NatHERS Assessment involves modelling a dwelling in a NatHERS certified thermal simulation software package, defining site conditions and, thermal simulation of the model. In performing a NatHERS assessment, certain established guidelines and protocols must be followed in order to preserve consistency and fair comparison of different dwellings with different climate conditions and when a different computer software is used for NatHERS assessment.

NatHERS Assessment is principally based on the concept of thermal comfort of a habitable zone in a residential space. NatHERS scheme defines a zone’s thermal conditions in which the occupants of that area will feel comfortable with regular clothing. Based on the climate zone of the development these conditions are slightly different. The building is modelled with a computer software package and the amount of heat that must be added or removed from each zone of the dwelling to make it comfortable for occupation is calculated. The heating and cooling loads are then represented in the form of NatHERS ratings which is in the form of star bands from 0 to 10 stars.

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NatHERS Assessment Process

NatHERS assessment is conducted by a trained and accredited NatHERS assessor, who uses a computer software program to simulate the energy usage of the home based on its design, materials, and location. The simulation takes into account factors such as the orientation of the home, the type and amount of insulation, the type of windows and doors, and the heating and cooling systems.

The NatHERS assessment process typically includes the following steps:

  1. Initial consultation: The assessor must communicate with the homeowner or builder to discuss the design and construction of the home, and to gather information about the materials and systems that will be used.
  2. Data input: The assessor will enter the information gathered during the consultation into the NatHERS software program. This includes details such as the size and layout of the home, the type and R-value of insulation, the type of windows and doors, and the type and size of heating and cooling systems.
  3. Simulation: The software program will use the inputted data to simulate the energy usage of the home. It will calculate the amount of heat that will be gained or lost through the walls, roof, floor, and windows, and the amount of energy that will be required for heating and cooling.
  4. Report: The assessor will provide the homeowner or builder with a report that includes the NatHERS star rating of the home, as well as information on the energy usage and energy savings potential. The report will also include recommendations for improving the energy efficiency of the home.
  5. Compliance: Once the assessment is done, the builder or homeowner can use the report to demonstrate compliance with the energy efficiency regulations in their area.

Before a NatHERS assessment can be performed the following set of information must be determined by the NatHERS assessor as a minimum required;
Site Information: Area, Orientation of true north, Climate zone (post code or address), Overshadowing elements like adjacent buildings, Lot and DP number of the development site, areas of landscape, total area of roof.
Dwelling Information: Complete geometry, layout and usage of each room, construction materials for all external and internal walls, floors, ceilings and roofs, Geometry and specifications of all shading elements and eaves

The dwelling is then modelled by the NatHERS assessor to introduce the building to the computer software package to perform a NatHERS assessment.
Based on the performance of the building a certain NatHERS rating is determined from the NatHERS assessment and allocated to the dwelling in form of a star rating.

In NSW, the heating and cooling loads of the assessment are entered in the BASIX online tool instead of the star rating so those are the numeric outputs of a NatHERS assessment in NSW.

Building thermal model will be uploaded into the Government HSTAR portal and a set of documents are produced by the government portal. These documents are then used for Development Application submission as well as stamped plans and the BASIX certificate if applicable.