Builders and designers are responsible for many of New Zealand’s sustainability outcomes. The way materials are specified at the design stage doesn’t just affect immediate budgets or timelines – it determines the long-term environmental legacy of our built environment. Every decision made about beams, columns and panels today will shape what can be reused, recycled or wasted tomorrow.
A roadmap for reducing carbon emissions
Carbon reduction is now front of mind across the sector. That progress should be celebrated, but the industry must be careful not to repeat a familiar mistake – optimising only for the build rather than the long-term outcome. Focusing solely on upfront embodied carbon, for instance risks ignoring how materials perform over decades or what happens when a building is deconstructed.
This theme was reinforced at the recent launch of the Sustainable Steel Council’s Roadmap to Net-zero Greenhouse Gas Emissions for Aotearoa New Zealand’s Steel Industry. A roadmap sets out a credible pathway to reduce direct and electricity-related emissions from steel used in buildings and infrastructure by more than 90% by 2050. Importantly, it makes clear that achieving this target will not rely on offsets, but on real changes across the value chain – including smarter design, increased reuse and more efficient use of materials. That is, the way we specify and use steel matters just as much as how it is made.
The roadmap also highlights demand-side decisions – particularly at the design stage – are among the fastest and most cost-effective ways to reduce emissions. Avoiding unnecessary material use, designing for adaptability and planning for reuse are not future aspirations. They are practical actions available today.
Another tool, SSC’s Responsible Products Audit programme, can help designers and fabricators to verify the steel they specify meets rigorous low-carbon and sustainability standards. This programme provides the transparency that gives clients confidence and ensures procurement decisions are based on evidence rather than assumptions or marketing claims. For builders, it offers a credible way to demonstrate due diligence in an environment where clients increasingly expect projects to align with climate goals.
Overspecifying is a problem
A critical issue is overspecification. Structural steel has often been specified in quantities far greater than required – sometimes double or even triple the optimal amount. Research has shown that material efficiency gains of 10-30% are achievable in many building types through better design coordination and optimisation, without compromising safety or performance. In buildings such as hospitals or emergency facilities, higher specifications are appropriate because they must remain safe and functional within an hour of a major event such as an earthquake. In many other cases, however, overspecification is due to procurement shortcuts, outdated design rules or a conservative approach that no longer fits carbon-conscious construction.
Historically, overspecification was commercially beneficial – more tonnes of steel sold meant higher revenues. Today, however, it risks undermining the sector’s decarbonisation efforts. Put simply, if a building uses more steel than it needs, it also carries more embodied carbon than necessary.
Unnecessary building materials are a broad liability
The increase in total building emissions won’t be one-for-one – because steel is only one component of a building – unnecessary material use directly increases the project’s carbon footprint. In an era where clients, financiers and regulators are scrutinising emissions, that excess has become a liability not an advantage.
Whole-of-building assessments, frequently used in environmental rating schemes, can add to the problem. They often evaluate a project as a single entity without distinguishing the fate of individual materials. This can verge on greenwashing and risks overlooking what matters – the future of the materials themselves. To achieve real impact, we must shift from whole-of-building to whole-of-product thinking.
Steel illustrates the importance of this change. Unlike other structural building materials, it can be reused, remelted and repurposed repeatedly without loss of quality. If materials are properly documented at the design stage – through initiatives such as the materials passport being developed by HERA – then buildings can function as materials banks. Each beam or column becomes an identifiable asset with measurable value at the end of a building’s life.
The idea of buildings as materials banks highlights that materials such as steel aren’t just a sunk cost – they can retain significant value at the end of a building’s life. Steel components can be recovered for reuse, for example as structural sections, or recycled into new products, and the future value of that material can be estimated based on long-term commodity trends.
However, realising this value depends on broader system changes, including standards for material reuse, design-for-deconstruction practices and regulatory settings that support traceability and quality assurance. These barriers mean the theoretical value is not always fully recoverable today, but the opportunity is increasingly recognised.
For designers, this requires thinking about documentation and verification as integral parts of the design process. For builders, it means managing materials so they retain maximum potential for reuse or resale. For clients, it reframes sustainability from being a compliance exercise to an investment strategy.
The Glenbrook steel mill’s transition to an electric arc furnace this year will accelerate this shift by reducing the carbon intensity of domestic steel significantly. Coupled with increased use of scrap and renewable energy, this positions New Zealand to supply world-class low-carbon steel. But the benefits will only be fully realised if the rest of the supply chain – designers, builders, fabricators and clients – also align their practices.
That requires embracing optimisation. It is not enough to specify low-carbon steel if the quantity specified is unnecessarily high. Nor is it sufficient to promote reuse in theory if documentation systems are not adopted in practice. The sector must take responsibility across the full life cycle – from design and fabrication to deconstruction and beyond.
This challenges everyone involved in construction. It means designers must interrogate assumptions and adopt design-for-deconstruction principles. Builders need to pay closer attention to procurement practices and waste streams. Clients must understand the cheapest upfront cost is not necessarily the best long-term investment. Industry bodies must continue to provide the tools, audits and verification systems that support this change.
By treating steel as both a structural material and a store of value, New Zealand can unlock a future where buildings are designed not just for use but also for reuse. By avoiding overspecification and optimising design, we can cut embodied carbon without compromising safety. And by adopting whole-of-product thinking, we can ensure our environmental frameworks focus on the environment rather than appearances.