To calculate project embodied carbon in a building involves multiplying the material quantities (from BIM or take-offs) by their specific emission factors (kgCO2e per unit) across life cycle stages, typically A1–A5 (cradle-to-gate plus construction).
Key Steps for Calculating Embodied Carbon
1. Define the Scope and System Boundaries
Before starting, determine which lifecycle stages (modules) to include. Standard assessments follow EN 15978 or RICS Professional Standards:
Upfront Carbon (A1–A5): Raw material supply (A1), transport to factory (A2), manufacturing (A3), transport to site (A4), and construction installation (A5).
In-Use (B1–B5): Maintenance, repair, and replacement.
End of Life (C1–C4): Demolition, transport of waste, and disposal.
2. Gather Material Quantities
Create a detailed Bill of Quantities (BoQ) by extracting material volumes or weights from architectural drawings, cost plans, or BIM models. Focus on major structural elements first (substructure and superstructure), as these typically account for the majority of a project's embodied carbon.
3. Apply Carbon Factors
Multiply the quantity of each material by its corresponding Carbon Emission Factor (ECF), typically measured in kgCO2e per kg or per m³. Use the following data hierarchy:
Environmental Product Declarations (EPDs): Product-specific "nutrition labels" from manufacturers that offer the highest accuracy.
Generic Databases: If specific EPDs aren't available, use the Inventory of Carbon and Energy (ICE) Database or Quartz Database for industry-average values.
4. Basic Calculation Formula
The total embodied carbon is the sum of emissions for every material and activity:
Total Embodied Carbon (kgCO2e) = Σ (Quantity of Material × Carbon Factor) + Transport + Site Activity Emissions
5. Recommended Tools for Automation
For professional projects, specialised software can automate these calculations by linking BIM data to EPD databases:
One Click LCA: A comprehensive tool for buildings and infrastructure.
EC3 (Embodied Carbon in Construction Calculator): A free, open-access tool focused on supply chain emissions.
Structural Carbon Tool: A free Excel-based estimator specifically for structural engineers.
This video explains the life cycle assessment process to estimate embodied carbon:
