1. What is a Whole Life Carbon Assessment (WLCA)?

Whole Life Carbon Assessment (WLCA) calculates the total carbon emissions from a building or infrastructure asset across its entire existence. From material extraction through to demolition, it captures every kilogram of CO₂ equivalent the project will produce. UK construction projects increasingly require WLCA under RICS WLCA 2nd edition, planning requirements, and sustainability certifications. 

The Scope of WLCA #

WLCA quantifies carbon dioxide equivalent (CO₂e) emissions across all life cycle stages defined in EN 15978:2011 for buildings and EN 17472:2022 for infrastructure. This encompasses three main categories: 

Embodied carbon covers emissions from materials, construction, maintenance, and end-of-life. This is the carbon held within the building’s physical substance. 

Operational carbon includes emissions from energy and water use during the asset’s operation. For most existing buildings, this dominates the total value. 

User carbon accounts for occupant activities through the buildings lifetime, though most assessments exclude this in practice due to uncertainty and client control limitations. 

According to RICS WLCA 2nd edition Section 4.1, a compliant WLCA must account for carbon removals and emissions across the entire life cycle (modules A through C), plus separately report benefits and loads beyond the system boundary (module D). 

WLCA vs Other Carbon Assessments #

Embodied Carbon Assessment #

Covers only the physical construction and materials (A1-A5, B1-B5, C1-C4). Misses operational emissions entirely. An embodied carbon assessment might show 11,200 tonnes CO₂e for a commercial building, for example, but WLCA reveals 68,400 tonnes over 60 years when including operational energy. This assessment shows a small section of the whole picture. 

Operational Carbon Assessment #

Covers only energy and water use during operation (B6-B7). Ignores the carbon cost of creating and maintaining the building. Part L calculations show compliance but miss the 30-40% contribution from embodied carbon in modern efficient buildings. As buildings become more energy efficient, this embodied portion grows proportionally larger. 

Carbon Footprinting #

May focus on single stages or specific scopes. Some carbon footprints only cover one year of operation, others might look at construction materials but ignore maintenance. WLCA provides the complete picture required for net-zero carbon targets and genuine sustainability claims. 

The Modular Structure #

WLCA uses the modular structure from EN 15804:2011+A2:2019. These can be thought of as chapters in a building’s life cycle: 

• Product Stage (A1-A3) covers raw material extraction, transport to factory, and manufacturing. A0 is typically negligible for buildings but can be significant for infrastructure projects. 
• Construction Stage (A4-A5) includes transport to site and all construction/installation processes.  
• Use Stage (B1-B7) spans the building’s operational life: use, maintenance, repair, replacement, refurbishment, operational energy, and operational water. This is typically measured as 60 years for buildings, and 120 years for infrastructure. 
• End of Life (C1-C4) covers deconstruction, transport, waste processing, and disposal.  
• Beyond the Boundary (D1-D2) captures reuse, recovery, and recycling potential as well as exported utilities. These are benefits for the next life cycle, reported separately. 

Will WLCA Become Mandatory #

The RICS WLCA 2nd edition became effective upon publishing in July 2024. RICS members undertaking carbon assessments must follow this methodology for compliance (RICS PS 2024, Section 1.3). However, for non-RICS members, the standard can be used as robust guidance for assessing the carbon impact of developments.  

Local authorities increasingly require WLCA through planning policy. The Greater London Authority requires WLCA for referable applications. Westminster City Council mandates WLCA for major developments whilst Manchester, Birmingham, and Bristol are all following suit. Check your local planning requirements early. 

Project Phases for WLCA #

RICS WLCA 2nd edition Section 2.3 requires WLCA at three key stages: 

• Concept Design (RIBA 2) establishes a baseline using generic data using industry benchmarks and typical specifications. This early assessment guides fundamental decisions about structure, form, and systems. 
• Technical Design (RIBA 4) refines calculations using specific manufacturer data. EPDs and U-values replace generic assumptions. This assessment validates earlier decisions and fine-tunes specifications. 
• Post-Completion (RIBA 6/7) verifies performance using as-built information. What actually got built? What products were substituted? This feeds back into industry benchmarks and improves future assessments. 

Early-stage assessment enables design decisions that reduce whole life carbon as waiting until construction eliminates most reduction opportunities.  

Small Project Exemptions #

Projects under 1,000m² GIA may exclude predictive energy modelling for module B6 (RICS WLCA 2nd edition, Section 3.8). These projects cannot make whole life carbon comparisons between operational and embodied carbon, only report them separately. You still calculate embodied carbon, but operational energy can use benchmarks rather than detailed modelling. 

Data Requirements #

The assessment requires four key data types: 

• Quantities come from material volumes extracted from BIM, drawings, or bills of quantities.  
• Carbon factors follow a strict hierarchy: EPD data for specific products, then generic databases (ICE, BEIS), or CIBSE TM65 calculations for MEP equipment without EPDs. 
• Scenarios define service lives (from ISO 15686-8), replacement cycles, and end-of-life routes. For example, how long will those windows last?  
• Energy models use SBEM, DSM, or PHPP calculations for operational energy. These must account for grid decarbonisation over time, not today’s carbon intensity. 

ISO 14044:2006 principles apply for data quality assessment, with preference hierarchies established in RICS PS 2024 Section 4.7. 

Integration with Cost Planning #

RICS WLCA 2nd edition Section 2.5 recommends parallel assessment with life cycle costing using ICMS 3 structure. This enables carbon cost-effectiveness analysis. Some options reduce both carbon and whole life costs, whereas others require trading higher capital cost for lower carbon emissions. This integration can reduce duplication and improve consistency. 

Reporting Requirements #

WLCA results must include specific metrics (RICS PS 2024, Section 6): 

• Absolute emissions by life cycle module in kgCO₂e to show where carbon occurs. 
• Normalised metrics in kgCO₂e/m² GIA to enable comparison between projects 
• Upfront carbon (A1-A5) reported separately to highlight the immediate emissions from construction. 
• Module D reported separately from A-C to show potential future benefits. 
• Data quality assessment for key materials to ensure confidence in results. 
• Assumptions and scenarios documentation to demonstrate transparency and repeatability. 

Software and Tools #

WLCA calculations use LCA software compliant with EN 15978 and ISO 14044:2006 requirements. Tools must handle the modular reporting structure, track biogenic carbon separately, apply time-dependent carbon factors for grid decarbonisation, and enable uncertainty assessment. 

Popular tools include OpenLCA, and other integrated BIM plugins. Spreadsheets work for simple projects but can become unwieldy for complex assessments. Developed software can better match projects with complexity and various team capabilities. 

Connection to Net Zero #

The UK Climate Change Act requires net-zero carbon by 2050. WLCA aids in this by identifying where emissions occur across an asset’s life, enabling targeted reduction strategies. Without WLCA, projects risk locking in decades of avoidable emissions. 

Theoretically, every building constructed today will still be operating in 2050, so design decisions made now determine whether that building helps or hinders net zero. WLCA quantifies these long-term implications, turning abstract targets into concrete design decisions. 

Standards Framework #

WLCA operates within interconnected standards. EN 15978:2011 provides the framework for environmental performance of buildings. EN 15804:2011+A2:2019 sets core rules for construction EPDs. ISO 14040:2006 and 14044:2006 establish LCA principles and framework. ISO 14025:2006 defines Type III environmental declarations. PAS 2080:2023 addresses carbon management in infrastructure. 

These standards ensure consistency, comparability, and credibility. They also prevent greenwashing and enable genuine progress toward net zero. 

The Complete Picture #

WLCA reveals the true carbon cost of construction decisions. That timber frame might sequester carbon initially but require more maintenance. Triple glazing reduces operational emissions but increases embodied carbon. Solar panels pay back their carbon debt, but when? These trade-offs become visible through WLCA. 

For complete requirements, the RICS Professional Standard for Whole Life Carbon Assessment for the Built Environment (2024) can be consulted. The standard provides detailed methodology, while this overview explains why WLCA matters and how it fits the broader sustainability picture. 

For complete requirements, consult the RICS Professional Standard – Whole Life Carbon Assessment for the Built Environment (2024)