The BASIX Materials Index calculates and reports the embodied emissions associated with construction materials entered for an applicable residential development in New South Wales.
Unlike the BASIX Water and Energy sections, the Materials Index does not currently apply a separate score or emissions limit that the project must achieve. Its present role is to quantify material-related emissions and record them within the BASIX assessment.
The result depends on the proposed building geometry, construction areas and selected material systems. Accurate information is therefore important even though the Materials Index is currently a reporting requirement rather than a standalone performance target.
In Brief
The BASIX Materials Index estimates the embodied emissions associated with materials used in a proposed residential building. The tool combines construction quantities and material selections with standard emissions factors. The resulting emissions are calculated and reported, but there is currently no separate BASIX materials score or maximum emissions limit that determines whether the project passes. The index is also narrower than a complete lifecycle assessment.
Knowledge Navigation
Calculation
How quantities, material selections and emissions factors produce the result.
Project Information
Floors, walls, ceilings, roofs, glazing and relevant construction systems.
Assessment Outcome
Why embodied emissions are currently reported without a pass/fail limit.
Framework Boundary
Why the Materials Index is not a complete lifecycle or carbon assessment.
Embodied emissions are greenhouse-gas emissions associated with the materials and products used to create a building.
They arise before and during construction through activities such as extracting raw materials, manufacturing products and preparing construction materials for use.
The term is different from operational emissions, which arise from the energy used while the completed home is occupied and operated.
Materials and Construction
Associated with producing the concrete, steel, timber, masonry, glass, insulation and other materials used to construct the home.
Home Operation
Associated with energy used for hot water, heating, cooling, lighting, appliances and other systems during occupation.
A Broader Emissions Picture
BASIX has traditionally focused on water use, operational energy and thermal performance. The Materials Index adds information about emissions arising before the home begins operating.
This creates a more complete regulatory dataset about the environmental impact of new residential development. It also recognises that improving operational performance can involve additional or different construction materials.
For example, additional insulation, higher-performance glazing or increased material quantities may reduce operational heating and cooling demand while also changing the embodied-emissions result.
The Materials Index therefore records a separate part of building performance rather than replacing the existing BASIX water, energy or thermal requirements.
The Materials Index combines the size of the proposed building elements with the construction systems selected for those elements.
The project geometry is used to establish quantities for relevant floors, walls, ceilings, roofs, glazing and other building elements.
The assessment identifies the construction system or material type proposed for each relevant element.
The BASIX Tool uses the project areas and selected systems to estimate the quantity or volume of materials represented by the design.
Standard emissions factors are applied to the estimated quantities. Default material factors used by the index are based on the EPiC database.
The resulting calculation is included in the BASIX project reporting and forms part of the information associated with the Certificate.
The exact screens depend on the BASIX project type and the construction selected. The Materials Index generally requires information describing the principal elements of the proposed residential building.
Element 01
Ground slabs, suspended floors, framed floors and other relevant horizontal construction systems.
Element 02
Masonry, lightweight cladding, concrete, timber, framed systems and other external wall assemblies.
Element 03
Internal partitions, party walls and other wall construction represented within the development.
Element 04
Ceiling systems, roof structure, roof coverings and relevant roof construction materials.
Element 05
Window, glazed-door and associated frame areas represented in the proposed development.
Element 06
Relevant structural framing, insulation products and panel systems associated with the selected construction.
The project team should follow the fields presented by the current BASIX Tool rather than assume that one generic list applies identically to every dwelling type or development configuration.
Assessment Information
The calculation should be based on the same proposed development shown in the architectural and supporting approval documentation.
Relevant information may be taken from:
The BASIX Tool can estimate material volumes from entered areas and standard construction assumptions. It is not ordinarily a substitute for a detailed quantity survey or construction bill of quantities.
The entered dimensions should nevertheless represent the project accurately enough for the calculated result to correspond with the proposed design.
There is currently no separate embodied-emissions limit that a residential project must remain below to pass the BASIX Materials Index.
This differs from the BASIX Water and Energy sections, where the calculated scores must meet or exceed an applicable standard. It also differs from thermal performance, where heating and cooling results must remain within applicable limits.
| BASIX Area | Reported Outcome | Current Assessment Principle |
|---|---|---|
| Water | Percentage reduction score | The score must meet or exceed the project’s applicable water standard. |
| Energy | Operational-emissions reduction score | The score must meet or exceed the applicable energy standard. |
| Thermal performance | Heating, cooling and applicable NatHERS results | The project must satisfy the applicable thermal-performance requirements. |
| Materials Index | Calculated embodied emissions | The result is currently calculated and reported without a separate pass/fail limit. |
The absence of a numerical limit does not mean the section can be omitted or completed without accurate information. Where the Materials Index is presented by the BASIX application, the required project details must still be entered before the assessment documentation is finalised.
Understand BASIX scores, standards and reporting outcomes →
Assessment Boundary
No. The BASIX Materials Index is a standardised residential reporting mechanism and should not be described as a complete lifecycle assessment.
| Assessment | Primary Purpose | Boundary |
|---|---|---|
| BASIX Materials Index | Provides consistent embodied-emissions reporting within an applicable NSW residential BASIX application. | Uses standardised material quantities and emissions factors and does not currently account for every lifecycle stage or environmental impact. |
| Lifecycle assessment | Examines environmental impacts over a defined product or building lifecycle. | Can include product-specific data and stages such as transport, construction, maintenance, replacement, demolition, reuse and disposal, depending on the assessment scope. |
The current Materials Index does not represent every issue associated with material sustainability. Product durability, maintenance, replacement cycles, construction waste, transport and end-of-life outcomes may require separate consideration.
A project requiring detailed embodied-carbon optimisation, product comparison or formal lifecycle reporting may therefore need a separate assessment beyond BASIX.
The BASIX Materials Index belongs to the NSW residential sustainability framework.
It should not be confused with embodied-emissions reporting pathways that may apply to non-residential development under the Sustainable Buildings framework or with separate NABERS embodied-emissions documentation.
A mixed-use development may therefore contain different reporting obligations for its residential and non-residential components. The residential dwellings may be addressed through BASIX, while commercial areas may require separate documentation.
The project team should keep these assessment territories separate even where the architectural or structural systems are shared across one building.
Some material and construction decisions appear in more than one part of the residential assessment, but for different reasons.
Materials Index
The material type and estimated quantity influence the emissions associated with producing the construction materials.
Thermal Assessment
The construction’s insulation, thermal mass, framing and heat-transfer characteristics influence modelled heating and cooling demand.
A construction system should therefore not be selected from its embodied-emissions result alone. It must still satisfy structural, fire, acoustic, moisture, durability and thermal-performance requirements.
Similarly, the lowest thermal loads do not necessarily identify the lowest embodied-emissions solution. The appropriate response often requires balancing material quantity with operational performance and practical construction outcomes.
Understand BASIX thermal performance separately →
Material Quantity and Performance
Not automatically. Thermal mass and embodied emissions describe different characteristics of a construction material.
Concrete, masonry and other high-mass materials can influence the way a dwelling stores and releases heat. Their thermal value depends on climate, orientation, solar access, insulation, shading and ventilation.
The same materials also contribute to the Materials Index according to their estimated quantities and applicable emissions factors.
Additional mass may improve one thermal result but increase the amount of material represented in the embodied-emissions calculation. Conversely, a lightweight system may reduce material mass but perform differently in the thermal assessment.
Explore thermal mass within the complete passive-design system →
The available selections depend on the construction category and the options contained in the current BASIX Tool.
Where recognised options are available, the assessment may distinguish between different construction systems or material grades. Current tool functionality includes greater flexibility for certain low-emissions concrete selections and can identify straw-bale panels where applicable.
Not every product marketed as sustainable will have its own selectable BASIX category or project-specific emissions factor. Where a new technology or material cannot be represented adequately, the project team may need to seek guidance about the appropriate BASIX entry or determine whether an alternative process is relevant.
The selected option should also match the intended construction. Choosing a lower-emissions category without delivering the corresponding material would make the assessment information inaccurate.
Larger Residential Projects
Multi-dwelling developments require the material information to represent the complete residential project included in the BASIX application.
The project structure may need to distinguish:
Where several buildings share common areas, the quantities should be allocated according to the guidance presented by the BASIX Tool so the materials are neither omitted nor counted more than once.
Repeating dwelling types can simplify the input process, but the complete project quantities should still reflect end conditions, differing building forms, garages, common structures and other material variations.
Understand the wider multi-dwelling BASIX pathway →
Material substitutions are common during design development, documentation and procurement. The significance of a substitution depends on which BASIX inputs or commitments it changes.
Changes that may require review include:
A change can affect the Materials Index, the NatHERS assessment or both. The embodied-emissions and thermal-performance implications should therefore be checked separately.
Where the BASIX assessment no longer describes the proposed development, the application and supporting documents may need to be revised before the changed construction is relied upon.
When does a BASIX Certificate need to be amended? →
Project Documentation
The materials information should describe the same proposed development as the architectural plans, NatHERS documentation and wider BASIX assessment.
| Document | Relevant Information | Coordination Check |
|---|---|---|
| Architectural drawings | Building dimensions, floor areas, wall areas, roofs, windows and dwelling counts. | The Materials Index should represent the same geometry and construction shown for approval. |
| Construction schedules | Wall, floor, roof, framing, insulation and glazing systems. | Selected BASIX material categories should be consistent with the nominated project systems. |
| NatHERS documentation | Thermally relevant construction, insulation, framing and glazing information. | A system should not be represented as one construction in NatHERS and a contradictory construction in BASIX. |
| Structural information | Slabs, concrete grades, framing and significant structural systems. | Developed structural selections should be reviewed where they change the Materials Index inputs. |
The level of detail available at development-application stage may differ from the later construction design. Material assumptions should be reviewed as the project becomes more resolved.
Establish the dwelling count, building arrangement, stages, common areas and Certificate coverage.
Identify the floor, wall, roof, ceiling, glazing and other construction areas required by the assessment.
Coordinate material selections with the architectural, structural and NatHERS documentation available at the assessment stage.
Enter the relevant areas and material categories using the current options and help information provided by the BASIX Tool.
Check that the output is based on the intended building geometry and construction rather than placeholder or outdated information.
Confirm that the materials, thermal-performance and project-detail sections consistently describe the same development.
Revisit the assessment where material systems, building quantities or development configuration change before construction.
The current BASIX Tool also calculates and reports embodied emissions through the Materials Index.
There is currently no separate BASIX materials score or maximum embodied-emissions limit.
The section still needs to be completed accurately where it applies and forms part of the project’s BASIX reporting.
The index has a narrower standardised calculation boundary and does not account for every lifecycle stage or environmental impact.
Materials must also satisfy structural, thermal, moisture, fire, acoustic, durability and construction requirements.
Thermal mass must be appropriate for the climate and design, and additional material quantity can also affect embodied emissions.
Changes should be checked where they alter Materials Index inputs, NatHERS assumptions or BASIX commitments.
Frequently Asked Questions
The BASIX Materials Index calculates and reports the embodied emissions associated with construction materials entered for an applicable residential development.
Embodied emissions are greenhouse-gas emissions associated with producing the materials and products used to construct a building.
There is currently no separate embodied-emissions limit that determines whether the Materials Index passes. The result is calculated and reported.
No. Where the materials section applies, the required project information must still be completed accurately before the BASIX documentation is finalised.
The BASIX Tool estimates material quantities or volumes from the entered building areas and construction systems and applies standard emissions factors to those materials.
The applicable inputs can include floors, slabs, external and internal walls, ceilings, roofs, framing, insulation, windows and glazing. The exact fields depend on the project and current BASIX Tool options.
No. The BASIX Materials Index uses a standardised and more limited calculation boundary. A lifecycle assessment can examine additional lifecycle stages, product-specific information and wider environmental impacts.
They can. Construction, framing, insulation and thermal mass influence heating and cooling performance, while the Materials Index separately considers material quantities and embodied emissions.
Yes. A substitution should be reviewed where it changes the material category, building quantity, thermal construction or another input relied upon by the BASIX or NatHERS assessment.
No. The Materials Index reports embodied emissions within its calculation boundary. Wider decisions about durability, sourcing, lifecycle impacts, maintenance, construction performance and suitability require separate project consideration.
Related Knowledge
Understanding BASIX Targets and Reporting Outcomes →
Thermal Performance and BASIX in NSW →
Passive Design Principles for BASIX and NatHERS →
Assessment note: Materials Index inputs and available material selections depend on the project type and current BASIX Tool. The calculated result should be based on coordinated architectural and construction information and should be reviewed where the design or material systems change.
For regulatory information, refer to the NSW Planning Portal guidance on the BASIX Materials Index.
Last reviewed: July 2026.
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