People power can reduce emissions

By - , Build 175

The entire building sector, from architects and specifiers to building owners and manufacturers, can work with their material suppliers to collectively decarbonise New Zealand’s built environment.

Build 175 p78
Build 175 p78

THE WORLD Green Building Council recently issued a bold vision for how buildings and infrastructure globally can reach 40% less embodied carbon emissions by 2030 and achieve 100% net zero emissions buildings by 2050.

Green Building Council’s plan to slash emissions

In New Zealand, where the building and construction sector could be responsible for up to 20% of New Zealand’s carbon emissions, the New Zealand Green Building Council has a plan to slash emissions.

It has published a roadmap laying out how the building and construction sector can help the country get to net zero carbon by 2050. As part of this work, opportunities have been identified to reduce the embodied emissions in our building and construction sector by 40%.

Under Construction: Hidden emissions and untapped potential of buildings for New Zealand’s 2050 zero carbon goal sets out strategies that could save approximately 1,200 kt CO2e per year. This is equivalent to taking 460,000 passenger cars off the road permanently, equivalent to 15% of New Zealand’s total light vehicle fleet.

How buildings contribute to GHGs

Buildings contribute to greenhouse gas (GHG) emissions in two key ways:

  • Embodied or upfront carbon emissions, created through the supply chain when building products are made.
  • Operational emissions from heating, cooling and lighting.

In a previous thinkstep ANZ study The carbon footprint of New Zealand’s built environment – Hotspot or not?, it was noted that buildings, roads and other infrastructure are responsible for up to 20% of New Zealand’s total greenhouse gas emissions – far greater than previously expected.

Approximately half of these emissions are embodied in building materials – buildings and infrastructure – half from operating our building stock and a small proportion from end of life.

Cutting emissions from manufacture

In the recent report, thinkstep ANZ focused on strategies to reduce the GHG emissions embodied in manufacturing building materials.

Operational emissions, such as electricity and gas use, are very visible as there is an associated ongoing cost and therefore more incentive to reduce them. Most embodied emissions, however, occur before the building is even constructed and are largely invisible to the architect, builder and owner. These are often locked in early in the building’s life cycle and cannot be changed later.

We looked at the actions that will make a difference on the supply side. Measures that affect the demand for materials, such as sustainable building design, are equally significant but were outside the scope of our work. BRANZ’s LCAQuick tool, available at www.branz.co.nz/lcaquick, can help to design out carbon. Importantly, there is potential to make even greater savings if supply-side and demand-side measures are applied together.

As many key building products are still manufactured in New Zealand, improvements to local manufacturing will yield the most significant benefits at the national level.

 

The building materials contributing most of the embodied GHG emissions in New Zealand’s buildings are steel and concrete – together contributing more than 50% of the carbon footprint of both residential and non-residential construction, excluding fit-out and building services.

Aluminium is a very significant contributor for non-residential construction, while for residential construction, timber framing is the next biggest contributor, followed by paint, aluminium and plasterboard.

Looking at the numbers

According to the study, a stand-alone house with a floor area of 200 m2 currently has embodied carbon of approximately 63 tonnes of CO2e over its 90-year life. In the short-term, these emissions can be reduced by 3 tonnes of CO2e (5%) by specifying low-carbon concrete.

In the long term, a saving of 18 tonnes of CO2e (29%) could be achieved by improving the ways in which key building materials are manufactured – equivalent to taking seven cars off the road for a year per house.

A non-residential building with a floor area of 900 m2 has embodied carbon of approximately 450 tonnes of CO2e. In the short term, these emissions can be reduced by 85 tonnes of CO2e (19%) just by specifying low-carbon concrete and aluminium.

In the long term, a saving of 230 tonnes of CO2e (51%) could be achieved by improving the ways in which key building materials are manufactured – equivalent to taking 90 cars off the road for a year per building.

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Making a difference

If the New Zealand construction sector is serious about achieving or exceeding the 40% decarbonisation potential we identified, a collaborative effort will be needed:

  • Material suppliers will need to implement low-carbon manufacturing technologies.
  • Specifiers and customers will need to consciously choose those materials. This could be encouraged by including embodied carbon considerations in public and private procurement policies and ensuring that the New Zealand Emissions Trading Scheme accounts for the emissions embodied in imports. The new Construction Procurement Guidelines for government departments, which require sustainable building practices such as using sustainable materials and minimising waste, are a step in the right direction.
  • Government could use life cycle assessments – such as that within Green Star – in their building programmes, helping to lead the sector towards low carbon.
  • Better data will be needed to specify low-carbon materials. Recent improvements include publishing product carbon footprints and environmental product declarations (which include a figure for embodied carbon) for some New Zealand-made building products.
  • Improving public statistics would enable better benchmarking of the embodied carbon in New Zealand’s building stock and tracking of improvements over time. In short, decarbonising the built environment will require:
  • collaboration among all players in the building sector
  • communication of good information and data
  • innovation in the manufacturing sector
  • policy development encouraging the use of materials with low embodied carbon.

For more

A free copy of the report Under Construction: Hidden emissions and untapped potential of buildings for New Zealand’s 2050 zero carbon goal is available at www.reports.thinkstep-anz.com.

Download the PDF

More articles about these topics

Articles are correct at the time of publication but may have since become outdated.

Build 175 p78
Build 175 p78

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