NatHERS Compliance
When Is a NatHERS Assessment Required?
A NatHERS assessment is usually required when a residential project needs to demonstrate thermal performance for energy compliance. The exact requirement depends on the type of project, where it is located and the approval pathway being used.
NatHERS requirements in brief
A NatHERS assessment is commonly needed for new homes, townhouses and apartments where thermal performance must be demonstrated for residential energy compliance. It may also be relevant for some alterations, additions or mixed residential projects, depending on the scope of work and jurisdiction. The safest approach is to confirm the requirement early, before the design is fully documented.
Why a NatHERS assessment may be needed
A NatHERS assessment helps show how well a home is expected to perform thermally in its local climate. It models the building fabric, glazing, shading, orientation, insulation, floor construction and other design details to estimate heating and cooling demand.
For many residential projects, this thermal performance result forms part of the energy compliance pathway. The assessment gives the project team a star rating and a set of construction commitments that need to align with the approved design and documentation.
This is why NatHERS should not be treated as a final paperwork item. It is connected to real design decisions that can affect approval, documentation and construction.
New homes
NatHERS is most commonly associated with new homes. When a new detached dwelling needs to demonstrate residential thermal performance, a NatHERS assessment is often used to model the home and show whether it meets the required star rating pathway.
The result can be affected by early design choices such as orientation, room layout, roof form, window placement, shading and construction systems. Later specification choices, including glazing and insulation, also matter.
For new homes, it is usually better to check the NatHERS pathway before the design is fully locked in. That gives the project team more flexibility if the rating needs improvement.
The practical point
A NatHERS assessment is usually triggered by the need to demonstrate residential thermal performance.
The earlier the assessment is considered, the easier it is to resolve design changes without disrupting the project.
Townhouses and multi residential projects
Townhouses, terraces and multi residential projects can also require NatHERS assessment where residential thermal performance needs to be demonstrated. These projects can be more complex because each dwelling may behave differently.
A townhouse on the end of a row may have more exposed walls than a middle dwelling. An upper level apartment may have different roof or solar exposure from a lower level apartment. Orientation, glazing and shading can also vary across the development.
For this reason, multi dwelling projects usually need careful documentation and coordination. Small differences between dwellings can affect the rating and the compliance pathway.
Apartments
Apartments may require NatHERS assessment where the approval pathway requires residential thermal performance modelling. Apartment assessments can involve additional complexity because dwellings may share walls, floors and ceilings with other conditioned or unconditioned spaces.
Apartment performance can also vary by level, orientation, glazing exposure and whether the dwelling is on a corner, below a roof or above a car park or unconditioned area.
Because of this, apartment projects benefit from early coordination between the architect, builder, developer and assessor, especially where façade design, glazing and construction systems are still being resolved.
Projects where NatHERS may be relevant
• New detached homes
• Dual occupancies and secondary dwellings
• Townhouses, terraces and villas
• Apartment developments
• Some alterations and additions
• Residential components of mixed use projects
Alterations and additions
Renovations, alterations and additions can be more variable. Some projects may not require a full NatHERS assessment, while others may need thermal performance assessment depending on the scope of work, jurisdiction and approval pathway.
For example, a major addition that changes the building fabric, glazing, roof form or conditioned floor area may have different requirements from a small internal alteration. The age of the existing home, the extent of new work and the local approval requirements can all matter.
Because renovation requirements vary, the best step is to check early. A project specific review can confirm whether NatHERS, BASIX or another energy pathway applies.
NSW projects and BASIX
In NSW, many residential projects need to address BASIX. NatHERS modelling may be used to support the thermal performance part of the BASIX pathway, depending on the project type and assessment method.
This is a common point of confusion. BASIX and NatHERS are related, but they are not the same thing. BASIX is the NSW sustainability certificate pathway. NatHERS is a thermal performance modelling method that may sit behind part of that pathway.
For a clearer comparison, see our guide to NatHERS vs BASIX.
NatHERS and Whole of Home
Current residential energy compliance may involve more than the NatHERS thermal star rating. Whole of Home looks more broadly at the dwelling’s fixed appliances, energy systems, solar and batteries where applicable.
The NatHERS assessment focuses on the building fabric and thermal demand. Whole of Home considers the wider energy profile of the home. Depending on the project location and pathway, both may be relevant.
For a more detailed distinction, see our guide to NatHERS vs Whole of Home.
Common misunderstanding
A NatHERS assessment is not only required because a home is large, expensive or architecturally complex.
It is usually required because the project needs to demonstrate residential thermal performance under the relevant approval and compliance pathway.
When should the assessment be arranged?
A NatHERS assessment should ideally be arranged before the design is fully locked in. The rating is affected by design decisions that are much easier to adjust earlier in the process.
If the assessment is left until just before lodgement, the project team may have fewer options. Improving the rating may require glazing changes, insulation upgrades, shading adjustments, roof colour changes or revisions to construction details.
Early review can reduce the risk of late design changes and help the project team understand the thermal pathway before documentation becomes too advanced.
What documents are usually needed?
The assessor needs enough information to model the home accurately. The clearer the documentation, the easier it is to produce a reliable assessment and reduce back and forth during the process.
Useful information includes:
• Site plan, floor plans, elevations and sections
• Project address and orientation
• Wall, roof, ceiling and floor construction details
• Window and door schedules, glazing and frame details
• Insulation values and locations
• Shading elements such as eaves, balconies, awnings and screens
• Roof colour, floor coverings and other relevant performance details where known
For a focused checklist, see our guide to what information is needed for a NatHERS assessment.
What happens if NatHERS is required?
If a NatHERS assessment is required, the home is modelled using accredited software. The assessor reviews the plans, enters the relevant construction and performance details, then calculates the thermal star rating for the dwelling.
If the design meets the required pathway, the assessment documentation can support the approval process. If the rating is too low, the project team may need to adjust the design or specifications before the documentation is finalised.
For more detail on the process, see our guide to what a NatHERS assessment is.
Design considerations for Australian homes
Whether NatHERS is required should be checked early because it can influence the design pathway. Orientation, glazing, shading, insulation, thermal mass, floor construction and roof colour can all affect the final result.
Project teams should avoid assuming that a design will comply simply because it uses familiar products or standard details. The NatHERS result is calculated from the full design in its specific climate zone.
The strongest pathway is usually a coordinated one: confirm whether NatHERS is required, model the design early and keep the construction documentation aligned with the assessment outcome.
Working with Certified Energy
Certified Energy provides NatHERS assessments for new homes, townhouses and multi residential projects across Australia. Our team can review the project type, location and documentation to help confirm whether NatHERS is likely to be part of the required pathway.
Where relevant, we can help connect NatHERS with related requirements including BASIX, 7 Star Rating, 6 Star NatHERS and Whole of Home.
For the broader framework, visit our NatHERS Knowledge Hub.
FAQ
When is a NatHERS assessment required?
A NatHERS assessment is commonly required when a new home, townhouse or apartment needs to demonstrate residential thermal performance for energy compliance. Requirements depend on the project type, location and approval pathway.
Do renovations require a NatHERS assessment?
Some renovations, additions or alterations may require thermal performance assessment, depending on the scope of work, jurisdiction and approval pathway. The requirement should be confirmed for the specific project.
Is NatHERS required for BASIX in NSW?
For many NSW residential projects, NatHERS modelling may be used to support the thermal performance component of the BASIX pathway. BASIX and NatHERS are related, but they are not the same thing.
Should NatHERS be done before approval?
Yes, where NatHERS is required, it should usually be completed before approval documentation is finalised. Early assessment gives the project team more time to resolve performance issues.
What documents are needed for NatHERS?
Useful documents include floor plans, elevations, sections, site orientation, construction details, insulation values, window schedules, glazing details, shading information and roof colour details where known.
