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The elephant in the room: embodied energy

The Shard’s embodied energy: 40 per cent in the steel structure, 25 per cent in the concrete

Footprint recently attended Built Environment Briefing: Minimising the embedded environmental footprint of construction and refurbishment, an event organised by Rushlight. Hosted by APCO Worldwide, the seminar presented approaches for measuring the environmental impact of both new and refurbished buildings. The event attracted 50 attendees, including representatives from The Concrete Centre, BioRegional, Architype, Deloitte, Sefaira, Spiralite and the University of Nottingham.

Introduced by APCO managing director James Acheson-Grey, the speakers included Sarah Williamson, commercial director at Sefaira, Jonathan Essex, sustainable construction manager at BioRegional and Elaine Toogood, senior architect at The Concrete Centre.

Sarah Williamson began by explaining that 85 per cent of the embodied carbon in buildings comes from materials while 15 per cent is due to transport. According to Sarah, embodied energy is difficult to measure since materials are not currently properly certified. She cited the Shard which, constructed after demolishing a 25 storey building including its foundations, had to use two fans to extract the excess heat generated due to an exothermic reaction during the concrete curing process. She explained that 40 per cent of the embodied energy in the building is contained in the steel structure while 25 per cent is in the concrete. Constructing a building like the Shard has an embodied carbon of almost 1,370 tonnes of CO2, leading Williamson to ask whether it is perhaps better to retrofit an old building instead.

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Sarah Williamson stressed the importance of reducing buildings’ embodied carbon

BioRegional’s Jonathan Essex focused on cutting waste during the construction stage as well as the use of reclaimed materials, citing examples from the Olympic site where 163 tonnes of steel were recycled saving 84 tonnes of embodied carbon. He suggested architects and developers should ‘start living over the shop’, encouraging them to build less while reusing the 39,500 hectares of derelict land in the UK.

Elaine Toogood, ended the presentation encouraging practitioners to take advantage of concrete’s thermal mass. She said that concrete’s carbon footprint has reduced by almost 45 per cent since 1990 while diminishing waste landfill by 72 per cent since 2008. She added that ground granulated blast furnace slag (GGBS) – used as an aggregate to make concrete – can reduce CO2 emissions by as much as 40 per cent. According to Elaine, approximately 30 per cent of all aggregates are recycled. It is importatnt to prioritise locally-produced over recycled ones since the former contains less embodied CO2. She added that 92 per cent of all concrete production is BES-6001 accredited, which requires responsibly sourced material. What caught my attention most was the emphasis Elaine put on the savings that can be achieved when using concrete’s thermal mass and resistance to fire, in comparison to timber, especially when considering London’s high thermal oscillation.

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NHBC report 2011: Operational and Embodied CO2 in new build housing. Presented by Elaine Toogood

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To conclude the event, Kirsten Henson from KLH Sustainability and John Newton from Ecology Consultancy joined the panel to discuss the lessons learnt from London 2012. They agreed that sustainability was a means ‘to deal with technical solutions’ while reducing running costs rather than being a target in itself. They called on architects ‘to make replicable the process of innovation’ implemented in London 2012, and urged them to retrofit existing buildings.

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Readers' comments (2)

  • I would not agree with Sarah Williamson that there is not currently certified embodied carbon for construction materials. Considerable numbers of independent, third party verified EPD are available for a wide range of construction products - these will include embodied carbon data, often called as labelled Global Warming Potential or Climate Change, and calculated using an agreed methodology. Please see page 15 of the CPA’s recent publication which I co-wrote (http://www.constructionproducts.org.uk/fileadmin/client/cpa/documents/Sustainability/Embodied_Impacts_brochure_small_V9.pdf) for relevant links to EPD programs.
    Jane Anderson
    PE International

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  • We must of course remember that concrete's thermal decrement means it is poor for use as thermal mass as its absorption/radiation timescale doesn't fit the human 24 hour cycle. Hempcrete on the other hand does.

    The embodied/operational energy graphs are incorrect. The 'carbon spike' as shown in Tom Woolley's latest book means the embodied energy can never be cancelled out by the operational. They are two gradients on the same graph line, not two intersecting.

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