Buildings in Sydney's Eastern Suburbs were the focus of a study assessing their future compliance to BASIX. Photo by Martyna Bober

Current benchmarks for residential energy and water efficiency, under the NSW Building Sustainability Index (BASIX), are outdated and unsuitable for contemporary climate change projections, according to a recent report. 

Conducted by global engineering consulting firm WSP with funding from Local Government NSW, the Future Proofing Residential Development to Climate Change report was released in January this year.

The authors aimed to test modern building standards against the impending effects of climate change to see how they stacked up across the categories of building thermal performance, energy consumption, greenhouse gas emissions and water demand.

They modelled the performance of compliant buildings against future climate projections for Eastern Sydney, encompassing the Randwick, Woollahra and Waverley council areas. 

They concluded that with increasing temperatures, demand for thermal cooling and water usage would increase, making most building types non-compliant with current BASIX requirements by as soon as 2030.

Former BASIX policy developer David Holden, who is now director of urban sustainability software company Kinesis, told The Fifth Estate that the current system was due for an overhaul. 

“BASIX was developed to address resource consumption and emissions of new dwellings.  But that was over 15 years ago,” Mr Holden said. 

“We’re already in a changed climate so we need to be thinking about resilience.  Will our homes and communities be liveable in 20, 50 years? Will our infrastructure stand up to changing demands?”

While the study was based on modelling for Sydney’s Eastern beaches, according to the authors the findings may also apply to other jurisdictions experiencing similar changes in temperature and rainfall. 

It is not the first call for an update to the current building standards, but it’s one of the most comprehensive and targeted studies in pinning BASIX against the more extreme impending effects of climate change. 

A spokesperson from Randwick City Council told The Fifth Estate the recommendations of the report would be presented at a meeting in June, after which they would be voted on.

Thermal Performance

With rising temperatures over the coming decades, the study predicted that during summer, energy demand for mechanical cooling such as airconditioning would dramatically increase. 

According to the study’s modelling, in 2030, cooling loads would  increase by 70 per cent on average above current baseline demand while by 2070 they would increase by 308 per cent on average above current baseline demand. 

The buildings most affected by heat would be the attached, detached and low-rise dwellings, while the least impacted would be high-rise buildings which would benefit from having a higher proportion of shared walls, floors and ceilings and access to better natural ventilation.

“These results show it is possible the dwellings approved for construction now will be unsuitable for occupation by 2070, without extremely high levels of mechanical cooling to maintain comfortable, safe and liveable conditions,” the report said. 

“The principles of climate responsive design would dictate that, in response to these results, residential building designs should be accounting for hot climate conditions to address primarily cooling comfort requirements most of the time.” 

Energy consumption was shown to be relatively flat by 2030, with demands for cooling offset by decreased demand for heating which was forecast to drop. However by 2070 major increases in cooling demand were shown to cause four of the five building types to fail BASIX Energy requirements.


In terms of water usage all building types failed the BASIX Water target when modelled in the 2030 climate scenario of reduced rainfall. 

Detached homes rated the worst due to factors including higher landscaping needs while high-rise buildings fell just one point short of passing the requirements.  

According to the report, 2070 is predicted to be potentially less dry than 2030, however it is still predicted to be drier than today’s climate, meaning all building types except high-rise failed the BASIX Water target for 2070. 

Findings and recommendations 

The key findings of the report are that NSW will have to take into account significantly higher demand for mechanical cooling such as airconditioning, both from peak demand and  greenhouse gas emissions perspectives.

In terms of thermal performance, the report’s long list of recommendations included updating the climate files used in the NatHERS software to ensure dwellings are designed to withstand future conditions and investigating design modifications for different building types to guide the Thermal Comfort policy setting in BASIX under future climate scenarios. 

As NSW has already experienced during prolonged drought over the past two decades, with a warming climate, water availability can become increasingly unpredictable. 

The report noted that demand for water is expected to increase as the climate warms. It also noted that given projections for extended periods of lower rainfall alternative water supplies may play a role in meeting the BASIX Water targets, suggesting treated storm water and recycled water reticulation as two possible solutions. 

It suggested that BASIX be updated to take into account projected increased demand and drier climatic conditions and that further testing of different building types be conducted to ensure future compliance to BASIX Water targets. 

The report also recommended that BASIX be reviewed and adapted every three years in line with National Construction Code (NCC) updates and that utilities are required to monitor the energy and/or water consumption of BASIX dwellings to improve system data.

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    1. Don,
      The environmental cost will not be outweighed as buildings typically last for many decades if not a century or more. There are many things that can be done to improve the efficiency of a new home that do not use more materials just better and more precise methods. An example would be making sure a home is well sealed with very few penetrations to the building envelope. This along with no gap well fitted insulation, no thermal bridging and appropriate shading can help to keep the interior temperatures very well controlled with very minimal if any heating and cooling. You would need mechanical ventilation if the number of air changes per hour is less than 3 but that should bee where we are aiming. Something as simple as the orientation of the building and where you place the living spaces change how the home behaves with temperature stabilisation. Many of these things are simply about better planning and better training for tradespeople and builders not about additional materials. Of course the finished product is only as good as the workers make it and equally important is the testing of the building standards many times throughout the build. Particularly the air pressure testing. The materials need to be appropriate and good quality but they need not cost more, if they become the standard this always brings their price down.