联合国环境规划署：Building_materials_climate

Building Materials and the Climate: Summary

Executive Summary

The built environment sector is responsible for at least 37% of global energy-related carbon emissions, with high growth rates in developing economies. Decarbonization requires a whole-life-cycle approach, focusing on avoidance, shift to bio-based materials, and improvement of conventional materials. Achieving net-zero emissions by 2060 necessitates rapid innovation and policy support across all strategies.

Life-Cycle Thinking

• Embodied carbon emissions from material extraction and production must be minimized alongside operational energy.
• Whole-life-cycle assessments (WLCA) evaluate impacts from extraction to end-of-use.
• Circular economy principles enable reuse and recycling to reduce virgin material extraction.

Avoid Waste, Build Less

• Design for disassembly, reuse, and recycling to extend building lifespans (e.g., renovations generate 50-75% fewer emissions than new construction).
• Use locally sourced, recycled, or secondary materials.
• Incentivize modular construction and off-site fabrication to reduce waste.

Shift to Bio-Based Materials

• Bio-based materials (e.g., timber, bamboo, agricultural residues) offer lower-carbon alternatives, reducing reliance on extractive industries.
• Challenges include scaling production, fair labor practices, and life-cycle impacts.
• Promote forest and agricultural sustainable management to ensure biodiversity.

Improve Conventional Materials

• Decarbonize concrete/cement through alternative binders (e.g., calcined clay), electrification, and carbon capture.
• Steel and aluminum production can use hydrogen-based methods and circular processes.
• Increase material efficiency and reduce demand through better design and standards.

Tools for Assessment

• Life-cycle assessment (LCA) and carbon footprinting tools are emerging to measure impacts across building phases.
• Digitalization, such as BIM and building passports, supports data transparency for circularity.

Policy Recommendations

1. Set Vision: Develop national roadmaps institutionalizing coordination.
2. Make Carbon Visible: Mandate standardized environmental product declarations and life-cycle assessments.
3. Adapt Norms: Allow alternative materials in codes (e.g., bio-based for structural applications).
4. Accelerate Industry Transition: Support electrification, R&D, and public procurement for low-carbon solutions.
5. Just Transition: Ensure equitable workforce standards, gender equity, and fair labor practices.
6. Global Collaboration: Close carbon loopholes and harmonize international standards.

Conclusion

Decarbonizing the built environment sector demands urgent multidisciplinary action across industries, from producers to users. International cooperation, transparent data, and circular design are key to reducing emissions and fostering climate-resilient materials.