A NatHERS star rating and detailed Whole of Home calulcation for your extension.
Extending a home can be an opporuntiy to increase the thermal performance of a building, but it can also be a challenge to meeting compliance.
Under a NatHERS assessment pathway, typically the entire home, including existing fabric not part of the extension works, will need to be assessed. This means we need a clear pciture of the existing conditions - what insualtion is present, the glazing specification of existing windows, details of existing heating and cooling systems. This is all critical to the accurate assessment of the bnew thermal envelope.
In some cases, where existing building fabric is proving to be an obstacle to compliace, a elemental provisions pathway is reccomended (click here to find out more). This pathway assesses seperate components of building fabirc against benchmark values as set out in the ABCB Housing Provisions. This results in less flexibility in the specification to the thermal envelope, but it will allow you to only consider the new additions for compliance, rather than the existing fabric.
This process will vary job to job. But to ensure you don't get caught out, ensure that an accredited assessor and building surveyor are engeged early, so the best pathway to a compliant project can be mapped out. Leaving this too late can be costly.
Energy efficiency compliance requirements as per the 2025 NCC - H6P1 (NatHERS pathway) and H6P2 (Whole of Home), including the issue of required certificates.
Additional advice regarding optimisation of the thermal envelope, guidance regarding products available on the Australian Market, energy efficiecny of the proposed dwelling.
Stage 1 — Project Initiation. Studio Bun will review your drawings of the existing dwelling and the proposed works, identify the NCC 2025 requirements that apply to your extension, and issue a propsed pathway for compliance along with a fee covering the entire process.
Stage 2 — Preliminary Assessment & Design Advice. The proposed design and is modelled, adjusted and assessed for compliance. A Preliminary Assessment Report with the requirement for compliance with both the NathHERS rating and Whole of Home assessment. Included in this stage is the identification of key challenges to the project, and proposed improvements to meet exceed compliance, or to reduce cost to achieve minium compliance.
Stage 3 — Design Iteration & Optimisation. Between the preliminary assessment and finalisation of the report, we allow for minor changes and tweaks to the design, and a meeting to review the recommendations proposed in the Preliminary report. From here, we can focus on cost efficiency of the design, or optimisation of performace, as the project requires.
Stage 4 — Certification & Final Reporting. Once the final specification and design has been documented, a final star rating and whole of home calculation will be detemined, and certificates issued.
Further changes after certificate issue will be changed at an additional rate, depending on the size and scope fo the change.
Thermal modelling of the proposed dwelling.
Preliminary report outlining requirements for compliance with NatHERS and Whole of Home assessments.
Pathways for cost reduction or optimisation if applicable.
two rounds of minor changes between preliminary report and finalisation.
A final asessement report.
NatHERS and Whole of home complaince certificates.
A few items sit outside this scope and can be quoted separately:
new dwellings (see the NatHERS for single dwellings service)
Assessments of calass 2 apartment buildings with centralised services
design changes beyond two rounds
blower door / air permeability testing
acoustic, daylight or mechanical assessments
BESS reports or SDAs
stormwater management (available as its own service)
This service assumes an alteration or addition to a Class 1 residential building in Victoria under NCC 2025, with PDF drawings of the existing dwelling and proposed works sufficiently complete for modelling.
Studio Bun offers fixed sum packages for NatHERS assessments, priced on the complexity of the build and extent of the works.
Contact us for a quote.
Does my extension need a NatHERS assessment?
It depends on the scale of the works and what your building surveyor or council requires. Larger extensions are generally assessed against the NCC 2025 energy efficiency requirements, and a NatHERS assessment is the most common way to demonstrate compliance. Send us your drawings and we will be able to confirm the applicable pathway as the first step.
Do you assess the whole house or just the extension?
The extension is the focus, but it can't be modelled in isolation. The existing fabric it connects to affects the result. The works are modelled alongside the relevant parts of the existing home.
Can an extension improve the performance of my existing home?
Absolutely, yes. An extension changes how the whole home holds temperature, and the works are a natural moment to address glazing, insulation and sealing in the existing fabric.
What do you need from me to start?
Drawings of the existing dwelling and the proposed works in PDF, your specifications, and the project brief. If anything's missing for modelling, we willflag it before we go further.
Send through your drawings for a fixed-fee quote.
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