NCC 2022 now requires NatHERS 7 Star rating to satisfy thermal energy efficiency requirements. This used to be NatHERS 6 Star energy rating under the previous version of NCC. There are still some allowances for outdoor living area and ceiling fans to reduce NatHERS rating requirements in tropical climates (climate zone 1 and 2).

Under NCC 2022, we use NatHERS star rating to meet the thermal performance requirements. These requirements are detailed in Specification 42 (S42C2) of NCC Volume Two (for Class 1 buildings) and clause J3D3 of NCC Volume One (for Class 2 buildings). The following is the new requirements and features that did not exist under the older version:

Updated Climate Files and Energy Star Bands

With the new NatHERS 7 star rating, NatHERS also updated the climate and weather files from its 2005 version. Along with updating the climate files, NatHERS has also updated the NatHERS star bands. Changes in the NatHERS Star bands are negligible. NatHERS has slightly reduced the new star bands to balance the effect of updated climate files.

Thermal Bridging

The New NatHERS 7 star energy rating requirements include the impact of thermal bridging. Thermal bridging is a major source of heat loss/gain that NCC 2019 didn’t consider a requirement for residential buildings. The impact of thermal bridging is major and is capable of dropping 0.5 stars. For instance, consider a typical 4 bed room single storey house with metal-framed floors, walls and ceilings. If thermal bridging is properly mitigated in NatHERS modelling, it can improve NatHERS Rating by 0.4 stars in Melbourne or Hobart and by 0.5 Stars in Sydney or Adelaide [CSIRO].

Whole of Home Rating

This new feature is a new requirement under NCC 2022 to push housing industry towards the use of high-efficiency services. In addition to assessing the building envelope, the new NCC requires  Whole of Home rating that to assess building services. This includes lighting, Cooking and plug-in appliances, air conditioning, heat pumps, domestic hot water, pool and spa pump, and onsite solar electricity and hot water generation and storage/battery. This will push future home builders to use more efficient appliances to achieve NCC compliance. This will also close a loophole in NCC 2019 where some assessors where using onsite solar PV to offset high heating and cooling energy demand due to a low-performing building fabric.

The whole of Home rating is different from 7 star energy rating for building envelope. The whole of Home rating ranges from 1 (poor) to 100 (net zero). NCC 2022 requires 50 Whole of Home rating for apartments and 60 for houses as minimum to achieve compliance.