A few years ago, embodied carbon was something a sustainability consultant calculated near the end of a project, often from a cost plan. Today it is a question structural engineers get asked at Stage 2, again at Stage 3, and again every time the frame changes.
The structure is usually the largest single source of upfront embodied carbon in a building. Clients know this, planning authorities know this, and the industry's carbon guidance increasingly puts the structural engineer at the centre of the assessment. What has not changed in most practices is how the number gets produced: quantities pulled out of a model by hand, pasted into a spreadsheet, matched to carbon factors one line at a time, and rebuilt from scratch when the scheme moves.
This guide covers what a structural embodied carbon calculation involves, where the manual effort sits, what it costs, and how practices can automate it so carbon becomes a design input rather than a report written after the decisions are made.
Why Embodied Carbon Has Become a Structural Engineering Problem
Three shifts have moved embodied carbon onto the structural engineer's desk.
The first is planning policy. The London Plan (Policy SI 2) already requires whole life-cycle carbon assessments for referable applications, and other local authorities have followed with their own requirements. Where these apply, the structural frame is the largest and most scrutinised part of the submission.
The second is regulation that has not yet arrived but is clearly on its way. Part Z, an industry-proposed amendment to the Building Regulations, would require whole-life carbon assessment for larger buildings, with the example threshold of over 1,000 m² or more than 10 dwellings, and would phase in embodied carbon limits over time. It is a proposal, not law. RIBA, UKGBC, CIBSE and Parliament's Environmental Audit Committee all back mandatory assessment, and practices that wait for the regulation before building the capability will be building it under deadline pressure.
The third is client demand. Developers with net zero commitments, institutional investors reporting on portfolio carbon, and public clients with procurement targets increasingly ask for embodied carbon figures alongside the structural scheme. The IStructE's guidance on calculating embodied carbon and its proposed Structural Carbon Rating Scheme (SCORS) give clients a way to compare structural options, and they expect engineers to use it.
The result is that structural engineers are now expected to answer a carbon question every time they answer a structural one. Most practices have not changed their workflow to match.
What a Structural Embodied Carbon Calculation Involves
At its core, a structural embodied carbon calculation multiplies material quantities by carbon factors and adds up the results across the relevant lifecycle stages. Each of those steps carries more work than the formula suggests.
Material quantities
Every element in the frame needs a quantity: tonnes of steel by section type, cubic metres of concrete by strength class, reinforcement tonnage, timber volume, connections, and foundations. These quantities live in the analysis model (ETABS, Robot, SAP2000) and the coordination model (Revit, Tekla), and the two rarely agree perfectly at any given moment.
Carbon factors
Each material needs a carbon factor, typically in kgCO2e per kg or per m³. The right factor depends on the specific product: recycled content in steel, cement replacement in concrete, the source of timber. Factors come from generic databases such as the ICE database or from product-specific Environmental Product Declarations (EPDs). Choosing and documenting the right factor is an engineering judgement, and it has to be consistent across options.
Lifecycle modules
Carbon assessments follow the lifecycle stages defined in EN 15978: A1-A3 for product manufacture, A4 for transport to site, A5 for construction, and further modules for use and end of life. Structural assessments usually focus on A1-A5 (upfront carbon) but increasingly report later modules too. Each module adds assumptions about transport distances, wastage rates and construction processes.
Reporting
The output has to be in a form the client, the planning authority or the sustainability consultant can use, often aligned to the RICS whole life carbon assessment methodology, and often benchmarked against a rating such as SCORS. That means formatting, normalising per square metre of floor area, and documenting every assumption.
Where the Manual Effort Sits
In most practices, the calculation itself is not the slow part. The slow part is everything around it.
Quantities come out of the model by export or schedule, then get cleaned up in Excel because element naming, material assignments and units do not line up with the carbon spreadsheet. Someone matches each material line to a carbon factor by hand. Transport and wastage assumptions get added row by row. The totals get normalised, formatted and checked.
Then the scheme changes. The architect moves a core, the client asks for a timber option, the column grid shifts by 600mm. Every one of those changes invalidates the quantities, and the whole process runs again.
This is the same pattern that drives cost across structural workflows: information that already exists in one environment has to be moved by hand into another. Embodied carbon adds one more destination to a list that already includes the calculation pack, the drawings and the coordination model. We cover the wider version of this problem in our guide to automated structural calculations.
What It Costs to Do It by Hand
Take a mid-sized practice running 12 projects a year that need an embodied carbon assessment.
A manual assessment, from quantity extraction through to a reported figure, typically takes 12-20 hours per iteration once you include cleaning the data, mapping factors and checking the result. Most projects need at least three iterations: an early optioneering comparison, a Stage 3 update, and a final figure at Stage 4.
16 hours × 3 iterations × 12 projects × £85/hr = £48,960/year
That figure covers only the assessments the practice actually runs. The larger cost is the comparisons it does not run. When each carbon iteration costs two days of engineer time, the team compares two structural options instead of five, and the carbon figure arrives after the frame decision instead of informing it. The cheapest carbon reductions come from early decisions about grid, frame type and material, which is exactly when a manual process is too slow to help.
Manual assessment also produces inconsistency. Two engineers mapping the same quantities to carbon factors will make slightly different choices, and when the result feeds into a client report or a planning submission, those differences become hard to defend.
What Can Be Automated
Most of the work in a structural carbon assessment is structured and repeatable, which makes it a good fit for automation.
Quantity extraction
Material quantities can be pulled directly from the analysis or coordination model through its API rather than exported and cleaned by hand. A script or plugin reads every element, groups it by material and specification, and produces a clean quantity schedule in the format the carbon calculation needs. When the model changes, the extraction runs again in minutes. The integration options for the main tools are covered in our guide to Revit, Tekla and ETABS integration.
Carbon factor mapping
A practice can define its carbon factor library once: which factor applies to which material and specification, which EPD to use for a given product, and which default to use when the product is unknown. Automation applies those rules consistently to every element. The engineering judgement goes into building and maintaining the library, not into repeating the same lookups on every project.
Option comparison
Once extraction and mapping are automated, comparing structural options becomes cheap. A steel frame, a concrete frame and a hybrid timber option can each be assessed from their respective models in the time a manual process takes to assess one. This is where automation changes outcomes, not just timesheets: carbon becomes a factor in the frame decision rather than a figure reported after it.
Reporting
Normalisation per square metre, breakdown by element and lifecycle module, benchmarking against SCORS bands, and formatting for client or planning submissions can all be generated directly from the calculation. The report updates when the model updates, and every figure traces back to a model element and a documented factor.
What Still Needs an Engineer
Automation handles the arithmetic and the data movement. It does not replace the judgement that makes a carbon assessment credible.
Engineers still decide which carbon factors are appropriate, particularly where product-specific EPDs are unavailable or where a supplier's figures look optimistic. They still decide the scope of the assessment and which lifecycle modules to include. They still interpret the results: whether a lower-carbon option is structurally sensible, buildable and affordable, and how to present trade-offs to a client.
And they still own the design response. An automated carbon figure is only useful if it feeds back into decisions about spans, grids, material specifications and frame type. That part is engineering, and it is where the value of a faster assessment actually shows up.
How to Start Automating Embodied Carbon in Your Practice
Practices that have done this well tend to follow the same sequence.
Standardise the method first. Agree on one calculation approach across the practice, aligned to the IStructE guidance and the RICS methodology, with a defined set of lifecycle modules and assumptions. Automation built on an inconsistent method just produces inconsistent results faster.
Build the factor library. Create a single, maintained library of carbon factors mapped to the materials and specifications the practice actually uses. This is a one-off effort with ongoing maintenance, and it removes most of the variation between engineers.
Connect to the model. Replace manual quantity exports with direct extraction from the analysis or coordination model. This is where most of the time saving comes from, and it is what makes repeated iterations practical.
Automate one report format. Pick the output format you are asked for most often, whether a client summary, a planning submission or a SCORS rating, and generate it directly from the calculation. Add other formats once the first one is reliable.
Use it early. The point of automation is to run carbon comparisons at Stage 2, when the frame is still open. If the automated process only ever runs at Stage 4, the practice has saved time but missed most of the value.
If your practice works with timber, the same approach extends naturally to mass timber and hybrid structures. We cover the timber-specific workflow in our article on mass timber design automation. For the wider sustainability case for structural automation, see the environmental impact of structural engineering.
The Starting Point
Embodied carbon is becoming a standard structural deliverable, driven by planning policy, client commitments and regulation that is on its way. Most practices are meeting that demand with a manual process that is slow, inconsistent and too late in the design to change the outcome.
The calculation is not the hard part. The hard part is moving quantities out of the model, mapping them to the right factors and rebuilding everything when the scheme changes. That is a data movement problem, and it is one that automation solves well.
The practices that get ahead on this will not be the ones with the best spreadsheet. They will be the ones where a carbon figure for a new structural option takes minutes, not days, so it can shape the design rather than describe it afterwards.
If you want to map out what that would look like for your practice, get in touch. It usually takes one conversation to see where the manual effort sits and what it would take to remove it.
Part Z status sourced from Thornton Tomasetti: UK Building Regulations Part Z. London Plan requirements from the Greater London Authority whole life-cycle carbon assessment guidance. SCORS background from the IStructE introduction to the proposed SCORS rating scheme.