SPONSORED ROUNDTABLE | DECARBONISING COOLING dating from the 1400s to the 1960s. There is a real urgency to find ways to decarbonise these buildings, otherwise they will fall into disrepair. Part of the problem, added Punter, is a lack of guidance on how to decarbonise these buildings, which have complex and challenging requirements, and must be assessed case by case. U-value measurement in listed buildings is straightforward; measuring air permeability is the real challenge, she said. There is a drive to decarbonise, but I question whether we will we see a shift in what conservation officers will accept. I hope they will be more lenient to allow decarbonisation of heritage buildings and accept cooling measures such as external shading. Punter added that the way to sensitively retrofit listed buildings is to share knowledge and push the boundaries. Beyond cooling equipment, Ben Gholam, structural engineer at Price & Myers, introduced his research and software development on embodied carbon optimisation in building structures. His team has THE TROUBLE WITH CONCRETE AS THERMAL MASS There is a conict between the desire to have thermal mass in a building which helps regulate internal temperatures while also trying to decarbonise, said Ben Gholam. Concrete is used to achieve thermal mass, which is the worst thing to do, he added, given that concrete is high in embodied carbon. We shouldnt be using concrete at all, said Gholam. The concept of packing mass into our buildings to save carbon over the long term is doing untold damage in the immediate term. Ground granulated blast-furnace slag (GGBS) has been proposed as a solution, as its a waste product from steel production, but about 20% of GGBS is currently produced to replace cement needs and there are supply problems, says Gholam. We need to look at global averages for materials based on the technologies we have and consider minimising the mass of our buildings, he said. Latini asked whether the upfront carbon cost of using concrete is lower than the operational savings that the thermal mass of concrete provides over the average 60-year life of the building. From a structures perspective, it makes little difference, Gholam replied, as the embodied carbon is set once the structure is built and the damage is done. He went on to say: If your building is designed well using limited amounts of steel, with timber and other low carbon materials for the buildings mass, that can work very well for embodied carbon and circularity; they go hand in hand. Part of the problem is a lack of guidance on how to decarbonise [historic] buildings Amy Punter created an ambitious database and identified issues with using concrete to achieve thermal mass in buildings to regulate internal temperatures. (See panel, The trouble with concrete). With a predicted tripling in energy used to cool buildings by 2050, it is essential building services engineers take a holistic approach and collaborate with other engineers and manufacturers to find solutions. The roundtable demonstrated how a meeting of minds from across the sector can stimulate original thinking that might just speed our journey to low carbon cooling. CJ References: 1 IEA, Cooling tracking report, Nov 2021 www.iea.org/reports/cooling The concept of packing mass into our buildings to save carbon over the long term is doing untold damage in the immediate term Ben Gholam Providing comfortable internal conditions for employees when temperatures rise, while also addressing energy efficiencies, will present challenges Stephen MacLoughlin 42 October 2022 www.cibsejournal.com CIBSE Oct 22 pp38-40, 42 Roundtable.indd 42 26/09/2022 16:07