The implementation of the new Nationwide Home Energy Rating Scheme (NatHERS) Technical Note legislation will result in closer building assessments with property developers, builders, assessors and designers. The question is will the new legislation support or hamper the building process?


Since it's inception in 1993, NatHERS has been the forefront of government legislation in regards to regulation of thermal newly built homes in Australia. Since then, NatHERS has gone through significant changes in the past 26 years, with the latest update having occurred from June 1, 2019. Some of those changes include:


  •  Window Opening Percentages
  •  Roof Colour Specification
  •  Glazed Verandas & Winter Gardens
  •  Ceiling Penetrations
  •  Mandatory Document Requirements
  •  Protected Trees


The changes being enforced are now placing more pressure on designers to pass thermal comfort targets and meeting overall home rating targets. In the new NatHERS legislation a new clause under the windows section (Table 5: Provisional Window Opening Percentages) requires all awnings, casements and louvres must be modelled to have a 10% opening instead of 90%. This means that homes with a greater quantity of windows will suffer from reduced cooling than before the NatHERS update.


However, in cooler climates such as states in Victoria and Tasmania the window restrictions would also provide an increase in heating loads, particularly during winter. Despite this, the negative impact will be felt in warmer states, especially in Queensland and the Northern Territory. Builders will be struggling to meet cooling targets due to the reduction in window openings.


Another addition to the NatHERS Technical Note update is that builders and designers will need to specify the colour of the chosen roof as part of the floor plan. With the new clause, builders and designers will require to simulate multiple versions to highlight worst case scenarios the thermal performance of a home if the roof colour is not specified in the floor plans. Previous to the June 1 NatHERS update, all roof cases were considered.


Assessors will also be impacted with glazed verandas now considered in the NatHERS legislation update. Balconies and other similar spaces need to consider solid, glazed or partially glazed walls as wing walls. Previously, assessors would would deal with balconies using best judgement. Post update though, assessors now have a specific guideline of how balconies are to be modelled.


The changes to the NatHERS Technical Note legislation will help establish a more detailed and accurate away for assessing the thermal comfort of homes being newly constructed and bring about gradual change for the standards that are required in Australia for developers, designers, builders and assessors.


At Certified Energy our ESD consultants can support you understanding the NatHERS Technical Note legislation changes and much more, to contact the team call  or email our team.

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Deniro Stocks

Written by Deniro Stocks

Deniro Stocks is the Digital Marketing Manager of Certified Energy