Embodied carbon of concrete in buildings, Part 2: are the messages accurate?

Abstract

This paper is the second output of a project that examines the embodied greenhouse gas emissions (‘embodied carbon’) from the use of concrete in buildings. In the current absence of either regulation or widespread industry practice in quantified carbon assessment, it seems likely that messaging will play a powerful role in influencing designers’ perceptions and decisions. Using the UK as a case study, this paper considers the current messages about the carbon implications of concrete in buildings from professional institutions and the cement and concrete trade body. Three mechanisms through which it is claimed carbon emissions are significantly reduced are identified: thermal mass, durability, and carbonation. By assessing each of these in turn against the available scientific literature, it is shown that they are likely to have a far more limited effect on the total impacts than suggested. More accuracy is needed from trade organisations if real carbon reductions are to be achieved. 'Practice relevance' In the current absence of whole life carbon assessment for buildings, messaging about the carbon impacts of different materials is likely to have a strong impact. The paper recommends that the cement and concrete industry should be more accurate with the messages it is sharing. In particular the claims that thermal mass, durability and carbonation are effective mechanisms, which suggest concrete is a low carbon option, should be reconsidered. Meanwhile designers should use the excellent advice being produced by the professional institutions and undertake whole-life carbon calculations to ensure the lowest carbon design. These should include a best estimate of future trends towards warming climates and decarbonisation of electricity, but should also recognise the importance of the immediate effects of the emissions from construction materials. There is also a key role for policymakers in legislating to make the measurement of embodied impacts of buildings mandatory.

Keywords

• buildings
• cement
• concrete
• construction industry
• embodied carbon
• greenhouse gas emissions
• life cycle assessment (lca)
• trade organisations
• whole-life carbon