In Australia, the National House Energy Rating Scheme (NatHERS) is used to provide a measure of the energy efficiency of residential buildings. Buildings are rated on a scale of 1 to 10 stars, with 10 being ‘extremely’ energy efficient and requiring low amount of energy for heating and cooling. Victoria, South Australia, Western Australia, Tasmania and the ACT, all apply the minimum six-star NatHERS requirement, while the other states have local variations to the standard and New South Wales uses the BASIX index to determine the environmental impact of housing.
The NatHERS is a measure of the thermal performance of the overall building and applies to the whole building envelope (i.e. the external structure of the home) including its walls, roof, floor and windows. All new homes and renovations must also include the installation of either a solar hot water system or a rainwater storage tank for flushing the toilets. The six-star requirements also include mandatory energy efficiency standards for the lighting in the home but does not include plug in appliances.
One would think that this all sounds reasonable and we all should be living in energy efficient, comfortable houses. Unfortunately, that is far from the reality as the six-star minimum falls short of what is optimal in terms of environmental, economic and social outcomes. It’s also below the minimum set by many other countries.
[bctt tweet=”Going beyond six stars reduces the heating and cooling demand. Despite that, four in five new houses built in Australia are being built to the minimum standard with only 1.5% designed to 7.5 stars or beyond.” username=”@ecokit_homes”]
Is increasing the minimum rating the solution then? Sadly, no…
The average homebuyer paying premium for additional stars, has no easy way to find out whether the home with higher NatHERS rating is actually performing like one. The issue is that the NatHERS rating is only calculated using a software and there is no actual performance check during the construction or after the house is completed. And it is a fact that the standard Australian design and construction approach is delivering poorly performing buildings and even homes designed for high NatHERS ratings are often using more energy than they should. That’s why many buyers find that even an 8, 9 or 10 Star home can have bills as high as the previous, lower rated home.
This was highlighted in the National Energy Efficient Building Program study undertaken by the federal government in 2016, which tested over 700 houses built to the 6 Star standard or above and found most were insulated to a 3-3.5 Star standard as actually built.
At ecokit, we believe we need to focus on real, measurable values such as the building envelope elements, including walls, floors and roofing, and also windows, air tightness and thermal breaks.
A solution, widely used over Europe and north America for decades, is to embrace the Passive House (from german term Passivhaus) standards. Passive house, a rigorous building standard for ultra-low energy buildings, ticks all these boxes.
No air sealing and leakage is a major factor in why houses in Australia (and New Zealand not far behind) are performing so poorly. The windows and glazing also have a large effect on the energy requirements.
We are paying for accepting a lower standard
Energy efficient houses can significantly reduce heating and cooling energy use and associated greenhouse gas emissions. Although achieving better performing home typically requires higher amounts of materials such as insulation and better quality glazing with thermally broken window frames, which might add extra cost, the higher energy efficiency or even environmental sustainability in housing provides significant benefits and will pay off over the life of the home.
Even if a once-off investment of $5000 results in savings of just $1000 a year, that still adds up to $20,000 over the average 20-year lifespan of a house.
In addition, better designs can significantly improve the energy savings and, more importantly, the overall level of comfort for the home’s occupants. Apart from focusing solely on materials and technological improvements, we should demand better building design as a means to achieve performance.
The evidence suggests that most consumers are happy to just accept the minimum performance the building sector delivers. However, if we continue to create a legacy of homes with poor energy performance, improving the situation later will get progressively more challenging and expensive.
Designing a high performance, energy efficient home is not difficult but must be considered in the early stages of design. Building your home using a construction system developed specifically to achieve high performing, energy efficient homes at a reasonable cost will lower the construction times, save you money and will provide a healthy home for years to come. It is a no brainer!