Too many ‘sustainable’ credits for buildings refer only to operation, but embodied energy accounts for much carbon output. There are digital tools to help green your design
As sustainability manager for Arup’s Structural Skills Network, helping to drive our pursuit of the UN Sustainable Development Goals and pledges like Structural Engineers Declare and SE 2050 Challenge, the role asks me to constantly reappraise my job as an engineer. I’ve worked on several projects that have been labelled ‘sustainable’ but that often refer just to operational energy, carbon and water use.
A key impact is embodied carbon – greenhouse gases emitted during the manufacture, transport and construction of building materials together with end-of-life emissions. One of our stated aims as a company is to ensure that sustainability is not simply a standalone discipline but a normal part of our language and thinking as building designers. We are continually improving the tools we use to take account of whole life carbon at each stage of the construction process.
For RIBA Stages 0-2 the Arup Structural Scheme Design Guide includes ‘rules of thumb’ for embodied carbon and energy to sit alongside traditional rules of thumb which help with grid selection and initial sizing of structural elements. We are also creating an ever-increasing, searchable database of case studies.
As options begin to firm up, the Arup Project Environmental Carbon Calculator (PECC) can be used – a spreadsheet-based tool, in which quantities of materials/components are input to calculate and benchmark embodied carbon. This can be done for structure and other element types, such as building envelope and internal finishes. The tool, containing benchmarks taken from the WRAP / RICS embodied carbon database, is transparent and customisable; for example Environmental Product Declarations can be ‘swapped in’ for the appropriate impact value. It is normally replaced by other tools once a BIM model has been created.
Arup’s in-house structural software, GSA and Adsec, both display environmental impacts, such as embodied carbon, in a similar manner to traditional structural parameters such as axial stress or deflections.
Once a BIM model of a design has been created, there are a number of tools available to carry-out the embodied carbon calculation, including specific, proprietary ones which have been approved for BREEAM or LEED credit calculations. However, our ‘Arup Carbon’ tool has been developed to allow all of our building designers to extract embodied carbon figures directly from BIM models. The tool uses the Speckle data processor to pull quantities from BIMs, calculates the A1-5 carbon equivalent (RICS, 2017) and graphically presents the results on an interactive web interface that can be shared with stakeholders. Users are not only able to see a breakdown of embodied carbon but also where it sits in a model, enabling designers to locate opportunities for improvement.
The approaches have been well received across the organisation, giving engineers immediate, real-time feedback with useful, graphical display of results. There’s a balance of ease of use with usefulness of information, all of which is easily customisable and integrated within design tools they are already using.
Conor Hayes is a chartered structural engineer in the Buildings team at Arup