What is the National Home Energy Rating System (NatHERS)?

We know there’s lot of jargon when talking about sustainable building, so we’ve decided to give you some background info on how energy ratings work and why it’s so important to consider when building or extending your dream home. Delivering your construction project isn’t our only aim; we seek to educate and share our passion for sustainable design with you, so you can make the best choices for your Ecoliv home. We’ll look at the key factors that determine the NatHERS energy rating system such as glazing, shading and insulation.

Over the past decade, sustainable building practices have drawn a sharp focus from Australian Government and industry bodies. A study from 2003 (1) showed that the international construction industry consumed just under a third (32%) of global resources and contributed to 40% of landfill waste and 40% of air pollutant emissions. These figures were startling and forced the construction industry to look into ways they could reduce their environmental impact.

In the same year, the Australian construction industry responded with the introduction of a renewed National Construction Code that included the a National Home Energy Rating Scheme, abbreviated to NatHERS, which called for a minimum four-star energy rating for any building built after 2003. In 2010, this was increased to a six-star minimum, which means many residential constructions built within the last decade do not meet current minimum energy ratings. At Ecoliv, we have a minimum seven-star energy rating for all our buildings by closely considering thermal performance, so what does thermal performance actually mean?

Firstly, we need to consider the bigger picture of energy use around your home. Heating and cooling accounts for 40% (2) of overall energy use around the home, so sustainable building designs should reduce your reliance on air-conditioning and heating. When you do heat or cool your home, a sustainably designed building should focus on maintaining that temperature for as long as possible yet allow for passive cooling when desired. This is called thermal performance (or efficiency) and you can read more about it here on AusGov’s YourHome website.

There are many factors that affect thermal performance but in a broad sense we consider window glazing, insulation and adequate shade around your home as the three main factors that contribute to energy ratings, so let’s take a look at them now.

Glazing

All Ecoliv Buildings feature double-glazed windows with a five-star WERS glass, which stands for Window Energy Rating System. The scale ranges from zero to ten stars, keeping in mind that extremely expensive ten-star WERS-rated glass would be used in welding masks or high temperature industrial settings, which makes it totally inappropriate for home windows. We chose five-star WERS glass as the optimal choice to balance cost, thermal performance and achieve our minimum seven-star HERS rating.

Insulation

We have carefully selected our insulation provider Earthwool Insulation by Knauf based on their best-in-industry practices for price, quality and environmental impact. This mineral wool insulation is made with recycled glass bottles and sand which are chemically neutral, fully recyclable, resistant to fungi, mould, pests and bacterial growth with a fifty year warranty.

Shading

All our designs use passive solar principles to take advantage of natural lighting and shade. This depends on a range of factors that are specific to your building site; things like elevation, which way the building faces, other nearby buildings or trees. All our building designs come with a 900mm eave overhang that provide shade across windows and outdoor areas with optional shade battens and strategically placed windows that support passive cooling and cross ventilation. We will assess your site and customise your modules for the best possible thermal control and this is called sitting efficiency.

So how do you calculate the energy rating?

Once we have designed your module to your unique needs, the floor plans are run through a software platform called FirstRate, designed to calculate the annual heating and cooling energy. This provides data for calculating a NatHERS rating and gives suggestions on improving the design beyond the minimum requirement. It’s incredibly smart technology and its saving our clients thousands of dollars in heating and cooling their home over the building’s lifespan.

If you’d like to know more about how to improve the energy rating of your next construction, contact our energy efficiency experts at Ecoliv here.

References

(1) Environmentally Sustainable Buildings: Challenges and Policies – a report by the OECD, 2003
Australia State of the Environment Report, Commonwealth Department of Environment & Heritage, 2001

(2) Department of the Environment, Water, Heritage and the Arts (DEWHA). 2008. Energy use in the Australian residential sector 1986–2020. Canberra. www.energyrating.gov.au