Jon Hall, Sustainability consultant – materials and embodied carbon specialist

As environmental awareness of businesses, governments and consumers grows, so does their scrutiny of the industries and sectors responsible for the greatest impacts. As a result, those involved in the construction and operation of buildings and infrastructure – which generate around a third of global carbon emissions – are starting to grasp the magnitude of their responsibility.

While operational carbon emissions for buildings have been measured (and managed, to varying degrees of success) for years, quantifying carbon emissions associated with procurement, manufacture, construction, maintenance and demolition impacts is relatively immature, and we know the impact of today’s new buildings is tomorrow’s problem. Moreover, we need to avoid the overuse of the earth’s finite resources – tackling the associated emissions is only part of the problem.

But we need to start somewhere. Undertaking Life Cycle Assessment (LCA) of embodied carbon allows us to quantify the carbon impact of a building (or elements of it) over its lifespan. Utilising Environmental Product Declaration, the impact of material extraction, product manufacture, transport and installation, and disposal of building elements can be evaluated. With the decarbonising energy supply network, the proportional environmental impact of building elements – particularly those that still rely on fossil fuel technologies, like extraction and manufacturing activities which occur before the building operation period – is growing.

We have been undertaking these studies since 2018 and, whilst we can quantify and provide support on where meaningful carbon reductions can be realised, we find we encounter a series of challenges during assessments. We are continuing to find and deliver the right solutions to improve our consultancy and reduce our impact on the environment.

 ‘How-to’ Guides

One of the initial challenges we encountered was the availability of resources and support to guide the process of completing a lifecycle assessment of a building. Whilst there are numerous resources on embodied carbon as a topic, there are few publications which describe, in an accessible digestible way, how to produce an effective and robust assessment.

We were early adopters of Bionova’s OneClickLCA tool and with that, we quickly determined the common obstacles to the most efficient monitoring of embodied carbon. This enabled us to develop our own ‘how-to’ guide for our internal digital designers and a short training package for the wider professions we’re introducing to the process.

We have now built a robust database of project performance, and are building a standard details library with pre-populated embodied carbon parameters to support the design process. The more studies we complete the more we understand about the impact of components and materials, and the better our consultancy becomes.

Building on the expertise we’ve developed, we are currently acting as ‘LCA coordinator’ on a major international project and have articulated our ‘how-to’ guide into a formal LCA Execution Plan. Following this, we have started to peer review and validate the assessments emerging from the design team knowing that common pitfalls have been avoided.

Building Services Guesswork

There are very few Environmental Product Declarations (EPDs) available to assess the manufacturing and material related impacts for building services. Assessing building services as part of the LCA usually requires several estimations, which are fit for purpose during the concept design stage, but become unsuitable as the design develops – particularly where a robust approach to net-zero carbon is sought by the client team. According to the Chartered Institution of Building Services Engineers (CIBSE), building services can account for anything between 40-70% of embodied carbon for refurbishments and fit-outs and 15-50% for new build developments.

OneClickLCA allows us to model building services and include actual quantities. Where estimations are necessary, we make use of the tool’s generic resources which include the systems, piping and cabling per square metre of gross internal floor area. We have found that proportionally, these resources account for an amount of embodied carbon comparable to industry figures but are aware that this should not be the long-term solution.

We have been holding regular webinars and workshops across our environmental design studio to encourage this topic to be part of regular conversations during early design. This has resulted in us having a better appreciation for our impact and has identified where improvements and interventions can be made based on lifecycle considerations.

Biogenic Carbon

The carbon sequestered by living material such as plants over their life is referred to as biogenic carbon. Despite ongoing research into accurately quantifying the impact of biogenic carbon reflected in LCA studies, the standards advocate that it is generally omitted from calculations. The recent LCA benchmark figures for embodied carbon in the LETI Climate Emergency Design Guide (LETI, 2020) excludes the benefit delivered by sequestration, whereas the UKGBC has shown that in certain scenarios, the 2030 emissions target can only be achieved by including sequestration. And more confusingly, other emerging policy documents, including the new London Plan, state that biogenic carbon should be included within the results.

Most of the time, In accordance with guidance within RIBA and LETI publications, we exclude biogenic carbon in the total embodied carbon figures we report (noting that OneClickLCA reports a biogenic carbon total ‘below the line’). But when testing elements during optioneering we have been struggling to demonstrate the benefit of using one structural solution over another, for example, where this figure isn’t attached directly to the element.

There is extensive debate on this subject and so we are continuing to monitor and research so we can continue to provide informative studies. In parallel, we are running several ‘test’ simulations to provide the evidence to help focus our professions on the areas of most significant impact when replacing technical materials with bio-based materials.

Embodied Carbon Data for New and Innovative Elements

One of our biggest challenges is determining the impact of newly emerging and innovative elements and materials where EPDs do not yet exist.

We recently carried out extensive research into technical and composite materials to determine what proportion of these could be replaced with a bio-based alternative. Where bio-based elements were identified that could replace these technical elements (in principle), we have explored a range of databases to find proxy materials that reflect the element or component.

Products and materials we have considered include bio-composite bricks, cement replacements, and reclaimed/remanufactured products, amongst others. In scenarios where it is not possible to identify these types of materials within LCA tools, manual calculations outside of these is required, working with manufacturer information to model not only construction related carbon but also product lifecycles, durability, maintenance and end of life options.

Through advocating the use of new and innovative materials on our projects, manufacturers are keen to support our analysis and their products, which is allowing us to test our proxy methodology and continue to advocate the use of progressive materials in our design work.

Refrigerant Impact

In addition to the challenge of accounting for building services due to the lack of EPDs, we have – like several other engineering consultancies – started to analyse the impact of refrigerant use within building cooling systems. With the growth in heat pump technology to capitalise on the decarbonising energy supply network, the impact of refrigerants is a critical consideration when developing the heating and cooling strategy.

The type of refrigerant can be a large contributor to these figures due to typically high global warming potential (GWP) and leakage rates. It is, therefore, extremely important that design engineers have an appreciation of the impact the different types of refrigerants can have on the life cycle impacts. For example, a heat pump strategy can have a higher carbon impact than a gas boiler strategy over its whole-life when high GWP refrigerants are selected. There are, of course, efficiency considerations that also contribute to refrigerants type, and air quality benefits that non-combustion technologies provide, but all of these parameters must be considered across the life of the component and development. 

With the climate crisis at a critical point, understanding whole-life embodied carbon is extremely important. Whilst is it important to consider operational carbon over the lifetime, making an impact and reducing carbon today requires immediate action.

The challenges discussed above are just a handful encountered and the industry as a whole is still getting to grips with the topic. It is hoped that these challenges can be solved in the coming months and years and with more knowledge comes more opportunity. In the LCA process, it is critical to:

• Bring cost consultants into the LCA process to support – from a financial perspective – the best opportunities for optimising the design
• Build an argument around the wider benefits of bio-based materials, including health and wellbeing, indoor air quality and the opportunities to support local or national supply chains
• Building circularity and identifying opportunities for retaining the value of elements and materials at the end of their life

We are working hard to push forward the use and efficacy of life-cycle assessments, continuing to capitalise on our unique position at the heart of a multi-disciplinary design firm.