The Study

The Study provides energy efficiency consulting services, architectural drafting and various other consulting services to the architectural and construction industry

NCC 2019 Energy Efficiency Changes

 NCC 2019 has brought increased stringency requirements to the energy efficiency provisions. Due to the impact of these changes, the energy efficiency provisions are subject to a 12-month transition period. Projects which may be submitted for building permits after 1 May 2020 should consider meeting the NCC 2019 energy provisions to ensure there are no issues with obtaining building permits after that time. 

The Study will start to include advice for compliance with NCC 2019 so that you can start to see how these changes may impact your projects from 1 May 2020.

 Residential Impacts for Energy Efficiency – NCC 2019

 The 2019 update of the NCC brings some changes to the energy efficiency requirements for residential buildings. The reference building method is seeing a major overhaul, there is a new verification method being introduced for building sealing and heating and cooling limits are being introduced. While not considered an increase in stringency by the ABCB, these changes will have a major impact from 1 May 2020: 

Verification using a reference building (VURB) method 

The ABCB are introducing a raft of additional parameters for modelling of the reference building, and effectively this method will not provide a less stringent compliance pathway than NatHERS (star ratings) in most circumstances. This will effectively spell the end of the VURB method as a viable option for compliance. 

The changes proposed affect the modelling of the reference building, which will now need to be modelled with low ceilings, insulated masonry veneer walls and no glazing size/location changes - in a thermal simulation software separate to NatHERS software. This has been tested to result in an improvement in the performance for the reference building where the reference building often rates over six stars – this means that the least stringent method for compliance will become the NatHERS (star rating) method.  

As the reference method will need to be a separate model to the NatHERS model – the additional time and cost of testing this method only to find that it is more stringent than NatHERS will effectively spell the death of the VURB method of compliance.

 Building Sealing 

There is a new verification method being introduced for building sealing – being a blower door test to achieve less than ~10 air changes per hour. This is not a particularly stringent requirement, and this test is not mandatory.  

We believe that the blower door testing is only being introduced at this stage and will likely become more stringent and compulsory in further revisions of the NCC. The deemed-to-comply provisions remain largely unchanged, with the addition of a requirement to weather seal any doors connecting a garage and residence.

Heating & Cooling Limits 

For NatHERS (star rating) method assessments, in addition to requiring a minimum six star rating, there will also be heating and cooling load limits introduced. Currently, a six star rating could have very high heating loads, offset by very low cooling loads (or vice-versa). The load limits are aimed to target the worst performing 10% of dwellings with disproportionate heating or cooling, and will require some modification of the design or spec to bring the performance into a more balanced heating and cooling loading. 

This requirement should only impact on a small proportion of projects but may result in some design amendments or improved insulation spec to achieve compliance.  

 Commercial Impacts for Energy Efficiency – NCC 2019

 NCC 2019 will bring sweeping changes to the Section J provisions. Section J was last updated in 2010, with the last major overhaul in 2006. This 2019 revision sees some significant changes, estimated to result in a ~40% energy usage reduction across commercial buildings. 

Verification methods 

Where verification using a reference building (JV3) has long been a part of Section J – new verification methods including NABERS energy and Green Star are being introduced. 

The Study is considering training in NABERS and Green Star to provide further options for compliance, particularly in light of the deemed-to-comply changes.


Dark coloured roofs will no longer be permitted under DTC provisions – commercial buildings will need a light coloured roof (SA Max. 0.45) to comply under this method. There has been a small performance increase for light roofs in Climate zone 5. 

Please note the solar absorptance requirements will now mean any roofs assessed under DTS will need to be Whitehaven, Surfmist, Classic Cream, Paperbark, Shale Grey or Evening Haze. All other colorbond colours, zincalume or tiles will need to use another compliance method. We are not yet sure how this will impact on alts/adds where added roof areas are proposed to match existing.

Walls / Facades 

Currently, walls and glazing are assessed independently – NCC 2019 groups both wall and glazing performance together into façade performance. Glazing has been assessed against a base case of 5% window size to provide minimum natural light with a basic window – and any increase in proportion of the window will require a relative increase in performance in the façade (wall and window combined). The stringency increase means that 63% of buildings tested against current requirements in climate zone 5 would not be compliant under NCC 2019 – so roughly two thirds of the projects will require changes to improve performance to match the top 1/3 of projects – this is a very marked increase in stringency. 

We expect full glazed facades to no longer be possible under DTS provisions, even for showroom/retail type uses. Heavily glazing facades will need to allow for very high-performance glazing systems and/or high performing wall systems. The benefit/cost ratios estimate that a wall with 45% window to wall ratio will cost up to 25% more under NCC 2019 than current requirements in climate zone 5.


Floor performance is now based on a ratio of floor area to perimeter calculations, and the inherit R-Value of a floor will be impacted by the wall thickness.

 The NCC does not have much information on how this method is calculated yet – but from our understanding it appears that slab on ground construction will require some additional insulation in most circumstances.

 Mechanical / Air Conditioning 

There are changes across the mechanical sections, which now include fans and pumps. Stringency is increased across all parts, including economy cycles and outside air requirements. Lifts are now also brought into Section J and have minimum energy efficiency requirements. 


The current regulations were written around the use of fluorescent lighting, but NCC2019 will be updated to reflect LED lighting technology. The result is that allowable lighting is being reduced to reflect the lower wattages of these lights – i.e. retail will be reduced from 22W to 14W/m² and office spaces from 9W to 4.5W/m²

 NatHERS (Star Rating) Scheme updates

Chenath – the simulation engine which runs behind all three NatHERS software options is also having a major updated released. There will be new modelling parameters for glazed corridors & basement carparking zones (Class 2 / apartments) and double height void spaces. There are also improvements to slab edge insulation modelling (currently not able to be included) and some additional materials being added to the library. 

The impact of these changes remains to be seen – hopefully these updates result in more accurate simulation. There is no mention of fixing long-standing issues such as the out of date and irrelevant window library, nor climate zoning issues in the South West.

 Alterations/Additions reminder 

Please remember that alts/adds are generally required to be assessed as a whole – we need details of the existing windows/glazing and shading as a minimum. If the project is not compliant under the elemental method and we need to move to thermal modelling options – more information on the existing building may be needed.  

Please ensure you are measuring existing windows, eaves/shading and taking lots of photos at alts/adds projects to enable us to assess the glazing accurately.

 So there are some pretty significant changes to energy compliance over the next twelve months, please let us know if you have any queries or concerns. Please continue to send projects or queries as early in the project as possible so that any items of concern can be addressed as early as possible. Changes become increasingly difficult and expensive the later in the project they arise!