NatHERS Software Protocol – Key requirements

The NatHERS Software Accreditation Protocol outlines in detail the requirements and processes for the accreditation of new software tools and new versions of previously accredited tools.

If you are the owner of an energy rating tool and interested in getting your software accredited, please:

Read the 2019 NatHERS Software Accreditation Protocol and contact the NatHERS National Administrator if you have any questions.

Minimum software requirements

Under details set out in the software protocol, all software must:

  • be based on well-established models that are in accordance with the principles of thermodynamics and fluid mechanics
  • include hourly calculations of heat flux across the building’s surfaces for every day of the year
  • include zoning of enclosable conditioned and unconditioned areas in a dwelling by function as described in the NatHERS Technical Note
  • produce hourly calculations aggregated to specific reporting requirements
  • use NatHERS climate zones
  • accord with NatHERS Energy Load, area adjustment and Star Banding modelling requirements
  • meet minimum NatHERS Universal Certificate reporting requirements
  • provide appropriate user training and support; and
  • meet all NatHERS software testing and accuracy requirements

Key modelling inputs

To ensure calculations are accurate, representative of Australian conditions and are comparable across different types of housing, the Software Protocol requires all NatHERS accredited software tools to meet strict performance standards and requirements for variables including (but not limited to):

  1. local climate and weather (including temperature, humidity, wind and sun)
  2. thermal resistance and capacitance of building materials
  3. window glazing values
  4. occupancy patterns (including internal heat loads, typical occupancy times and occupancy behaviour)
  5. window coverings (which are standardised for all ratings, noting they are likely to change over the life of the building)
  6. different types of zones in the house and whether they are conditioned/unconditioned
  7. thermostat settings (temperatures at which artificial heating/cooling is no longer required to achieve thermal comfort, noting this varies depending on climate zone)
  8. shadowing/overshadowing by adjacent buildings and features
  9. size of the building being assessed (noting smaller buildings generally have a larger wall surface area than bigger buildings)

For more information about some of these parameters, see How NatHERS Star Ratings are Calculated.

Accuracy Requirements

In order for any new software to become NatHERS accredited it must firstly be rigorously tested. During testing, independent assessors, approved by the NatHERS Administrator, compare the results of multiple simulated NatHERS ratings against the benchmark software tool, Accurate.

Each simulation is run using the new software tool developer’s own procedures and processes, as specified in its user manuals and guidance materials.

The results of each simulation are then compared against the results obtained by the benchmark tool when performing the same simulation.

All the individual simulations must achieve the following minimum result:

  1. the simulated heating load is within either ±10 per cent or ±10 MJ/m2.annum of the benchmark load and
  2. the simulated cooling load is within either ±10 per cent or ±10 MJ/m2.annum of the benchmark load

Furthermore, at least 95 per cent of the individual simulations must achieve the following more stringent result:

  1. the simulated heating load is within either ±5 per cent or ±5 MJ/m2.annum of the benchmark load and
  2. the simulated cooling load is within either ±5 per cent or ±5 MJ/m2.annum of the benchmark load, OR
  3. the Energy Rating must not be more than 0.2 stars different from the Energy Rating of the Benchmark Software.

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