Upfront embodied carbon and how to report it

Upfront embodied carbon reporting means modules A1 to A5: the product stage, transport to site and the construction process. Everything else in a whole life carbon assessment sits outside it. Get the module boundary wrong, or report a single number without saying which modules it covers, and the figure cannot be compared with a benchmark or with another scheme, which is the whole reason anyone asked for it.

For a developer, the number matters in two places. It is the figure a planning committee will quote, and it is the figure a reduction strategy has to move.

What upfront carbon covers and what it excludes

The module structure comes from the European standard for assessing the sustainability of construction works, and the assessment methodology published by the Royal Institution of Chartered Surveyors applies it in the United Kingdom.

Two exclusions cause most of the arguments. Operational energy sits in B6 and belongs in the energy assessment, not here, so a scheme cannot offset a heavy structure with an efficient heating system in this metric. And module D is reported alongside rather than subtracted, because a claimed future benefit is not a reduction now.

The full picture belongs in the Whole Life Carbon Assessment, which the authority will normally want on a major scheme, with the upfront figure pulled out and stated separately.

Module boundaries and why they matter

A5 is where reported figures diverge most between consultants.

It should include site energy use, construction waste of the materials brought to site, and the works needed to enable construction: demolition, temporary works, piling platforms, dewatering, and the transport associated with all of it. A report that treats A5 as a small percentage uplift applied to A1 to A3 is taking a shortcut, and on a site with deep basements or extensive demolition the shortcut hides a large number.

State explicitly what is inside each module, which building elements are included, and what has been excluded with the reason. External works, below-ground services, fit-out beyond shell and core, and tenant works are the usual exclusions, and each of them can be defensible if it is declared.

On a scheme involving retention, the interaction with the structural appraisal matters. The carbon comparison between retention and demolition needs the structural conclusion as an input, and the two documents have to describe the same options.

Where benchmark figures come from

Do not quote a benchmark from memory. Name the source, the building type, the metric and the version.

The Greater London Authority publishes benchmarks in its whole life carbon assessment guidance for referable schemes, expressed per square metre of gross internal area by building type, with a target and an aspirational level. Industry bodies including the low energy transformation initiative and the professional institutes publish their own targets, which are not identical. Local plan policies in some authorities set their own figures, and those take precedence in that authority.

So the reporting sequence is: identify which benchmark the decision maker uses, report against that one, and only then add any others for context. A report benchmarked against a source the authority does not use invites a request for further information and loses a determination cycle.

Where no benchmark applies, say so plainly and report the figure with the breakdown, rather than inventing a comparison.

Quantity take-off quality and its effect on the answer

At planning stage the assessment is built on a concept or early developed design, and the quality of the quantities drives the reliability of the answer far more than the choice of carbon factors does.

Three things to establish and record.

The design stage the quantities came from, and who produced them. A structural engineer's preliminary sizing gives a very different answer from an architect's area schedule with assumed build-ups.

The data sources for the carbon factors, distinguishing product-specific environmental product declarations from generic database values. Report the proportion of the total that rests on each, because a figure built almost entirely on generic data cannot support a claim of a small percentage improvement.

And the elements that dominate. On most buildings, substructure and superstructure together carry the majority of upfront carbon, with the facade next. Concentrating effort on accurate quantities for those elements, and accepting coarser figures for finishes, is the right allocation of a planning-stage budget.

Reporting per square metre and per unit

Report the total in tonnes of carbon dioxide equivalent, and the intensity per square metre of gross internal area, and state which area measurement you used. Gross internal area and net internal area give different answers and the difference is not small.

On residential schemes, a figure per dwelling is often asked for as well. Give it, but give the area-based figure alongside, because a per-dwelling number rewards small units and tells the reader little about the efficiency of the building.

Three presentational rules that make a report usable:

1. A table by module, with A1 to A3, A4 and A5 shown separately rather than aggregated.
2. A table by building element, so the reader can see where the carbon is.
3. The benchmark comparison stated as a single sentence with the source named.

Reduction measures and their evidenced effect

A list of intentions is not a reduction strategy. Quantify each measure against a stated baseline.

The measures that move the number most are structural and early:

• Retaining and reusing existing structure, which removes substructure and frame carbon rather than reducing it.
• Reducing the quantity of material: shorter spans, thinner slabs where the acoustic and vibration criteria allow, fewer transfer structures, and a basement no deeper than the scheme needs.
• Cement replacement in concrete, using ground granulated blast furnace slag or fly ash within the limits the durability and early strength requirements allow.
• Timber and other lower-carbon structural systems where the building type, fire strategy and insurance position permit.
• Reusing materials from the site, and specifying reused or recycled content where it is available in the quantities needed.
• Reducing finishes and leaving elements exposed, which also cuts replacement cycles.

For each one, report the baseline assumption, the proposed change, and the resulting saving in the same units as the headline figure. Where a measure is aspirational rather than committed, label it, because a committee will otherwise treat the reduced figure as the scheme's number and condition it.

The circular economy consequences of these choices belong in the Circular Economy Statement where the authority requires one, and the operational side sits in the Sustainability Statement. On large sheds and distribution buildings the balance between upfront carbon and roof-mounted generation is a specific argument, set out in our note on energy statements for warehouse and logistics schemes.

Presenting the figures for a planning committee

Members are not carbon assessors and the report has to work for them.

Lead with the total upfront figure, the intensity per square metre, and whether it meets the benchmark the authority uses. Then give the three biggest contributors by element. Then give the measures adopted and the saving each delivers against the baseline. Then state the exclusions and the uncertainty honestly, in one paragraph.

Two things to avoid. A comparison against a hypothetical worse scheme, which reads as advocacy rather than assessment. And a claimed net figure that subtracts module D benefits, which a competent consultee will pick apart in public.

One honest uncertainty. Upfront carbon figures for the same building, assessed by two consultants at concept stage, can differ by a wide margin because of quantity assumptions and data sources rather than because of any disagreement about the building. The way to make a figure credible is transparency about those assumptions, not precision in the final digit.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.

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