In July 2017, CSIRO issued an alert highlighting the inconsistency of temperature settings required for Reference Building (NCC 2016 V2.6.2.2 Verification Using a Reference Building) assessments and NatHERS (6 Stars) accredited software tools.  It has come to light that the temperature setting requirement for each assessment varies, as follows:

  • Reference Buildings (VURB) space temperature requirements range between 25°C to 28°C for cooling and 20 °C to 21°C for heating.
  • NatHERS space temperature requirements range between 22.5°C and 27°C for cooling and 15°C to 20°C for heating.

Therefore NatHERS software tools, in regulation mode are not suitable to conduct VURB assessments.

Since July, each NatHERS software tool has commented on the suitability of their software for VURB assessments.

FirstRate5: ‘Sustainability Victoria has no intention to alter FirstRate5 to enable it to be used in the Reference Building Verification Method (NCC section v2.6.2.2).’

BERS: ‘BERS Pro may be used for NCC Vol 2. Verification Method V2.6.2.2 when in “BERS mode”. ’

AccuRate: ‘AccuRate cannot be used for VURB.’

It is the responsibility of assessors, building certifiers/surveyors and regulators to look closely at the energy efficiency report to determine all NCC requirements are satisfactory for VURB assessments. Information to be included in VURB assessments are:

  • Total heating and cooling loads for proposed building and reference building as per V2.6.2.2:

    BCA Climate Zone Cooling and Heating Loads
    1 and 2 Cooling load equal or less than the reference building
    7 and 8 Heating load equal or less than the reference building
    3, 4, 5, and 6 Heating and cooling loads equal or less than the reference building

  • Proposed final buildings plans and all information relevant to the current NCC regulations
  • Reference building information pertinent to the current NCC regulations that have been incorporated into the reference model
  • The software used to conduct the assessment

Until FirstRate5 and AccuRate incorporate a “reference building mode” and give users the ability to change zone temperatures, or alternatively the temperature requirements in the BCA for VURB are altered to align with NatHERS assessments, BERS is the only NatHERS software tool capable of assessing energy efficiency VURB assessments.

In Western Australia by accepting the energy assessment, the building surveyor takes responsibility for the assessment. Over the years the 3 accredited NatHERS software tools have been the most common tools used to model VURB assessments, mainly due to building surveyor confidence in the quality assurance regulated by AAOs (Assessor Accrediting Organisations). There are other tools capable of modelling VURB assessments that energy assessor can, through their expertise, deem suitable. In these cases the certifying building surveyor should ensure the assessor is appropriately qualified which is at the determination of the building surveyor based on the merits of the case.


National Construction Code 2016, Volume Two. 2016