How the position of a housing development impacts its footprint
The annual convention of the Green Building Council of South Africa (GBCSA) is home to inspiring speakers and dynamic discussions. But sometimes it’s even just the networking over a drink that leads to ground-breaking ideas. One such discussion happened a few years ago, when GBCSA’s head of technical, Georgina Smit, had a conversation with Carel Kleynhans, CEO of Divercity Urban Property Fund.
The discussion revolved around understanding the magnitude associated with a development’s location on its carbon footprint. Essentially, what is the comparative contribution of transport related emissions in a building’s whole lifecycle carbon trajectory? The question was then asked whether we could even assess this; do any quantitative resources around this exist? Eventually, the conversation led to a two-year investigation, resulting in a report being released in September 2021.
Carbon costs and context
The GBCSA and Divercity Urban Property Fund joined forces to research the impact of the location of housing developments in relation to the overall emissions across a development’s lifespan. Arup were appointed as the technical consultants to conduct the study and the results of the research were published under the title of Does location matter? in September 2021.
While it is generally understood that densification in cities supports healthy community networks where more people can benefit from services, community facilities, public transport networks, and recreation areas, there has not previously been any local quantifiable studies that attempt to understand the order of magnitude.
This research, therefore, set out to investigate the carbon costs associated with the lifestyle impact of housing in an urban centre versus housing on the periphery of a city, assuming a high concentration of amenities in the urban centre and a low concentration on the urban periphery.
AREA OF STUDY: JOHANNESBURG
In keeping with South Africa’s Paris Agreement commitment to reduce climate change, Johannesburg’s Climate Action Plan aims to have the city’s emissions peak by 2030, and to reach net zero by 2050. The city is set to achieve megacity status (home to 10-million people) by 2030, meaning that housing is becoming the most in-demand building typology in the city. In 2016, stationary energy and transportation made up the largest chunk of Johannesburg’s emission contributions, highlighting the requirement to reduce and decarbonise these sectors.
Johannesburg is also Diversity’s base of operations, and can be considered to be representative of other South African cities, both in terms of population growth and the tendency to sprawl. So this was the city selected for the study.
The study set out to add the building lifecycle carbon emissions (embodied and operational carbon emissions) to the occupant transport emissions (travel distance, travel mode, and travel behaviours) to establish a figure that represents the total whole carbon lifecycle based emissions. This value was to be established for household typologies for low and
middle income households in both the “urban core” and the “urban periphery”.
Using both the City of Johannesburg Metropolitan Spatial Development Framework (MSDF) and the City of Johannesburg Nodal Review Policy (NRP), Johannesburg was subdivided into zones defined as urban core and urban periphery. Core zones are those defined as higher density and in closer proximity to infrastructure, networks, activity nodes, and services. Conversely, peripheral zones are lower density, relatively isolated, and have less connection to nodes and activity.
For purposes of comparison, the study defines four family typologies with imagined names and personas. Using various sources, definitions and characteristics that help to define certain household types were developed. Typical low and middle income households in South Africa were outlined and given family demographics and biographies to personalise them. Average household sizes were considered, as well as the type of jobs each individual might have. In the end, four families were introduced, each with two adults and one child.
A low income and a high income family were located in an urban core setting with a second low income
and middle income family in an urban periphery context. Their movements and behaviours were mapped out spatially to be able to analyse the effects of their movements, distances travelled to access various places and services, as well as their transport choices.
Does location matter?
For the study, only new builds were assessed in terms of their embodied and operational emissions. And this was considered over a 60-year lifecycle. When the embodied carbon was assessed, urban buildings tended to have a lower value than their peripheral counterparts, largely due to the usually smaller size. Operational emissions were significantly higher than embodied carbon in all unit types, accounting for approximately 72% of emissions in each case when considered across the 60-year lifespan. This highlights the potential impact of introducing more renewable energy resources in order to decarbonise the grid.
When occupant travel statistics were assessed, results showed that middle income households on the periphery accounted for three times the emissions of the lower income households on the periphery, despite the fact that they tended to have similar travel distances. This is due to middle income occupants tending to utilise private cars while lower income individuals were dependent on the taxi network.
A similar variance between households existed within the urban core setting, however the figures were much lower than on the periphery. This is due to reduced dependence on private transport, and easier access to services within a 1km walking radius. Statistics showed that, while the middle income units in both cases had higher all round emissions than the low income units, there was, in fact, a significant difference between the core and periphery locations.
The urban core settings had a much smaller proportion of the total being attributed to occupant transport impact, meaning the operational carbon of the building had the largest impact. However, the occupant transport impact in the periphery settings was a significant proportion of the whole. Considering the longevity of spatial planning and the built environment, it is evident that occupants can get “locked in” to an emissions cycle for decades to come, unless the right decisions are made now for the future.
The study then extrapolated the findings for development only in the urban core versus only on the periphery for the period up to 2050, in order to calculate a value for the difference in emissions between the two scenarios over the time period. The cumulative emissions gap for the period was calculated to equal 224MtCO2e. That is almost 10 times the total emissions for Johannesburg in 2016! Kleynhans highlights that “It is clear that decisions in development locations made now will have a significant impact on the emissions (and climate change) of the future, for better or worse.”
What can be done?
The report sets out a helpful set of recommendations for built environment professionals and other stakeholders. The overarching requirement to make a meaningful reduction in emissions in the city is to reduce both operational and transport emissions. The former can be done by working to decarbonise the grid and optimise the energy efficiency of a building. The latter needs to be addressed by rethinking the spatial framework and urban planning of our cities so at to locate developments close to amenities and economic opportunities.
By 2050, the cumulative emissions gap between these two scenarios (development in the urban periphery vs the urban core) is 224MICO2e, almost 10 times the annual total omissions of Johannesburg in 2016 (21 MtCO2e).
Policy makers can play a role in setting out how and where development can take place, making it easier or mandatory to develop higher density residential areas as opposed to extending the urban sprawl. Property owners and developers should be incentivised to upgrade and develop urban core areas rather than expand the city limits into green field sites. This requires the right stakeholder collaboration to address market conditions and demands.
Ideally, government and private funding could be more effectively utilised to introduce or upgrade services, community facilities, transport infrastructure, and security in localised, higher density nodes rather than spreading resources thin on the outskirts of the city. “Built environment professionals in South Africa are already using their technical skills to support the reduction of embodied, operational and transport related emissions at different points in the decision-making process of a project’s feasibility and design,” says Smit. “We, however, need to scale up our efforts in order to reach our net zero targets for the future.”
The evidence is clear that considering the location of residential developments more carefully will significantly impact our future on the planet. Our urban design and spatial planning now will lock in residents’ behaviours for decades to come. We need to ensure we lock in sustainable and healthy patterns now that will serve us all in future.