Beyond buildings ::assessing the carbon footprint of outoor spaces in construction projects

The built environment is a major contributor to global CO₂ emissions, with 37% of total emissions. While efforts to reduce building emissions have progressed, the impact of outdoor spaces remains largely unquantified. Existing carbon accounting frameworks focus primarily on building structures, leaving outdoor landscaping overlooked in emissions assessments. Furthermore, there is a lack of literature addressing the carbon footprint of these spaces, particularly in relation to their contribution to overall building emissions. This study aims to bridge this gap by assessing the carbon impact of outdoor surfaces and integrating them into construction-related emissions evaluations. A four-step methodology is applied: (1) defining the functional unit as one m² of low-traffic urban surface, (2) identifying commonly used materials, (3) performing a Life Cycle Assessment (LCA) to determine the carbon emissions of each material, and (4) integrating these emissions into the building’s overall carbon budget using urban planning regulations and building archetypes. The results highlight significant variations in emissions depending on material choices. Gravel has the lowest impact, while perforated concrete paving also performs well due to its reduced cement content. In contrast, natural stone can generate up to 10 times more CO₂ than gravel when polished and transported over long distances. In the end, when outdoor areas are fully utilized, they can account for up to 20% of a building’s carbon footprint. This underscores the need for integrating outdoor surface regulations into urban planning. By providing insights for architects and policymakers, this research supports the development of more sustainable built environments