Is urban density really more environmentally sustainable?

Dr Tony Recsei, president of the Save Our Suburbs community group which opposes over-development, has challenged the notion that high density urban planning is more environmentally sustainable than lower density:

The assumption that high-density is environmentally superior seems to be based on intuition as no proof is provided to support this claim. Rather, considerable evidence is emerging that this is not the case…

What the Evidence Tells Us

A comprehensive study on greenhouse gas emissions that people in Australia are responsible for was published online by the Australian Conservation Foundation (ACF). This is no longer available on line but the underlying paper can be referenced. The report showed carbon dioxide equivalent emissions per postal code (zip code) a person is responsible for at the final point of consumption. Contrary to expectations, the findings revealed that emissions are greater per person living in inner city high density areas. The annual per capita in the inner city high density areas came out to average 27.9 tonnes and in the outer low density areas 17.5 tonnes.

The study summarised the proportion various aspects from households contribute to these emissions (Figure 1)…

Surprisingly it is apparent that annual emissions per person in multi-family high-rise exceed that of those living in single-residential dwellings…

Reasons for this result include the energy consumed by the use of elevators, clothes dryers, air-conditioners as well as lighting and air conditioning common areas such as parking garages and foyers… Embodied energy, which is the energy of construction amortised for the life of the building is much higher from high-rise, due to its steel and concrete components and its method of construction including excavation. An additional factor relating to greater per person emissions probably relates to lower occupancy rates revealed in the ACF study in high-rises compared to single-family residences…

The ACF data in Figure 1 reveals that consumption of goods, services and food account for 57.7% of household emissions. It has been suggested that as people living in inner suburbs tend to be wealthier than those in outer suburbs so they produce more emissions. However a sample of households with equivalent incomes (table 6 in the underlying paper) indicates emissions from those living in the denser inner suburbs emit an annual average of169 GJ per capita which exceeds the 96 GJ per capita emissions from households with equivalent income living in the outer suburbs…

Another consideration regarding emissions is that traffic congestion increases whenever high-density policies are imposed…

Another environmental misconception relates to water consumption. Figure 4 shows there is no significant difference in per capita water consumption between those living in multiunit dwellings or separate houses situated in Eastern Sydney in spite of the necessity to water gardens for the latter…

Let’s Get Beyond the Mythology

The rationale behind the imposition of high density in Australia is perplexing. Australia is not short of land, only some 0.2% is urbanised. In addition to negative environmental aspects other studies show the densification policy causes housing unaffordability, traffic congestion, overcrowding, reduced housing choice, decreased community amenity and negative health aspects. Policies should be based on reality, not on mere intuitive supposition or ideological fantasy.

Here’s an extract of the ACF’s main findings in relation to urbanisation [my emphasis]:

Inner cities are consumption hotspots

Urban living patterns offer many opportunities for efficiency and reduced environmental impacts, compared to more dispersed populations. For example, access to public transport, as well as shops and facilities within walking distance, help make inner city dwellers less car dependant.

Further, the prevalence of more compact housing such as apartments in urban centres could lead to lower per person electricity and heating costs.

Yet despite the lower environmental impacts associated with less car use, inner city households outstrip the rest of Australia in every other category of consumption. Even in the area of housing, the opportunities for relatively efficient, compact living appear to be overwhelmed by the energy and water demands of modern urban living, such as air conditioning, spa baths, down lighting and luxury electronics and appliances, as well as by a higher proportion of individuals living alone or in small households.

In each state and territory, the centre of the capital city is the area with the highest environmental impacts, followed by the inner suburban areas. Rural and regional areas tend to have noticeably lower levels of consumption.

These trends in are closely correlated with wealth. Higher incomes in the inner cities are associated with higher levels of consumption across the board.

Another study, entitled Downtown High-Rise vs Suburban Low-Rise Living, also shows that high-density living is less environmentally friendly than suburban living:

The three-year US study shows that apartment dwellers consume more energy, spend more of their time travelling and use their cars more.

“The findings are a little surprising to us all,” says Dr Anthony Wood, executive director of the Chicago-based Council on Tall Buildings and Urban Habitat (CTBUH), a research professor in the college of architecture at the Illinois Institute of Technology, Chicago, and co-author of the landmark report.

“We’ve all grown up thinking that urban density and verticality is a good thing but there has never been a study that has really looked at this in any detail; they’ve all been generic studies, based on large sets of generalised data. So we thought we should undertake a more focused study to prove it. And the results have been quite the opposite to those we thought we would find.”

The study, Downtown High-Rise vs Suburban Low-Rise Living, minutely examined the lifestyles, movements and energy bills and usage of 249 households living in high-rise towers in the city of Chicago. At the same time, it collected the equivalent data for 273 households residing in houses in the suburb of Oak Park, 11 kilometres from the CBD, and compared the two.

The outcomes, released on Tuesday at the annual international CTBUH conference this year being held in Australia, were staggering.

Downtown high-rise residents were found to consume 27 per cent more electricity and gas per person than the suburban residents, and on a square metre of space average, they consumed 4.6 per cent more.

Despite the fact that some of the energy use in high-rise was from the lifts in buildings and common lighting, pools and gyms, suburban homes have a far greater surface-to-volume area, with high ceilings, unattached walls and large roofs, and most of the houses in the study were large, wooden-framed and, on average, 98 years old.

In terms of embodied energy – the quantities and specifications of materials used in the construction of both types of housing – high-rise fared even worse. The project found that high-rise buildings required 49 per cent more embodied energy to construct per square metre, and a stunning 72 per cent more on a per person basis…

High-rise residents were also found to own more cars (0.6 cars per person as against 0.5 in the suburb) and travel longer distances in them, 9 per cent further per year…

On the plus side for city centre high-risers, they were discovered to use less water – 73 per cent of the water used in suburban households, they took fewer separate journeys a year (92 per cent of those taken in the suburbs), and they walked and cycled nearly three times more.

One factor that may have skewed the findings is that high-rise city residents were generally older than those in the suburbs with an average age of 51 compared to 31.8, and were wealthier.

Both studies are likely skewed by the fact that inner city residents tend to have higher incomes, and that higher incomes tend to correlate with more consumption and worse environmental outcomes.

Nevertheless, the assumption that urban density necessarily delivers better environmental outcomes does need to be challenged. If done poorly – such as via the proliferation of poorly designed high rise dog boxes – then environmental outcomes are likely to be poor.

But the same can be said about many of the detached houses being built on the fringe, which tend to be built to the boundary, have no eaves, poor aspects, and little tree or grass cover (creating a heat island effect), thus also creating poor environmental outcomes.

Of course, Australia having some of the most expensive land costs in the world does not help the situation, since it encourages developers to cut costs on construction in order to maintain some semblance of affordability.

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