA model provides a basis for more informed decision making regarding processes which can be ignored during the collection of traditional LCA data. This paper proposes a hybrid LCA method for construction in which national input-output data fill those ‘gaps’ not accounted for by traditional LCA data. Regardless of the level of detail at which data are collected, LCAs can now be performed at similar overall levels of framework completeness.

Embodied energy in buildings: wood versus concrete—reply to Börjesson and Gustavsson

We analyse the wood and concrete designs of the Walludden building described by Borjesson et al. (Energy Policy 28 (2000) 575) in terms of their embodied energy, employing an environmentally extended input–output framework in a tiered hybrid life-cycle assessment, and in a structural path analysis. We illustrate the complexity of the inter-industry supply chains underlying the upstream energy requirements for the building options, and demonstrate that higher-order inputs are difficult to capture in a conventional process analysis. Our calculations show that Borjesson and Gustavssons estimates of energy requirements and greenhouse gas emissions are underestimated by a factor of about 2, and that corresponding greenhouse gas balances are positive at about 30 t C-eq. Nevertheless, Borjesson and Gustavssons general result—the concrete-framed building causing higher emissions—still holds.

An analysis of factors influencing waste minimisation and use of recycled materials for the construction of residential buildings

Residential building construction activities, whether it is new build, repair or maintenance, consumes a large amount of natural resources. This has a negative impact on the environment in the form depleting natural resources, increasing waste production and pollution. Previous research has identified the benefits of preventing or reducing material waste, mainly in terms of the limited available space for waste disposal, and escalating costs associated with landfills, waste management and disposal and their impact on a building companys profitability. There has however been little development internationally of innovative waste management strategies aimed at reducing the resource requirement of the construction process. The authors contend that embodied energy is a useful indicator of resource value. Using data provided by a regional high‐volume residential builder in the State of Victoria, Australia, this paper identifies the various types of waste that are generated from the construction of a typical standard house. It was found that in this particular case, wasted amounts of materials were less than those found previously by others for cases in capital cities (5‐10 per cent), suggesting that waste minimisation strategies are successfully being implemented. Cost and embodied energy savings from using materials with recycled content are potentially more beneficial in terms of embodied energy and resource depletion than waste minimisation strategies.

An analysis of the embodied energy of office buildings by height

Aims to compare the energy embodied in office buildings varying in height from a few storeys to over 50 storeys. The energy embodied in substructure, superstructure and finishes elements was investigated for five Melbourne office buildings of the following heights: 3, 7, 15, 42 and 52 storeys. The two high‐rise buildings have approximately 60 percent more energy embodied per unit gross floor area (GFA) in their materials than the low‐rise buildings. While building height was found to dictate the amount of energy embodied in the “structure group” elements (upper floors, columns, internal walls, external walls and staircases), other elements such as substructure, roof, windows and finishes seemed uninfluenced.

Building materials selection: greenhouse strategies for built facilities

This paper aims to consider the embodied energy of building materials in the context of greenhouse gas emission mitigation strategies. Previous practice and research are highlighted where they have the potential to influence design decisions. Latest embodied energy figures are indicated, and the implications of applying these figures to whole buildings are discussed. Several practical examples are given to aid building designers in the selection of building materials for reduced overall life cycle greenhouse gas emissions.

Embodied energy analysis of fixtures, fittings and furniture in office buildings

The energy required to operate office buildings has been the focus of much research in the past three decades. There have been limited attempts to quantify the embodied energy consumed in construction. Some embodied energy studies have been relatively detailed. But the energy embodied in fixtures, fittings and furniture which is used by occupiers of buildings is rarely mentioned. The potential significance of the energy embodied in fixtures, fittings and furniture has yet to be established. Aims to establish the likely importance of the energy embodied in fixtures, fittings and furniture relative to other life cycle energy requirements of office buildings in temperate climates. Implementation actions are suggested for the optimisation of the energy embodied in fixtures, fittings and furniture used in buildings. Assists facility managers and businesses with their decision making with respect to the environmental impacts associated with energy use throughout the life cycle of their buildings.

A framework for implementing ISO 14000 in construction

ISO 14000 has been developed as a new international standard series for promoting environmental protection and sustainable development. Since the introduction of ISO 14001 in September 1996 it has attracted great attention from organizations in various industries. ISO 14001 specifies the requirements and procedures for establishing an environmental management system. An increasing number of organizations from various industrial sectors have actively participated in implementing this new standard. However, very few construction companies – for example, in Australia – have actively pursued certification to this standard despite having an obligation to implement it, as the services and products they produce directly impact the environment. By reviewing the strategic issues posed by the entire family of ISO 14000 standards, this paper analyses its relevance to construction and the difficulties and problems that may be encountered in their implementation. A framework for implementing the standard in construction companies is proposed. It is suggested that the adoption of ISO 14000 by construction companies may enable them to improve their environmental performance as well as the built environment, which in turn will contribute to sustainable development.

Improving the reliability of embodied energy methods for project life‐cycle decision making

Embodied energy is the total amount of energy required to produce a product, and is significant because it occurs immediately and can be equal over the life cycle of a building to the transient requirements for operational energy. Methods for embodied energy analysis include process analysis, input‐output analysis and hybrid analysis. Proposes to improve the reliability of estimating embodied energy based on input‐output models by using an algorithm to extract systematically the most important energy paths for the “other construction” sector from an Australian input‐output model. Demonstrates the application of these energy paths to the embodied energy analysis of an individual commercial building, highlighting improvements in reliability due to the modification of energy paths with process analysis data. Compares materials and elements for the building, and estimates likely ranges of error.