EMBODIED CARBON | LIFE-CYCLE ASSESSMENTS EMBRACING THE BUILDING LIFE-CYCLE ASSESSMENT BDP carries out life-cycle assessments of its designs, despite the current lack of information available on embodied energy in building services equipment. BDPs Jon Hall explains how it works U ndertaking a life-cycle assessment (LCA) of embodied carbon allows us to quantify the carbon impact of a building over its life. We have been doing these studies since 2018, and while we can quantify and provide support on where meaningful carbon reductions can be realised, we encounter challenges during assessments. How to guides There are numerous resources on embodied carbon, but few describe how to produce an effective and robust assessment. For example, Pomponi and Moncaster1 note there is often considerable variability in the application methodology across studies. We have developed our own how to guide for our internal digital designers and are acting as LCA coordinator for an external team on an international project. Using our guide, the design teams have produced LCAs that we are peer reviewing. Building services estimations There are relatively few Environmental Product Declarations (EPDs) available to assess the embodied impact of building services. This is significant when it can account for 40-70% of embodied carbon for refurbishments and fit-outs, and 15-50% for new builds.2 Estimations for building services impact is often necessary, and across our environmental design studio we have been encouraging this conversation during early design. As a result, we have identified where improvements and interventions can be made based on life-cycle considerations. Refrigerant Impact With the growth in heat-pump technology, the impact of refrigerants is a critical consideration when developing a heating and cooling strategy. Refrigerant can be a large contributor to embodied impact because of the global warming potential (GWP) and leakage rates. So design engineers must have an appreciation of the life-cycle impacts of different refrigerants. A heat-pump strategy, for example, can have a higher environmental impact than a gas boiler one over its whole life when high GWP refrigerants are selected. Efficiency considerations also contribute to refrigerants type, and there are air quality benefits of non-combustion technologies, but all these parameters must be considered across the life of the component and development. Biogenic carbon Understanding the biogenic carbon benefit can be challenging; the recent LCA benchmark figures for embodied carbon provided by LETI3 exclude the benefit delivered by sequestration, whereas the UKGBC4 has shown that, in certain scenarios, the 2030 emissions target can only be achieved by including sequestration. We often exclude biogenic carbon in our studies to align with these LETI benchmarks. When testing elements during optioneering, however, we have struggled to demonstrate the benefit of using one structural solution over another, for example, where this figure isnt attached directly to the element. We are monitoring the research to provide informative studies. EPDs for new elements The lack of EPD data can be challenging. We researched technical and composite materials to determine what proportion could be replaced with a bio-based alternative. We had to explore a range of databases to find materials to use as proxies. By advocating the use of innovative materials on our projects, manufacturers are keen to support our analysis and their products, which is allowing us to test our proxy methodology. Advice summary n Bring cost consultants into the LCA process to support the best opportunities for optimising the design n Build an argument around the wider benefits of bio-based materials, including health and wellbeing, indoor air quality and supporting local or national supply chains n Design with circularity principles and identify opportunities for retaining the value of elements and materials over the life-cycle. CJ J ON HALL is a sustainability consultant and materials and embodied carbon specialist at BDP References: Using cross-laminated decking on timber joists instead of a concrete or composite flooring system saved around 115 tonnes of CO2e over the life-cyle of the University of Essex Business School 1 P omponi, F & Moncaster, A (2018). Scrutinising embodied carbon in buildings: the next performance gap made manifest. Renewable and Sustainable Energy Reviews, 81, 2431-2442. 2 Getting to grips with whole-life carbon, CIBSE Journal, December 2019, bit.ly/CJJan20JH1 3 Climate emergency design guide, LETI (2020), www.leti.london/cedg 4 Building the case for net zero: a feasibility study into the design, delivery and cost of new net-zero carbon buildings, UKGBC (2020), bit.ly/CJJan20JH2 28 January 2021 www.cibsejournal.com CIBSE Jan21 pp28 BDP embodied carbon.indd 28 18/12/2020 14:36