CityReads│Five Myths and Five Truths about Urban Density

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Five Myths and Five Truths about Urban Density

Density is a sustainability multiplier.

Peter Newman，2014. Density, the Sustainability Multiplier: Some Myths and Truths with Application to Perth, Australia, Sustainability, 6, 6467-6487; doi:10.3390/su6096467

Picture source: http://www.i2c.com.au/2018/04/singapore-green/

The divisive urban issue of density has critical importance for sustainability. It is particularly important to resolve for the low density car

dependent cities of the world as they are highly resource consumptive.

The exponential relationship between urban density and transport fuel per person in the world’s cities can be seen to be very strong. This alone should make the case for density as a sustainability multiplier: for each step in increasing density there would appear to be an exponential reduction in transport fuel.

The most important set of cities in terms of a need for density increases is the highly automobile dependent cities of North America, Australia and New Zealand. However, there is a move to lower the density in all cities in Europe, Asia and Latin America as part of the need to accommodate different lifestyles.

Peter Newman proposes ten myths and 10 truths about density to help us better understand the relationship between density and sustainability. Here I select 5 myths and 5 truths about density.

Five myths about density

1 High Density Housing is Bad for Your Health and Creates Social Problems

There is no correlation between these levels of density and health. Health levels relate mostly to income. Poverty is the biggest cause of ill health. Hong Kong has 300 people per ha—nearly 30 times Perth’s density but has high life expectancy and low infant mortality like Perth. If industrial pollution is high then building densely within the air shed will increase respiratory issues but this can be more effectively addressed directly within the industries, and if cities are sprawled to reduce exposure to pollutants it just increases the pollution due to cars.

There is little evidence social problems like crime are increased in high density areas. Crime is also mostly related to poverty. In America, the higher the density the lower the crime rate though this is more than likely because low density cities are poorer. There is some evidence that low density areas have greater obesity and depression due to less walkability and higher crime rates due to less “eyes on the street”

Why is there such a myth about blocks of flats being bad for health and local neighborhood security? Two reasons can be found:

First, because biologists suggested it was unnatural and did tests with rats and monkeys in overcrowded conditions showing how their social organization collapsed. None of this research seems to have been repeatable. When transferred to human conditions no evidence of density causing health and social problems can be found.

Second, because from the industrial revolution cities there was a long held view that disease was spread through the air and thus the early town planners in Britain sought to reduce densities to provide a “wholesome supply of good air”. Disease was afterwards discovered to be caused mostly by water-borne germs but the myth continued. In the 1960s, poor people in the UK, Australia and America were put into high-rise public housing; the result was health problems and crime with high-rise being blamed. Now crime and health problems are higher in low density poor suburbs but we do not tend to blame the housing density.

2 Nobody Likes High Density Housing

There are many cultures who like dense, high-rise housing in Asia, Europe, and Latin America. There is a long tradition of living in close proximity for security and ease of access between friends and family. The great cities of Europe are dense, especially in their core areas and are in great demand to live and visit. Whenever fast train or highway access is built to enable lower density fringe development then any city will begin to spread out but that does not mean the general culture is anti-density. English traditional culture favors the village and rural spaciousness (in literature this is called “pastoralism”), especially after the industrial revolution with its dense, slum housing. There has however always been a more urban tradition in cities like London and Manchester with their amenity and attractions and in the US from writers like Mumford, Jacobs and Gratz.

3 High Density Housing Consumes More Energy and Produces More Greenhouse Gas

The recent arguments against high-rise housing are suggesting that these building types are dangerous to the future of the planet as they consume more energy and produce more greenhouse gases than single detached low density housing. This is not true based on first principles of

architectural design and in the scientific evaluations that are happening.

The argument depends on high-rise housing having large energy consuming areas like public lift spaces, public parking and public common areas for spas and swimming pools. The data used to support this invariably include buildings with the high energy consuming areas (mostly very wealthy) compared to the whole low density housing stock which mostly do not have such facilities as spas and swimming pools. This is wrong scientifically.

One of the key reasons for compact houses was to share walls to conserve energy for heating and cooling. Thus, most evidence comparing high and low density housing (using similar wealth levels) shows that high density consumes less energy as heating and cooling are the biggest factors

The biggest difference between housing types is in their associated transport energy. Here, the main factor is location and in Australian cities this is easily measured by how far from the CBD the housing is. Central/inner denser housing is between four and 10 times less transport energy consuming than low density outer/fringe suburbs. There may be a congestion increase from density increases but only if the opportunities for more walking, cycling or transit are not enabled.

Energy increases due to congestion are much smaller than locational factors. High density housing is attracted to areas closer in and hence most high density housing is not only lower in its building energy, it is much lower in its transport energy.

4 High Density Housing is Not Necessary as Renewable Energy and Electric Vehicles will Mean we can Drive as Much as we Like

This is also a new argument by those who concede that high density can indeed save energy, but perhaps they say this will not be needed as renewables and electric vehicles will mean we can have fossil fuel-free cities and low density. Even with renewables and electric vehicles in our cities they are still car dependent with rapidly growing suburbs.

By 2050 when the world needs to have removed 80% of fossil fuels, there will still be huge areas of American and Australian cities with low density car-dependent suburbs. To be truly sustainable, these areas will need to have totally converted to renewables and electric vehicles.

There is a bigger problem: traffic. Automobile dependent city roads are already full. It is not sensible to imagine traffic increase based on electric vehicles rather than reducing the need to use a car. This will happen if high density well-located housing redevelopment is provided around rail

stations and inner/middle suburban areas with good access. Future cities will need renewables, electric vehicles and transit oriented high-rise—as fast as possible

5 High Density Housing is Not Good for the Economy

In fact, it is the low density housing that cost the economy more. Urban fringe housing is subsidized by State and Local governments. In Australia, this is around $100,000 per dwelling. Similar data are found in American cities. In Perth, this means $45.4 billion in the next 30 years unless redevelopment happens on appropriate sites in inner and middle suburbs.

Urban fringe housing costs the economy hugely in extra transport costs due to the extra car travel. In Australian cities, each dwelling built on the fringe involves an additional $250 k over the lifetime of the house in travel cost. In the next 30 years, this will cost Perth $133.6 billion just in time lost to travelling. Denser cities have 5%–8% of their GDP spent on transport, low density cities have 12%–15% of their GDP spent on transport.

Walkable high density areas have improved health due to greater walkability and improved productivity outcomes due to greater attentiveness and less days lost.

Much more of the revenue from its residents is spent locally on personal services such as restaurants, childcare and entertainment rather than on cars and housing DIY, which invariably go out of the local economy.

The following table describes the benefits of redevelopment at higher densities over urban fringe development in Perth. High density housing will improve the economy of any low density city.

Five truths about density

1 High Density Housing Contributes to Solving the Big Problems of Oil Vulnerability and Climate Change

Large sprawling low density cities like Perth are not sustainable. They use transport fuel two to three times as much as medium density European cities and five to ten times as much as high density Asian cities of similar levels of wealth.

The shared walls of high density housing generally means lower energy in the home as well as in transport. New technology in lighting, appliances, construction materials and design can also be very low carbon.

The irrevocable global trend is to move to a world where low fuel, low carbon cities, are the norm. This will mean that the economic benefits of being part of low carbon, low cost housing will grow as fuel and power based on oil and coal will be phased out. New high density precincts that allow such low carbon opportunities will be increasingly needed and are likely to be the dominant market in years to come.

2 High Density Housing is the Only Way to Provide Affordable Housing in Good Locations that Enable Affordable Living

Affordable housing can be built by going out (to cheap land) or going up (to enable the unit price of a development to be lowered.) However, only high density can provide both cheap housing (if sufficient density is allowed) and the location that can enable cheaper living due to lower transport costs.

Like many automobile dependent cities, Perth is becoming highly unaffordable. Well located housing is now extremely costly because the provision of high density affordable housing in these areas is not allowed. In new suburbs on the fringe, families are purchasing cheaper homes but have to pay larger and larger transport costs. The average annual cost of car-based transport in outer suburbs is now more than a mortgage. Wealthy inner suburbs have around half the car ownership of poor outer suburbs and the wealthy, in well located inner areas, have much greater use of public transport, cycling and walking than in poorer areas. More high density affordable housing in well located areas is an important priority for cities like Perth. If present trends continue, the city will be highly divided into “eco-enclaves surrounded by mad max suburbs.

3 High Density Housing is Necessary to Enable New Distributed Small-Scale Green Technologies

There is an emerging new model for how the footprint of cities can be dramatically reduced, the Urban Sustainability model. It consists of new urban infrastructure, new urban form and new urban management and is based around neighborhoods or precincts.

The kind of infrastructure required will enable significant reductions in fossil fuels, water, other materials and waste (thus reducing the footprint) whilst enabling cost-effective urban areas that are better places to live

The need to adopt the new urban infrastructure of decentralized energy, water and waste systems is rapidly becoming mainstream policy. The massive gains in decarbonizing a city in a short period of time are appealing to urban policy makers across the globe.

They really only work when sufficient density is available and in the case above it required medium to high density buildings to make sufficient quantity for the infrastructure to work. Normal low density suburbs would not work with such infrastructure

4 High Density Housing Provides Greening Opportunities through Biophilic Urbanism

A new approach to building high-density housing is being pioneered in some cities like Singapore, Berlin, Toronto and Chicago where there is a commitment to providing more greening—not just between buildings but on them with green roofs, green walls and green balconies. These cities have introduced a Green Plot ratio where the footprint of the building is replaced by an equal amount of greening. In many cases, buildings have been able to replace three times their space with green roofs and walls. Singapore is moving from being a garden city to a city in a garden or even a forest.

Requiring urban greening to replace urban building space has so far only happened in high density areas with the extra height to enable multistorey gardens like a forest. The different dimension of height enables very different greening structures and habitats to be created, more like a forest than a grassland or steppe. The results are stunning and at least demonstrate that high density need not mean less green.

5 High Density Housing Provides the Best Opportunities to Build Connected City Fabric, without Car Dependence, Especially with Urban Rail

Sustainable transport options such as trains, buses, bicycles and even car sharing, need density to work properly. Trains work best when there are dense centers being linked together like pearls on a string. Buses, bikes and walking are much slower than cars and trains. They will only be used if distances are short otherwise the time lost in transport is just too great and people will switch to a car. Density shortens distances, especially when well located.

Walking and cycling cannot be useful options in a city if distances beyond a few kilometres for walking or 5–10 km for cycling are needed. Thus, to enable more sustainable walkable environments you must have higher densities. The numbers have been scientifically assessed at 100,000 people and jobs within a 1 km radius for a center to be mostly walkable, and 10,000 people and jobs within a 1 km radius if it is to be a viable transit oriented sub center or station area.

The best way to reduce car dependence is to create focused density in centers linked by quality transport, especially rail. Density, oriented around quality transit, is the multiplier for the sustainability gains.

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