Measure it to manage it
Signing the Climate Emergency declaration is the easy bit. When we signed it, we made a commitment to record the embodied carbon within our designs. To achieve this a means of calculation was needed. Our Climate Action Group built a basic calculation tool using data from the ICE database and this was used to develop our initial carbon database, published in March 2020.
In parallel to this, our close work with the University of Cambridge on our PANDA software was giving our team a much deeper level of knowledge and understanding into the processes that create the carbon emissions for different materials. We therefore realised that simply calculating wasn’t enough, and that we needed to ensure that every engineer within the practice had a detailed understanding of these processes and the implications that our decisions have on the overall emissions.
We decided to setup internal research groups looking in depth into the three major construction materials: Steel, Concrete and Timber and each group was tasked with researching the material in as much detail as possible. In Autumn 2020 we compiled this information into our own customised material dataset and guidance notes, and this has led to the launch of our advanced carbon calculator – aided by the guidance launched by the IStructE.
This excel-based tool is now in use on all projects at all design stages. It allows our Engineers to assess the embodied carbon throughout the life of the design and track how it rises or falls with the development of the project. The results from our tool should broadly align with those produced from other calculation software – including the new IStructE calculation tool launched in March 2021. There are a number of carbon calculators on the market at the moment, but none are as comprehensive as the Price & Myers edition. Let us tell you what makes ours unique.
Our Approach
We believe that carbon counting should be transparent and clear. This means all calculations are provided with both material quantities and the embodied carbon factor (ECF) value used to calculate them. This is critical to allow fair comparison between options, or to allow for the incorporation of data from other disciplines.
We also believe that the aim of this exercise is to record carbon honestly. This means using realistic values for materials that reflect the actual picture in the industry. If a project performs poorly, then we will actively state this and try and understand the reasons behind it. In practice, this means taking control over how the calculations are carried out by our engineers by restricting the material properties they can use depending on the stage of the design.
For concrete, this means restricting the amount of cement replacement material (CRM) that our engineers are allowed to use at scheme and early design stages to realistic, sustainable levels. For steel this means using industry average values for recycled content (broadly equivalent to around 1/3) and for timber this means recording the sequestration of biogenic carbon as a separate value. By doing this, we ensure that we can focus on reducing embodied carbon by providing a lean and efficient design, as opposed to relying on artificially high levels of low-carbon materials.
Carbon calculation is an area that is still very much in its infancy and our research has also led us to appreciate the current levels of uncertainty with many of these values. We have factored this into our calculations and our embodied carbon tool is able to factor this in. Each of the standard modules is calculated with an upper and lower estimate, and results are presented both in terms of the ‘typical’ industry average value and a best and worst case. Our engineers are trained to consider this in their decision making – particularly at early stages – with the worst-case value being used as the target.
Useful links:
• Read the original article about our embodied carbon work in The Structural Engineer magazine from June 2020 here.
• Our carbon data is mostly based on the excellent ICE database.
• IStructE carbon guidance document.
