SESOC 2021_S3A P3 – Mitchell_Carman

Across the construction industry worldwide there is a growing focus on embodied carbon.
Whilst by no means a new area of study, with the life cycle assessment (LCA) of construction
projects a well-established practice, it is apparent that over the coming years the Aotearoa-New
Zealand industry will need to agree a method to calculate, report and improve embodied
carbon values for new buildings accurately and fairly across the sector. The charge is being
led on the policy side by MBIE, tackling emissions from the construction section through its
‘Building for Climate Change’ (BfCC) framework. The result is that many professionals in this
industry are becoming, or will need to become, more closely acquainted with embodied carbon
as a metric of design, along with time, cost, and quality.

Based on some recent experiences and projects quantifying embodied carbon for buildings in
Aotearoa-New Zealand, the purpose of this paper is to discuss the fundamentals of LCA for
buildings and present some example results from recent studies, from the viewpoint of an
engineer entering into the world of LCA. The complexity of embodied carbon should not be a
barrier to those looking to measure it, and to a certain extent a good estimate of embodied
carbon could be achieved in four columns of a spreadsheet. However, the outturn figures will
only be as accurate as the quantities derived, factors used, and consistency of the boundary
of the analysis. A few key areas of uncertainty are discussed, such as appropriate steelwork
embodied carbon factors (ECFs), comparison between as-designed and as-constructed
measures, and whether the use of timber to decarbonise a project is a silver bullet.

Our studies, and others globally, indicate that typically more than half of the total embodied
carbon impact of a project is associated with the systems and materials designed and specified
by the structural engineer. This is why the structural engineering community must engage with
this topic with a similar seriousness as the cost and safety impacts of projects.