Table of Content
Calculating whole life carbon means adding up every kilogram of CO₂ your building will ever cause, from quarrying the aggregate for its foundations to crushing the concrete when it’s demolished decades later. The RICS Professional Standard 2024 sets out how to do this calculation, but at nearly 200 pages, it can feel overwhelming. This guide shows you how to navigate it.
Understanding Your Project Stage
Your approach depends entirely on your project stage. If you’re at concept design with just a massing model, you’ll work with benchmarks and educated guesses. By technical design, you’ll need manufacturer data and detailed quantities. The RICS standard (Section 2.3) maps out what’s expected at each stage, but the key message is simple: start early. Once concrete is poured, your carbon is locked in.
The calculation always follows the same life cycle modules. A for construction, B for use, C for end-of-life, and D for what happens next. Think of these as chapters in your building’s carbon story. The RICS standard inherited this structure from the European norm EN 15978, and once you understand it, every assessment follows the same pattern.
Getting Your Quantities
The hardest part isn’t the carbon factors; it’s knowing how much stuff you have. A cost plan is your best friend here. Your QS has already measured everything for pricing, so use their work. Table 6 in the standard shows which sources are acceptable at each stage.
For early stages when you’re working with less information, the standard offers escape routes. Section 4.5.2 lets you use benchmarks, perhaps 380 kg/m² of materials for a typical office. But beware: MEP systems often hide 20-30% of your upfront carbon and frequently get missed. The standard points you to CIBSE TM65 for handling these when manufacturers haven’t provided Environmental Product Declarations.
Finding Carbon Factors
Once you know what you have, you need its carbon intensity. The RICS standard is strict about data hierarchy (Section 4.7). Manufacturer EPDs come first because these are verified documents stating exactly how much carbon their specific product contains. Industry averages come second, generic databases third.
Reality check: you’ll use all three. Your structural steel might have a specific EPD, your concrete uses industry averages, and your door handles come from the ICE database. The standard accepts this mix but requires you to score your data quality for the ten materials that matter most.
Calculating Each Module
The maths is straightforward multiplication (quantity times carbon factor) but the devil lurks in the details.
Transport and Construction (A4-A5)
For transport (A4), the standard provides default distances unless you know better. Construction site emissions (A5) typically run 50-150 kgCO₂e/m² depending on complexity. These might seem small against your tonnes of concrete, but they add up.
Use Stage (B1-B7)
The use stage is where things get interesting. How many times will you replace the windows in 60 years? The standard mandates using service life data from ISO 15686-8 or BCIS. Your windows might last 30 years, so in a 60-year assessment, you include one replacement.
Operational energy (B6) requires particular care. You cannot use today’s grid carbon intensity for energy used in 2050. The standard requires Treasury Green Book projections showing how the grid will decarbonise. Missing this adjustment is a rookie error that overinflates your results.
End of Life (C1-C4)
What happens in 60 years when your building comes down? Section 5.4 provides standard scenarios. Demolition emits about 3.5 kgCO₂e/m². Steel gets recycled at 90%, concrete becomes aggregate, timber might generate energy. Module D captures these benefits, but the standard insists you report them separately because they’re potential benefits, not guaranteed savings.
Normalising Your Results
Raw numbers mean nothing without context. The standard requires normalisation, typically kgCO₂e/m² GIA for the full 60-year life, then divided down to annual figures. This lets you compare options fairly. That super-insulated wall might have higher embodied carbon but saves more operationally. The assessment shows whether it’s worth it.
Quality matters. The standard’s Table 13 provides a scoring system for data quality. Under 24/40 suggests your results are too uncertain to rely on. You’ll also need uncertainty analysis. What if service lives are 20% shorter? What if the grid decarbonises slower? Present scenarios, not false precision.
Using Software
While you could calculate this in Excel, most practitioners use LCA software like OneClick or eTool. Just ensure it complies with RICS PS 2024 since some still use the old 2023 version. The software handles the equation chains but you still need to understand what it’s doing. Garbage in, garbage out applies doubly to carbon assessment.
Common Mistakes
The standard highlights frequent errors:
Static grid factors: Using current grid factors throughout the study period overinflates operational carbon by 300% or more
Missing replacements: Forgetting replacement cycles (B4) typically misses 10-20% of embodied carbon
Excluding MEP: Ignoring MEP because “we don’t have the data” misses potentially 30% of upfront emissions. Use CIBSE TM65 instead
Double counting: That concrete in the frame estimate might also appear in the upper floors section. Section 4.5 warns about this specifically
Key RICS PS Sections
When stuck, these appendices answer most technical questions:
- Appendix F: MEP systems methodology
- Appendix G: Operational energy calculations
- Appendix K: Module D benefit calculations
- Appendix M: BIM quantity extraction
For broader context, the standard recommends UKGBC’s Bitesize Guides for beginners and points to international standards for those going deeper. But remember: in the UK, RICS PS 2024 is mandatory for any assessment claiming compliance.
Data Reality
Perfect data doesn’t exist. You’ll make assumptions, estimate gaps, and use proxy data. The standard accepts this reality while demanding transparency. Document your assumptions. Score your data quality. Run sensitivity analysis. Better an honest assessment with acknowledged limitations than false precision.
Reporting Requirements
The RICS PS mandates specific outputs (Section 6):
- Upfront carbon (A1-A5): kgCO₂e/m²
- Life cycle embodied (A-C excluding B6-B7): kgCO₂e/m²
- Whole life carbon (A-C): kgCO₂e/m²/year
- Module D benefits: Reported separately
Use the RICS reporting templates for consistency. These ensure you capture all required information and present it in the industry-standard format.
The Bottom Line
Whole life carbon assessment is complex but systematic. The RICS Professional Standard provides the framework and rules. Your job is to apply them intelligently to your project, making reasonable judgements where data is imperfect while maintaining the rigour the climate emergency demands.
Start early, document everything, and remember that an imperfect assessment done at concept stage beats a perfect one delivered after construction starts. The carbon you save is the carbon you never emit.
For complete requirements, consult the RICS Professional Standard – Whole Life Carbon Assessment for the Built Environment (2024)
Need LCA, EPD, or CBAM consultancy?
Or have a research proposal to collaborate on?
Global commercial consultancy • Horizon Europe, UKRI & Innovate UK research partner