Embodied GHGs in a Fast Growing City: Looking at the Evolution of a Dwelling Stock using Structural Element Breakdown and Policy Scenarios

Abstract

Africa is currently experiencing rapid population growth and accelerated urbanization. This demographic shift will require a large amount of new construction material resulting in substantial environmental impact. For many cities on the continent, data gaps make specific quantification and robust prediction of this impact highly difficult. This article presents a method to assess the stock dynamics and embodied emissions of a rapidly growing urban built environment using a bottom-up, typological approach. This approach allows for the identification of appropriate engineering solutions for decarbonization by localizing embodied greenhouse gas (GHG) emissions in the different constructive elements with a revisited Sankey diagram. Different alternatives regarding housing type and construction techniques are compared. The city of Johannesburg is used as a case study to illustrate the relation between building types, technologies, and embodied GHG of its residential building stock. This new visualization uncovers the most material-and GHG-intense dwelling types and building elements. The adapted Sankey represents the building stock and its drivers in a simple way, allowing clear understanding of the consequences of potential alternatives. The business-as-usual scenario indicates 100.5 megatons carbon dioxide equivalent (Mt CO 2eq) for new construction between 2011 and 2040. The results of the dynamic model over time show that only a combination of a densified building stock with multistory buildings and the use of alternative construction materials and techniques show real potential to decelerate GHG emissions (33.0 Mt CO 2 -eq until 2040) while aiming to provide adequate and sustainable housing for all.

Carbon budgets for buildings: harmonising temporal, spatial and sectoral dimensions

“…In the meantime, urbanisation is expected to add 2.5 billion people to the global urban population by 2050 (Swilling et al 2018). Together with the pressure to overcome the already sizable housing deficit and lack of decent built environment, this urbanisation peak will increase the construction material requirements and GHG emissions associated to their production (Göswein et al 2018). Recent studies show the small amount of progress achieved in reducing GHG emissions associated with construction of new buildings (Röck et al 2020).…”

Exploring the regional-scale potential of the use of wood products in non-residential buildings: A building permits-based quantitative approach

“…When quantifying the building material consumption, many studies are limited to residential buildings due to the lack of data for non-residential buildings (Augiseau and Barles 2017;Göswein et al 2017). The literature reports that the building stock evolution does not depend on the same parameters that drive the material consumption of the residential sector.…”

“…The literature reports that the building stock evolution does not depend on the same parameters that drive the material consumption of the residential sector. Indeed, the non-residential building stock depends on the industrial activity or the concentration of headquarters in specific cities (Göswein et al 2017). Even if the methods may vary related to assumptions and available data, an overall trend exists in the methodology.…”

Log Mean Divisia Index Decomposition Analysis of the Demand for Building Materials: Application to Concrete, Dwellings, and the U.K.

“… 37 Key factors influencing the metabolism of a household have been analyzed using MFA, showing that the material inputs and stocks depend on household size and income. 38 The stock dynamics of an urban environment have also been assessed using dMFA, which illustrates the drivers (e.g., population, building types, and materials) of the building stock at material, structure, and building type levels. 39 In summary, dMFA has used population as a key socio-economic driver, and often additionally building type and material intensity, to quantify material stocks and flows.…”