Towards Net-Zero Energy (NZE): Strategies for achieving NZE High-rise Residential Buildings in Australia

Net-zero energy buildings (NZEB) have become known globally as one of the solutions for reducing operational energy consumption and greenhouse gas emissions in the building industry. One of the challenges attributed to the achievement of NZEB performance is the uncertainty in selecting appropriate solution strategies that could deliver quality per-formances. With high-rise residential buildings, the additional challenges of high energy consumption due to central and communal facilities and reduced potential for solar en-ergy generation in a high-density urban environment further increase uncertainty. Conse-quently, dissenting opinions exist in the research community on the possibility of achieving NZE performance for high-rise residential buildings. This research aims to reduce this uncertainty by investigating strategies that can deliver NZE performance for high-rise residential buildings in Australia. A design sciences research paradigm was adopted for the investigation, enabling a sequential use of the mixed methods approach. An existing high-rise residential building in Melbourne served as the ‘artefact’ and improvement strategies focusing on energy performance and maximising renewable energy production became ‘the intervention’. This design intervention was conducted on the reference building by locating it in five cities and climate zones across Australia. Specific guidance on the composition of solution sets that can deliver the NZEB goal for each climate zone is presented. The research findings generally show that NZE performance for high-rise residential build-ings is achievable in Australia, albeit with some limitations. Findings suggest that various strategies for improving energy efficiency could deliver up to 60% improvement over the baseline operational energy performance in heating-dominated and mild Australian cli-mates. The result also shows that efficient design and optimisation of the envelope are some of the most critical strategies for the cooling dominated climates to attain NZE per-formance. The impact of shading from neighbouring buildings and objects presented the largest im-pediment to energy production through the façade. Results from a hypothetical scenario of 25 m spacing (setback) between ‘the artefact’ and neighbouring buildings suggest larger space allowances (above 25m) would be required in order to gain adequate solar access. This enables the building to generate adequate renewable energy to achieve NZE performance in all climates and locations. The study concludes by providing solution set recommendations that design practitioners could consider in the designing of NZE high-rise residential buildings. Some key challenges that need to be addressed through both policy and technology were also identified. These include but not limited to; city planning and issues of solar access for renewable energy generation, building regulations that allow for and recognise the use of other renewable energy technologies such as wind and phase change materials (PCM), the need for innovation in materials and build-ing technologies. Addressing these issues will involve local city planning policies, the construction code, and support structure from the different levels of government and jurisdictions. Addressing these issues can help reduce the uncertainty that remains. Also, it may encourage stakeholders and the public to invest in NZE high-rise residential buildings, thus accelerating such developments in the Australian built environment.