The construction sector accounts for 31% of CO₂ emissions and massive material flows like 20 Gt of sand and gravel extracted in 2015. In France, it generates 227.5 million tons of waste annually. Rennes Metropole, a pioneer in urban planning, aims to reduce GHG emissions by 42% by 2030 and 91% by 2050 while addressing a housing crisis. The region has a rich heritage of raw earth buildings, accounting for 20% of its historic built stock, and a growing sector (artisans, associations, training centres, research projects) supports its revival. This PhD project adopts a material-based approach at the intersection of urban planning, civil engineering, architecture and history to explore the feasibility of scaling up raw earth construction for housing by 2050 using locally excavated soils, ensuring circularity and low carbon impact. The methodology includes completing the metabolism study of construction materials, quantifying suitable soils, and developing prospective scenarios for different housing typologies. Life Cycle Assessments (LCA) will evaluate environmental impacts, comparing results with IPCC scenarios. The goal is to propose an alternative, low-carbon materiality for housing construction and renovation, aligning with Rennes Metropole's decarbonation and waste reduction targets.

The construction sector accounts for 31% of CO₂ emissions and massive material flows like 20 Gt of sand and gravel extracted in 2015. In France, it generates 227.5 million tons of waste annually. Rennes Metropole, a pioneer in urban planning, aims to reduce GHG emissions by 42% by 2030 and 91% by 2050 while addressing a housing crisis. The region has a rich heritage of raw earth buildings, accounting for 20% of its historic built stock, and a growing sector (artisans, associations, training centres, research projects) supports its revival. This PhD project adopts a material-based approach at the intersection of urban planning, civil engineering, architecture and history to explore the feasibility of scaling up raw earth construction for housing by 2050 using locally excavated soils, ensuring circularity and low carbon impact. The methodology includes completing the metabolism study of construction materials, quantifying suitable soils, and developing prospective scenarios for different housing typologies. Life Cycle Assessments (LCA) will evaluate environmental impacts, comparing results with IPCC scenarios. The goal is to propose an alternative, low-carbon materiality for housing construction and renovation, aligning with Rennes Metropole's decarbonation and waste reduction targets.