Tools to fire the journey to net zero

Carbon reduction is becoming central to architectural practice with whole life carbon assessments (WLCA) increasingly driving design decisions. Many local authorities are now asking for WLCA as part of a planning submission. For example, in the greater London area it is mandatory for schemes above a certain size (see Policies SI2, and SI7). Broadly speaking, in London, applications that are referable to the mayor are residential developments of more than 150 units, buildings over 30m in height, and commercial buildings over 2,500m². Many other local authorities including Manchester, Bristol and Dundee are making similar requirements.

We know that global construction – reckoned to be the equivalent of building an entire greater London every six weeks – has enormous negative impacts on both climate and resources. By the end of this century, even if governments meet national carbon reduction pledges, temperatures are expected to increase by as much as 3º- 3.5º. The UK is legally committed to achieving net zero by 2050, with interim targets for 2030 and 2035, as shown in diagram 1. This is a key requirement for limiting temperature increases.

As we move to a more resource efficient and ‘zero carbon’ world this has become a major determining factor affecting all architectural design. Much of today’s architecture is still informed by the modernism of the 1920s, but that offers no answers to the climate crisis and resource depletion. Understanding whole life carbon and the relationship between embodied and operational carbon will help architects maximise the opportunities for innovation as we embark on huge changes in the way we design, construct and use buildings.

Diagram 1 shows the significant difference between the business as usual ‘most newbuild’ and we should be delivering – ‘low carbon new build’. This year we should be over half way down the arrow, with building projects completed today 55-60% lower in overall emissions than their 1990 equivalents. This can be difficult to achieve with newbuild as the supply chain is still evolving, although there is now significant data showing that reducing carbon also reduces cost.

The numbers

In September 2023 the RICS published a second edition of its 2017 Standard ‘Whole life carbon assessment for the built environment’. This update of the RICS standard provides a methodology for assessing carbon emissions for all project types, ie the ‘numbers’. It is the source methodology that underpins BREEAM, LETI and the UKGBC which all provide guidance and advice on what we should be doing to achieve reductions, and the forthcoming Net Zero Carbon Building Standard (NZCBS). A RICS WLCA will provide the data you need for appropriate BREEAM credits (for example Mat 01). The RICS standard is aligned with the revised version of the European Standard EN 15978 and is designed to be both UK and internationally applicable.

In practice, most assessors will not refer directly to the RICS Standard, but will use one of the software tools available (for example Feilden Clegg Bradley Studios’ free ‘FCBS Carbon’, or pay for tools such as: VERT, OneClickLCA or eTool). Make sure the tool you chose is RICS 2023 compliant to ensure best consistency and comparability on any platform. Assessment consistency will also help integration with BIM as the data used will be more dependable.

Extended application

There had been limits to the typologies which the RICS standard could evaluate as the 2017 1st edition applied to new construction only, with an emphasis on offices. This edition enables a whole life carbon assessment to be undertaken on offices, housing, infrastructure (local and national), and for fitout, retrofit and refurbishment. A mixed-use scheme assessment can therefore now include all building types as well as all local infrastructure.

The standard also gives guidance on what to do at different project stages, for example how to make early strategic carbon decisions against more detailed assessments as the project progresses. Diagram 2 shows how the ability to influence carbon reductions is greatest at the earliest stages when key strategic design decisions are being made.

The ability to translate energy use (kWh) into carbon emissions (kgCO₂e) is a crucial new section as it means that not only can we now look holistically at the combined operational and embodied carbon performance of a built asset, but we can also understand the carbon cost/benefit impacts of, say, insulation. This helps identify the operational benefits of various insulation options with different embodied carbon costs. The ability to do this is a key new feature of the RICS guidance, and enables us to factor in grid decarbonisation. Diagram 3 shows how a combination of low carbon actions, both operational and embodied, can combine to make significant reductions possible.

Aligning systems

Cost is a key issue on every project, and the new RICS WLCA standard aligns cost and carbon using the same reporting structure. This in essence means that cost plans will be able to feed directly into WLCA. Cost plans also typically include a contingency, and the new guidance describes how to include a carbon contingency. This is made up of three elements: the RIBA project stage, the reliability of carbon data, and the reliability of quantities data.

A key part of any WLCA are the emissions during the use phase – after practical completion. This encourages construction professionals to take a far greater interest in the resilience and durability of their designs over their expected design life and back that up with figures for their clients. The RICS WLCA standard uses 60 years as the life cycle assessment period. It is important to note that this does not mean buildings should only last 60 years – far from it, generally the longer the better. The 60 year period is to enable a reasonable projection into the future and comparability between assessments. The longer buildings last and the less maintenance they need, the better their lifetime resource efficiency, and the lower the lifecycle emissions. We have got used to the idea that buildings can have a short life of only a few decades. The Pantheon in Rome has a concrete dome that has lasted nearly 2000 years, and with no reinforcing steel.

Today's newbuild, tomorrow's retrofit

Another feature of more holistic long-term thinking is how materials and elements of construction evolve through successive life cycle stages of an asset (see Diagram 4). As shown in Diagram 1 earlier, a comprehensive retrofit or refurbishment is typically the lowest carbon option where a building already exists. This is not always possible, but generally the efficient reuse of material, whether an entire building or retained construction elements, has direct carbon benefits. Any demolition at the outset of a project should be included in the WLCA.

In conclusion, a WLCA gives us the information we need to design better, more resource efficient, long life, low maintenance and low carbon buildings. This will help the built environment industry to move to a net zero, circular economy. It enables us to better understand how our buildings will perform over their expected lives, and how they will be dismantled and disposed of. Remember, today’s newbuild is tomorrow’s retrofit; a WLCA can help us understand how our buildings will perform in the future. This is not only helping to reduce future emissions but, through more resilient design, helps to future proof asset value.

In the next two articles I will explore the practical implementation of WLCA, and what achieving net zero means for the evolution of architecture. 

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