Seeing 7-stars: new home energy efficiency standards explained

The next iteration of Australia’s National Construction Code (NCC) will bring with it a change to the minimum energy rating of new homes from 6 to 7-stars – plus other important efficiency measures. This is great news, as the improved standards will ensure that the homes built today will be more comfortable to live in and cost less to run now and into the future.

In Australia, our homes are responsible for 7.9 per cent of all energy use, 29 per cent of all electricity use and 11 per cent of all greenhouse gas emissions. Making them more energy efficient can cut household energy bills and emissions, as well as provide better protection from extreme climate events like heatwaves. Homes are long-lived assets, and retrofitting later to improve efficiency is much more difficult and costly than getting it right the first time. That’s why improving the performance of new homes is vital to ensure our homes can provide comfortable, affordable and climate-resilient shelter into the future.

With mandatory changes to energy efficiency on the way, if you’re thinking about building or renovating a home, now is the ideal time to talk to your design team and builder about planning for a 7-star (or better) home.

What’s changing?

The updated requirements call for a minimum energy efficiency for a new home’s building shell of 7 stars out of a possible 10 through the Nationwide House Energy Rating Scheme (NatHERS). The rating measures the amount of energy needed to heat and cool a home, with adjustments for different climate zones. In most locations, the increase means it will take 20 to 25 per cent less energy to heat and cool a home.

The changes to the NCC will also introduce a new ‘Whole of Home’ approach. Alongside the minimum 7-star rating for thermal efficiency, a new ‘energy budget’ will be applied that takes into account efficient appliances and solar. The energy budget sets a maximum annual energy use for heating and cooling, hot water and lighting (and swimming pool and spa pumps where relevant) that can be offset by adding solar PV to the home.

A Whole of Home assessment can predict whether a home will be net zero for operational energy (Net Zero Carbon), meaning that over a year it produces the same amount of energy as it consumes (or even more) – definitely something to aim for.

This move to a Whole of Home approach is urgently needed to support homes to reduce ongoing greenhouse gas emissions, and the energy efficiency industry agrees. Jan Talacko, Managing Director of ESD advisory firm Ark Resources, comments: “The move to a Whole of Home assessment in NCC 2022 is revolutionary. In addition to the upgraded 7-star minimum, homeowners will for the first time receive a report that will predict their ongoing energy use and associated emissions, with their house benchmarked against a net zero energy target. This will be a potent driver towards net zero housing.”

The new NCC also includes a universal design standard based on Livable Housing Australia’s Silver Level guidelines, to increase the stock of homes with accessibility features and support flexibility of use for all Australians.

Will it cost more to design to 7-stars?

In many cases, it need not cost much more. Designing with passive solar principles is one of the most important things to consider when building a 7-star home. As the requirements for the energy performance of new homes increase, optimising the orientation of the home by placing living areas to the north and providing appropriate shading from summer sun will continue to be the most cost-effective way to maximise the star rating.

Architects and designers will know the importance of considering orientation and the local climatic conditions when designing an energy-efficient home. Shannon Battisson, National President of the Australian Institute of Architects, wants to ensure that homes are designed and built for their specific climate zone. “Even in the harshest of climates, achieving the new 7-star minimum isn’t difficult as long as we start by getting the design right first. If you’re looking to build, get the right team together to help guide you through the design and build of what will be a piece of built legacy for generations to come.”

Appropriate design will differ from house to house depending on factors like climate, orientation and construction materials, but in most cases, the new standard can be met through relatively simple and low-cost changes early in the design process. The key differences between a 6-star and 7-star rating for a home may include taking better advantage of opportunities to heat the home passively in winter while shading it in summer. As well as good orientation for solar gain when it’s desired, this can be done using improved ceiling, wall or underfloor insulation to suit the local climate, and high-performance glazing to better insulate the home from heat loss in winter and heat gain in summer. Homes that have poor orientation will need to work harder to achieve 7-stars through increased levels of insulation, better glazing, careful consideration of window sizing and smarter floor plans.

This Department of Energy, Environment and Climate Action’s factsheet shows 3 steps to a Code-compliant, energy-efficient home.

What about the builders?

Some building industry groups have expressed concern that adjusting their practices to build to 7-stars will be difficult, but learnings from the introduction of the 6-star standard suggest that industry will in fact adjust quickly and at low cost.

One key issue will be ensuring that the finished home performs as the energy rating of its design predicts. In Victoria, the state government already runs a program to improve the capacity and capability of the building industry through training and rebates for builders who build their new homes to a 7-star rating with a Whole of Home assessment.

Arden Homes, a participating builder in Sustainability Victoria’s 7 Star Homes program, is taking an industry-leading position on sustainable homes. “Moving to a 7-star minimum energy rating makes a lot of sense for us, as well as for our clients,” says director Dean Morrison. “Increasing the energy rating of new homes isn’t just better for the environment; it also means our clients benefit from greater comfort in every season, plus year-on-year savings when it comes to energy bills.”

Going beyond 7-stars

Of course, as Sanctuary readers well know, market leaders and many informed homeowners are already aiming for homes that are 8-stars and above. As 7-stars become the new minimum standard, achieving better than the minimum will become easier and more cost-effective. The new regulations are a step change towards even better-performing homes, with the goal (according to the national Trajectory for Low Energy Buildings) being homes that are “zero energy and carbon ready”, or in other words Net Zero Carbon or even True Zero Carbon, offsetting embodied energy as well as operational. Additionally, future-proofed homes should provide for electric vehicles by including electrical wiring to the garage or carport for the installation of an EV charger in the future.

As buildings become more efficient and better sealed, it also becomes important to consider ventilation to ensure fresh internal air. This can be done by designing for natural cross and stack ventilation through windows opened and closed at appropriate times through the day, or by installing a mechanical ventilation system with heat recovery for extra efficiency. Such a system becomes important in very airtight homes with less than five air changes per hour at 50 pascals (ACH50). The NCC effectively requires new homes to be under 10 ACH50, but post-build airtightness testing is not yet mandatory.

When is it all happening?

The 7-star minimum energy rating has been endorsed at a national level by the coalition of state and territory building ministers, and now it is up to each jurisdiction to develop its own process for implementing the changes. The Australian Building Codes Board made the updated NCC available from 1 October 2022 for those who wish to use the new provisions voluntarily.

NCC 2022 will commence on 1 May 2023, with a transition period to 1 October 2023 for the Modern Homes provisions for energy efficiency, condensation mitigation and livable (accessible) housing. However, some states and territories have indicated that they will delay its implementation beyond this date. Check with your local state or territory building authority to find out how and when the amendments will apply to your project.

Conclusion

The change in the minimum standard from 6-star homes to 7-star homes with a Whole of Home energy budget will ultimately ensure that the homes that are built today and into the future are more resilient to climate extremes and have lower running costs. Improvements to the energy efficiency of new homes will have long-lasting impacts for future generations and bring us all one step closer to homes that are truly net zero for carbon emissions, reducing our overall carbon footprint and impact on the planet.

This article was first published in Sanctuary magazine issue No. 62.

More information

View the changes in the Australian Building Codes Board's infographic.