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.

The effects of urbanization and climate change are dangerously converging. The most affected populations are the urban poor, settled in informal settlements vulnerable to increasingly frequent disasters. This severely contributes to the existing housing gap of these regions, already struggling with housing demand. The speed of shelter delivery becomes key for an efficient response in order to prevent spontaneous informal resettlements on unsafe lands. The present study aims to understand the impact of material choice on post-disaster shelters delivery through a multiscale analysis of construction speed. The scales considered are: Constructive technology, Shelter Unit and Post-disaster settlement. At the the Constructive technology scale, nine different reconstruction solutions for the Nepal earthquake are compared, covering a range from local to industrialized. Successively, twelve shelter designs by the International Federation of the Red Cross have been studied under the same lens at the Shelter unit scale and for Post-disaster settlements. The study identifies a clear correlation between material procurement and speed at the constructive technology scale. At the shelter scale, this correlation becomes secondary and construction time is seriously impacted by the complexity of roof design. Moving to the settlement scale, the choice of local over industrialized materials seems to drive the speed again. The study indicates how a multiscale approach is necessary to analyze the impacts of material selection, providing efficient guidelines for post-disaster reconstruction. Beyond that, it highlights that effective reconstruction can be developed with diverse materials, but its emergency responsiveness can seriously be compromised by a non-appropriate design.

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