Issue 8 - May 2019

New NatHERS tools are on their way

Later this year NatHERS software tool providers will start releasing NatHERS accredited tools that use the new Chenath Engine version 3.21. The Chenath Engine (currently version 3.13) has been developed by the CSIRO, and is used by each software tool to perform the calculations and modelling behind NatHERS energy ratings.

Version 3.21 of the Chenath Engine incorporates improvements to double height void modelling, basement zones and shared wall adjacency in apartment buildings, improved edge slab insulation and waffle pod modelling, and the addition of limestone in the materials list. Tools will be released once accreditation is completed using the 2019 Software Accreditation Protocol.

NatHERS Assessors should transition to the NatHERS accredited tools that use Chenath Engine 3.21 as soon as they become available. However, there will be a period where both Chenath Engine 3.21 and 3.13 based tools can be used. 

NatHERS assessors will receive notification from their software tool provider about when the updated tools using Chenath Engine 3.21 will be available for download

Final NatHERS Technical Note

Following extensive review and consultation, the final version of the new NatHERS Technical Note (version June 2019) will be released on the NatHERS website by 31 May 2019. The key purpose of this update was to improve the structure, consistency and clarity of language and to incorporate changes associated with the forthcoming update to Chenath Engine version 3.21.

Assessors must use Technical Note (version June 2019) for all NatHERS assessments commenced from 1 June 2019. For NatHERS assessments commenced prior to 1 June 2019, assessors may instead use one of the previous versions of the Technical Note as outlined below, and make a note in the ‘Additional Notes’ section of the NatHERS Certificate about which version of the Technical Note was used:

·         Technical Note 1 (version 1.2 – 2014)

·         Technical Note (version May 2019)

Tables 3 and 4 from Technical Note 1 (version 1.2 - 2014) have been added as Appendices (2 and 3) to the new Technical Note (version June 2019). This will enable assessors to meet the new requirements when using software underpinned by Chenath Engine version 3.13.   

In April 2019 the NatHERS Administrator presented an overview of the new NatHERS Technical Note in a webinar to over 240 participants. Please visit the Building Designers Association of Victoria website or contact the Australian Building Sustainability Association directly if you would like to access the recorded webinar.

A draft version of the NatHERS Technical Note (version May 2019) was released on the NatHERS website on 18 April 2019. The final Technical Note (version June 2019) will include a few minor adjustments. 

Keep an eye out for the new NatHERS Certificate

A new NatHERS Certificate is being rolled out by NatHERS software tool providers. This will be accessible through new software tools underpinned by Chenath Engine version 3.21.

Once called the ‘NatHERS Universal Certificate’, it has undergone a major overhaul to improve its structure and usability, and will now be referred to as the ‘NatHERS Certificate’.  

A preview of the new NatHERS Certificate will be uploaded to in the coming months. 

Split heating and cooling loads

To improve the year-round performance of Australian homes, the 2019 National Construction Code (NCC) requires NatHERS assessments to meet separate heating and cooling load limits in many climate zones.

NatHERS tools already calculate separate heating and cooling loads as well as the total combined load and these are displayed on the Certificate in MJ/m2 per annum.

NatHERS assessors will need to check these loads against the split heating and cooling load limit tables in the ABCB Standard to make sure they comply. NatHERS accredited software tools will implement a tick box or prompt to remind assessors to check this requirement.

There is a transition period for NCC 2019 from 1 May 2019 to 30 April 2020 where the current (2016) requirements will still be accepted.

Custom windows substitution

A new interim rule in the NatHERS Technical Note (version June 2019) will allow NatHERS assessors to substitute custom windows as follows:

Clause 8.3: If a custom window is specified on the design documentation but not available in the NatHERS custom window library, assessors must model;

- a default window with the specified opening type; or

- an available custom window that meets all of the following parameters:  

  • identical opening type (e.g. fixed, awning, casement, sliding.) to the window specified on the documentation and;             
  • a total window system U-value equal to, or less than, the window specified on the documentation and; 
  • a total window system Solar Heat Gain Coefficient (SHGC) +/- 5% of the window specified on the documentation.

This interim rule is one of a number of enhancements to improve modelling of windows in NatHERS software. Assessors can apply this interim rule when the window specified is not available in the NatHERS custom window library. It can also cover substitution at the building stage when a window installed is different (but within the rule) from the one used in the assessment.

The updated NatHERS Certificate will include a note about this interim rule. Any additional changes to guidance on modelling windows will be reflected in future updates to the NatHERS Technical Note as appropriate.

Editors Note (28 May 2019)The NatHERS Star Newsletter distributed on Wednesday 22 May 2019 included an extract of the proposed changes to Clause 8.3 regarding custom windows substitution. There was an error in this draft text (and therefore in the above quoted newsletter article text), which has since been corrected in Clause 8.3 of the new NatHERS Technical Note. Please refer to the NatHERS Technical Note (version June 2019) for the correct text of Clause 8.3.

Rating student accommodation & boarding houses in NatHERS

Under the National Construction Code, student accommodation and boarding houses are considered as Class 3 buildings and treated as commercial premises, so they are not subject to residential energy efficiency requirements. However, a recent finding by the New South Wales (NSW) Land and Environment Court has classed some of these buildings as dwellings that are subject to NSW BASIX requirements. This finding has resulted in more NSW Councils requesting NatHERS assessments for such buildings. 

NatHERS accredited software tools are intended for rating Class 1 and 2 buildings only. Assessors asked to perform a NatHERS rating on a Class 3 building should follow the rulings of the individual Principal Certifying Authority (usually the local council).

NatHERS stakeholder workshop

The 2019 NatHERS Stakeholder Workshop will take place on the 21 October 2019 in Canberra. Places will be limited. More information will be provided in coming months.

Artibus Innovation seeking comments on the Certificate IV in Home Energy Efficiency and Sustainability

Artibus Innovation have released the final draft of the Certificate IV in Home Energy Efficiency and Sustainability for stakeholder comment. They are interested in feedback regarding whether the qualification accurately reflects current industry skills, knowledge, practices and job functions.

A short online questionnaire will be open from Monday 6 May until Wednesday 22 May 2019.


New lifestyle show takes sustainable housing to a mass audience

A new TV show concept, Renovate or Rebuild, aims to crack open sustainable building options to a broad audience. It combines reality-TV with behavioural science by encouraging Australian home owners to choose healthier and more energy efficient homes.

Renovate or Rebuild is a 30-minute lifestyle show where two teams compete to convince a Sydney-based family that they have the best solution to providing more space, comfort and reduced energy bills. Star ratings are also considered by the teams.

The pilot episode will be released on YouTube on 28 May 2019. To find out more and get involved you can visit the Renovate or Rebuild website.