Expanding on these aspects, as mentioned, a study of energy-related emissions at the final point of consumption (by Lenzen et al1) finds the per capita energy usage in a group of low density Sydney suburbs to be only 96 GJ per annum compared to 169 GJ for high-density suburbs. Part of the explanation for this difference is lower average incomes in the low density areas and hence less expenditure on food, goods and services.
Multivariate regression shows no significant correlation of energy usage with density.
There are additional aspects relating to the higher energy consumption in high-density in Australia that need to be considered.
- The climate in the areas of Australia where most of the population lives is more benign than is generally the case in the United States and there is less demand for energy for house heating and cooling.
- Furthermore, when such energy is required, dwellings too close together (as is the case with apartments) are more difficult to cool whereas it is easier to heat them. Cooling technically needs more energy than heating as a much larger volume of air needs to be circulated. This factor can differentiate between cold and warm climate density comparisons. Also, free-standing houses are more easily shaded by overhanding eaves and trees than are multistorey units.
- Looking at particular emission sources, in Sydney household energy per person (gas and electricity) is significantly less in single-residential dwellings compared to high-rise. Frequently high-density data does not take into account the significant common electricity consumption of the whole apartment block which includes energy used by such items as lifts, lighting common areas such as foyers and car spaces and the common components of air conditioning3.
- Embodied energy in low density buildings is also less in single-residential dwellings than in high-rise4.
- There are more people per household in the lower density areas (average 3.89 compared to 1.49 for the high-density areas), so spreading the household energy usage over a greater number of individuals. In the calculations of energy usage Glaeser’s publication2 models a “standard household” of 2.2 people. One wonders whether differences where they occur in the number of people per dwelling in high-density and low density areas can be adequately catered for in such models. In considerations of environmental sustainability surely energy usage per person rather than per household is the measure that should be applied.
1 Lenzen, M., Dey, C., Foran, V., Energy requirements of Sydney Households, Ecological Economics, 49 (2004) 375-379.
2 Glaeser, E.L., Kahn, M., The Greenness of Cities, Harvard University, March 2008
3 Myors, P., O’Leary, R., Helstroom, R., Multi-Unit Residential Building Energy & Peak Demand Study, EnergyAustralia,
NSW Department of Planning (October 2005), Energy News VOl 23 no 4 Dec 05
4 Perkins, A., Hamnett, S., Pullen, S., Zito, R., Trebilcock, D., Transport, Housing and Urban Form: The Life Cycle Energy Consumption and Emissions of City Centre Apartments Compared with Suburban Dwellings, Urban Policy and Research, 27: 4, 377 — 396, (2009)