Inaccuracy Issues in Embodied Carbon Assessments

Sean Lockie
As energy prices shoot upwards, buildings need to be operated in a low carbon manner. A sustainable built environment focuses not only on operational carbon, but also on the reduction of embodied carbon – the impact of CO2 emissions generated during the manufacture, transport and construction of building materials, together with end of life emissions.

Industry has been struggling to deal with the disconnect between embodied and operational carbon, exacerbated by the lack of consensus on exactly how embodied carbon should be defined and calculated (see Fig. 1).

Carbon Lifecycle

Undertaking embodied carbon assessments is not as straightforward as it sounds and without agreed rules, data and data structures, significant problems can occur. BIM is likely to change all this but we are still at least three to four years away from BIM models containing useful comparable carbon data.

Quantity surveyors might be the best equipped to quantify the embodied carbon in projects, as they are close to the budgets, the quantities of materials and the specifications.  However using current methodology they would need to assess the weight of a material to complete the calculation, and on this aspect data and knowledge are poor. Embodied carbon ‘factors’ (ie. the emissions from a brick, a sheet of glass, a tonne of steel), currently obtained from academic sources, lack reliability, relevancy and rigour, but they are a start.  To complete the picture and create a whole life carbon assessment, emissions from asset maintenance and replacement would need to be factored in – and these values are rarely dealt with satisfactorily.

We are seeing some changes in approach. Both government and clients have begun to drive the embodied carbon agenda forward. In October 2010 the government’s Innovation Growth Team (IGT), (PDF), reported that rules and methodologies for quantifying whole life carbon were a necessity. Industry bodies have responded by taking up the challenge. The Green Building Council, ICE (Institution of Civil Engineers) and RICS have taken the lead, with Faithful+Gould as lead author of an embodied carbon guide on behalf of RICS.

However embodied carbon is not a requirement in Building RegulationsPart L focuses only on operational emissions from heating, lighting and cooling, and embodied carbon calculation and mitigation doesn’t count for much in BREEAM and LEED assessments.  The government is not currently embedding any fiscal or regulatory driver into the system, although it seems very possible that this will change, making embodied carbon management mandatory. In 2010 we surveyed 166 leading property and construction companies in the UK, US, Middle East and Asia Pacific regions. Fifty-three per cent responded that their main reason for not counting their embodied carbon is that it currently has no commercial value.

Faithful+Gould's Sustainability and Carbon Management team has scored some early success with reducing embodied carbon for clients. At Farringdon Station, for example, we saved 30 per cent of the potential embodied carbon emissions by retaining aspects of the building structure, local materials sourcing, specifying less carbon intensive materials, on- and off-site material re-use, efficient load and route planning, durable finishes and construction plant maintenance.