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
What Is the BASIX Materials Index?
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
Understanding Materials Reporting in BASIX
Calculation
How the Index Works
How quantities, material selections and emissions factors produce the result.
Project Information
What Must Be Entered?
Floors, walls, ceilings, roofs, glazing and relevant construction systems.
Assessment Outcome
Is There a Target?
Why embodied emissions are currently reported without a pass/fail limit.
Framework Boundary
BASIX Versus LCA
Why the Materials Index is not a complete lifecycle or carbon assessment.
What Are Embodied Emissions?
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
Embodied Emissions
Associated with producing the concrete, steel, timber, masonry, glass, insulation and other materials used to construct the home.
Home Operation
Operational Emissions
Associated with energy used for hot water, heating, cooling, lighting, appliances and other systems during occupation.
A Broader Emissions Picture
Why Does BASIX Record Construction Materials?
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.
How Does the BASIX Materials Index Work?
The Materials Index combines the size of the proposed building elements with the construction systems selected for those elements.
1. Building areas and dimensions are entered
The project geometry is used to establish quantities for relevant floors, walls, ceilings, roofs, glazing and other building elements.
2. Construction materials are selected
The assessment identifies the construction system or material type proposed for each relevant element.
3. Material volumes are estimated
The BASIX Tool uses the project areas and selected systems to estimate the quantity or volume of materials represented by the design.
4. Emissions factors are applied
Standard emissions factors are applied to the estimated quantities. Default material factors used by the index are based on the EPiC database.
5. The embodied-emissions result is reported
The resulting calculation is included in the BASIX project reporting and forms part of the information associated with the Certificate.
Which Building Elements Are Entered?
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
Floors and Slabs
Ground slabs, suspended floors, framed floors and other relevant horizontal construction systems.
Element 02
External Walls
Masonry, lightweight cladding, concrete, timber, framed systems and other external wall assemblies.
Element 03
Internal and Shared Walls
Internal partitions, party walls and other wall construction represented within the development.
Element 04
Ceilings and Roofs
Ceiling systems, roof structure, roof coverings and relevant roof construction materials.
Element 05
Windows and Glazing
Window, glazed-door and associated frame areas represented in the proposed development.
Element 06
Insulation and Framing
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
Where Do the Materials Index Quantities Come From?
The calculation should be based on the same proposed development shown in the architectural and supporting approval documentation.
Relevant information may be taken from:
- floor plans and floor-area schedules
- elevations and external-wall dimensions
- sections and construction details
- window and glazed-door schedules
- wall-type schedules
- roof and ceiling plans
- structural and framing information
- material specifications
- NatHERS construction information where relevant
- common-area and building schedules for multi-dwelling developments
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.
Is There a BASIX Embodied-Emissions Target?
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.
Assessment Boundary
Is the BASIX Materials Index a Lifecycle Assessment?
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.
BASIX Materials Reporting Is a Residential Pathway
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.
How Do Materials Affect Both Embodied and Thermal Performance?
Some material and construction decisions appear in more than one part of the residential assessment, but for different reasons.
Materials Index
Embodied-Emissions Role
The material type and estimated quantity influence the emissions associated with producing the construction materials.
Thermal Assessment
Operational-Performance Role
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.
Material Quantity and Performance
Does More Thermal Mass Mean Better BASIX 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 →
Can Lower-Emissions Materials Be Selected in BASIX?
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
How Is the Materials Index Completed for Multi-Dwelling 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:
- separate residential buildings
- townhouse or dwelling groups
- apartment buildings and unit counts
- private dwelling construction
- party walls and shared structural elements
- common floors, roofs and walls
- shared common areas
- different construction systems used in different buildings or stages
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.
What If Materials Change After the Assessment?
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:
- changing a concrete slab or structural system
- replacing masonry with lightweight wall construction
- changing framing materials
- altering roof or ceiling construction
- changing window-frame or glazing systems
- changing insulation products or thicknesses
- adding or removing substantial building elements
- changing the floor area, wall area or glazing area
- altering the dwelling or building count
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.
Project Documentation
Which Documents Should Match the Materials Index?
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.
A Practical Materials Index Process
1. Confirm the BASIX project structure
Establish the dwelling count, building arrangement, stages, common areas and Certificate coverage.
2. Review the current architectural design
Identify the floor, wall, roof, ceiling, glazing and other construction areas required by the assessment.
3. Confirm the proposed construction systems
Coordinate material selections with the architectural, structural and NatHERS documentation available at the assessment stage.
4. Complete the Materials Index inputs
Enter the relevant areas and material categories using the current options and help information provided by the BASIX Tool.
5. Review the calculated result
Check that the output is based on the intended building geometry and construction rather than placeholder or outdated information.
6. Coordinate the complete BASIX assessment
Confirm that the materials, thermal-performance and project-detail sections consistently describe the same development.
7. Review later design changes
Revisit the assessment where material systems, building quantities or development configuration change before construction.
Common Misunderstandings About the Materials Index
BASIX only assesses operational energy
The current BASIX Tool also calculates and reports embodied emissions through the Materials Index.
The Materials Index has a minimum passing score
There is currently no separate BASIX materials score or maximum embodied-emissions limit.
No limit means the material information does not matter
The section still needs to be completed accurately where it applies and forms part of the project’s BASIX reporting.
The Materials Index is a complete lifecycle assessment
The index has a narrower standardised calculation boundary and does not account for every lifecycle stage or environmental impact.
A material with lower embodied emissions always produces the best building
Materials must also satisfy structural, thermal, moisture, fire, acoustic, durability and construction requirements.
More thermal mass automatically improves sustainability
Thermal mass must be appropriate for the climate and design, and additional material quantity can also affect embodied emissions.
Materials can be substituted after approval without review
Changes should be checked where they alter Materials Index inputs, NatHERS assumptions or BASIX commitments.
Frequently Asked Questions
BASIX Materials Index FAQs
What is the BASIX Materials Index?
The BASIX Materials Index calculates and reports the embodied emissions associated with construction materials entered for an applicable residential development.
What are embodied emissions?
Embodied emissions are greenhouse-gas emissions associated with producing the materials and products used to construct a building.
Does the BASIX Materials Index have a target?
There is currently no separate embodied-emissions limit that determines whether the Materials Index passes. The result is calculated and reported.
Can the Materials Index be left incomplete because there is no target?
No. Where the materials section applies, the required project information must still be completed accurately before the BASIX documentation is finalised.
How does BASIX calculate embodied emissions?
The BASIX Tool estimates material quantities or volumes from the entered building areas and construction systems and applies standard emissions factors to those materials.
Which materials are included in the index?
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.
Is the Materials Index the same as a lifecycle assessment?
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.
Do construction materials also affect NatHERS?
They can. Construction, framing, insulation and thermal mass influence heating and cooling performance, while the Materials Index separately considers material quantities and embodied emissions.
Can a material substitution affect the BASIX Certificate?
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.
Does BASIX identify the most sustainable material?
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
Continue Exploring BASIX Materials and Performance
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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