BASIX and the 7 Star NatHERS Standard

BASIX and the 7 Star NatHERS standard are closely connected in NSW residential projects because BASIX includes a thermal performance section, and NatHERS is commonly used to assess that thermal performance. For many new homes, this means the design needs to perform well enough thermally before the BASIX Certificate can be finalised for approval.

The 7 Star standard is part of a broader shift toward better residential performance. Instead of treating energy compliance as a final formality, projects now need stronger coordination between the building design, glazing, insulation, shading, orientation, construction systems and BASIX commitments.

What is the 7 Star NatHERS standard?

NatHERS stands for the Nationwide House Energy Rating Scheme. A NatHERS star rating provides information about the thermal performance of a home, including its likely heating and cooling needs. The rating is out of 10 stars and considers the home’s design, orientation, construction materials and local climate.

A 7 Star NatHERS rating generally indicates stronger thermal performance than older minimum standards. A home with better thermal performance should usually need less artificial heating and cooling to remain comfortable, assuming the modelling inputs are accurate and the home is built according to the assessed design.

How does BASIX use thermal performance?

BASIX covers water, energy use and thermal performance for NSW residential development. The thermal performance section is designed to support occupant comfort, reduce greenhouse gas emissions from artificial heating and cooling and reduce peak demand for energy infrastructure. This means thermal comfort is not only a modelling exercise. It has a direct relationship to the way the home is designed and documented.

In many projects, NatHERS modelling is used to complete or support the thermal performance part of BASIX. The assessor models the dwelling using approved software and the results inform whether the project meets the required thermal comfort outcome. If the dwelling does not perform well enough, the design may need to be adjusted before the BASIX Certificate can be finalised.

Why the standard changed

NSW increased its BASIX thermal performance standards to align with the National Construction Code 2022 changes. The NSW Planning Portal explains that the new thermal performance standards increased from a range between 5.5 and 6 Star NatHERS on average to 7 Stars, aligning with NCC 2022.

For project teams, the practical effect is that designs which may have passed more easily under older standards may now need better building fabric performance. This can affect glazing choices, insulation levels, shading strategy, ventilation assumptions and the relationship between orientation and internal comfort.

Does every BASIX project need 7 Star NatHERS?

Not every BASIX project is assessed in exactly the same way. BASIX includes different project types and assessment pathways. Some projects use NatHERS thermal comfort modelling, while others may use a different BASIX thermal comfort method depending on the project type and circumstances.

The safest approach is to confirm the project type, approval pathway and thermal comfort assessment method before assuming the exact requirement. New homes, dual occupancies, townhouses and many multi dwelling residential projects often need careful BASIX and NatHERS coordination because the thermal performance outcome can affect the final certificate.

What design choices affect the 7 Star outcome?

The 7 Star outcome is influenced by the building design. It is not only about adding one product at the end of the process. The assessor needs to model how the home is likely to perform in its climate, with its actual orientation, windows, construction systems, insulation, shading and layout.

Design items that commonly affect the NatHERS and BASIX thermal performance outcome include:

• Building orientation and solar exposure.
• Window size, location and performance.
• External shading, eaves, awnings and neighbouring overshadowing.
• Wall, roof, ceiling and floor insulation.
• Wall, roof and floor construction types.
• Skylights, roof windows and glazed doors.
• Ceiling heights and internal zoning.
• Ventilation assumptions and openings.
• Thermal mass and lightweight construction choices.
• The local climate zone used in the assessment.

Why glazing matters more under higher standards

Glazing is often one of the most sensitive parts of the assessment. Windows bring light, views and ventilation, but they can also increase heat gain in summer and heat loss in winter. Large or poorly oriented windows may make it harder for a dwelling to achieve the required thermal comfort outcome unless they are supported by shading, improved glass performance or other design measures.

This does not mean high performance homes cannot have generous glazing. It means the glazing strategy needs to be coordinated with orientation, shading, frame type, glass type, U value, SHGC and the rest of the building fabric. If the design includes large areas of glass, it is better to review BASIX and NatHERS early rather than after the design is locked in.

Why insulation and construction details matter

Insulation and construction details are central to thermal performance. The NatHERS model needs to understand the wall, roof, ceiling, floor and insulation assumptions used in the design. If those assumptions are missing or unclear, the assessor may need clarification before the rating can be finalised.

The BASIX Certificate should also align with the construction documentation. If the certificate relies on certain insulation levels or construction systems, those commitments should be reflected in the plans, specifications or construction notes so that the approved design can be built as assessed.

What happens if the project does not reach the required outcome?

If the dwelling does not meet the required thermal performance outcome, the assessor will usually identify which inputs are contributing to the result. The design team can then consider changes such as improving insulation, adjusting glazing performance, adding shading, reducing excessive heat gain, changing construction assumptions or reviewing ventilation and zoning assumptions.

The earlier this happens, the easier it is to resolve. If the assessment is left until just before lodgement, the project may need last minute design changes that are harder to coordinate with the architect, client, builder or certifier.

How to prepare for BASIX and 7 Star NatHERS

A smoother assessment starts with clear documents. Before asking for a BASIX and NatHERS review, it is helpful to provide enough information for the assessor to understand both the design and the construction assumptions.

• Site plan showing orientation and surrounding context.
• Floor plans showing room layout and floor areas.
• Elevations showing window sizes and external wall areas.
• Sections showing ceiling heights, roof form and construction build ups.
• Window schedule or glazing performance details, if available.
• Wall, roof, ceiling, floor and insulation specifications.
• Shading information, including eaves, awnings, balconies and neighbouring overshadowing where relevant.
• Known hot water, heating, cooling, ventilation, rainwater and solar details for the BASIX Certificate.

How Certified Energy can help

Certified Energy prepares BASIX Certificates and NatHERS assessments for NSW residential projects. Our team can review the available drawings, identify the likely thermal comfort pathway and coordinate BASIX and NatHERS so that the certificate, modelling assumptions and approval documentation remain aligned.

This is especially useful for custom homes, renovations, secondary dwellings, dual occupancies, townhouses and multi dwelling projects where glazing, insulation, orientation and construction details can strongly affect the final result.

Related resources

• Complete Guide to BASIX Certificates in NSW
• BASIX Certificate Service
• NatHERS Assessments
• BASIX vs NatHERS: What Is the Difference?
• What Happens If My Project Fails BASIX?

Frequently asked questions

How does BASIX connect with 7 Star NatHERS?

BASIX includes a thermal performance section for NSW residential development. The updated BASIX thermal performance standards increased to align with 7 Star NatHERS under NCC 2022, meaning many projects need stronger building fabric, glazing, insulation and shading performance than under earlier standards.

Does every BASIX project need a 7 Star NatHERS rating?

Not every BASIX project is assessed in the same way. Many new homes use NatHERS thermal comfort modelling, while some project types may use other BASIX pathways. The correct requirement depends on the project type, assessment method and approval pathway.

What does a 7 Star NatHERS rating measure?

A NatHERS star rating measures the thermal performance of a home. It estimates the heating and cooling needs of the dwelling based on design, orientation, construction materials and local climate. A higher star rating generally means the home needs less artificial heating and cooling.

What design items affect 7 Star NatHERS and BASIX?

Design items that commonly affect 7 Star NatHERS and BASIX include orientation, glazing size and performance, external shading, insulation, roof form, wall construction, floor construction, ventilation assumptions, thermal mass and the local climate zone.