Whole life carbon assessments for referable schemes

A whole life carbon assessment is required for applications referable to the Mayor of London, and it is a different document from the energy statement in scope, method and units. The energy statement counts operational carbon at the design stage. The whole life carbon assessment counts the emissions of the building from material extraction through construction, use, maintenance, replacement and demolition, reported in kilograms of carbon dioxide equivalent per square metre of gross internal area. Getting the two confused, or producing one late, is a common reason a referable scheme stalls at the Greater London Authority stage 1 response.

Which applications need one

Referability is set by the Town and Country Planning (Mayor of London) Order 2008, which captures larger residential schemes, tall buildings above stated heights depending on location, development on Green Belt or Metropolitan Open Land above a threshold, and certain other categories. If the application goes to the Mayor, the assessment is expected.

Boroughs also ask for whole life carbon work below the referral thresholds through their own local plans, and the number of them doing so has grown. Check the borough's validation list rather than assuming the Mayor's thresholds define the requirement.

Where the scheme is not in London, there is no national equivalent requirement. That is worth saying plainly to a client who has read about whole life carbon and assumes it applies everywhere. A voluntary Whole Life Carbon Assessment can still support a planning case outside London, particularly where a local plan has an embodied carbon policy or where demolition is contested.

The modules the assessment has to cover

Whole life carbon uses the life cycle module structure from the European standards for sustainability of construction works, and a London assessment is expected to report all of it rather than the product stage alone.

Module D is reported alongside the total, never inside it. Adding the benefits of future recycling to the headline figure to improve it is the single quickest way to lose a reviewer's confidence.

The A5 module deserves attention because it is where site activity, waste and temporary works sit, and it is often filled with a default percentage rather than a calculation. Say which you did.

Benchmarks and what the numbers are compared against

The Mayor's guidance publishes benchmark and aspirational figures per square metre of gross internal area for different building types, and expects the assessment to report against them. Take the figures from the current version of that guidance, because they have been revised and an assessment quoting a superseded benchmark reads as recycled.

A result above the benchmark is not automatically fatal. What the reviewer looks for is whether the design team tested options to bring it down and recorded the outcome. Structural frame choice, foundation design, substructure extent and the decision to retain or demolish an existing building move the number far more than specification changes to finishes.

Retention is the biggest single lever. Where an existing building is being demolished, expect the assessment to carry a comparison of retention, partial retention and full redevelopment, with the carbon consequence of each. That comparison is now part of the planning argument rather than a technical appendix.

Data sources and the assumptions to declare

An assessment is only as credible as its declared assumptions, and reviewers read the assumptions page first.

• The carbon factor source for each material, and whether generic or product specific data was used.
• The reference study period, normally 60 years, and any departure from it.
• Replacement cycles assumed for components with shorter lives.
• The gross internal area used, which must match the area quoted in every other document in the application.
• The stage of design the quantities came from, and how provisional they are.
• The software or template used, and its version.

Where quantities are estimated from area rates rather than measured, say so. An assessment at outline stage is inevitably coarse, and a reviewer would rather see that admitted than discover it.

Reporting at planning and again after construction

The London regime does not stop at determination. The assessment is submitted at planning stage and then a post-construction assessment is expected once the building is complete, using the same template so the two can be compared.

That has two consequences worth planning for. Someone has to hold the duty after the planning team has moved on, and the contractor's procurement decisions have to be captured as they are made rather than reconstructed afterwards. Writing the data collection requirement into the main contract preliminaries costs nothing at that stage and a great deal later.

The obligation is normally secured through the section 106 agreement rather than by condition, since it involves submitting information years after completion.

How it sits with the energy statement and the circular economy statement

These three documents share inputs and contradict each other more often than they should.

The Energy Statement supplies the operational energy figures that feed module B6. If the energy statement changes after the carbon assessment is drafted, the assessment has to be rerun, and late changes to the heating strategy are common.

The Circular Economy Statement shares the material strategy, the reuse commitments and the demolition waste position. Reused material claimed in one document and absent from the other is the contradiction reviewers find first.

Where demolition is involved, the Pre-redevelopment Audit provides the inventory of what is on site and what can be recovered, which feeds both the end of life modules and the circular economy commitments.

Agree one set of shared figures at the outset: gross internal area, unit numbers, storey heights, structural system and reference study period. Circulate them as a single controlled sheet. It sounds bureaucratic, and it prevents the most common review comment.

The gaps reviewers pick up

Four recur. Module D folded into the total. A gross internal area that differs from the planning statement. Benchmarks quoted from a superseded guidance version. And an assessment that reports a number without any evidence that the design team tried to reduce it.

The fourth is the one that changes officer recommendations. A whole life carbon assessment presented as a measurement exercise gets treated as paperwork. One presented as a record of design decisions, with two or three options priced in carbon and the chosen route explained, becomes part of the case for the scheme.

This is general guidance, not legal advice. Check the current London Plan guidance and the borough's validation list before relying on it.

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