The construction industry accounts for close to 40% of global carbon emissions. In New Zealand, where the built environment is a major component of the economy and the country has made significant emissions reduction commitments, this statistic has real weight. Yet many people working in and around construction have limited understanding of where those emissions actually come from — or what they can do about them.
Carbon literacy is the starting point. It means understanding how materials, designs, and construction practices affect carbon emissions, and knowing enough to make better decisions in your own role.
Operational Carbon vs Embodied Carbon
When most people think about a building’s carbon footprint, they think about energy use — the electricity and gas consumed heating, cooling, and lighting the building over its lifetime. This is called operational carbon, and it’s the focus of most energy efficiency regulation.
But there’s a second category that is increasingly important: embodied carbon. This is the carbon emitted during the extraction, manufacturing, transport, and installation of building materials — before the building is even occupied. For a well-insulated new home, embodied carbon can represent 50% or more of total lifetime emissions. For a commercial building constructed with large volumes of concrete and steel, it can be higher still.
Where the Emissions Come From
The biggest contributors to embodied carbon in NZ construction are typically:
- Concrete: Cement production is one of the world’s largest industrial CO₂ sources. Every cubic metre of concrete has a carbon cost, and construction uses enormous volumes of it.
- Steel: Both the structural steel used in framing and the rebar in concrete slabs carry significant embodied carbon.
- Insulation: Some insulation products — particularly those with high global warming potential blowing agents — carry meaningful embodied carbon despite reducing operational emissions.
- Transport: Materials imported from overseas or transported long distances add transport emissions to the embodied total.
What You Can Do in Practice
Carbon literacy doesn’t require becoming an expert in lifecycle analysis. It means asking better questions and being open to alternatives. For builders and designers, practical steps include:
- Specifying lower-carbon concrete mixes (replacing some cement with supplementary materials like fly ash or slag can significantly reduce the carbon intensity)
- Choosing timber framing where structurally appropriate — NZ timber is a low-embodied-carbon material that also stores carbon
- Sourcing materials locally where quality and cost allow
- Using Environmental Product Declarations (EPDs) to compare the carbon footprint of alternative products
New Zealand’s green building frameworks — including Homestar and Green Star — increasingly incorporate embodied carbon metrics. Clients who target these ratings will start asking about embodied carbon; being able to engage with those conversations is a professional advantage.