Residential Energy Rating

To obtain a building permit for a new construction or a major renovation, applicants need to provide a compliance evidence that the proposed building design meets the minimum energy efficiency requirements specified in the Building Code Australia (BCA). There are two options available: First option is Energy Rating under Nation Wide House Energy Rating Scheme (NatHERS) and achieving minimum of 6 star. Second option is Deemed to Satisfy (DTS)-Elemental Provisional to satisfy all the listed minimum insulation R values for roofs, walls and floors. These options are described in more details below.



Option 1: NatHERS/6 Star Energy Rating

Energy rating is mostly a cheaper and more cost effective option. It allows to model the building response to different levels of insulation, various orientations, different methods of shadings and window selection. Energy rating also allows to avoid unnecessary insulation or double glazing. GeoFlow provides both options to home owners as a compliance certificate to meet energy efficiency requirement of NCC. You can check and download the minimum data required to finalise your building energy rating here


Reference Building Verification

The Reference Building Verification is software approach and an alternative to NatHERS energy rating which is suitable for complex building plans. This method requires modelling the building with minimum energy efficiency requirements of the Building Code Australia like minimum wall, roof, and ceiling insulation and minimum glazing requirements of the (BCA). Then the model is altered based on the preferences of the owner/architect and the annual energy consumption for heating and cooling the building are compared to the BCA reference building. If the heating load and cooling load of the proposed building are less or equal to that of the reference building then the actual building complies to the BCA requirement s and GeoFlow issues the certificate of compliance.
This method provides a 3D modelling of the building and with more flexibility allows architect and the owners to see and apply their energy efficiency ideas in a more efficient way.


Option 2: DTS method-Elemental Provisions

With this option, your building construction will require to satisfy all the minimum energy efficacy provisions no matter how well your building thermal performance is. The minimum requirements in these sections of building code (NCC) will apply in full:

3.12.1: Building fabric (Minimum insulation thickness/R-Value for walls, roofs, floors)

3.12.2: External glazing and shading

3.12.3: Building sealing

3.12.4: Air movement

The DTS- Elemental provision is essentially a checklist and the accompanying glazing calculator which demonstrates your buildings ability to meet the minimum required energy efficiency for your climate zone as specified by the building code. The DTS – Elemental provision report costs half the energy rating and building owner can save couple of hundred dollars in meeting the building permit requirements but it may potentially introduce couple of thousands extra cost in unrequired insulation for your building. Note that the excess insulation may only save few dollars in running heating and cooling system with payback periods over 10-15 years.




*: Based on Building Code, In Victoria, it is also required to have either a rainwater tank connected to all sanitary flushing systems, or a solar water heater system.

Buildings in climate zones 1 and 2 (Hot humid summer, warm winter) may satisfy the NCC requirements with 5 and 5.5 stars.


6 star

Picture from 6 Star fact Sheet (Building commission)

Why Choose GeoFlow rating Service

GeoFlow energy rating and energy audit experts have PhD qualifications with experience over a range of different kinds of buildings. We provide our services to many leading architects, developers and builders right across Australia. We are accredited by ABSA and trained and certified to use the latest FirstRate5 6 Star Energy Rating software. For 3D modelling and compliance assessment we use and Energy Plus and open studio 3D modelling tools developed by US Department of Energy.

Extra Requirements for Victoria

In Victoria,Based on VBA/BCA, a new class 1 building also requires:
A rainwater tank receiving rainfall from a minimum catchment area of 50 square metres and having a minimum capacity of 2000 litres connected to all toilets in the
building for the purpose of sanitary flushing, or
A solar water heater system (which may include a heat pump water heater system) installed in accordance with the Plumbing Regulations 2008.
class 1 building is classified as detached house

For a competitive price assessment and solar passive house design and other sustainable solutions, please check out our services website and contact us.