Refurbishing for net-zero carbon

This Issue This is a part of the Net-zero carbon buildings feature

By , , and - , Build 182

Buildings have a major role to play in climate change mitigation. Research is under way to develop a tool to support zero-carbon decision making in the refurbishment process for buildings.


BUILDINGS CONTRIBUTE significantly to greenhouse gas emissions (GHG).To meet targets of reducing emissions by 2050, New Zealand needs to build net-zero carbon buildings. It also needs to implement zero-carbon refurbishment strategies for the existing building stock to current Building Code requirements rather than demolishing and rebuilding. This is often more difficult than new builds.

Research to understand decision making

International research suggests that successful zero-carbon refurbishment for existing buildings can be achieved if effective decisions are made throughout the refurbishment process. To date, little research on this has been conducted in New Zealand.

A new research project is under way at the School of Built Environment, Massey University in collaboration with BRANZ. The project aims to understand refurbishment decision making in existing public buildings with a view to incorporating zero-carbon refurbishment practices.

The research will help develop a decision support tool for building professionals that enables them to make zero-carbon decisions in building refurbishment projects.

Focus on upgrading existing buildings

Research has highlighted that the construction sector contributes roughly 16% of New Zealand’s greenhouse gas emissions, so the sector will play a major part in climate change mitigation. The Ministry of Business, Innovation and Employment Building for climate change programme and BRANZ’s Transition to a zero-carbon built environment programme (see Build 180, Preparing for climate change)provide a platform for reducing GHG emissions from buildings while also improving building resilience to climate change.

Encouraging the low-carbon performance of new and existing buildings will contribute to New Zealand’s ability to be net-zero carbon by 2050. Climate change mitigation actions in the built environment should focus on existing buildings as much of this building stock will still be in use in 2050. For example, existing buildings will account for an estimated 65% of the total climate impact of New Zealand's detached house sector between 2018–2050, while new builds will make up the remaining 34%.

Zero-carbon refurbishments

Building refurbishment is defined as modifying and improving an existing building to bring it up to an acceptable condition. Refurbishment towards a zero-carbon target is referred to as a zero-carbon refurbishment (ZCR), which is a crucial component in the mitigation of climate change to meet specified climate change targets.

The New Zealand building industry needs to prioritise existing buildings for several reasons:

  • Building refurbishment projects have only half the embodied carbon impacts compared to new builds.
  • Refurbishment is a better mitigation measure than a new build. For instance, a life cycle assessment of Press Hall in Wellington showed that the refurbishment building saved approximately 3,100 tonnes of carbon emissions compared to a new reference building (see for more).

Decision making for ZCR projects

Decisions need to be made throughout the refurbishment process on zero-carbon renovation strategies. This can be difficult due to judgements that must be made before any work can begin.

The process of ZCR is influenced by various constraints and limitations,such as project objectives, budget and available building techniques. In the refurbishment decision-making process, it may be challenging to manage clients’ requirements with the need to focus on zero-carbon strategies.

For a ZCR project to be successful, a building’s life cycle carbon performance must be integrated with other project criteria, particularly client's requirements and stakeholders’ values.

ZCR also face challenges in mitigating GHG emissions, such as enabling building regulations, social pressure, standards of service and expected user comfort. These challenges can be critical for the building operation and usability and must be addressed in the refurbishment decision-making process.

Decision making for ZCR projects is complex and challenging, so how can we better support and encourage construction practitioners to make zero-carbon decisions throughout the building refurbishment process?

Developing a decision support tool

The project at Massey University found that there is a lack of tools to support decision-making processes for ZCR both internationally and in New Zealand.

Findings from international experience shows that decision making at an early stage of the refurbishment process is most important in alleviating problems later in the construction and post-occupancy evaluation stages. Recommendations for zero-carbon refurbishment decision support tools include:

  • involving project stakeholders and end users in the process of choosing refurbishment so they can be better informed of the need to use zero-carbon techniques
  • developing acceptable New Zealand-specific refurbishment strategies for the New Zealand building stock
  • integrating incentive schemes to take up zero-carbon approaches. Current research is focusing on developing a tool that will support zero-carbon decision making in the refurbishment process of New Zealand’s existing public buildings. This will improve construction practitioners’ understanding and support them in developing and delivering projects that can meet our zero-carbon targets. It is expected that the tool will be available in 2023.

For more

If you are interested in participating in this research, contact Thao Bui (Alice) at [email protected]

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