houses on street
Photo by Steve Doig on Unsplash

It’s time that the National Construction Code and, in NSW, BASIX, be updated to drive the trajectory to net zero energy homes.

An opportunity has arisen to make major improvements in the energy efficiency and renewable energy generation of new buildings, following recent consultations and current analysis for the next update of the National Construction Code (NCC) in 2022.

The NCC provides the minimum necessary requirements for safety and health, amenity and accessibility, and sustainability in the design, construction, performance and livability of new buildings (and new building work in existing buildings) throughout Australia. It’s a uniform set of technical provisions that allows for variations in geographic conditions, such as climate.

For the energy efficiency of residential buildings, the consultation by the Australian Building Codes Board considered two options:

  1. NCC provisions that achieve a level of thermal comfort equivalent to 7 stars NatHERS and net zero annual energy use for regulated building services, that is, space conditioning, heated water systems, lighting and pool and spa pumps.
  1. NCC provisions that achieve a level of thermal comfort equivalent to 7 star NatHERS and maximum energy use budget greater than zero for regulated building services.

Although option 1 doesn’t include whitegoods, other appliances or pool and spa heating, its adoption would be a real step forward for both energy efficiency and renewable energy in residential buildings. It would boost the installation of rooftop solar, because net zero annual energy use may be achieved by offsetting the energy use of the designated energy services with on-site renewables. Furthermore, the improvements in energy efficiency will reduce the magnitude of the task faced by renewable energy in substituting for fossil fuels.

In particular, for every unit of fossil fuelled electricity saved by energy efficiency or replaced by a unit of renewable electricity, about three units (range 2-4 units) of primary fossil fuelled energy are avoided. Most GHG emissions and air pollution emitted by the electricity sector come from the primary energy stage – the combustion of fossil fuels (or any fuel) is a very inefficient process for generating electricity.

Therefore improving energy efficiency in buildings could achieve a double dividend in cutting GHG emissions, by fostering both energy efficiency and renewable energy. Conversely, as solar modules become cheaper, they can help achieve net zero energy buildings when the limits of affordable energy efficiency measures are reached. At present, in many countries, energy efficiency is neglected while renewable energy receives more attention.

Returning to the NCC, it should be noted that state governments are not bound by the NCC. In NSW, BASIX replaces energy efficiency provisions in the NCC, but there is pressure for BASIX to align with what happens nationally. The NSW Planning Minister, Rob Stokes, supports this and has indicated that that his department is working on possible updates to BASIX. In a webinar discussion on the new Time and Place State Environmental Planning Policy (SEPP), the minister also mentioned embodied energy, which will become increasingly important as the efficiency of energy use in the operation of buildings (and appliances and vehicles) increases. Including embodied energy would, for example, give an incentive for the use of more timber in home construction and less energy- and greenhouse-intensive materials such as aluminium and steel and concrete based on Portland cement.

Unfortunately BASIX hasn’t received adequate funding for years. Reforms in funding, stringency, technology options and calculations are needed to update BASIX and make it useful for assisting a trajectory to net zero energy homes. So far the Minister has not made this explicit commitment.

Better design of our cities, towns and precincts will also enable people to reduce their energy consumption by changing their behaviour. For example, by limiting most trips to their local areas and by walking, cycling and taking public transport (post-Covid-19) more frequently to local destinations. In a situation where it now appears to be too late to limit global heating to 1.5ºC above the preindustrial level, behaviour change to reduce consumption is needed as well as technological change, in order to avoid runaway climate change.

Dr Mark Diesendorf is an Honorary Associate Professor in the School of Humanities & Languages at UNSW Sydney.

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