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 are interested in getting your software accredited, please contact the NatHERS National Administrator following review of the NatHERS Software Accreditation Protocol.

NatHERS Software Accreditation Protocol Review

A review of the Software Accreditation Protocol is currently underway as agreed by the NatHERS Steering committee (the Energy Efficiency Advisory Team (EEAT)) as one response to the 2016 NatHERS Governance and Operational Review.

To facilitate this review a discussion paper was developed and feedback was invited at the end of 2016. This feedback is being considered and further information about the progress of the review, and opportunities for comment, will be published on the NatHERS website as it becomes available.

The review of the Protocol is aimed at better documenting the principles and functional specifications of the NatHERS software tools, clarifying software tool requirements and regulatory obligations applying to changes to the software tools, as well as review the software accreditation process. 

The paper is available here [PDF 681 KB] [DOC 81 KB].

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 Technical Note 1 ‘Principles for Ratings in Regulation Mode’
  • 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 of 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.

Businesspeople working on report

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 Version

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
  3. if conditions 3.2.4.b i and ii are not met, the Energy Rating must not be more than 0.25 stars different from the Energy Rating of the Benchmark Software as determined after rounding down results to the nearest quarter star by the National Administrator.