NatHERS Foundations
NatHERS works by modelling how a proposed home design is expected to perform in its local climate. The assessment turns design information into a thermal star rating that helps show how much heating and cooling the home may need.
NatHERS works by using accredited software to model a home’s design, construction and local climate. The software estimates the heating and cooling energy needed to keep the home comfortable across the year. The result is a thermal star rating out of 10, where a higher rating generally means the home should need less heating and cooling.
A NatHERS assessment starts with the design documentation. The assessor reviews the plans, elevations, sections and specifications to understand how the home is arranged, what it is made from and how it responds to its site.
The home is then entered into accredited NatHERS software. The model includes information such as orientation, room layout, construction systems, insulation, glazing, shading, roof colour, floor type and climate zone.
The software calculates the predicted heating and cooling loads for the home. These loads are then translated into a NatHERS thermal star rating, which can be used to support residential energy compliance and design decision making.
NatHERS does not simply check whether a home has a certain product or insulation value. It models how the whole dwelling is expected to behave thermally. The assessment considers how heat enters, leaves and moves through the home in relation to the local climate.
This means the same feature can have different effects depending on the design. A window may improve winter solar access in one room, increase summer heat gain in another or contribute to heat loss in a cooler climate. Insulation may improve one part of the home but still need to be balanced with glazing, shading and construction details.
The purpose of the model is to estimate how much heating and cooling the home needs to stay within comfortable temperature ranges. The lower the predicted need for heating and cooling, the stronger the thermal performance outcome is likely to be.
NatHERS is not just asking whether the home has insulation, glazing or shading.
It is asking how all those features work together in the specific design, on the specific site, in the specific climate.
A NatHERS result depends on the quality and completeness of the information provided. Clear documentation helps the assessor model the home accurately and reduce the need for assumptions.
• Site location and NatHERS climate zone
• Floor plans, elevations and sections
• Orientation and room layout
• Wall, roof, ceiling and floor construction
• Insulation values and construction assemblies
• Window and door sizes, frame types and glazing performance
• Eaves, awnings, balconies and other shading elements
• Roof colour, floor coverings and other thermal performance details
If these details are incomplete or inconsistent, the assessor may need clarification before the rating can be finalised. This is why NatHERS is easier to manage when the project documentation is coordinated before submission.
The NatHERS software estimates annual heating and cooling loads for the dwelling. These loads are influenced by the home’s orientation, fabric performance, solar exposure, shading, climate data and internal layout.
The calculated heating and cooling demand is converted into a star rating on the NatHERS scale. A higher star rating indicates that the home is expected to need less heating and cooling to stay comfortable in its climate.
This is why the rating is a performance result, not a simple checklist. Two homes can use similar products but achieve different star ratings because their orientation, layout, glazing, shading, climate and construction details are different.
NatHERS works with local climate data because Australian homes face very different conditions. A home in a hot humid climate, a cool temperate climate and an alpine climate will not have the same heating and cooling needs.
The climate zone affects how the home is modelled and which design features become more important. In some locations, solar control and cooling load reduction may dominate. In others, insulation, heat retention and winter solar access may have a stronger influence.
For a deeper explanation, see our guide to NatHERS climate zones.
The NatHERS thermal star rating focuses on the heating and cooling needs created by the home’s design and building fabric.
It does not, by itself, assess the full operational energy profile of the home.
Broader system and appliance energy use is considered through Whole of Home where applicable.
For many new homes, NatHERS is used to demonstrate the thermal performance component of residential energy compliance. The required rating depends on the project type, location, approval pathway and applicable requirements.
In many current projects, the NatHERS pathway is closely connected to 7 Star Rating requirements. In NSW, NatHERS modelling may also support the thermal performance part of BASIX.
Because NatHERS affects compliance documentation, design decisions should be aligned with the assessment. Late changes to glazing, insulation, shading, roof colour or construction details can affect the rating and may require documentation updates.
NatHERS works best when it is considered during design rather than treated as a final compliance step. Early modelling can help identify whether the home is likely to meet the required rating and which design factors are influencing the result.
This can be especially useful for homes with large glazing areas, challenging orientations, lightweight construction, raked ceilings, exposed floors or complex shading conditions. These features are not automatically a problem, but they need to be understood in the thermal model.
A good NatHERS outcome usually comes from coordinated design. Orientation, glazing, insulation, shading, roof colour and construction systems need to work together rather than being resolved separately at the end.
Certified Energy provides NatHERS assessments for new homes, townhouses and multi residential projects across Australia. Our team reviews the project documentation, models the design and helps identify the thermal performance pathway for the project.
Where needed, we can help project teams understand how the rating is affected by climate zone, orientation, glazing, insulation, shading, roof colour and construction details. We can also help connect the assessment with related requirements such as NatHERS, BASIX, 7 Star Rating and Whole of Home.
For the broader overview, visit our NatHERS Knowledge Hub.
NatHERS works by modelling a home design in accredited software to estimate heating and cooling needs in the local climate. The result is a thermal star rating out of 10.
What information is used in a NatHERS assessment?The assessment uses information such as plans, orientation, climate zone, insulation, glazing, shading, construction materials, roof colour, floor type and other building fabric details.
Does NatHERS assess the design or the finished home?For new homes, NatHERS commonly assesses the proposed design before construction. The result is based on the documentation and specifications provided for the project.
Why can two similar homes get different NatHERS ratings?Two homes can receive different ratings because orientation, glazing, shading, insulation, construction details, climate zone and layout can all affect heating and cooling demand.
Does NatHERS include Whole of Home?The NatHERS thermal star rating focuses on heating and cooling needs created by the home’s design and fabric. Whole of Home looks more broadly at major energy use, systems, solar and batteries where applicable.