This paper is the second output of a project that examines the embodied greenhouse gasemissions (‘embodied carbon’) from the use of concrete in buildings. In the current absenceof either regulation or widespread industry practice in quantified carbon assessment, itseems likely that messaging will play a powerful role in influencing designers’ perceptionsand decisions. Using the UK as a case study, this paper considers the current messagesabout the carbon implications of concrete in buildings from professional institutions andthe cement and concrete trade body. Three mechanisms through which it is claimedcarbon emissions are significantly reduced are identified: thermal mass, durability, andcarbonation. 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 thansuggested. More accuracy is needed from trade organisations if real carbon reductionsare to be achieved.