2024年房地产与建筑业生命周期评估LCA报告-实现真正的碳减排与环境效益英文版-高力国际_16页_1mb

Life Cycle Assessments: Delivering True Carbon Reductions and Environmental Benefits in Real Estate and Construction
SUSTAINABILITY RESEARCH Summary

The built environment accounts for nearly 40% of global carbon emissions, making decarbonization critical to achieving net zero by 2050 and mitigating climate change impacts. While much focus has been on reducing operational emissions (e.g., heating, cooling, energy use), the proportion of a building's lifetime emissions attributed to operational energy is declining as advancements in materials and technologies increase. Instead, embodied carbon—related to material extraction, production, construction, and disposal—now dominates, particularly for fit-outs and renovations. This paper emphasizes the need to measure a building’s full environmental impact through life cycle assessments (LCAs), which evaluate both operational and embodied emissions, as well as broader environmental effects beyond carbon.

LCAs are a scientific method for modeling and evaluating environmental impacts across a system’s life cycle, divided into three phases: (1) defining the scope of life cycle stages, (2) conducting resource and material flow inventories, and (3) calculating environmental impacts. The functional unit—defining the service or output a building provides—is crucial for equitable comparisons. For example, comparing cars and airplanes without accounting for passenger numbers or lifespans would yield misleading conclusions. Similarly, materials like timber and concrete must be evaluated based on their functional properties (e.g., load-bearing capacity), not just volume.

Phantom savings occur when reducing operational emissions shifts impacts to other life cycle phases, such as material extraction or disposal. Over-insulating a building, for instance, may increase embodied carbon more than it reduces operational energy use. Pollution shifts can also lead to geographic changes, like moving environmental burdens from oil-based systems to electricity generation or metal extraction. LCAs help identify these transfers, ensuring interventions genuinely reduce overall environmental impacts.

In the construction and real estate industry, LCAs are integral to certifications like LEED, BREEAM, and the Australian Green Star. These frameworks require reductions in life cycle impacts, such as 30% below standard practice. The French RE2020 regulation mandates LCA for new buildings, setting embodied carbon thresholds (e.g., 1,200 kg CO2e/m² for offices by 2024) and aligning with national decarbonization goals. However, many jurisdictions still prioritize operational carbon accounting, neglecting the significant role of embodied emissions.

Case studies on office buildings reveal that over 80% of their lifetime emissions are embodied, with operational contributions around 18%. Fit-outs and interior upgrades, such as HVAC systems, electrical infrastructure, and flooring, account for 500 kg CO2e/m² over 50 years, far exceeding operational energy use. Embodied carbon from structural components (e.g., walls, ceilings, plumbing) often dominates, with frequent renewals and outdated assumptions in initial models (e.g., undervaluing plug loads and other energy uses).

Decarbonization strategies should address both operational and embodied impacts. Recommendations include:

1. Prioritizing sustainable materials for fit-outs and equipment, extending their lifespans, and adopting reduce-reuse-recycle principles.
2. Creating flexible workspaces to minimize renovations and moves.
3. Investing in passive design strategies (e.g., heating/cooling systems) to reduce mechanical dependencies and operational energy.

Beyond carbon, LCAs assess impacts like acidification, eutrophication, water pollution, and resource depletion. Multi-criteria analyses ensure environmental savings in one area do not cause greater harm elsewhere. For example, using timber for structural elements reduces carbon but may require more material, increasing other impacts.

The paper concludes that focusing solely on operational carbon overlooks critical embodied contributions. As the industry advances its environmental goals, LCAs must guide decarbonization efforts, offering a holistic view to support informed decision-making. Thorough, multi-criteria assessments are essential to avoid trade-offs and ensure real estate strategies align with long-term sustainability and value preservation.

Key takeaways:

• Embodied carbon now exceeds operational emissions in many buildings.
• LCAs provide a comprehensive framework for evaluating environmental impacts.
• Certifications and regulations increasingly integrate LCA requirements.
• Fit-outs and renovations are major sources of embodied carbon.
• Multi-criteria analyses ensure balanced, evidence-based decisions.
• Passive design and sustainable material choices are critical for reducing both carbon and broader environmental footprints.