Robert H. Crawford

Life cycle assessment in the built environment

1. Global Environmental Issues and the Built Environment 2. Towards a Sustainable Built Environment 3. Life Cycle Assessment 4. Quantifying Environmental Impacts in the Built Environment 5. Case Studies: Examples of Life Cycle Assessment in the Built Environment 6. Opportunities for Reducing the Environmental Impact of the Built Environment

The path exchange method for hybrid LCA.

Hybrid techniques for Life-Cycle Assessment (LCA) provide a way of combining the accuracy of process analysis and the completeness of input-output analysis. A number of methods have been suggested to implement a hybrid LCA in practice, with the main challenge being the integration of specific process data with an overarching input-output system. In this work we present a new hybrid LCA method which works at the finest input-output level of detail: structural paths. This new Path Exchange method avoids double-counting and system disturbance just as previous hybrid LCA methods, but instead of a large LCA database it requires only a minimum of external information on those structural paths that are to be represented by process data.

VALIDATION OF THE USE OF INPUT-OUTPUT DATA FOR EMBODIED ENERGY ANALYSIS OF THE AUSTRALIAN CONSTRUCTION INDUSTRY

This paper evaluates a recently developed hybrid method for the embodied energy analysis of the Australian construction industry. It was found that the truncation associated with process analysis can be up to 80%, whilst the use of input-output analysis alone does not always provide a perfect model for replacing process data. There is also a considerable lack in the quantity and possibly quality of process data currently available. These findings suggest that current best-practice methods are sufficiently accurate for most typical applications, but this is heavily dependant upon data quality and availability. The hybrid method evaluated can be used for the optimisation of embodied energy and for identifying opportunities for improvements in energy efficiency.

A comprehensive framework for assessing the life-cycle energy of building construction assemblies

Building environmental design typically focuses on improvements to operational efficiencies such as building thermal performance and system efficiency. Often the impacts occurring across the other stages of a buildings life are not considered or are seen as insignificant in comparison. However, previous research shows that embodied impacts can be just as important. There is limited consistent and comprehensive information available for building designers to make informed decisions in this area. Often the information that is available is from disparate sources, which makes comparison of alternative solutions unreliable. It is also important to ensure that strategies to reduce environmental impacts from one life cycle stage do not come at the expense of an increase in overall life-cycle impacts. A consistent and comprehensive framework for assessing and specifying building assemblies for enhanced environmental outcomes does not currently exist. This article presents the initial findings of a project that aims to establish a database of life cycle energy requirements for a broad range of construction assemblies, based on a comprehensive assessment framework. Life cycle energy requirements have been calculated for eight residential construction assemblies integrating an innovative embodied energy assessment technique with thermal performance modelling and ranked according to their performance.

A multi-scale life-cycle energy and greenhouse-gas emissions analysis model for residential buildings

Current assessments of residential building energy demand focus mainly on their operational aspect, notably in terms of space heating and cooling. The embodied energy of buildings and the transport energy consumption of their occupants are typically overlooked. Recent studies have shown that these two energy demands can represent more than half of the life-cycle energy of a building over 50 years. This study presents a holistic model and software tool which take into account energy requirements at the building scale, i.e. the embodied and operational energy of the building and its refurbishment, and at the urban scale, i.e. the embodied energy of nearby infrastructures (roads, power lines, etc.) and the transport energy (direct and indirect) of its occupants. All associated greenhouse-gas emissions are also quantified. A case study, located near Melbourne, Australia, confirms that each of the embodied, operational and transport requirements is nearly equally significant. Embodied and transport energy consumptions represent on average 63% of the life-cycle energy and 60% of the life-cycle greenhouse-gas emissions. The developed holistic model provides building designers, planners and decision-makers with a powerful means to reduce the overall energy consumption and associated greenhouse-gas emissions of residential buildings.

Post-occupancy life cycle energy assessment of a residential building in Australia

A comprehensive analysis of the energy demand of a building over its entire life, based on actual operational energy data and a comprehensive analysis of both initial and recurring embodied energy, is extremely rare. To address this, the aim of this study was to analyse the total energy demand associated with a case study house located in Australia, based on post-occupancy building energy data. An input–output-based hybrid embodied energy assessment approach was used to quantify initial and recurring embodied energy over a 50-year period, providing the most comprehensive assessment of embodied energy possible. The study showed that the total life cycle energy demand of the case study house was 10,612GJ or 36.4GJ/m2. Of this, operational energy was shown to account for 40%, initial embodied energy 37% and recurring embodied energy 22% of the total. This demonstrates that the energy embodied in buildings is much more significant than previously thought. With on-going building operational energy efficiency improvements this component of a buildings energy demand is likely to become even more important as is the need to utilize best-practice approaches for quantifying embodied energy.

Towards a comprehensive approach to zero-emissions housing

There are a growing number of examples of housing developments around the world that claim to be zero energy or zero emissions. Some of these clearly indicate that this only refers to the ability to minimize energy requirements for heating and cooling. However, others simply fail to recognize the energy and emissions needed to produce the materials and other components required for housing construction and ongoing maintenance and repair. For a house to be considered as truly net zero emissions, all of the emissions occurring across every stage of its life must be offset. This study calculates the life cycle emissions associated with a new house located in Melbourne, Australia. Based on the findings, an estimate is made of the capacity of a solar photovoltaic (PV) system needed to offset these emissions over the life of the house including the emissions associated with the manufacture and maintenance of the PV system itself. It was found that a 14.9kW system would be needed. The findings from this article provide a great deal of insight into the life cycle global-warming impacts associated with housing and the capacity for these to be offset by on-site solar energy production.

A comprehensive life cycle water analysis framework for residential buildings

Most studies on the environmental performance of buildings focus on energy demand and associated greenhouse gas emissions. They often neglect to consider the range of other resource demands and environmental impacts associated with buildings, including water. Studies that assess water use in buildings typically consider only operational water, which excludes the embodied water in building materials or the water associated with the mobility of building occupants. A new framework is presented that quantifies water requirements at the building scale (i.e. the embodied and operational water of the building as well as its maintenance and refurbishment) and at the city scale (i.e. the embodied water of nearby infrastructures such as roads, gas distribution and others) and the transport-related indirect water use of building occupants. A case study house located in Melbourne, Australia, is analysed using the new framework. The results show that each of the embodied, operational and transport requirements is nearly equally important. By integrating these three water requirements, the developed framework provides architects, building designers, planners and decision-makers with a powerful means to understand and effectively reduce the overall water use and associated environmental impacts of residential buildings.

The relationship between material service life and the life cycle energy of contemporary residential buildings in Australia

Energy use and related greenhouse gas emissions of buildings have a significant effect on the environment. To reduce energy consumption in buildings, it is important to understand energy use occurring across the building life cycle. While previous studies have shown the significance of both the energy required for building operation as well as the energy embodied in initial building construction, an understanding of the total energy embodied in replacement materials over a buildings life is not as well developed. One of the key factors affecting this ‘recurring’ embodied energy is the service life of materials. The aim of this study was to investigate the relationship between the service life of materials and the life cycle energy demand associated with contemporary residential buildings in Australia. The initial embodied energy, operational energy and recurrent embodied energy of a detached residential building were calculated with material service life values based on average figures obtained from the literature. These values were then varied to reflect the extent of service life variability likely for a selection of the main building materials and recurring embodied energy recalculated for each scenario. Selected materials of the building were then replaced with commonly used alternatives and the buildings initial and recurrent embodied energy recalculated for a range of materials service life scenarios. The results from this initial study indicate that the service life of materials can have a considerable effect on total energy demand associated with a building over its life. This demonstrates the need for further clarity around the service life of materials and the importance of considering the durability of materials when designing and managing buildings for improved energy efficiency. Results from this study also suggest the importance of including the recurrent embodied energy of buildings in building life cycle energy analyses, which in this case represented between 19 and 31% of the life cycle energy of the building as built and 21 and 34% with the use of alternative materials.

An Economic and In-Service Emissions Analysis of Conventional, Hybrid and Electric Vehicles for Australian Driving Conditions

Hybrid and fully electric vehicles are becoming more common as a response to rising fuel prices and greenhouse considerations. While the benefits of electrification on urban air quality have been studied quite widely, financial assessments of the various alternative vehicle forms are less common, particularly for Australian driving conditions. The aim of this paper is therefore to identify the scenarios under which different vehicle configurations are attractive to the vehicle owner. A Class-E conventional vehicle is compared with full-electric, plug-in hybrid, parallel hybrid, series hybrid and mild hybrid electric vehicle configurations. A simulation model of a conventional internal combustion engine based large sized car is developed and validated against experimental data. The conventional vehicle model is then systematically altered to obtain its increasingly electric variants. The fuel consumption and greenhouse gas emissions are simulated on the legislative NEDC drive cycle and the more representative Australian Urban Drive Cycle (AUDC). The outcomes of these tests are used to estimate the total cost of ownership and in-service emissions, thus allowing the cost of emissions mitigation to be approximated for the different vehicles. Different scenarios are considered for the pricing of energy and major powertrain components. This provides a baseline assessment based on current prices and projections, as well as ‘electrification favorable’ and ‘electrification unfavorable’ scenarios. The impact on vehicle emissions of significant penetration of renewable energy into the Australian electricity grid is also considered.