New home ratings: saving energy, reducing bills and supporting a net zero future
The Nationwide House Energy Rating Scheme’s new Whole of Home rating is one way you can comply with the NCC 2022 annual energy use budget. NatHERS Director Leonie Wilson explains what the rating is and how it’s supporting the energy efficient homes of the future.
Rating the whole home
The addition of an energy use budget to the National Construction Code (NCC), alongside the move to a minimum 7-star thermal (building shell) rating, has been the result of years of consultation and detailed impact analysis.
Despite the complex work underpinning the new requirements, the end goals remain straight forward – saving energy, reducing bills and helping Australia reach net zero emissions by 2050.
To support the NCC changes, the Nationwide House Energy Rating Scheme (NatHERS) certificates now include a Whole of Home rating out of 100, which can be used to show how a building meets the new NCC energy use budget.
The rating has been purpose built with CSIRO to estimate the cost of the energy used by Australian homes. It considers fixed appliances such as hot water, heating and cooling, pool and spa pumps and lighting, as well as solar energy generated and stored onsite.
Leonie explains.
“NatHERS has been estimating the energy required for heating and cooling for years using a star rating out of 10. This is the first time we have included the rest of the energy used by a home and estimated the costs of that energy.
“The new rating out of 100 uses a number of calculations to give us an overall energy budget snapshot. This includes the predicted costs for the consumer, the cost to the energy network and the cost to the environment in greenhouse gas emissions.
“This rating will help lower bills for newly built homes as people can choose the most energy efficient appliances.”
Save time and money with early assessments
NatHERS assessors are undertaking training to prepare for the introduction of NCC 2022 and the new Whole of Home rating as it is adopted across the country. Like never before, they are playing an important role in creating the energy efficient homes of the future.
“I always recommend getting a NatHERS assessment early. This helps you make smart choices to improve your rating, before the home’s design and appliances are locked in.
“By assessing early, you can choose the right combination of appliances to get you that Whole of Home pass mark of 50 (for apartments) or 60 (for detached homes).
“You can also make low-cost design changes to improve your thermal and Whole of Home ratings, such as adjusting orientation to take advantage of sunlight, choosing the best window placement, or including fans and the right shading.
“If you can get these elements right from the beginning, you can avoid costly inclusions like triple-glazing or unnecessary solar at the end of the process, once the design is fixed,” Leonie said.
Carefully consider climate
One size does not necessarily fit all when it comes to Whole of Home energy assessments – and local climate is a key consideration.
The great thing about the Whole of Home rating is that it lets you meet the requirement in the way that best suits you.
As always, if you’re building in the tropics, shading and cross ventilation are key, but in cooler climates, a good thermal shell is a high priority to trap the warmth inside in winter.
A better thermal shell means the home won’t need as much energy to get it to a comfortable temperature.
And things get more interesting when you are considering how you use appliances in these different scenarios.
“In cooler climates, a rating can be significantly improved by a good thermal shell that keeps in the heat, and by adding more efficient appliances you’ll cut costs as you won’t be using much energy to get it warm in the first place.
“While there is some benefit from adding solar PV in cool climates, it’s not as pronounced when heating is your priority. This is because your energy will be mainly used for heating in winter when less sun is available to power it.
“In warmer climates you can benefit significantly from adding solar PV and improved appliances because of the emphasis on cooling. The sun shines during the day when it’s hot and so you’ll have plenty of solar energy to run your AC in really hot weather,” Leonie added.
Find out more
Check out the NatHERS expansion page for more on home energy assessments and the addition of the new Whole of Home rating.
Energy assessors can visit the NatHERS Assessor Toolkit page for more technical information and guidance.
Get up to speed with the changes to the NCC and the new energy use budget on the ABCB’s website.