Response to ABCB on the proposed changes to the NCC 2022

Dear members of the Board,

The proposed changes to energy efficiency do not provide a clear path towards Net Zero, which is disappointing. The knowledge, the modelling tools and the building components required for this target exist. Because of our European background, we are using energy efficiency regulations and the Net Zero Energy Buildings [NZEB] concept in Europe as reference points for comparison with Australia.

We want to draw your attention in particular to our “case study about airtightness”, and we ask you to consider making the Blower Door Test compulsory for the Certificate of Occupancy.

Energy efficiency in Europe

The research for energy efficiency technologies and products in Europe started 40 years ago. PV panels for domestic hot water were the first popular solar gain products, soon to be followed by PVC and thermal break aluminium windows, double-glazing and thermal insulation products like EPS and XPS. The Passive House Institute started researches in 1991 with great help from German institutions and the industrial sector.

Despite this background, it took Germany more than 30 years to reach 50% of the net-zero targets by 2050. The rest of Europe is moving even slower. It soon became a common perception of the need of reducing energy consumption to a level that renewable resources can cover the demand.

NZEB buildings

All new buildings in the European Union must comply with the Nearly Zero Energy Building standard [ΝΖΕΒ], which refers to a building that can offset its energy demand from on-site or close-by RES[1]. Because renewables can only meet a small portion of current energy demands, reduction of consumption is critical. The locality of RES is essential for regions with limited investing capabilities and for those with difficulties in connecting solar farms with the grid. The latter applies to Australia.

A similar standard is gaining momentum in the US and Canada, however, NZEB there stands for Net Zero Energy Building.

Passive House

A house certified to the Passive House standard has an energy demand of 15kWh/m2 per annum for heating, cooling and hot water. Compared to a conventional building, PH has approximately 80-90% lower demand. Computational modelling is done through the Passive House Planning Package (PHPP), which is a comprehensive and sophisticated tool that takes into account thermal insulation, mechanical ventilation with heat recovery and an airtight building envelope and also complying with many building standards:

  • Thermal comfort calculation according to ISO 7730
  • Indoor air quality according to DIN 1946
  • U-value of window frames and thermal bridges according to EN/ISO 10077-2
  • U-value of glass according to EN 673
  • G-value (solar transmission of glass) according to EN 410
  • Mechanical services as per AHSRAE’s guidelines

About NatHERS

We believe that NatHERS is an empirical model without serious scientific backup, presented in a complicated manner.

Three random examples:

  1. The concept of the “average R-value” does not base on any building physics standard. How will double thermal insulation outside a bedroom help the thermal comfort in another bedroom on the opposite side?
  2. Thermal bridges are under consideration. With many modelling software available (Flixo, Heat3, THERM, Psi-therm), we expected to see relevant calculations incorporated in the NCC.
  3. The standard treatment of thermal bridges is to wrap exposed surfaces with insulation and not to “resolve thermal bridges with air cavities”. Who is supposed to understand this description and document it? The domestic builder?

The future of energy efficiency in Australia

There are many constraints in Australia developing its path towards carbon-free buildings:

  • With 0.322% of the global population, the size of the Australian economy is relatively small, making overseas investments in R&D non-feasible.
  • While the rest of the developed world is buying expensive energy, Australia is exporting fossil fuels. Any changes to this industry will cause political and social side effects. Unless statutory changes (like the NCC) are drive towards net-zero, there is no reason to expect that developers and builders will do that voluntarily.
  • There is a bipartisan policy to prioritise trade qualifications versus University Degrees. The current status sees trade qualified builders designing, overseeing and to some extend certifying their works. We cannot see how Australia can compete with countries where engineers and architects drive research and production.
  • «Tracking towards 2020: Encouraging renewable energy in Australia» lapsed in 2020, and there is no official policy following up.
  • Solar farms have had difficulties connecting to the old and sensitive grid since 2019.[2]

Conflicting messages are sent to the public:

  1. The Premier of Victoria confirmed three years ago that the State «has enough renewable energy projects on the way», assuring that «soon we will generate enough energy to power every home in Victoria»[3].
  2. In April 2021, «renewable energy from sources like wind, solar and hydro provides about 21% of Australia’s electricity supply».[4]
  3. Daniel Westerman (CEO, Australian Energy Market Operator) announced Australia’s transition to 100% Renewable Energy Resources by 2025[5].

Combining the global status towards net-zero with the proposals about upgrading 6-star to 7-stars in Australian buildings, we don’t see Australia reaching net zero within this century.  

Comparing Passive House with NATHERS

AreaPassive HouseNatHERS standard
Certification60,000 buildings around the globe have been tested and certified.No provision
Thermal insulationRequirement for continuous thermal insulation layer around the building envelopeThe “average R-value” concept balances local poor insulation by additional insulation in another area.
Air tightnessMaximum of 0.6CPH and this is tested during construction.NatHERS assumes 10CPH
Heat recoveryMechanical ventilation with a minimum of 75% heat recovery.No provision
Electricity demand0.45 Wh/m3No provision
Heating & hot water energy demand<15kWh/m2 per year, alternatively, 10kW/m2No validated data is provided.
Cooling demand<15kWh/m2 per year + dehumidification contribution, or 10kW/m2 cooling loadNo validated data is provided.
Primary energy demand<120kWh/m2 per yearNo provision
Thermal bridgesLinear and point thermal bridges calculated according to EN-ISO 10211.No provision

Case study about airtightness

  1. A three-bedroom certified Passive House in Melbourne with a floor area of 120m2 and ceiling height 2.70m has an air volume of 324m3. The Blower Door test measured 0.6CPH[6] during the certification process, while the PHPP confirmed an energy demand of 15kWh/m2/annum.
  • This demand equals 54MJ/m2/annum, which, as per the NatHERS star band criteria[7] classifies the house at 8-star.
  • We drill one hundred and twenty eight holes in the external walls where we put toilet fans to all of them. Half of the fans blow 50m3/h and the other half extract 50m3/h.
  • We have now created an air circulation of 64 X 50m3= 3,200m3per hour, increasing the air changes to 10CPH.
  • This house is not a Passive House anymore, but it still is 8-stars in NatHERS.


  • Energy efficiency in Australian homes is some decades back from Europe.
  • While Europe and the USA use dynamic analysis in energy efficiency modelling, double-glazing is still a voluntary and luxurious feature in Australia
  • The discussion about upgrading the minimum requirement from 6 to 7 stars is outdated. In global terms, the NatHERS system is a primitive tool, and results will still be very far from energy efficiency as is meant in the rest of the world.
  • Even with the 7 stars, implementation will base on the builder’s confirmation, as there is no testing requirement.


  • Accept the Passive House standard as a thermal assessment tool in the NCC-2022
  • All thermal and energy computational modelling tools must prove a minimum interior temperature of 12.6o when the relative indoor humidity is 50% to prevent mould growth.
  • Airtightness test must become compulsory.
  • Include heat recovery performance of mechanical services in the Certificate of Occupancy.
  • Certified Passive House Designers hold a degree in architecture or engineering. We find additional training requirements at a lower level needless.

[1] Renewable Energy Resources

[2] Clean Energy Council outlook report

[3] Daniel Andrews’ Facebook page, 18/7/18

[4] Energy Australia’s website, accessed on 19/7/21

[5] Sydney Morning Herald, 13.07.21 and Clean Energy Council’s page on LinkedIn, 15.07.21

[6] Changes Per Hour at 50Pa air pressure


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