Category: Conference

This paper discusses the learnings from the structural engineering for the Ashburton District
Council (ADC) Civic Centre with a focus on the timber connections which is easily the trickiest
part of timber design. It is expected to be of interest to structural engineers interested in the
practical realities of the growing field of timber design.

This paper provides an overview of sustainability opportunities in structural engineering design.
It discusses advantages and disadvantages associated with various design choices, to achieve
good system sustainability outcomes. Two case studies of recent projects are used to
demonstrate the points from the first part of the paper.

As the construction industry, and the society within which we operate, seeks mitigations to our
present climate emergency, structural engineers are seeking ways to transform from part of
the problem, to part of the solution. In this paper, the Author examines the barriers that face
practicing engineers in the meaningful implementation of low-carbon structures, and how those
barriers might be hurdled, either by individual design teams, or by the industry at large.

This paper will first consider industry or society wide issues. This will include: New Zealand’s
minimal regulatory environment and lack of green property market drivers in comparison to
other countries; and the relative lack of readily available carbon calculation information for the
New Zealand supply chain’s carbon impact.

It will then consider common project level challenges, including: Client and industry
perceptions on cost; the dominance of operation carbon impact on building sustainability
decision making and the impact of their inapplicability to embodied carbon impacts; and the
dearth of reliable, local, benchmark data available to design teams.

Finally, it will consider some of what are, in the author’s opinion, the biggest technical
challenges. This will include the current environmental impact of New Zealand concrete based
construction, and some simple improvements that any project could adopt; and enormous
improvements in embodied carbon available via timber construction, alongside some of the
ways that the timber industry is making it difficult to make timber structures feasible in New
Zealand.

For each of these challenges, some of the solutions available to practicing engineers will be
discussed. Both established solutions available internationally, and nascent New Zealand
solutions.

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.

Structural engineers make design decisions with the objectives of making buildings materially
efficient, seismically resilient, and now increasingly, low carbon. This paper discusses the
importance of embodied carbon of buildings in the context of New Zealand’s emissions
reduction targets, and outlines MBIE’s Building for Climate Change (BfCC) programme
proposals to drive transformational change in the sector to reduce these emissions. It explores
the role that greater seismic resilience could play in achieving reductions in embodied carbon
of New Zealand buildings, including which elements of a building contribute significantly to
embodied emissions, and how these emissions can be minimised. Further research work is
required to determine the existence of the perceived trade-off between resilience and material
efficiency in structural design.

The “Zero Carbon Act” will be implemented from 2021, gradually altering the objectives and
constraints driving professional engineering practice in New Zealand. Sluggish reductions in
New Zealand’s emissions to date indicate that we are yet to:
a) recognise and adopt the engineering constraints associated with the climate crisis,
b) envision and evaluate future options for preserving the climate, and
c) generate practical projects that result in a significant reduction in fossil energy use.
Transition Engineering is the interdisciplinary field that addresses these problems. Key
Transition Engineering concepts are summarised in this paper, then used to identify
implications for structural engineers over the coming decade.