Building Materials and the Climate: Constructing a New Future
About this book
Building Materials and the Climate: Constructing a New Future, published by the United Nations Environment Programme (UNEP) in 2023 in collaboration with Yale University, is the most comprehensive global assessment of the embodied carbon challenge in building materials and its implications for climate policy, industry transformation, and sustainable urban development. It emerges as buildings become one of the most significant battlegrounds for climate action: the built environment currently consumes 50% of all material resources and contributes over 35% of global CO₂ emissions. The report establishes the fundamental asymmetry between operational and embodied carbon in the context of decarbonising the building sector.
As electricity grids decarbonise and building energy codes tighten, operational carbon — the emissions from heating, cooling, lighting, and plug loads during a building's service life — is projected to decline significantly. Simultaneously, embodied carbon — the emissions from manufacturing, transporting, and installing building materials, as well as from demolition and disposal — remains largely unaddressed by current policies and is projected to account for 49% of cumulative building sector emissions between now and 2050 under business-as-usual scenarios. The material-level analysis is the report's most distinctive contribution.
It provides the most detailed global inventory available of the embodied carbon of construction materials: Portland cement clinker (approximately 0.83 tCO₂/tonne), primary structural steel (approximately 1.8–2.5 tCO₂/tonne depending on process route), primary aluminium (approximately 11–16 tCO₂/tonne due to smelting electricity demand), architectural glass, insulation materials, and timber products. The analysis shows that cement and steel together account for approximately 15% of global CO₂ emissions — larger than the entire aviation sector. Material efficiency strategies receive quantitative treatment: designing structures with minimum material use through computational optimisation, substituting high-carbon materials with lower-carbon alternatives (engineered timber, geopolymer concrete, recycled content steel), extending building lifespans to amortise embodied carbon over longer service periods, and reusing structural components at end-of-life rather than recycling.
The report estimates that implementing the full package of available material efficiency strategies could reduce building sector embodied carbon by approximately 50% by 2050. Policy recommendations focus on mandatory embodied carbon disclosure and performance standards in building regulations, government green procurement requirements for low-carbon materials, carbon pricing mechanisms that cover industrial material production emissions, and international frameworks for harmonising embodied carbon accounting methodology.