Knowledge · Planning
BASIX and energy efficiency,
compliance that starts in the design.
A new Australian home has to meet sustainability and energy-efficiency requirements, the NSW BASIX commitments and the national NCC energy provisions, before it can be approved and occupied. This reference explains what builders must comply with, where it sits in design and approval, and what the commitments mean on site. Requirements and star ratings change, so it states no figures and routes them to the current source. General information, not compliance advice.
01 / Overview
Two layers of sustainability compliance
A new home in Australia has to satisfy sustainability and energy-efficiency requirements before it can be approved and, at the end, occupied. For a builder those requirements come in two overlapping layers. In New South Wales, BASIX, the Building Sustainability Index, sets sustainability commitments for new residential development across areas that have included water, thermal comfort and energy. Nationally, the energy-efficiency provisions of the National Construction Code set requirements for the energy performance of new homes, adopted through each state and territory, with the NatHERS star-rating framework as one recognised way to demonstrate the thermal side of that compliance.
This is a distinctly Australian area, and it is one where the detail moves. Required star ratings and BASIX targets have been strengthened over time, and jurisdictions adopt changes on their own timing, so this reference deliberately states no numbers, no star rating, no target, no threshold, and directs every specific to the current source. What it does explain is the shape: what the requirements are, where they sit in the job, and what they mean once the trades are on site. Everything here is general information, not legal, planning or compliance advice, so confirm the current requirements for the specific jurisdiction and job.
Why it matters
The operator’s observation is that energy compliance is cheap in the design and expensive on site. The insulation, glazing and services that hit the required performance are decisions best made while the home is still on paper and the allowance is being set. Discovered late, as a substitution that dropped the home below its assessed rating or a commitment that never reached the trades, the same requirement becomes rework and an unfunded variation. The compliance is not the hard part; the hard part is carrying the commitments faithfully from the certificate to the completed home.
02 / What applies
What builders must comply with
Three things a builder needs to hold in view. Which of them applies depends on where the home is built, so the first job is knowing which layers are in force for the specific job.
BASIX (New South Wales)
The Building Sustainability Index is the NSW planning tool that assesses a new home’s sustainability, across areas that have included water, thermal comfort and energy. A BASIX certificate sets the commitments the design must meet, and it is required as part of the approval for new residential development. It is a NSW instrument, so it applies to homes built in New South Wales.
NCC energy efficiency (national)
The National Construction Code sets energy-efficiency requirements for new homes across Australia, adopted through each state and territory. They cover the building fabric and services, and a home has to demonstrate compliance one way or another before it can be approved and, ultimately, occupied. This is the national layer that applies everywhere the NCC is in force.
NatHERS star rating
The Nationwide House Energy Rating Scheme expresses a home’s modelled thermal performance as a star rating. It is one of the recognised ways to demonstrate the thermal side of NCC energy-efficiency compliance, produced by accredited assessors modelling the design. The required rating is set by the code and changes over time, so it is confirmed against the current source rather than assumed.
For a home in New South Wales, BASIX and the NCC energy provisions work together, and a NatHERS assessment can feed both. For a home elsewhere, the NCC energy-efficiency requirements apply through that jurisdiction’s framework without BASIX. The practical first step is therefore jurisdictional: establish which layers are in force where the home is built, and confirm the current requirements of each, rather than assume the process from the last job or the last state carries over.
03 / Where it fits
Where it sits in design and approval
Sustainability and energy compliance is a design input, not a late compliance step. In New South Wales a BASIX certificate is required as part of the approval for new residential development, so it is produced as the design develops and lodged with the application, whether the job takes the development application or the complying development pathway. The NCC energy-efficiency compliance is part of demonstrating the design meets the building requirements before work can start. Both sit inside the approvals pathway mapped in the building approvals hub, and both influence the design and the price early because they drive the fabric and the services.
From there the commitments have to travel into the documents the job is actually built from. The insulation values, glazing performance, hot water and heating systems and, under BASIX, the water fixtures and any landscaping commitments belong in the specification and the client selections, so the trades build to them and the certifier can verify them. And because the commitments carry cost, they belong in the estimate and the feasibility before a price is fixed. The contract then sits over the top, with the sustainability commitments part of the documented scope rather than an assumption. Compliance verified through the job feeds the final occupation certificate.
04 / On site
What the commitments mean on site
The certificate is a scope document. Everything it assumed about the fabric and the services is something the finished home actually has to have, verified by the certifier.
The building fabric
Insulation levels, glazing performance, wall and roof construction and sealing are where the thermal commitments become real. What the assessment assumed has to be what is actually built, because the rating was modelled on specific materials and specifications, not on whatever is convenient on the day.
Services and fixtures
Hot water systems, heating and cooling, lighting and, under BASIX, water fixtures and sometimes rainwater or landscaping commitments, all flow from the certificate. Each is a selection that has to match what was committed, so the commitments belong in the specification and the client selections, not in someone’s memory.
Verification and certification
The certifier checks that the home is built to the commitments, and compliance feeds into the approvals and ultimately the occupation certificate. A substitution that lowers performance below what was assessed is a compliance problem discovered late, when it is most expensive to fix.
The single most common way this goes wrong is substitution. A rating or a certificate is modelled on specific materials and specifications, so swapping the specified glazing, insulation or hot water system for a cheaper equivalent can quietly drop the home below the assessed performance. Any substitution to a fabric or services item the assessment relied on has to be re-checked against the commitment before it goes in, not discovered at the final inspection. The commitments built faithfully are routine; the commitments quietly eroded by convenient substitutions are a compliance problem found at the worst possible time.
05 / Australian considerations
The instruments, the ratings and the moving target
The points below are labelled by evidence class and each carries a confirm-for-your-jurisdiction caveat. This page states no figures, and none should be inferred from it. None of this is compliance advice.
- Legislation. BASIX is a New South Wales instrument under the NSW planning framework. A BASIX certificate sets the sustainability commitments for a new home and is required as part of the approval for new residential development in NSW. The areas it covers and the targets it sets are set by that framework and have changed over time, so confirm the current BASIX requirements through the NSW planning source.
- Industry standard. The energy-efficiency provisions of the National Construction Code apply to new homes across Australia, adopted through each state and territory. They cover the building fabric and services, and a home must demonstrate compliance before approval. The NCC is updated periodically, and the energy provisions have been strengthened over successive editions, so the applicable edition and requirement are confirmed for each job.
- Industry standard. The Nationwide House Energy Rating Scheme (NatHERS) expresses modelled thermal performance as a star rating and is one recognised way to demonstrate the thermal side of NCC energy-efficiency compliance. The required minimum rating is set by the code and has been raised over time. This page quotes no rating; the current required figure is confirmed against the current NatHERS and NCC source.
- Government guidance. The NSW planning authority administers BASIX and the online certificate process; the Australian Building Codes Board maintains the NCC; and the NatHERS scheme accredits assessors and software. These are the sources a builder confirms the current requirements against, per job, rather than relying on a previous project.
- Professional recommendation. Because the requirements move and are jurisdiction-specific, the BASIX certificate and the energy assessment for a home are produced by the appropriate assessor for the current requirements, and any change to the fabric or services is checked back against them. Treating an old certificate or a previous job’s standard as still current is a genuine risk when requirements have recently been strengthened.
06 / Common mistakes
Where energy compliance goes wrong
Almost every one of these is a document or substitution problem rather than a construction one. The requirement was clear; the commitment did not survive the journey from certificate to completed home.
Treating the certificate as paperwork
A BASIX certificate or an energy assessment is a set of binding commitments, not a form to file. Every insulation value, glazing spec and fixture it assumes is something the finished home has to actually have, and building to a lesser spec is a compliance failure the certifier can catch.
Substituting materials without re-checking
Swapping glazing, insulation or a hot water system for a cheaper equivalent can quietly drop the home below the assessed performance. Any substitution to a fabric or services item the assessment relied on needs to be re-checked against the commitment before it goes in.
Leaving the commitments out of the specification
When the sustainability commitments live only on the certificate and never make it into the specification and the client selections, the trades build to the drawings and the commitments get missed. The certificate’s requirements have to become part of the documented scope the job is built from.
Pricing before the assessment
The insulation, glazing and services needed to hit the required performance carry real cost. Pricing a home before the energy assessment is done risks an allowance that cannot buy compliance, turning a compliance requirement into an unfunded variation.
Assuming last year’s requirements still apply
Energy-efficiency requirements and required ratings are periodically strengthened. Carrying an old assumption, or an old certificate, into a new job can mean designing to a standard that no longer applies. The current requirement is confirmed against the current source for each job.
Assuming NSW rules apply interstate, or vice versa
BASIX is a NSW instrument; the NCC energy provisions are national but administered through each jurisdiction. A builder who assumes the NSW BASIX process applies in another state, or that a non-NSW process covers a NSW job, can misjudge what compliance actually requires.
07 / Best practice
How experienced builders handle it
The builders who never have a compliance scramble at handover treat the certificate as a scope document from the start. They get the BASIX certificate and the energy assessment done as the design develops, price the fabric and services needed to meet them before fixing a number, and carry every commitment into the specification and the client selections so the trades build to them by default. When a substitution comes up, and it always does, they check it against the commitment before it goes in, rather than after the certifier flags it. And they confirm the current requirements for each job rather than carrying an old certificate or a previous standard into new work, because the requirements move. None of this is sophisticated; it is document discipline applied to a requirement that punishes its absence late and expensively.
Where software fits the workflow
Energy compliance survives or fails on whether the commitments reach the people building the home. In VIABUILD the sustainability commitments can live in the same specification and client selections the job is built from, on one understanding of the job, so a specified glazing or insulation value is visible to the trade fitting it and a substitution is a change made against a known commitment rather than a quiet swap. The assessor still sets the requirement and the certifier still verifies it; the software keeps the commitment from going missing between the certificate and the wall.
08 / FAQ
Common questions.
BASIX, the Building Sustainability Index, is a New South Wales planning tool that assesses the sustainability of a new home and sets the commitments the design has to meet, across areas that have included water, thermal comfort and energy. A BASIX certificate is produced for the proposal and forms part of what is required for the approval of new residential development in NSW, and the commitments on it, things like insulation, glazing, hot water and water-efficient fixtures, become obligations the finished home must satisfy. It is a NSW instrument, so it applies to homes built in New South Wales, while the national energy-efficiency layer comes from the National Construction Code. The specific targets and requirements change over time, so this page states none and directs you to confirm the current BASIX requirements through the NSW planning source. General information, not compliance advice.
They are two layers that overlap. BASIX is a New South Wales sustainability instrument that sets commitments across water, thermal comfort and energy for new homes in NSW, and sits within the planning approval. The National Construction Code energy-efficiency provisions are the national requirements for the energy performance of new homes, adopted through each state and territory, and they sit within the building side of compliance. For a NSW home the two work together; for a home in another state the NCC provisions apply through that jurisdiction’s framework without BASIX. A builder needs to know which layers apply where they are building, because the process and the documentation differ. Confirm the current requirements for the specific jurisdiction.
The Nationwide House Energy Rating Scheme (NatHERS) expresses a home’s modelled thermal performance as a star rating, produced by an accredited assessor who models the design’s fabric and orientation. It is one of the recognised ways to demonstrate the thermal-performance side of the NCC energy-efficiency requirements, and it can also feed the thermal comfort element of a BASIX assessment. The higher the rating, the better the modelled thermal performance. The minimum rating required is set by the code and has been strengthened over time, so this page quotes no number; the current required rating is confirmed against the current NatHERS and NCC source for the job. The important operational point is that the rating is modelled on specific materials and specifications, so the home has to be built to what was assessed.
It sits inside design and approval, not as an afterthought at the end. In New South Wales a BASIX certificate is required as part of the approval for new residential development, so it has to be produced as the design is developed and lodged with the application, whether the job goes down the development application or the complying development pathway. The NCC energy-efficiency compliance is part of demonstrating the design meets the building requirements. Because the commitments shape the fabric and services, they influence the design and the price early, and because the certifier checks them, they carry through to the inspections and ultimately the occupation certificate. Treating them as a late compliance step rather than a design input is how they turn into rework.
It means the commitments on the certificate have to be built, exactly. The insulation values, glazing performance, hot water and heating or cooling systems, and the water fixtures the assessment assumed are the ones the finished home has to have, because the certificate was produced on those specifics. The practical risk is substitution: swapping a specified item for a cheaper equivalent can drop the home below the assessed performance and create a compliance problem the certifier catches late. The reliable approach is to carry the commitments into the specification and the client selections so the trades build to them, and to re-check any substitution against the commitment before it goes in. On site, in short, the certificate is a scope document, not a filing document.
Yes, and this is one of the reasons the page states no figures. The NCC is updated periodically and the energy-efficiency requirements, including required star ratings, have been strengthened over successive editions, with jurisdictions adopting changes on their own timing. BASIX targets are likewise updated over time. What this means for a builder is that the requirement for a new job is confirmed against the current source at the time, rather than carried over from a previous project or an old certificate. Designing or pricing to a superseded standard is a real risk when requirements have recently moved. Confirm the current NCC and BASIX requirements for each job.
09 / Terms
Glossary for this topic
BASIX (the NSW Building Sustainability Index), BASIX certificate (the document setting a NSW home’s sustainability commitments), NCC energy efficiency (the National Construction Code’s energy provisions for new homes), NatHERS (the Nationwide House Energy Rating Scheme), star rating (the expression of modelled thermal performance under NatHERS), thermal performance (how well the building fabric moderates heating and cooling loads), building fabric (insulation, glazing, walls, roof and sealing), commitment (a requirement on the certificate the finished home must meet), accredited assessor (the person who models and certifies the rating). The wider vocabulary lives in the construction glossary.
The natural next reads are the building approvals hub for the pathway this compliance sits inside, and specifications for how the commitments become the scope the job is built from.
10 / Keep reading
Related knowledge, guides and features
11 / Further reading
Primary sources
- NSW Planning Portal , for the current BASIX requirements and the certificate process. This page states no figures; confirm the current targets here.
- Australian Building Codes Board , for the current National Construction Code energy-efficiency provisions and the edition in force in your jurisdiction.
- Nationwide House Energy Rating Scheme , for the star-rating framework, accredited assessors and the current required rating.
- Your certifier, assessor and the relevant state or territory authority, for how the requirements apply to the specific home.
Carry the commitments from the certificate to the wall.
VIABUILD can hold the sustainability commitments in the same specification and selections the job is built from, on one understanding of the job, so a specified fabric or services item is visible to the trade fitting it and a substitution is a deliberate change, with the assessor and certifier still setting and verifying the requirement.