A new residential dwelling in New South Wales generally requires a BASIX assessment before the development application or complying development certificate documentation can be lodged.
For a new home, the assessment considers the complete proposed dwelling. This includes its water measures, energy systems, thermal performance and construction materials. The information entered into BASIX must correspond with the architectural plans, glazing, insulation, services and other specifications intended for approval and construction.
The best time to begin is when the design is sufficiently developed to provide reliable dimensions and construction information, but before the approval drawings are fully locked. This leaves time to resolve performance issues without introducing avoidable late-stage design changes.
In Brief
What Does a New Home Need for BASIX?
A new home requires a project-specific BASIX assessment covering water, energy, thermal performance and construction materials. The thermal component may use the BASIX DIY Method, NatHERS Simulation Method or Passive House Standard pathway, depending on the dwelling and design. Once the applicable requirements are satisfied, the BASIX Certificate and any supporting thermal-assessment documentation must remain consistent with the plans submitted for approval.
Which New Residential Projects Require BASIX?
BASIX applies to new residential development throughout NSW. The assessment structure depends on the dwelling type and the way the development is arranged.
New-home applications can include:
- detached houses
- attached houses
- secondary dwellings and new granny flats
- dual occupancies
- townhouses and villas
- residential flat buildings
- shop-top housing and other residential components of mixed-use development
- new dwellings created through qualifying residential development pathways
The BASIX tool separates single-dwelling and multi-dwelling applications. A detached house and a townhouse development therefore do not necessarily use the same project setup, modelling scope or documentation process.
Read when BASIX is required in NSW →
New-Home BASIX Requirements at a Glance
| Assessment Area | What Is Reviewed |
|---|---|
| Water | Fixtures, rainwater storage, connected roof catchment, reuse connections, landscaping, pools, spas and shared water systems where relevant. |
| Thermal performance | Building geometry, orientation, glazing, shading, insulation, walls, roofs, floors, thermal bridging and modelled heating and cooling performance. |
| Energy | Hot water, heating, cooling, ventilation, lighting, cooking, photovoltaic systems and other nominated operational-energy measures. |
| Materials | Construction and glazing materials used to calculate and report the embodied emissions associated with the proposed development. |
| Approval documentation | The BASIX Certificate, architectural plans and any NatHERS or other supporting thermal documentation must describe the same proposed dwelling. |
The New-Home Assessment Boundary
The Complete Proposed Dwelling Is Assessed as One Coordinated Design
Unlike an alteration or addition, a new-home assessment does not begin with an existing building that is partly retained. The external walls, roof, floors, glazing, insulation and services are all proposed as part of the new development.
This creates more opportunity to coordinate orientation, glazing, shading and construction from the beginning, but it also means that a large number of related specifications must remain consistent across the BASIX assessment and approval drawings.
How Water Is Assessed for a New Home
The BASIX water section assesses the water-efficiency measures proposed for the new dwelling. The result is influenced by both the selected fixtures and the way alternative water sources are incorporated into the design.
Information may be required for:
- showerheads, toilets and tapware
- rainwater-tank capacity
- the roof area connected to the rainwater tank
- toilet, laundry and outdoor-tap connections
- reticulated or recycled alternative water supplies
- garden, lawn and low-water-use landscape areas
- swimming pools and spas
- shared systems for multi-dwelling development
Rainwater information should be coordinated with the roof plan, landscape design and hydraulic documentation. A nominated tank is not considered in isolation: its effective catchment and connected uses can also form part of the BASIX commitments.
If those details change later, the water assessment may need to be revised before the approval or construction documentation is finalised.
How Thermal Performance Is Assessed
Thermal performance assesses how much heating and cooling the proposed home is expected to need to maintain comfortable internal conditions. It is strongly influenced by the relationship between the building design, local climate and construction.
Relevant design information includes:
- site orientation and dwelling geometry
- room layout and conditioned zones
- window and glazed-door sizes
- glazing U-values and solar heat-gain coefficients
- eaves, awnings, balconies and external shading
- neighbouring buildings and other external obstructions where applicable
- external wall, roof, ceiling and floor construction
- insulation levels and installation locations
- steel-frame thermal bridging and thermal breaks
- roof and wall solar absorptance where relevant
- ceiling fans and natural-ventilation assumptions available to the selected method
Many new homes are now subject to higher thermal-performance requirements aligned with a 7 Star NatHERS outcome. The exact standard depends on factors including the building type and climate zone, so the required result should be confirmed for the specific project rather than assumed from a general statewide figure.
A home does not achieve its thermal result through insulation alone. Glazing, shading, orientation, roof exposure, floor construction and thermal bridging can all materially affect the outcome.
Which Thermal-Performance Method Applies?
Method 01
BASIX DIY Method
A web-based deemed-to-satisfy pathway available to eligible single dwellings. It uses defined limitations and requires nominated insulation, glazing and shading inputs within the BASIX tool.
Method 02
NatHERS Simulation
A detailed thermal model prepared in approved NatHERS software by an accredited assessor. It provides greater flexibility for complex geometry, glazing, shading and construction systems.
Method 03
Passive House Standard
An alternative thermal-performance pathway available for projects designed and documented through the recognised Passive House assessment process.
The method should be selected early enough to inform the documentation. A design that exceeds the limits of the DIY Method may need to move to Simulation rather than being forced into an unsuitable simplified pathway.
When Is NatHERS Required?
NatHERS simulation is used when the BASIX Simulation Method is selected or when the dwelling cannot be assessed through the available DIY Method criteria.
Simulation is commonly relevant for:
- larger or geometrically complex homes
- multi-dwelling developments and apartments
- projects with extensive or unusually arranged glazing
- split-level and multi-level designs
- projects relying on detailed external shading or obstructions
- unusual wall, roof or floor systems
- designs requiring more flexible thermal testing and optimisation
The thermal simulation must be completed by an appropriately accredited NatHERS assessor. Where Simulation is used, both the BASIX Certificate and NatHERS Assessor Certificate must be included with the relevant DA or CDC application.
Who can perform a NatHERS assessment? →
How Energy Is Assessed for a New Home
The BASIX energy section considers the operational systems and equipment proposed for the home. Its purpose is separate from the thermal-performance assessment: thermal performance examines the building envelope, while the energy section examines systems and related greenhouse-gas emissions.
Energy inputs may include:
- hot-water-system type and energy source
- heating and cooling systems
- system efficiencies and areas served
- bathroom, kitchen and laundry exhaust ventilation
- ceiling fans
- lighting
- cooking energy source
- photovoltaic systems
- pool and spa equipment where relevant
- shared systems within multi-dwelling development
Selections relied upon to achieve the energy result can become BASIX commitments. Substituting a lower-performing hot-water, heating, cooling or photovoltaic system later may require the assessment to be reviewed.
The proposed services should therefore be sufficiently resolved before the final Certificate is issued, even where exact product models will be selected later.
How Construction Materials Are Recorded
New-home BASIX applications include a materials section that records construction and glazing materials so the embodied emissions associated with the development can be calculated and reported.
The materials information may cover:
- floor and slab systems
- external and internal walls
- structural frames
- roof and ceiling construction
- insulation
- windows and glazed doors
- construction areas and material quantities represented within the tool
The BASIX Materials Index is a reporting mechanism rather than a complete project lifecycle assessment. It should not be interpreted as replacing detailed LCA or project-specific embodied-carbon analysis.
Construction changes made after the assessment should still be checked, particularly where the new material differs from the type entered into the BASIX application or supporting thermal model.
BASIX, NatHERS and Whole of Home
These terms describe related but distinct assessment layers.
BASIX
The NSW residential sustainability framework covering water, energy, thermal performance and materials reporting.
NatHERS Thermal Rating
A modelled rating of the home’s heating and cooling performance, used when the BASIX Simulation Method is selected.
NatHERS Whole of Home
A separate rating of major household energy use, generation and storage. NSW continues to use the BASIX energy section for regulatory compliance rather than replacing it with a mandatory Whole of Home rating.
A Whole of Home assessment can still provide useful additional performance information where it is requested or forms part of a wider project objective. It should not, however, be assumed to replace the BASIX Certificate required for a new NSW home.
Explore Whole of Home residential energy performance →
What Documents Are Needed?
An accurate new-home assessment requires enough information to describe the complete proposed development. Concept plans may support an early review, but final certification needs coordinated approval-stage information.
Plans
Architectural Documentation
- site plan with true north
- floor plans
- elevations
- building sections
- roof plan
- window and door schedule
Envelope
Construction Information
- wall constructions
- roof and ceiling systems
- floor and subfloor systems
- insulation specifications
- frame types and thermal breaks
- glazing performance
Systems
Water and Energy Selections
- rainwater-tank details
- landscape areas
- water-fixture ratings
- hot-water system
- heating and cooling systems
- ventilation, pool, spa and solar information
The BASIX Process for a New Home
1. Review the proposed dwelling
Confirm the project type, dwelling count, design stage and available architectural and specification information.
2. Select the thermal method
Determine whether the new home is suitable for the DIY Method or requires NatHERS Simulation or another accepted pathway.
3. Complete thermal modelling or inputs
Enter or model the geometry, glazing, shading, insulation and construction used to demonstrate thermal performance.
4. Complete water, energy and materials
Record the proposed fixtures, water systems, building services, renewable-energy measures and construction materials.
5. Resolve performance issues
Review practical changes where the proposed home is not satisfying an applicable water, energy or thermal-performance requirement.
6. Generate the Certificate
Issue the BASIX Certificate and, where Simulation is used, the associated NatHERS assessment documentation.
7. Coordinate the approval set
Check that the certificate commitments, thermal documentation and architectural plans describe the same proposed development before lodgement.
How the BASIX Certificate Must Align with the Plans
The BASIX Certificate is not a standalone summary that can be disconnected from the drawing set. Its commitments form part of the proposed development and must be carried through into the relevant plans and specifications.
Coordination should include:
- floor areas and dwelling geometry
- window and glazed-door dimensions
- glazing U-values and solar heat-gain coefficients
- wall, roof and floor construction
- insulation and thermal breaks
- eaves, awnings and other shading
- rainwater-tank size, catchment and reuse
- hot-water, heating, cooling and ventilation systems
- photovoltaic-system capacity where nominated
- materials recorded through the assessment
Where NatHERS Simulation is used, the BASIX Certificate, NatHERS Certificate and endorsed plans should also contain consistent project details and thermal specifications.
See what is included in a BASIX Certificate →
What Happens If the New-Home Design Changes?
New-home designs frequently continue to develop after an initial assessment has been completed. Not every clarification changes the BASIX result, but relevant amendments should be reviewed before revised plans are lodged or substituted products are installed.
A review may be required for changes to:
- building geometry, floor area or room layout
- window sizes, locations or specifications
- roof form or external shading
- wall, floor or roof construction
- insulation and thermal-break details
- rainwater systems or landscape areas
- hot-water, heating, cooling or ventilation systems
- photovoltaic systems
- construction materials entered into BASIX
Where the change affects an assessment input or certificate commitment, the BASIX and supporting thermal documentation may need to be updated so the approved project remains internally consistent.
Common New-Home BASIX Documentation Issues
The window schedule does not match the elevations
Different window sizes, opening numbers or glazing specifications can cause the thermal model, BASIX Certificate and approval drawings to describe different designs.
Construction systems are still unresolved
Generic notes such as “lightweight wall” or “insulation to BASIX” may not provide enough information to model or document the actual construction accurately.
Steel framing is not identified
Changing from timber to steel framing can introduce thermal-bridging requirements and materially change the assessed wall or roof performance.
Rainwater commitments conflict with the roof plan
The connected catchment assumed in BASIX may not be available where roof areas drain elsewhere or are allocated to a different stormwater system.
Systems are changed after certificate issue
A different hot-water system, air-conditioning efficiency or photovoltaic capacity may affect the BASIX energy result and certificate commitments.
The assessment is completed too late
Waiting until the drawing set is complete can leave little flexibility to resolve glazing, shading, insulation or energy-system issues without reopening finished documentation.
Frequently Asked Questions
BASIX for New Homes FAQs
Does every new home in NSW need a BASIX Certificate?
BASIX applies to new residential development throughout NSW. The application type, assessment method and specific requirements depend on the dwelling type, building arrangement and project circumstances.
Does every new home need a NatHERS assessment?
Not every single dwelling must use NatHERS Simulation. Eligible homes may use the BASIX DIY Method. Simulation is required where that method is selected or where the proposed dwelling falls outside the DIY Method limitations.
Does a new NSW home always need a 7 Star NatHERS rating?
Many new homes are subject to higher thermal-performance standards aligned with 7 NatHERS stars. However, the applicable requirement varies with building type, climate zone and assessment pathway. The project-specific standard should be confirmed before design assumptions are finalised.
Is Whole of Home required with BASIX in NSW?
NSW continues to use the BASIX energy section for regulatory new-home compliance. A NatHERS Whole of Home rating may be prepared as an additional assessment, but it does not replace the required BASIX Certificate.
Can BASIX be completed before the plans are final?
An early assessment can begin from sufficiently developed plans and can help identify performance issues. The final Certificate should be based on coordinated documentation that reflects the dwelling intended for approval.
What happens if the glazing changes after the assessment?
Changes to window size, location, frame, glass or shading can affect thermal performance. The assessor should review the revised glazing before the plans are lodged or the substituted windows are ordered.
Can a BASIX Certificate be used for the DA and CDC pathways?
A BASIX Certificate can form part of the relevant residential DA or CDC documentation. The Certificate and supporting plans must correspond with the development being submitted through that pathway.
Who prepares the thermal simulation for a new home?
Where the Simulation Method is used, the NatHERS thermal assessment must be completed by an appropriately accredited assessor using accepted software. The results are then coordinated with the wider BASIX application.
Related Knowledge
Continue Exploring BASIX for Residential Projects
Assessment note: New-home BASIX requirements vary according to the dwelling type, climate zone, assessment method and BASIX tool version. The project-specific Certificate and supporting approval documentation should always be reviewed together.
Last reviewed: July 2026.
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