Nationwide House Energy Rating Scheme
NatHERS is short for Nationwide House Energy Rating Scheme which is a national government regulatory framework that sets the performance standards for building thermal assessment computer software packages to rate the thermal comfort performance of dwellings across Australia. A certain NatHERS star rating is required according to the BCA to show compliance with the requirements of the code.
By provision of a national regulatory framework NatHERS delivers consistent and reliable energy efficiency ratings for a dwelling regardless of the software package for the assessment and the climate conditions of the development. NatHERS also sets the standards for training provider organizations and assessment procedures to train and test qualified accredited assessors to work with NatHERS thermal simulation software tools.
A NatHERS certificate is what the government HStar portal creates to certify the outcome of a thermal modeling by an accredited assessor. The certificate is in form of a multi page PDF file which summarises the most important information about the building, its overall performance and the performance requirements of each relevant element of the building. The NatHERS certificate can be downloaded from the government portal individually for each dwelling in a multi unit development and there is also an option to download a summary certificate which list the performance figures of all units of the development.
Australian Government introduced NatHERS regulatory framework to provide legal and technical guidelines for computer thermal simulation packages for residential developments to deliver consistent and auditable results and to be accredited in a transparent and fair fashion. It requires computer software packages to simulate how heat enters and leaves the the residential spaces of a dwelling based on the standardised building material thermal properties and normal behavioral patterns of regular families in operating the space. NatHERS currently recognizes AccuRate, FirstRate and BERS Pro as the accredited thermal simulation software packages.
By defining guidelines for training and evaluation of NatHERS assessors, NatHERS scheme ascertains professional and educated use of thermal simulation software packages. These NatHERS accredited assessors can use and report a dwelling's thermal loads by use of a NatHERS accredited computer software. Currently the only organizations which are accredited to provide training and certification services for NatHERS accredited assessors are Association of Building Sustainability Assessors or ABSA which trains, test and audits the performance of ABSA Accredited Assessors in all Australian states and Building Designer Association of Victoria or BDAV which perform similar task for BDAV Accredited Assessors nationwide.
NatHERS Simulation Procedures
Certain themperature and environmental conditions are required in a building space for human beings to feel comfortable. NatHERS defines inside thermal conditions of a dwelling which brings comfort to the occupants of the dwelling. NatHERS thermal simulation packages then measure the amount of heat that must be added or removed from each zone of the house in order to keep the house comfortable throughout the year. Standard materials referenced in the NatHERS accredited software packages are used to model the geometry of the building and its orientation, climate zone and exposure conditions introduced to the software. A NatHERS star rating of 0 to 10 is then assigned to each zone as well as the whole dwelling which must be under a certain limit to satisfy the energy efficiency requirements of that dwelling based on the BCA and local and state government codes and regulations.