How Significant an Influence Is Urban Form on City Energy Consumption for Housing and Transport?

How significant an influence is urban form on city energy consumption for housing and transport? Authored by: Dr Alan Perkins South Australian Department of Transport and Urban Planning and University of South Australia [email protected] How significant an influence is urban form on city energy consumption for housing & transport? Perkins URBAN FORM AND THE SUSTAINABILITY OF CITIES The ecological sustainability of cities can be measured, at the physical level, by the total flow of energy, water, food, mineral and other resources through the urban system, the ecological impacts involved in the generation of those resources, the manner in which they are used, and the manner in which the outputs are treated. The gap between the current unsustainable city and the ideal of the sustainable city has been described in the following way (Haughton, 1997). Existing cities are characterised by: The Sustainable city would be A high degree of external dependence, characterised by: extensive externalisation of Intensive internalisation of economic environmental costs, open systems, and environmental activities, circular linear metabolism and ‘buying-in’ metabolism, bioregionalism and additional carrying capacity. urban autarky. Urban forms are required therefore which will be best suited to the conception of the more self-sustaining, less resource hungry and waste profligate city. As cities seek to make their energy, water, biological and materials sub-systems more sustainable, the degree to which the intensification of urban development is supportive of these aims will become clearer. Nevertheless, many who have sought to portray what constitutes sustainable urban form from this broader perspective have included intensification, both urban and regional, as a key element (Berg et al, 1990; Register et al, 1990; Owens, 1994; Trainer, 1995; Breheny & Rookwood, 1996; Newman & Kenworthy, 1999; Barton & Tsourou, 2000). One of the reasons for this rests with the difficulty of conceptualising low-density settlement patterns that are sustainable under the prevailing conditions of a high level of mobility for a majority of people in western countries, at least, while there remains such a strong nexus between mobility and negative environmental impacts. Aspirations for moving cities towards greater ecological sustainability have tended to coalesce around the themes of ‘energy’, ‘water’, ‘biodiversity’ and ‘wastes’ (eg. Australian Parliament, 2003). The research reported here explored the ‘energy’ theme, posing the question: does urban form have a significant influence on the energy expenditure of a city? As the dominant ecological impact of energy State of Australian Cities National Conference 2003 Page 1 How significant an influence is urban form on city energy consumption for housing & transport? Perkins expenditure is greenhouse gas emissions, calculations were of greenhouse gases emitted as well as energy consumed. LIFE CYCLE ENERGY AND EMISSIONS DUE TO URBAN STRUCTURE If one inserts the word ‘transport’ before ‘energy expenditure’ in the above question, we have a question that has been asked many times before. Indeed there is such a body of research literature on this topic that at least six summary articles have been written to try to come to grips with the interwoven threads of what has become a complex field of research (Steiner, 1996; Handy, 1996; Stead & Marshall, 1998; Badoe & Miller, 2000; Bunting, 2000; Crane, 2000). However, transport, which in the literature equates to motorised travel, is not the only emissions-expending activity within the city that may logically be influenced by urban form. Emissions are produced in situ, in the city, from the operation on a daily basis of motor vehicles and appliances within buildings, but also in far away places in the manufacture of the “hardware” of the transport and building systems, the concrete, bricks and steel, the motor vehicles and road materials. The energy that is consumed and the greenhouse gas (ghg) emissions that are released on a daily basis by the end users can be conveniently categorised as “operational” energy and emissions. The energy that is consumed and the emissions that are produced in the manufacture of buildings, roads and vehicles are “embodied” in these products. The research reported here draws on four strands of investigation that have largely been conducted separately under the auspices of the relevant disciplines. Urban planners in particular have investigated the influence of urban form on motorised travel and its associated energy consumption. Architects have analysed the influence of building design on the quantity of energy required to heat and cool buildings to provide comfort to the occupants. These analyses have been of operational energy use. Building scientists have investigated the energy consumed and emissions produced in the manufacture of building materials. Embodied energy/emissions values can be State of Australian Cities National Conference 2003 Page 2 How significant an influence is urban form on city energy consumption for housing & transport? Perkins calculated for whole buildings based on the unit energy embodied in the constituent materials, plus the energy used to construct and maintain the building. It is possible to then compare the significance of the energy embodied in the building with the energy used in its operation. It is also possible to compare the embodied energy of different forms of buildings. Finally, in the field of mechanical engineering, the quantities of energy embodied in motor vehicles have been analysed so that the energy impacts of changes in manufacturing systems can be compared. An analysis which brings together operational and embodied energy and emissions can be broadly described as “lifecycle energy/emissions analysis”, that is an analysis which estimates the emissions produced for the whole life cycle of a product or system. In life cycle analysis the energy consumed by operational activities can be compared with the energy embedded in products by adopting a common time unit. For example, the energy from a car trip can be multiplied by the annual frequency of the trip to obtain an annual energy score, and the energy embodied in the vehicle can be divided by the expected lifetime of the vehicle to obtain a comparable annual energy score. In combination, the operational and embodied energy and emissions from transport and housing activity constitute a substantial proportion of the total energy/emissions expenditure of a household. Energy analysis of the Australian Household Expenditure Survey shows that the ‘average’ Australian household expends around 45% of its total annual energy consumption on passenger transport and housing (plus a further proportion for freight and vacation travel) (Australian Bureau of Statistics, 1995). As shown in Figure 1, 18% of annual energy is spent on travel using household cars, while just 1% is spent on public transport and taxis. 15% is expended on household appliances – space heating and cooling, water heating, cooking, refrigeration and all the other electrical appliances. 4% of energy is embodied in the cars owned by the household, and 5% is embodied in the dwelling itself. Energy expenditure on urban infrastructure is less readily identified, as much is incorporated in the general category of “government services”. State of Australian Cities National Conference 2003 Page 3 How significant an influence is urban form on city energy consumption for housing & transport? Perkins Figure 1: Household Primary Energy Consumption - derived from the Australian Household Expenditure Survey Vacations Vacation Travel Other finance & misc. 6% 4% 4% Household Motorised Travel Food and beverages 18% 16% Vehicles 4% Personal belongings & services 11% Public & Other Transport 1% Communications 1% Household Appliance Use House 15% Government Services Construction & 15% Maintenance 5% Note: the vacation and infrastructure aspects of transport and housing expenditure are incorporated to the right of the dashed line. What constitutes urban form Urban form has a number of dimensions. It concerns the size, shape and density of cities, the characteristics of the transport and infrastructure networks, the configuration of land use patterns, the design of subdivisions, and the form and orientation of buildings Urban form may be considered at the macro level of a city and its region, at an intermediate level of a town or suburb, or at the micro level of a subdivision or group of buildings. Travel related energy consumption and emissions are most likely to be influenced by macro-level urban structure factors, where the differences in the State of Australian Cities National Conference 2003 Page 4 How significant an influence is urban form on city energy consumption for housing & transport? Perkins density and distribution of activities and the location of households within settlement patterns may influence the amount of motorised travel people need to undertake. The urban form determinants of housing related energy consumption are micro- scale, and can be better described as built form variables. The research method was designed to capture a wide variation between households in many of these urban form parameters. INNER CITY AND FRINGE CASE STUDIES The empirical research, conducted in Adelaide, relates to a sample of 547 persons living in 212 households of varying family composition and income levels, residing in dwellings of varying types, from two storey terraced houses to single storey

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