Getting the numbers right and getting the right numbers: quantifying the embodied carbon of building structures

The buildings we live in, work in, and shop in all contribute to the UK's carbon emissions. In fact, they account for more than 40% of the total national emissions.

These emissions can be divided between operational and embodied emissions. The operational emissions are those related to running the building (e.g. heating, lighting) whereas the embodied emissions are those occurred in every activity necessary to extract and manufacture the raw materials, transport them on site, and assemble and maintain them up to the end of life disposal.
Embodied carbon emissions have a peculiar characteristic: once they have been emitted in the atmosphere there is no way back. Any intervention, even if beneficial in the future, instantly provokes an increase of the embodied carbon. This is why embodied carbon is so important: we need to reduce embodied emissions now or we simply will not be able to do it in the future.

The majority of the embodied emissions in buildings are often related to the building structure. This is because the structure generally takes up most of the building's total mass, and it is often made of materials that require a lot of energy (and therefore emit a lot of carbon) to be produced. It is therefore imperative to measure correctly the embodied carbon of building structures, in order to understand where the opportunities for carbon mitigation are and how to access the untapped reduction potential.

The project will seek to answer the following questions:

I. How do different materials affect the whole life carbon emissions of building structures?

II. What are the whole life carbon emissions of building structures for different building types in the UK?

This project will establish how different structural materials affect the whole life carbon emissions of building structures through rigorous numerical assessments across the main building types in the UK (i.e. residential, non-domestic). This shall move us away from the current 'sentimental' discourse over how green a material is to allow to choose the material with the lowest environmental impact over a building's life cycle for the specific project at hand. The aim is not therefore to promote one material over the others but rather to allow for informed decisions based on comparable assessments of the different materials by looking at the correct comparative unit, i.e. the building structure within a given building type.

The project will collect primary data from industry where no robust information is available on the carbon emissions of the different materials across their whole life cycle, and will adopt stochastic modelling and uncertainty analysis to produce probability distributions of the likely carbon emissions. This will contribute to superseding the current deterministic mind-set, which results in single-value assessments that are of very little use. The findings will be published as guidance to architects and designers, planners and policy-makers, and in the professional press, as well as in academic papers.

The major output of this research will be represented by robust and detailed assessments of the embodied carbon of building structures. While this is certainly beneficial to the UK wider construction industry, it can also contribute towards evidence based policy-making as well as influencing legislation and building regulations.

Organisations and professional bodies such as the UK Green Building Council (UKGBC) and the Royal Institution of Chartered Surveyors (RICS) will be informed of the outcome of the research and this will spur opportunities for partnerships in terms of data storage and distribution. Both have shown a great deal of attention and interest in embodied carbon, the last evidence of which has been the publication of an embodied carbon guidance for clients (UKGBC) and a professional statement for embodied carbon calculation (RICS - forthcoming in August 2017).

In addition to these two national bodies, the findings from the research could also inform and feed in international building rating schemes such as BREEAM (Building Research Establishment Environmental Assessment Method) and LEED (Leadership in Energy and Environmental Design). Both schemes have understood the importance of embodied carbon assessments and it is foreseen that whole life carbon analysis will become the norm for these building rating schemes in the future.

Industry, and therefore the UK economy, will also and greatly benefit from this research. The UK construction sector lags behind in terms of environmental impact assessment of its buildings, and this is demonstrated by the low number of Environmental Product Declarations (EPDs) available in the UK compared to the leading-countries in Europe such as Germany, France, Norway and Sweden. The availability of data, and in particular of robust and reliable data, will facilitate a quicker and wider uptake of whole life carbon assessment of buildings, which will also enable UK construction firms to compete at a better level in Europe. Moreover, both BREEAM and LEED increasingly require embodied and whole life carbon assessments as a means to get extra credits to increase the building's rating. If UK practitioners cannot offer these services to obtain such credits clients will look elsewhere.

Given the PI's involvement in the Annex 72 project of the International Energy Agency (Life Cycle Environmental Impacts Caused by Buildings), this project also has the opportunity of informing and shaping construction practices in all other participating countries to the Annex 72.

Lastly, but by no means least important, is the societal contribution towards environmental sustainability and global warming and climate change mitigation. By identifying building structures with a truly lower embodied carbon compared to others over a whole-life perspective there is great potential of actually reducing their carbon emissions. If such reduction is even just 1% of the current embodied emissions of buildings it could lead to the overall reduction of over 1,000,000 tonnes/CO2 year. In terms of CO2 savings, this is the equivalent of removing 210,000 cars from the road every year, according to figures from the US Environmental Protection Agency.