As the construction industry faces mounting pressure to address its environmental impact, the spotlight is shifting from operational emissions to a less-discussed but equally significant contributor: embodied carbon. According to a recent PBC Today report, reducing embodied carbon in new buildings is critical for achieving meaningful climate action. Unlike operational emissions, which can be mitigated over time through renewable energy and efficiency upgrades, embodied carbonโlocked into the building materials and construction processesโcannot be undone after construction.
A study published in the Journal of Building Engineering titled โPromoting Decarbonisation in the Construction of New Buildingsโ introduces a groundbreaking technical framework. It provides a roadmap for measuring and minimising embodied carbon from the early stages of building design and construction.
Understanding Embodied Carbon
Embodied carbon encompasses the greenhouse gas (GHG) emissions generated throughout a buildingโs lifecycle, divided into the following stages:
- Stage A: Raw material extraction, manufacturing, and transportation to the site.
- Stage B: On-site construction and installation activities.
- Stage C: Maintenance, refurbishments, and replacements during use.
- Stage D: End-of-life processes, including demolition, material recovery, and disposal.
The significance of embodied carbon lies in its permanence. Once emitted during construction, it cannot be reduced. This makes early intervention and strategic planning imperative for decarbonising the built environment.
Challenges in Embodied Carbon Accounting
Despite its importance, the industry faces several obstacles in accurately measuring and addressing embodied carbon:
- Data Transparency: Limited disclosure from material manufacturers on carbon footprints.
- Inconsistencies in Lifecycle Assessments (LCA): Many LCAs omit emissions from transportation, waste, or end-of-life stages.
- Material Variability: Emissions from the same material can vary significantly due to differences in production methods and locations.
Proposed Strategy for Embodied Carbon Reduction
The study outlines a three-phase strategy, leveraging Lifecycle Assessment (LCA) tools and Environmental Product Declarations (EPDs) to ensure precise and actionable carbon accounting.
Phase 1: Define the Scope and Analyse Carbon Hotspots
Buildings are divided into functional sections, allowing for targeted carbon reduction strategies:
- Building Structure (Load-Bearing Elements):
- High-carbon materials: Concrete, steel.
- Solutions: Low-carbon concrete, recycled steel, modular designs.
- Building Envelope (Thermal Barriers):
- High-carbon materials: Glazing, conventional insulation.
- Solutions: Bio-based insulation, high-performance facades.
- Building Interiors (Non-Structural Elements):
- High-carbon materials: Drywall, HVAC systems.
- Solutions: Prefabricated panels, circular economy products.
- Building Exterior (Landscaping & Infrastructure):
- High-carbon materials: Asphalt, concrete paving.
- Solutions: Permeable paving, green infrastructure.
Phase 2: Comprehensive Data Collection
Accurate carbon accounting requires detailed input from various sources:
- Material-Specific Emissions:
- Sources: EPDs, databases like ICE or Ecoinvent.
- Challenges: Variability in manufacturing processes.
- Material Quantities:
- Collected from Bills of Quantities (BoQ).
- Converted to kg COโe per unit mass, factoring in material waste.
- Transportation and Construction Emissions:
- Inputs: Transport distance, fuel type, on-site machinery use.
- Optimisation: Prefabrication and electric-powered equipment.
- End-of-Life Scenarios:
- Focus on material reuse, recyclability, and disposal impacts.
Phase 3: Embodied Carbon Calculation and Optimisation
Once the data is compiled, emissions are calculated at the material, section, and building levels using advanced equations. This methodology identifies carbon-intensive areas and enables targeted optimisation.
Key Findings and Recommendations
The study highlights actionable strategies for reducing embodied carbon:
- Prioritise Low-Carbon Materials:
- Substitutes for concrete (e.g., supplementary cementitious materials).
- High-recycled content steel and bio-based insulation.
- Optimise Design Practices:
- Use modular and prefabricated components to reduce waste.
- Adopt “design for deconstruction” principles to enable future recycling.
- Align with Policy and Certification Goals:
- Compliance with the European Green Dealโs carbon-neutral targets by 2050.
- Achieving certifications like LEED, BREEAM, or WELL.
- Future-Proofing with Circular Economy Principles:
- Emphasising material reuse and recycling to offset embodied carbon.
Building a Low-Carbon Future
This technical framework equips construction professionals with the tools to address embodied carbon head-on. Early adoption of these strategies will be crucial as governments tighten regulatory standards and carbon taxes become inevitable.
By integrating carbon-conscious practices into design, material selection, and construction processes, the industry can make strides toward a sustainable and climate-resilient built environment.
