How does NatHERS software work?
A NatHERS rating depends on how much cooling or heating a "standard family" may need to stay comfortable during a typical year. The computer simulates how heat enters the dwelling or escapes every hour of every day, assuming the "standard family" opens and closes windows and any blinds or awnings to make best use of the local climate.
NatHERS rules
Each software package uses the same:
- hourly weather records
- occupancy settings for a "standard family"
- the star rating scale for the home's location.
Weather records
Weather data is compiled from Bureau of Meteorology records and includes air temperature, humidity, solar radiation and wind speed and direction.
Occupancy settings
NatHERS rules tell the software what rooms the "standard family" uses at different times of day and the temperatures that make them want to cool or heat the rooms. The temperatures vary from climate to climate because studies show that people adapt to their local conditions.
Second generation software can also allow for the cooling effects of natural air movement or ceiling fans.
Star rating scale
- Heating and cooling calculations - The software calculates the family's annual cooling and heating needs, which are compared to the size of the dwelling and the NatHERS scale to set the star rating.
- Rating by climate - NatHERS star rating scales recognise that some climates are more demanding than others. 5 stars can be achieved in Hobart, for example, with annual heating and cooling needs four time higher than those allowed for 5 stars in Sydney.