As the construction industry designs and constructs buildings with ever-decreasing operational energy use, embodied carbon is increasingly important in the whole life cycle costing of a building. Sophie Chisholm reports the findings at a recent CBx event.
16 July 2015 | By Sophie Chisholm
Embodied carbon has been the focus for much academic research for 20 years, but only recently became part of the construction industry's wider agenda.
Originally the province of quantity surveyors, it has now been adopted as an objective by the whole building cycle. As the built environment tends towards zero-operational energy use, the embodied carbon of those buildings becomes increasingly important in comparison.
In 2014 the UK Green Building Council ran an Embodied Carbon Week and produced a report capturing main themes of the event. Of the 15 challenges identified by attendees across the programme the top four were: consistency in method, availability of comparable data, industry attitude - legislation not forthcoming and worry of extra cost and complexity. Headway has been made but, as the CBx event highlighted, these challenges are ongoing.
Embodied vs operational
The main unintended consequence of the tightening of the Building Regulations' requirements for operational efficiency has been observed as the increase in embodied energy of buildings. In many cases, designers will employ a high-tech approach to minimise operational consumption - using highly processed materials, complex plant equipment and a sophisticated, automated control system.
In terms of whole-life performance, this tends to shift the carbon 'cost' from operational use to the embodied carbon of the fabric. The University of Bath, which produced the industry's first authoritative database on embodied carbon of materials in 2005 (Inventory of Carbon & Energy - ICE), endorses the standardisation of the industry's reporting of embodied energy to stop merely shifting the time at which energy is 'spent' and reducing the net carbon cost of any project.
The Royal Institute of Chartered Surveyors (RICS) produced guidance that sets out a way to calculate embodied carbon from cradle to end-of-life across four main sectors with case study figures for each. These show that over 30 years around 50 per cent of the total carbon is tied up in embodied (vs operational) which includes the embodied carbon of the initial material, emissions during construction and the maintenance and repair cycle.
And the embodied versus operational split differs from sector to sector with embodied carbon more pronounced in buildings housing low-energy intensity activities such as warehouses; in offices embodied carbon accounts for over half the whole life carbon cost, in supermarkets it is 50 per cent and in a semi-detached house it is higher than 50 per cent.
The water industry's regulator has required embodied carbon analysis of all assets since 2004. There has been development in determining carbon factors for pumps and other elements to get accurate calculations for any replacement projects. Network Rail and the Highways Agency also include embodied carbon calculations in design, refurbishment and maintenance proposals. Embodied carbon calculations are much simpler in these industries as they comprise standard, modular components.
It's not all bad news; things are progressing with a number of metrics and data sources and with BS 15978 setting framework for embodied carbon analysis. An EU standard published in 2011, BS 15978 is the standard upon which all Lifecycle Cost Analysis (LCA) is based and is gaining traction in the industry. The RICS method mentioned is a globally applicable process that simplifies life cycle cost analysis.
There are also a number of publicly available tools; the Environment Agency first published its embodied carbon calculator in 2007 and uses this as one of three metrics upon which to judge a project. These tools can also be mined for embodied carbon figures.
There is still much uncertainty in embodied carbon values at the manufacturing stage and this creates difficulties for the contractor, who must deliver against specifications assumed at design stage. Further uncertainty is introduced where assumptions are made in terms of building use and refresh cycle. End-of-life details are also hard to predict.
The industry relies on a few global averages, but it's expected that more embodied carbon data will come from Environmental Product Declarations (EPD) - verified documents that report data of products based on LCA and other relevant data. Only seven EPDs exist in the UK: the US has hundreds registered, while Germany has 1,000. But BIM will have embodied carbon capabilities, thus allowing more accurate and less time-consuming calculations.
Legislation in place
There is no embodied carbon requirement in Part L and in BREEAM there are one or two credits available per project. The Green Guide is tangentially linked to embodied carbon including the requirement as a proportion of an A-rating.
Brighton Council has required an embodied carbon plan since 2011, however, there is no record of the council pushing for more stringent measures or holding applicants accountable to these. In Westminster, such plans are appearing and the Department for Communities and Local Government is working on a White Paper probing the potential for using allowable solutions as a mechanism for embodied carbon mitigation.
This article is an abridged version of CBx's white paper: Embodied Carbon - are we there yet? This paper was put together following a CBx event in March 2015. To download a copy of the full report, click here.
Sophie Chisholm is programme and technical manager at CBx