SPONSOR CPD PROGRAMME Continuing professional development (CPD) is the regular maintenance, improvement and broadening of your knowledge and skills, to maintain professional competence. It is a requirement of CIBSE and other professional bodies. This Journal CPD programme can be used to meet your CPD requirements. Study the module and answer the questions on the final page. Each successfully completed module is equivalent to 1.5 hours of CPD. Modules are also available at www.cibsejournal.com/cpd Determining whole life carbon for built systems This module explores the concept of whole life carbon, considers its components, and reflects on the current guidance for the built environment As governments and businesses around the world commit to net zero targets, whole life carbon (WLC) assessments are becoming increasingly important as a metric to help inform decisions in the construction and operation of built environments. This CPD article will consider the concept of WLC, the relative impact of its constituents, and will reflect on current guidance that may be used to steer the building services community towards systems that have a more carefully considered impact of the future environment. Whole life carbon (WLC) is a measure of the total carbon emissions associated with a building over its entire life-cycle, from the extraction of raw materials through to the demolition and disposal of the building. WLC is increasingly being used to assess the environmental impact of buildings and to inform decisions about design, construction, and operation. The components of WLC are embodied carbon and operational carbon. Embodied carbon is that emitted during the construction of a building including the extraction, processing, and transportation of materials; the construction process, which includes the fabrication of components, transport and construction; and the post-hand-over maintenance, repair and replacement, demolition, dismantling and ultimate disposal of the building materials. Operational carbon is the carbon emitted during the operation of a building, such as the direct and indirect emissions resulting from the energy consumed by heating, cooling, lighting, and the use of appliances. In building services applications, there is likely to be a complex relationship between the embodied and operational components, which will be influenced by the performance of the thermal envelope, occupancy patterns and building use, the loads in the space, and the design of components, systems and sub-systems. WLC assessments provide a tool to benchmark and minimise a buildings environmental impact across the entire life-cycle of a building and they can help to improve the value of buildings, by demonstrating that efforts have been made to reduce its environmental impact while also complying with corporate social responsibility (CSR) goals, which include reducing environmental impact. As highlighted by the 2017 RICS Professional statement on whole life carbon assessment for the built environment,1 embodied carbon can make a larger contribution than that of the operational carbon across the buildings life when considering the whole building. The RICS document includes an illustration of the constituents of modelled whole life carbon over a 60-year building life-cycle for several examples including those for a London speculative office development, as shown in Figure 1. When considering the whole building, as reflected in this data, the embodied carbon accounts for a significant proportion approximately 70% of the total over a buildings lifetime, and undoubtedly is an important consideration when assessing the design options for fabric and systems. However, it is inappropriate to draw the conclusion that embodied energy is so dominant that it eclipses the need for careful consideration of operational performance of specific elements, particularly those www.cibsejournal.com September 2023 55