Whole life carbon assessment competence and scope

Two whole life carbon assessments of the same building can differ by a wide margin and both be defensible. The reason is almost never arithmetic. It is module scope, the reference study period, the source of the carbon factors and what was counted as part of the building. So whole life carbon assessment competence is mostly about the discipline to declare those choices and the experience to make them consistently.

The RICS professional standard exists to narrow that gap. It is mandatory for RICS members and regulated firms, and it is the methodology London boroughs and an increasing number of authorities outside London expect to see cited.

What the methodology requires of the assessor

The RICS whole life carbon assessment standard, second edition published in 2023, sets rules for scope, data, calculation and reporting. The important consequence for an architect is that it fixes things that used to be left to the assessor's discretion.

It specifies the life cycle stages to be reported, following the framework in BS EN 15978. It sets the reference study period for buildings, which is 60 years, so an assessment run over a different period is not comparable. It sets rules for data quality and for how carbon factors are sourced. And it prescribes the reporting format, including normalisation by gross internal area.

Competence is not licensed. Nobody is legally required to hold a certificate to produce one of these assessments. What authorities look for is familiarity with the standard, experience of the building type, and a report that declares every assumption. Councils generally expect a suitably qualified author for this report, and professional review is strongly advised.

Data quality and the sources used for materials

The carbon factors do most of the work in the result, and where they come from matters.

Product-specific environmental product declarations prepared to the European product standard are the strongest data, because they relate to the material actually specified. Generic industry average data from a recognised database is acceptable at early stages and is weaker, because it averages across manufacturing routes that differ substantially.

Three practical rules follow.

• Use product-specific data for the materials that dominate the total, which on most buildings means concrete, steel, reinforcement, glazing and insulation.
• Record the data source for every line, with the declaration reference and date, in a schedule the reviewer can check.
• Do not mix a product-specific factor for one concrete mix with a generic factor for another in the same element, because the comparison between design options then means nothing.

Quantities deserve the same scrutiny. An assessment built from a quantity surveyor's measured bill is a different animal from one built from a design stage model with assumed build-ups, and the report should say which it is.

Module scope and where assessments diverge

Module D is the one that causes arguments. Benefits beyond the system boundary, such as the future reuse or recycling of materials, are reported separately from the building's own total, and an assessment that deducts them to produce a flattering headline figure has not followed the standard.

The second edition widened what has to be reported compared with the first, so check which modules the current version requires rather than reusing a template from an earlier project. That is also the most common reason a resubmission is asked for.

Reviewing an assessment submitted by someone else

Ask for the workings. A summary figure in kilograms of carbon dioxide equivalent per square metre tells you nothing about whether it is right.

1. The completed reporting template, in the format the standard or the authority requires.
2. The quantities source, and whether it is a measured bill or a model-derived estimate.
3. A materials schedule with the carbon factor for each line and its data source reference.
4. The modules reported, the reference study period and the scope boundary, stated explicitly.
5. The treatment of sequestration and of module D.
6. The gross internal area used for normalisation, and how it was measured.

Then run one sanity check. Compare the proportion of the total attributable to the structure and substructure against your own experience of similar buildings. A result that looks unusually low in those elements usually means something has been left out of the scope, not that the design is remarkably efficient.

Authority requirements and reporting templates

In London, the London Plan policy on whole life-cycle carbon requires an assessment for referable applications, submitted on the Greater London Authority's own reporting template at planning stage and again post-construction. The template is prescriptive, and a report written to the RICS standard but not transposed into the template will be returned.

Outside London, requirements vary and are growing. Some authorities require an assessment through local plan policy, some ask for one through pre-application advice and some condition it. Check the adopted policy and the validation checklist for the authority rather than assuming.

Where an assessment is required, it usually sits alongside the Whole Life Carbon Assessment material in the submission and relates closely to a Circular Economy Statement, because reuse and material efficiency decisions show up in both documents. Keep the two consistent. Reviewers read them together and notice when the retained structure in one is demolished in the other.

Timing the assessment against design stages

An assessment produced after planning submission is a compliance document. One produced at concept design is a design tool, and the difference in outcome is large.

The decisions with the biggest effect on upfront carbon are made early: whether to retain existing structure, the structural material and grid, the substructure solution, the floor build-up and the facade system. By the time those are fixed, the remaining scope for reduction is in specification detail.

So run a first assessment when the structural concept is being chosen, with option comparisons on a like-for-like scope boundary. Update it when the design is coordinated, and again post-construction where that is required. Each update should hold the scope and the study period constant, because a reduction achieved by narrowing the boundary is not a reduction.

What to require in the appointment

Write the deliverable into the scope of services. The appointment should name the standard and edition, require the authority's template where one applies, and require the materials schedule with data sources, the stated scope boundary and the model or measurement basis. It should set the assessment points against design stages and allocate the post-construction update to someone who will still be appointed.

Add professional indemnity cover with a stated limit, and the right to receive the calculation file rather than a locked summary. A report you cannot interrogate is a report you cannot defend at committee.

Where the figures are contested or the scheme is large, an independent second opinion on the technical evidence is proportionate, and our professional directory is the route to a reviewer who can sign off a draft.

For specialist technical reports, qualified professional input may be required. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.