The National Construction Code (NCC formally known as the BCA) requires all new residential dwellings in Australia (Except NSW)* to achieve a minimum of a 6 Star Rating using the Nationwide House Energy Rating Scheme (NatHERS), approved software.
This NatHERS software estimates the internal temperature in each room of a dwelling for each hour of the year based on assumptions about occupant behaviour, information about the structure and specification of the dwelling and standard weather data for the dwelling's location.
The internal temperature is compared against a comfortable temperature range and occupancy pattern to estimate the annual heating and cooling loads per square metre of floor area to keep the temperature within the comfort range. The loads are adjusted and converted into a star rating between 0 and 10. A 10 star home is unlikely to need any artificial cooling or heating to maintain comfortable internal conditions, whereas a 0 star home would offer virtually no protection from the external temperature.
TheNCCsets a minimum acceptable thermal performance rating by specifying a minimum 6 star rating for all new residential dwellings.
*NSW remains the only State or Territory which is exempted from this requirement as they use individual Heating and Cooling targets that must be met in lieu of achieving a 6 star rating.