Something in the National Construction Code to compensate for the mass of black roofs?

Every three years, the codes that ensure new buildings in Australia are safe, functional and efficient get a refresh.

For the latest round of National Construction Code updates for the residential sector, a promising suite of measures to improve the energy efficiency of Australia’s housing stock is on the table.

These adaptations align with the Trajectory for Low Energy Buildings policy that was adopted by the former COAG Energy Council in 2019.

Among the changes advocated are increasing minimal thermal performance and whole-of-home annual energy use requirements.

Other proposed changes include:

  • a new set of Deemed-to-Satisfy elemental provisions for apartments 
  • new provisions designed to allow easy retrofit of on-site renewables and electric vehicle charging equipment for properties not including houses
  • enhanced condensation management provisions, including additional ventilation and wall vapour permeability requirements

According to Neil Savery, chief executive officer of Australian Building Codes Board, there’s only so much the shell of a building can do to bring down energy consumption or increase efficiency.

It’s a key reason, he says why the proposed upgrade to the National Construction Code has explored a whole-of-home system.

It’s one of the proposed changes to the NCC flagged last week on our pages.

See A big week for energy efficiency standards in Australia

The system is akin to the BASIX scheme but for class 1 buildings (a singular home, not an apartment block), there is also the opportunity to trade off renewables.

Mr Savery said that this PV offset system is not recommended for class 2 buildings (multi-residential buildings) due to roofspace limitations.

The proposed requirements around EV-ready buildings also differ between class 1 and class 2 buildings. With class 1s, there is no requirement as there’s an expectation that most standalone homes will already have capability to plug into a car to a power point.

Another new development is the issue of condensation, alongside energy efficiency.

Mr Savery said it was important that iterative improvements to energy efficiency do not come at the expense of condensation issues, such as mould or mildew growth.

“Energy efficiency is not the only reason condensation occurs in homes, but it will contribute to the potential for condensation, because ultimately there’s a move to make buildings more airtight.”

He added that there were no proposals to increase airtightness in this version of the code. Instead the intention was to educate the market about dealing with condensation using ventilation first.

Industry reactions

The raising of the minimum NatHERS standard from six to seven has attracted support from Energy Efficiency Council head of policy Rob Murray-Leach.

He labelled the increased minimum rating “unequivocally a good thing”. Australian Sustainable Built Environment Council acting chief executive Alison Scotland was also very keen to see the changes go ahead.

On the home energy budget, Mr Murray-Leach said that he was pleased to see no proposed tradeoff between the thermal envelope and fixed appliances, noting that super energy efficient ovens and fridges, which have short lifespans and can be removed from the building, will not be able to be substituted for an efficient thermal envelope.

“The thermal envelope lasts decades.”

The code should apply caution to the use of renewables in the whole-of-home annual energy use requirement.

While he’s yet to investigate these requirements in detail, the concern is that if this condition isn’t applied carefully, it could inadvertently set back the clean energy transition and lead to higher bills.

“If we want lots of renewables you need homes that don’t use much energy in the evening, which means efficient heating and cooling.”

He says that while solar panels can be located anywhere to meet our low carbon energy needs, energy efficiency is not so flexible. It needs to be built into the house.

“If not designed carefully you’ll get builders putting in cheap appliances and covering that off with solar. That’s problematic from a grid perspective and a household energy use perspective.”

Mr Murray-Leach said his organisation would investigate the proposed ventilation improvements with interest, noting that “this mythical tradeoff between energy efficiency and ventilation is nonsense.”

We need to move away from using “uncontrolled ventilation”, or leaky buildings, as a strategy to manage condensation. The focus should be on “controlled ventilation” that allows fresh air in when you need and want it.

“We do need to move away from the idea that we can passively ventilate homes and we do need to move towards controlled ventilation.”

RMIT senior industry fellow Alan Pears pointed out that Covid is prompting a focus on the tensions between indoor air quality, high ventilation rates and energy efficiency.

“These can be resolved by energy recovery ventilation, which preheats or precools incoming air using exhaust air, or by high efficiency air purifiers.”

He also said that there needs to be more focus on summer performance.

“The 2019 NCC introduced separate requirements for summer and winter, which was a step forward. 2022 will see updated climate data, but not data reflective of conditions that will exist over the life of a new dwelling.”

He called for an inclusion of performance in late summer and autumn, when the sun is lower in the sky but extreme heat will be more likely. “This will require more focus on adjustable shading.”

“New home buyers deserve better information to guide their decisions. For example, existing rating tools can show how each room performs in extreme hot and cold weather. Regulations should require that this information be provided before a buyer signs up.”

ASBEC’s Alison Scotland is very keen to see the new provisions go ahead in this round of updates.

“We want to reinforce the message that a delay of three years to the next edition of the NCC would badly impact on our carbon emissions.”

Before the proposed changes come into effect, they will need to secure approval from both building ministers and energy ministers. There is also independent impact analysis (a Consultation Regulation Impact Statement – CRIS) in the wings that is yet to be released publicly.

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  1. In the chart above, heating the hot water with solar PV would eliminate the net energy consumption of hot water heating.
    & If the HWS was a heat pump, 3/4 of the heat comes from the air, so electrical energy could be used for other purposes. – of course, all of this could come from rooftop solar too.
    There are still far too many house roofs that are being built which are not suitable for a reasonable-sized PV system – at the detriment to the energy system & all Australians as well most obviously to the resident – who will undoubtedly be wanting an EV anytime from now on.

  2. A fundamental weakness of the NCC 2022 draft is the adoption of a “fuel neutral” stance. New residential buildings should be actively encouraged to be efficient all-electric homes to progressively eliminate gas (a fossil fuel) as an energy source.

  3. I agree with those proposed changes, but also the construction process and materials selection is an unmissable opportunity to slash carbon emissions, whilst keeping an eye on build costs — the trend toward high-energy materials and processes needs to be evaluated, and concrete and steel should be discouraged — CSIRO has been telling the industry about embodied energy for more than 20yrs, and the message isn’t getting through.