Comparing the whole life cycle carbon impact of conventional and biogenic building materials across major residential typologies in Ghana and Senegal

Across West African built environments, patterns of high greenhouse gas emissions are driven by the widespread importation of high embodied carbon building materials by a largely self-built industry and recurring operational carbon costs driven by increased access to fossil-fuel based energy services. Using a whole life cycle assessment (LCA) of major residential typologies in two case-study West African countries, Ghana and Senegal, this paper compares the greenhouse gas emissions of imported building materials with local alternative biogenic and geogenic materials within conventional housing typologies. Results indicated that locally sourced biogenic and geogenic materials may be rendered ineffective in buildings if future typologies do not address the effective space density, passive design strategies and increased renewable energy-use. For the building typology with the highest carbon footprint, the Ghanaian detached house, the substitution of conventional building materials with non-fired earth masonry did not have any significant impact. As shown in the housing typology with the lowest operational to embodied carbon ratio, the Senegalese vertical housing case study, optimizing the thermal mass design of earthen building envelopes can significantly drive down lifetime operational carbon emissions. For tropical low-rise building typologies dominated by high roof area to building volume ratios, roof insulation could drive down operational carbon of the building by a factor of 4 to 5. Although each additional storey results in approximately 10–12 % increase in greenhouse gas emissions, the vertical expansion of housing represents an important driver in reducing greenhouse gas emissions per capita.