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Whole life carbon assessments: where should architects start?

Words:
Simon Sturgis

In the second in his series, Simon Sturgis asks why we, as architects, should carry out whole-life carbons assessments, where we should start, and what we should consider through the RIBA Stages

The aim of whole life carbon assessments (WLCAs) is to understand what happens at each stage of a building’s life, from material sourcing to eventual demolition and disposal, and therefore how, from the earliest design stages, we can optimise the use of resources and keep carbon emissions to a minimum.

Diagram 1 shows the life cycle assessment modules to be considered for a WLCA. (Note that ‘biogenic carbon’ is shown separately from each of module’s A, B, C within ‘whole life carbon’. This is because when using, say, timber, the initial carbon benefits must be balanced by the end-of-life disposal carbon costs to get the true total carbon picture).
Diagram 1 shows the life cycle assessment modules to be considered for a WLCA. (Note that ‘biogenic carbon’ is shown separately from each of module’s A, B, C within ‘whole life carbon’. This is because when using, say, timber, the initial carbon benefits must be balanced by the end-of-life disposal carbon costs to get the true total carbon picture). Credit: RICS

This means lessening the ‘upfront carbon’ (Module A); while also minimising ‘in-use’ energy, and repair and maintenance (Module B); facilitating eventual efficient deconstruction (Module C); and assisting the potential for reuse (Module D). This will help us design buildings that are as efficient as possible in terms of shape, materials, resilience and life expectancy.

To successfully deliver low-carbon outcomes requires architects to get much closer to the supply chain so they can really understand the products and systems available and their carbon impacts over both the immediate and long term. It also means developing a ‘carbon intuition’ so that we can make good design decisions without necessarily doing the numbers. The importance for the design process is that to be successful in this, we really need to understand how our buildings will evolve over their expected lives, including adapting to future climate change and to possible changes in use.

It is worth remembering that today’s new build is tomorrow’s retrofit, and that the materials we use can be thought of as borrowed. The EU has formalised this around the idea of ‘buildings as material banks’ or BAMB. This is to enable a shift to a more circular economy where building products retain value through repeated use.

It is important to engage with the WLCA process from the earliest project stages as this is when we can make good strategic choices and the most effective reductions. The RICS WLCA Professional Standard (RICSPS) can be downloaded free from the RICS website, and although reading it all is somewhat daunting, I would certainly recommend that all architects read chapters 1 and 2, which give a very good and accessible overview of WLCA in plain English. Chapter 3 talks about assessing different types of projects and is also very useful. Chapters 4, 5 and 6 and the appendices cover the technical detail and are recommended for anyone with a detailed involvement with WLCA.

As I mentioned in my previous article there are various tools available (eg Feilden Clegg Bradley Studios’ free .xls based tool, FCBS Carbon, or paid-for tools such as: VERT, One Click LCA, eTool, etc.), and unless you develop your own assessment tool, you will probably use one of these for assessments. Most of these are Revit compatible.

The RICSPS does not specifically use the RIBA Project Stage numbering system as it is intended for international consumption. It does, however, state that assessments should be done at the following four phases; concept design, technical design, construction and post-completion. Using RIBA Stage numbering, the first WLCA should ideally be undertaken at the earliest RIBA Stages 1 or 2 using generic data figures. The RICSPS explains how this should be done, and how to calculate an additional contingency or risk percentage. The aim at these early stages is to inform the design process at a strategic level to be able to, for example, select structural options or different massing possibilities and to check performance against any relevant targets. These might include client requirements, local authority targets (eg GLA Policy SI2), LETI or Net Zero Carbon Building Standard (NZCBS) benchmarks.

Diagram 2: The steps recommended for undertaking a WLCA. These steps can be repeated at different project stages as the design evolves.
Diagram 2: The steps recommended for undertaking a WLCA. These steps can be repeated at different project stages as the design evolves.

The initial assessment should then be revisited at RIBA Stage 3 based on more precise material choices. The RICSPS also provides a number of default carbon values for these early project stages. Increasingly, local authorities are asking for WLCA as part of the planning submission. Further updates should then be undertaken for inclusion within the tender documentation (Stage 4, technical design) and revisited throughout the construction process. A final post-completion assessment can then be taken to check on the final outcome against expectation and to assist with marketing. The NZCBS will, when published later in 2024, also require an assessment of energy use a year after completion to confirm any claims in relation to achieving net zero.

The extent of your WLCA can cover all elements of a scheme as shown in the following diagram.

Diagram 3: The extent of a WLCA for a mixed-use scheme.
Diagram 3: The extent of a WLCA for a mixed-use scheme.

WLCA should be carried out on projects of all sizes. For the 2023 RICSPS, Part L calculations are typically not acceptable, with the requirement being for predictive energy modelling (eg TM54, NABERS, PHPP etc). However, for small projects (less than 1000m2 GIA or 10 dwellings or fewer), Part L is allowable.

Diagram 4: Requirements for most projects vs small projects.
Diagram 4: Requirements for most projects vs small projects.

Integral to the assessment are the associated direct benefits to the client. These include a significant contribution to value engineering. A WLCA that optimises material use, shape and overall resilience is also contributing to a more efficient building from a cost perspective.

It is worth noting that the life cycle modules as shown in Diagram 1 also align with the new cost measurement standard ICMS3, which means that cost and carbon measurement have the same basic reporting structures. Further, the lifecycle examination of energy use and repair and maintenance helps contribute to lower operating costs and can also give insurers and potential purchasers confidence in the long-term resilience and, therefore, value of an asset.

The lifecycle assessment can also include a review against future climate change, ie how easy is it to adapt the building to future temperature changes by, for example, the addition of louvres. WLCA can also help future-proof a building against regulation changes, eg a possible Part Z to the Building Regulations on embodied carbon.

To achieve the best outcome, it is important to ensure that we, as architects, have the best possible understanding of what is available from the supply chain. There is increasing availability of low-carbon and recycled materials and, even if we are unable to specify specific products for contractual reasons, we need to ensure that our performance specifications are correctly worded to ensure the appropriate low-carbon outcome.

Innovation across the supply chain is increasingly ‘low carbon’ as demand increases. Growing numbers of products, internationally, now have Environmental Product Declarations (EPDs) which provide carbon and other relevant data. On many projects now, products will not be considered unless an EPD can be provided.

It is worth noting here that timber is often seen as the answer to creating a low-carbon building due to its ‘natural’ production and carbon sequestration benefits. Although this is true, it should be noted that currently only 4-5 per cent of construction products across Europe are timber. If this was to increase significantly, it could have a detrimental effect on global forestry.

Recycled materials and products can help reduce the carbon impacts of a scheme, meaning their condition, life expectancy etc become important. Many products now have materials passports (see BAMB), which are intended to provide their use history.

If you are new to WLCA and wish to experiment and get a basic practical understanding of how it works, I would recommend using FCBS Carbon and trying it out on a live project. I would also, as mentioned above, read the first three chapters of the RICSPS. For those who wish to engage in more detail, Construction Carbon is offering courses on WLCA training and certification. 

In my third and final article, I will discuss the impact WLCA will have on architectural design.

Simon Sturgis is lead author of the RICS' Whole Life Carbon assessment for the built environment, 2nd Edition, 2023

Read Simon Sturgis on tools to fire the journey to net zero carbon.

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