NatHERS is the nationwide house energy rating scheme which provides homes rated with the FirstRate5 software a star rating out of ten. The star rating is based upon an estimate of a homes potential heating and cooling energy use. A star rating will range from a score of 0 to 10, with 10 being the highest score achievable. A 10 star rating is considered that there is no need for any heating or cooling systems to be installed as the house alone will be thermally comfortable for its occupants.
A NatHERS rating will determine the thermal comfort of an existing or proposed dwelling. This can lead to a greater awareness of the thermal performance of the building, thus leading to a smarter and more optimal design choices which in turn will help with greater savings on energy bills.
The NatHERS star rating is based upon the homes house design, its construction materials and the climate in which it is being built also take into account how the areas of the dwelling which are expected to be used. It does not however take into account electrical appliances apart from the installation of ceiling fans and how it affects air flow.
A NatHERS accredited assessor simulates a model of the residential dwelling which is to be accessed whilst the following data is added
The software will then be able to model the amount of heating and cooling will be required to keep the occupants comfortable. It achieves this by simulating how the local climate heats and cools the house every hour of everyday of the year.
The NatHERS software used for the rating calculates the star rating by calculating the internal temperatures and only once the temperature falls outside the comfortable range. It assumes that the occupants use the house effectively buy opening and closing any doors or windows at desirable times and utilise the effectiveness of any blinds and or awnings, before any use of any heating and or cooling systems come into play. The outcome of the star rating is then derived from the total estimated annual heating and cooling requirements of the dwelling, then a star rating out of 10 is determined.
Australia has a diverse climate, so NatHERS has divided Australia into 69 different climate zones.
The effects of these various climate zones come into play when modelling the dwelling, doing so by determining the heating and cooling requirements.
Air temperature, humidity, solar radiation and wind and speed direction information compiled from the past 25 years of the Bureau of Meteorology are used to determined each specific climate zone. The software then uses these weather files to determine the impact of the weather on the buildings internal temperature. This calculation is done for every hour over a 12 month period.
When using the NatHERS software to model a dwelling it is also based upon assumptions of how the occupants will be using the home. It determines which rooms will be used at a particular time of day. Whether its use will be daytime, nighttime, and whether the space is either conditioned and or unconditioned. The rating software also takes into account the heat energy generated by the occupants and the heat generated from cooking, lighting and electrical appliances.
For more detailed information on how to achieve a energy efficient and environmentally sustainable home, see www.yourhome.gov.au
For more detailed information on the Nationwide House Energy Rating Scheme (NatHERS) please see www.nathers.gov.au
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