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Wednesday , 22 February 2017
Urban density reduces greenhouse emissions: study

Urban density reduces greenhouse emissions: study

Densification is one of those difficult concepts that can perplex people no matter where they stand on the issue of urban growth. There are plenty of pro-densification, anti-sprawl types who live in comfortable homes on older, tree-lined streets in central Toronto, and who would be appalled by the idea of building a high-rise condo building in their neighbourhood. This is nothing more than normal NIMBYism. Home builders, on the other hand, insist that their only goal is to give consumers what they want when they build those large, multi-bedroom, multi-car-garage homes in the suburbs. Densification, to them, is for those who want to live downtown in a condo, a matter of personal choice.

Some opposition to urban densification is NIMBY related.

A new global study, published in the prestigious Proceedings of the National Academy of Sciences in the US, looks at densification from a different, very specific point of view: its effect on greenhouse gas emissions. The main finding is that denser city development leads to lower emissions.

This emissions-benefit argument has been used for a long time by pro-densification advocates, mostly on the basis of reduced transportation emissions that result from people living closer to where they work. This study, however, found that the buildings themselves generate fewer emissions when they are built in denser development patterns. People living in multi-residential buildings tend to live in smaller units, for one thing, and this tends to promote the use of less energy. As well, attached buildings were found to be more efficient for heating and cooling, also resulting in lower emissions.

What’s more, densifying cities has the potential to cut emissions more than doing energy-saving retrofits on existing buildings. This finding is important for cities in parts of the world where urban density is already increasing, particularly China. While retrofitting remains an important option, the study found that greater benefits could be achieved by waiting until technology has improved, rather than “locking in” an existing building to “subpar” retrofit options. Existing retrofit technology typically results in energy savings of 20–40 per cent, while savings of 70–90 per cent could be achieved with state-of-the-art retrofits.

Deep retrofitting a building can result in energy savings of 70–90 per cent.

Urban form significantly affects both direct (operational) and indirect (embodied) energy. Beyond energy use, urban form also affects two other dimensions of sustainability: human well-being and economic productivity. Urban form that enables nonvehicular transport, characterized by smaller city blocks, higher street connectivity, mixed land use, and higher population and built-up densities, has been shown to be beneficial for health by promoting more physical activity, such as walking and bicycling.

The study says that urban areas today account for between two-thirds and three-quarters of global energy consumption and about 76 per cent of fossil fuel-related CO2 emissions. The world’s population is projected to increase by another 2.5 billion people by the year 2050. But it isn’t just the rate or scale of urbanization that matters when looking at energy use. It is the “spatial patterns” of urban development that matter, the relationships between the physical elements, the spaces, and the activities that make up urban settlements. What the report calls “urban form” significantly affects both the operational and the embodied use of energy.

It also affects human well-being and economic productivity, in the now widely accepted sense that walkable neighbourhoods with less vehicular traffic, smaller blocks, vibrant street life, mixed land use and higher population densities are good for people.

Vienna, Austria. High density should not be confused with high rise, says a new study of densification. Mid-rise development achieves the same ecological and social benefits.

Surprisingly, urban densities have actually been declining over the past three decades, across all countries, income levels and geographies, and are likely to continue to decline for the first half of this century. While more people are moving to cities worldwide, those cities are not necessarily developing in more compact ways. In North America and Europe, cities are exhibiting trajectories toward “more dispersed” urban forms, with populations below fifty persons per hectare. Cities need to be “steered” into building more energy-efficient urban forms if they are to realize the greatest possible energy savings. Europe stands to benefit most from densification as it currently has the most divergent urban density features in the developed world.

The study also points out that urban densification does not depend solely on constructing high-rise buildings. High density, they argue, is not synonymous with high-rise. Rather, the same or greater level of density can be achieved through other building configurations, such as mid-rise. Built-up density is higher in traditional European urban forms, consisting typically of six- and seven-storey buildings occupying a larger footprint than a high-rise tower on a smaller footprint. Mid-rise development has long been promoted as an ideal form of future development for Toronto.

About Josephine Nolan

Josephine Nolan is the chief editor of Condo.ca—Canada's Condominium Magazine. You can reach Josephine via our contact form. She reads all her mail.

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