Updated WLCA standard informing better decision-making on carbon

In November 2025, RICS and the Institution of Civil Engineers (ICE) shared a joint message on the complementary nature of RICS' Whole life carbon assessment standard (WLCA) for the built environment second edition and the PAS 2080 carbon management standards.

Arup's sustainability team has applied the WLCA standard across numerous UK and global projects as assessors, third‑party reviewers and contributors to policy and certification.

We use the standard to help project teams achieve lower carbon outcomes through three key metrics:

• robust estimates
• reliable early‑stage baselines
• decision‑ready insight where carbon sits alongside cost, programme and quality.

The close alignment between the WLCA standard and Carbon Management in Buildings and Infrastructure – PAS 2080:2023 is particularly useful in this regard.

Achieving lower‑carbon outcomes requires expert judgement, collaboration and rigorous alignment with the WLCA standard's principles.

The Arup team draws on the expertise and leadership of a diverse and collaborative group of assessors and we seek engagement across project teams to support our efforts to drive meaningful carbon reduction.

As projects progress and resolve decisions, carbon reduction opportunities diminish and interventions become more costly (Figure 1). Therefore, our baseline assessments perform an important function by supporting the early decisions that will set the direction of the project.

Core elements like massing, structure and facade are usually sufficiently defined to study in approximate detail. Doing so can identify valuable carbon management opportunities and inform decision-making at early stages.

In contrast, partitions, finishes and furniture fixtures and equipment designs are not finalised at this point, so trying to manage their carbon totals prematurely is not helpful. The assessor will need to represent these with an appropriately evidenced benchmark until design information is available.

The WLCA standard acknowledges these early‑stage limitations and provides pragmatic guidance on using high‑level measures. Where this is not possible, benchmarks and assumptions may be used if they meet minimum quality criteria as outlined in section 4.5 of the standard.

Conducting a WLCA early and working closely with designers and cost consultants helps to make these early-stage assessments more reliable, comparable and useful for decision‑making.

Using the WLCA standard – as well as complementary guidance such as the Centre for Window and Cladding Technology's embodied carbon guidance – project teams can establish robust early baselines and benchmark emerging designs.

This creates space to focus on the key decisions that will lead to achieving lower‑carbon outcomes – building nothing, building less, building cleverly, and building efficiently – and this facilitates predictable development as the design matures.

In reality, quantities and specifications capture main components but overlook secondary elements, while benchmarks can be based on aspirational targets whose completeness is not always comparable to a cost plan.

This can misrepresent carbon hotspots, validate unrealistic expectations and contribute to a phenomenon called 'carbon creep', where a project's estimated embodied carbon impact increases over time.

This can result in frustration on the part of the client and a corresponding loss of confidence in the carbon assessor.

We manage this uncertainty through the quality of the WLCA input, including the representativeness of environmental data, specifications and quantity, following the methodology outlined in section 4.10 of the WLCA standard.

However, this only manages uncertainty in approximated elements.

We also manage for completeness as per the standard by working with cost consultants and quantity surveyors to approximate the completeness of assessment inputs.

If completeness is low, we use a simple cost-scaling mechanism. For example, if completeness is assessed as 80%, we multiply the assessment by 1.25% to scale it to 100% completion.

Such adjustments are transparently reflected in our assessment results, reflecting the quality and completeness of information developed to date. This alerts teams to the potential of under-representing early-stage impacts and provides an indication of potential blind spots (Figure 2).

These steps provide a clear starting point for everyone to consider the broader context and begin managing carbon during the next design stage.

The WLCA standard points to PAS 2080:2023 on this, which guides us in setting targets and leading carbon reductions in the built environment.

Our leadership in carbon management between assessments contributes substantially to carbon impact reduction.

It is at this point between assessments that our leadership in carbon management and collaborative work processes can substantially reduce the carbon impact of a project.

We use past WLCA data to generate visualisations and advice that steers how activities are prioritised, encouraging briefs to be challenged in a positive environment and to avoid overdesign or unnecessarily conservative design.

We do this by breaking down traditional working silos and encouraging collaboration between stakeholders such as structural and service engineers and architects for example to find ways to retain existing elements or use reclaimed materials.

This also supports the development of correct specifications that follow procurement best practices to avoid overreliance and to appropriately manage globally constrained materials such as steel.

With project team support, we apply data analysis and visualisation to make sense of otherwise complex data process to advise on design decisions, direct focus in developing design and specifications, and inform procurement discussions (Figure 3).

Providing this transparency makes managing expectations easier or can direct the appropriate design team members' attention towards resolving risks.

This register helps teams manage expectations around achieving their carbon ambitions, especially by highlighting reliance on riskier strategies such as low-carbon material procurement from constrained supply chains, and encourages more effective, lower-risk strategies such as building less and building efficiently.

WLCAs are becoming central to credible, informed decision‑making in the built environment. 

As industry practice matures, RICS' WLCA standard will improve the consistency and quality of measurement and support project teams to actively manage and reduce carbon impacts over time.

For our team at Arup, three purposes – robust estimates, reliable early baselines and decision‑ready insight – underpin how we apply the WLCA standard in practice.