RICS' Whole life carbon assessment for the built environment (WLCA) is increasingly recognised as the authoritative document for calculating, reducing and reporting carbon in construction and infrastructure.
It is the most prescriptive and robust methodology for carbon calculations available, including practices and behaviours intended to protect clients and other stakeholders, as well as ensuring that their reasonable expectations of ethics, integrity, technical competence and diligence are all met.
When I tell clients that we at RPS run calculations using RICS' WLCA standard I see their confidence grow, knowing that our figures are grounded in a respected framework.
Repeat assessment ensures rigour of figures
One key feature of the standard is its emphasis on repetition. Whereas many carbon assessments treat each project as unique, the RICS standard recognises the value of learning from repeated action.
The process enables us to make informed decisions while helping to refine carbon reduction targets, design selection, construction methods, financial impacts and project management.
With clear and accurate insights into a building's carbon hotspots, we can identify where reductions can be made and where they will have the most significant impact.
The RICS framework is modular, allowing for in-depth analysis of results under separate, easily identifiable sections.
Module A looks at upfront embodied carbon, B focuses on operations, repair and maintenance, C is centred on waste and end-of-life scenarios, and finally module D looks to encompass and include aspects that formally fall outside a project scope, such as exported energy.
By repeatedly applying the various modules of the standard across different project stages and types, we can collect meaningful data that influences market choices, manufacturing practices, project costs and programmes.
The assessment data already feeds into a number of databases, such as the Built Environment Carbon Database (BECD).
Another example of collaboration can be seen in the pilot version of the UK Net Zero Carbon Building Standard, which was published in October.
Supported by industry stakeholders including RICS, this operational, performance-based standard emphasises the need for a whole-life carbon assessor before net-zero status can be claimed, which makes understanding of the assessment process even more relevant.
Embodied carbon gauged from concept stage
We begin at the concept-stage design, focusing on the building's appearance, orientation, size, ground conditions and basic materials – for instance, steel or concrete frames and composite or built-up facade systems.
At this early stage, details such as the main contractor, material suppliers and exact quantities are often unknown, requiring us to make educated guesses. This uncertainty is an accepted part of the process, which is why RICS' standard provides baseline information to use for this stage.
These specifications cover carbon associated with commonly used materials, transportation distances, waste metrics and material lifespans, enabling design consultants to make informed assumptions about the project's carbon footprint even in the absence of detailed designs.
This early concept assessment is crucial for identifying potential carbon quantities in the design. It provides a robust baseline and framework, allowing us to advise clients on the financial impacts or benefits that may arise from a more carbon-friendly building.
By identifying hotspots early, we can make informed design decisions to reduce carbon impact. This process allows us to test various design options and materials over a 60-year or 120-year timeframe, depending on the project type.
In this context, it is vital to consider material lifespans using reference study periods (RSPs). For instance, we typically design industrial hardstandings for distribution centres with a lifespan of 30 years.
However, when we evaluate this design over a 60-year RSP, we realise that we may need to replace a significant portion of the yard during the building's life cycle, incurring additional carbon costs for materials and labour.
Conversely, designing for a lifespan of 60 years from the outset – typically requiring a 20–30% increase in pavement thickness – can eliminate the need for such replacement, leading to substantial carbon reductions over the building life cycle despite a higher initial embodied carbon score.
'By identifying hotspots early, we can make informed design decisions to reduce carbon impact'
Supply chain collaboration needed throughout
This brings us to the technical-stage assessment in the standard, at which stage we update our reports and showcase the design choices made to reduce carbon to our clients and other stakeholders.
By this point, intricate design details have been finalised and a main contractor has usually been appointed.
This stage is critical for discussing strategies to keep carbon low and focus on the supply chain. Specifying materials with excellent carbon scores is futile if these are not readily available from manufacturers or come without environmental product declarations (EPDs).
Once we complete the technical-stage assessment, we can compare it with the concept stage. This reveals whether our design choices have been successfully implemented, how much carbon we have saved and, most importantly, why these changes occurred.
We collaborate with the main contractor and supply chain throughout the construction stage, maintaining ongoing discussions about carbon impacts. However, challenges inevitably arise on construction projects: supply chains may falter or material prices may fluctuate.
Sometimes value engineering may have also been carried out, proposing a change in product, manufacturer or material quantities without anyone checking whether this results in a higher or lower carbon output – or indeed checking whether an EPD exists for the new product.
There can also be unforeseen issues such as inclement weather, which can cause delays or additional carbon costs.
On a more positive note, innovation at technical and construction stages can lead to new products or methods being used on site, and the main contractor may do everything possible to reduce the carbon associated with running a project.
Comparison across process offers insight
The most accurate estimate of the total whole-life carbon for a project is only possible on completion, which is where the construction stage assessment comes into play.
At this stage, we have robust figures for the quantities of everything purchased, the amounts of carbon required to run the project, supplier details and material travel distances.
We can directly compare this with the technical-stage assessment, identifying where design and contractor choices have succeeded or failed, and understanding the reasons for these outcomes.
Repetition is not just limited to the project; it is ongoing across every WLCA conducted. This enables understanding of carbon impacts not only at design stages but also at company level, and in turn feeds into larger databases such as BECD.
As a national source of information this can then be used to benchmark your next project, leading to carbon savings and reductions across the UK.
This is the most useful aspect of the WLCA, and it's only through repeat application at different stages that we can achieve these insights.
Understanding why something has happened enables us to identify and address problems effectively, allowing us to pinpoint issues with and implement meaningful changes to a project.
Therefore, while completing a WLCA is a great start, one assessment is not enough. Without assessments at each of the stages mentioned above, accurate claims of a reduction in carbon cannot be made.
This is particularly the case if the only assessment is made at the construction stage. By this time, the opportunity to make meaningful changes and reductions has been missed.
WLCA is not just a tool; it's a vital framework for understanding and reducing carbon in our projects. By embracing repetition and collaboration, we can make informed decisions that lead to a lower-carbon built environment.