- Owners and Builders
The Australian Building Codes Board (ABCB) have approved the following updates for the Chenath engine in line with the 2019 update to the NCC. These Chenath updates will improve accuracy of ratings and solve some long-standing issues with the software. The items to be updated include:
- Improve double height voids modelling
The new double height voids modelling methodology will incorporate the upper void area into the downstairs zone to become one zone. Along with improved calculation of air flow between vertical and horizontal openings between adjoining zones, this approach allows heat from windows in the upper portion of the zone to be correctly allocated to the floor of the zone.
- Improve basement zones in apartment buildings modelling
The new basement zone applies to basements below apartments (typically carparks) where the floor of the basement is in contact with the ground and the external walls are either fully or partially adjacent to earth. This will improve the precision of assessments by applying a more accurate air infiltration/ventilation rate for relatively enclosed basement car park zones in apartment buildings.
- Improve modelling of apartment corridor zone
The new corridor zone has been developed to replace interim procedures and give assessors the option to model the corridor as external to the dwelling. The new zone is un-air-conditioned and includes glazed windows and/or glazed doors on one or more external walls. This will improve the precision of assessments by applying more accurate characteristics (primarily heat transfer) to the zone ‘neighbouring’ the apartment being assessed.
- Improve edge slab insulation modelling
The improved edge slab insulation modelling results in no changes to the scratch file for Chenath calculations. Neither software tools nor assessors are required to incorporate or learn a new modelling approach, but these changes will provide better slab-on-ground heat transfer calculations as part of an assessment.
- Improve waffle pod modelling
Recent CSIRO modelling showed that waffle pod values should be adjusted to represent their true performance. The improved waffle pod modellilng does not require software tools nor assessors to incorporate or learn a new modelling approach, but the overall accuracy of an assessment will be improved.
- Addition of limestone material
Limestone and its relative thermal properties has been included in the materials database of the Chenath engine library.
These updates will be accompanied by an updated Technical Note and an updated NatHERS Universal Certificate (which is also addressing items raised in the recent review that is available here). An updated Software Accreditation Protocol is also being finalised to ensure these updates are rolled out uniformly in all tools.
Split heating and cooling loads
The ABCB recently announced maximum heating and cooling load limits for the NatHERS pathways in the NCC, to support improving the performance of new homes in Australia. The NatHERS Administrator is currently working through the implementation of this amendment and advice on changes to assessments will be provided to assessors before modifications become live. There will also be a transition period for these requirements from 1 May 2019 until 1 May 2020 where the current requirements (NCC 2016) will still be accepted. For more information about the work already undertaken on split heating and cooling load limits, have a look at the ABCB report.