NCC energy efficiency for residential buildings: Part H6, Section J, and BASIX

TL;DR

Under NCC 2022, every new Class 1 building (house, duplex, townhouse) must hit a minimum 7-star NatHERS thermal rating plus a Whole-of-Home (WoH) score of at least 60 out of 100. These two requirements work together: the NatHERS rating covers the building shell (walls, roof, glazing, floor); the WoH budget covers fixed appliances (hot water, heating and cooling, lighting, pool pumps). Get both wrong and the certifier won’t issue the CC. The most common cost hit is late glazing changes: if the window schedule changes after the NatHERS model is locked, the rating must be redone. NSW runs BASIX instead of the national NatHERS pathway for Class 1; from 1 October 2023, BASIX targets align to 7 stars. Class 2 apartments use Section J (Volume One) with J1V5 as the verification method for individual units. Performance Solutions are permitted under H6 for both classes but add time and cost; most residential work stays on the DTS or NatHERS path.

In plain English

Energy efficiency under the NCC is split by building class and code volume:

Class 1 buildings (houses, duplexes, townhouses): NCC Volume Two, Part H6. Most builders and designers work with the complementary detail in the ABCB Housing Provisions Standard 2022, Part 13 (building fabric, glazing, sealing, services).
Class 2 buildings (apartments, strata units): NCC Volume One, Section J. A separate regime applies to each sole-occupancy unit (SOU) and to the building’s common areas.
Class 4 parts (the dwelling in a commercial building): also Volume One, Section J.

The NCC sets the Performance Requirements. Compliance can be demonstrated three ways:

Pathway	Mechanism	Typical use
NatHERS energy rating (DTS)	Accredited assessor models the building, must achieve 7 stars and WoH 60	New Class 1; most detached houses
Elemental DTS provisions	Look-up tables in ABCB Housing Provisions Part 13 for building fabric, glazing, sealing	Simple designs without modelling
Performance Solution	Designer demonstrates equivalent outcome to the Performance Requirements by other means	Complex or unusual designs

NSW replaces the national NatHERS pathway for Class 1 with BASIX (Building Sustainability Index), delivered under the State Environmental Planning Policy (Sustainable Buildings) 2022. From 1 October 2023, BASIX thermal targets align to 7 NatHERS stars for detached and attached houses. The NCC’s Part H6 still applies in NSW but the thermal performance pathway flows through the BASIX certificate rather than directly through Part H6 (verified 2026-05-09, NSW Planning Portal: BASIX standards).

What it requires

Class 1: NCC 2022 Part H6 and ABCB Housing Provisions Part 13

The two DTS options

Option 1: NatHERS energy rating (Specification 42)

This is the standard path for new Class 1 buildings. Key requirements from Specification 42:

Thermal performance (S42C2): The building must achieve a minimum of 7 NatHERS stars, with two reduced allowances in climate zones 1 and 2 only: 6.5 stars if the building has a fully covered outdoor living area (R-value ≥ 1.5), or 6 stars if it also has at least one permanently installed ceiling fan (verified 2026-05-09, NCC 2022 Specification 42).
Whole-of-Home energy rating (S42C3): The building must achieve a WoH rating of at least 60 out of 100. The WoH score accounts for fixed energy appliances: heating and cooling equipment, hot water system, lighting, pool and spa pumps, and on-site photovoltaic generation. The score is calculated using ABCB-accredited software and lookup tables (verified 2026-05-09, ABCB: New whole-of-home energy efficiency).
Heating and cooling load limits (S42C4): The modelled heating and cooling loads must not exceed the separate limits in the ABCB Standard for NatHERS Heating and Cooling Load Limits.

Practical consequence for appliance selection: reverse-cycle heat pump plus heat-pump hot water plus roof-mounted PV typically passes WoH 60 without difficulty. Resistive electric heating or gas hot water alone usually does not. The appliance mix drives the WoH score as much as the building shell.

Option 2: Elemental DTS provisions (ABCB Housing Provisions Part 13)

For buildings up to 500 m², Part 13 of the Housing Provisions provides prescriptive look-up tables that replace the NatHERS modelling. The elemental path covers:

Part 13.2 Building fabric: minimum R-values by climate zone for ceiling, walls, and floor. See Insulation: where to use it and which type to choose for the full climate-zone table and installation rules.
Part 13.3 External glazing: performance limits based on U-value and SHGC (solar heat gain coefficient) integrated across all glazing for each storey. No single maximum U-value applies universally; compliance uses a conductance-to-solar-heat-gain ratio formula (CU/CSHGC) that varies by climate zone, orientation, and floor type. The SHGC for each glazing element must not exceed 0.7 regardless of climate zone (verified 2026-05-09, ABCB Housing Provisions Part 13.3).
Part 13.4 Building sealing: controls for air infiltration through floors, walls, and ceilings.
Part 13.7 Services: whole-of-home energy budget for the prescriptive path.

The elemental path trades flexibility for simplicity: no modelling required, but no trade-offs between elements. Overshooting on glazing area in one direction can’t be compensated by better insulation elsewhere.

Part H6 Performance Requirements

The underlying Performance Requirements drive both DTS options:

H6P1 Thermal performance: heating, cooling, and thermal energy loads must not exceed the limits in Specification 44, determined by climate zone.
H6P2 Energy usage: the energy value of domestic services must not exceed 70% of a defined baseline (3-star ducted heat pumps for heating and cooling, 5-star instantaneous gas water heater, 4 W/m² lighting power density). This is the formal statement of the WoH concept (verified 2026-05-09, NCC 2022 Part H6).

NSW variation: BASIX

In NSW, Class 1 buildings satisfy thermal performance through a BASIX certificate rather than directly through H6P1. BASIX uses NatHERS software as its measurement tool, so the 7-star standard still applies but the compliance pathway is the BASIX certificate lodged with the DA. The NCC’s building sealing, glazing, and services requirements continue to apply in NSW alongside BASIX (verified 2026-05-09, NSW NCC Part H6 variation).

Performance Solutions under H6

H6D1(2) permits Performance Solutions where the DTS or NatHERS paths don’t fit the design. A Performance Solution must demonstrate compliance with H6P1 and H6P2 through an alternative assessment method accepted under NCC Section A2. This adds independent review time and cost; in practice it is used for unusual geometries or high-performance designs that want to demonstrate compliance differently, not as a cost-saving shortcut (verified 2026-05-09, ABCB NCC 2022 energy efficiency performance).

Class 2: NCC 2022 Volume One Section J

Class 2 buildings (apartment buildings, strata units) are governed by Volume One, Section J. The structure differs from Volume Two:

Provision	Covers	Applies to
J1P2 Thermal performance	Heating, cooling, thermal energy loads	Each Class 2 sole-occupancy unit (SOU)
J1P3 Energy usage	Domestic services energy budget (same WoH concept as Class 1)	Each Class 2 SOU
J1P4 Renewable energy and EV infrastructure	Provision for future solar and EV charging	The whole building
Section J common areas	Lighting, HVAC, hot water for lifts, corridors, carparks	Common areas of the building

Verification methods for Class 2

J1V3: reference building verification for common areas and Class 3, 5, 6, 7, 8, and 9 buildings. Also used for Class 2 common areas.
J1V5 (new in NCC 2022): reference building verification for Class 2 SOUs. The proposed SOU must demonstrate heating and cooling loads not exceeding 120% of the J1P2 thermal load limits, or match the reference building performance. J1V5 is the Class 2 equivalent of the NatHERS pathway used for Class 1 (verified 2026-05-09, NCC 2022 Part J1).

Part J3 provides the elemental DTS provisions for Class 2 SOUs (building fabric, glazing, sealing, services), equivalent to Housing Provisions Part 13 for Class 1.

NSW note: In NSW, J1P2, J1P3, and J1V5 do not apply to Class 2 buildings up to 5 storeys: BASIX covers those SOUs instead. For Class 2 buildings above 5 storeys, the Section J provisions apply.

Building fabric requirements (both classes)

For Class 1 under the elemental path, and as a baseline for the NatHERS model, the building fabric must meet minimum R-values by climate zone per ABCB Housing Provisions Part 13.2. The same R-value logic applies to Class 2 under Part J3.

Key elements:

Ceiling insulation: mandatory in all climate zones. R-values range from R1.5 (zone 1) to R4.5+ (zones 7-8). The ceiling plane is the highest-return element in most climates.
Wall insulation: required in zones 4-8 for timber and metal framing. Metal-framed walls require a thermal break of at least R0.2 to address thermal bridging through the studs.
Floor insulation: required for suspended floors in zones 4-8. Slab edge insulation required in zones 7-8.
Reflective insulation: contributes only where an unobstructed airspace (minimum 20-25 mm) is maintained adjacent to the reflective surface. Foil with no airspace delivers zero R-value for thermal performance.

Full installation detail, product selection, and climate zone R-value tables: see Insulation: where to use it and which type to choose.

Glazing requirements

Glazing is the most variable energy efficiency element: it lets in solar heat gain in summer and loses heat in winter. The NCC does not set a single maximum U-value for windows. Instead, Housing Provisions Part 13.3 (Class 1 elemental path) uses an integrated calculation that accounts for:

Total glazing area per storey
Orientation (eight compass directions)
U-value and SHGC of each glazing element
Climate zone
Whether the space is a bedroom or living area
Floor level and frame solar absorptance

The universal rule: the Total System SHGC (glass plus frame, combined) for each glazing element must not exceed 0.7. Beyond that, the numbers depend on the specific building geometry and climate zone (verified 2026-05-09, ABCB Housing Provisions Part 13.3).

In practice, most 7-star NatHERS designs for climate zones 5-8 (Sydney, Melbourne, Hobart, Adelaide) use double-glazed or low-emissivity (low-e) glazing to stay within the heating load limits. This is not mandated by a rule, but by the physics of hitting the star rating. See SHGC and WERS for the product rating systems used to specify glass.

What it doesn’t cover

State planning requirements: DA requirements, setbacks, floor space ratios, and development controls are planning instruments, not NCC. They sit outside the energy efficiency provisions.
Heritage buildings: NCC Part A5 has variations for heritage; energy requirements may be modified.
Existing buildings (alterations): the energy efficiency obligations for substantial alterations and additions are dealt with in the NCC but are less stringent than for new buildings. Check the relevant state’s building regulations for the threshold.
Embedded network or centralised systems in Class 2: energy efficiency obligations for centralised hot water and HVAC in large apartment buildings involve additional provisions beyond J1P3.
NCC 2025 EV pre-provisioning: the new requirement from NCC 2025 for EV circuit pre-provisioning at car parking spaces is covered in NCC version transitions, not this article.

Practical implications

Before quoting a new Class 1 project

Confirm the state and the NCC edition in force at the anticipated CC lodgement date (see NCC version transitions).
In NSW: confirm that a BASIX certificate is required and include it in the pre-DA checklist. In all other states: confirm whether the NatHERS path or elemental DTS path is more suitable.
A NatHERS-accredited assessor should be involved early: before the window schedule is locked, before the slab is poured, and before the hot water system is specified.
Confirm the hot water system type against the WoH budget. Swapping from resistive electric to heat pump during construction is a real cost; swapping during design is a spreadsheet change.

Checklist: NatHERS pathway (Class 1, non-NSW)

Item	Action	When
NatHERS assessor engaged	Confirm accreditation via nathers.gov.au	Pre-DA or pre-CC
Building orientation input to model	Confirm solar north with survey data	With assessor, pre-design
Window schedule locked	Match exact U-value and SHGC to model	Before CC lodgement
WoH budget: hot water	Confirm heat pump or solar hot water type	Pre-CC
WoH budget: HVAC	Confirm reverse-cycle type and star rating	Pre-CC
WoH budget: PV	Confirm panel size if offsetting WoH score	Before CC
Insulation specification	Confirm R-values match NatHERS model	Before frame inspection

Checklist: BASIX pathway (NSW Class 1)

Item	Action	When
BASIX certificate obtained	Via basix.nsw.gov.au, submitted with DA	Pre-DA
BASIX commitments on plans	All thermal, energy, and water commitments noted on drawings	Before CC lodgement
Window schedule matches BASIX	U-value and SHGC on window schedule matches BASIX model	Before CC lodgement
BASIX thermal compliance inspector	Confirm who signs off on thermal commitments at PCI	Before PCI

Cross-version risk: NCC 2022 vs NCC 2025

NCC 2025 does not revisit the 7-star or WoH requirements. The residential energy bar stays at 7 stars. The NCC 2025 addition for Class 1 is EV pre-provisioning (a dedicated circuit to the parking space), not a lift in the energy or NatHERS requirements. See NCC version transitions for the full transition timeline.

State variations

VIC

Victoria adopted the NCC 2022 energy efficiency provisions on 1 May 2024, with new Class 1 dwellings required to meet 7 NatHERS stars and a Whole-of-Home score of 60, and Class 2 SOUs averaging 7 stars (no unit below 6) with WoH 50. Compliance is administered by the Victorian Building Authority (VBA) under the Building Regulations 2018. Victoria pairs the 7-star rule with a separate planning instrument: from 1 January 2024, all new homes requiring a planning permit must connect to all-electric networks (no new gas connections), administered through the Department of Energy, Environment and Climate Action (energy.vic.gov.au: 7-star energy efficiency building standards, Premier of Victoria: New Victorian homes to go all electric from 2024, verified 2026-05-09). The NatHERS pathway runs as per the national NCC; no Victoria-specific star variation applies.

QLD

Queensland adopted the NCC 2022 energy efficiency provisions on 1 May 2024 via amendment to the Queensland Development Code (QDC) Part 4.1, administered by the Department of Housing and Public Works. New Class 1 dwellings must hit 7 NatHERS stars plus WoH 60; Class 2 SOUs must average 7 stars (no unit below 6) with WoH 50. Compliance flows through QBCC-licensed building certifiers under the Building Act 1975 (Queensland Government: Residential energy efficiency standards, verified 2026-05-09). Both NatHERS and elemental DTS pathways from NCC 2022 Part H6 apply unchanged; no Queensland-specific star or WoH variation is set in QDC 4.1.

WA

Western Australia ran a staged adoption. From 1 May 2024, Class 2 buildings above six storeys had to meet a 7-star NatHERS average (5-star minimum per unit). From 1 May 2025, full NCC 2022 Part H6 applies to all Class 1 dwellings: 7 NatHERS stars plus WoH 60, with Class 2 of any height also at 7-star average and WoH 50 (NatHERS: NatHERS News - 7 March, verified 2026-05-09). The Building and Energy division of the Department of Energy, Mines, Industry Regulation and Safety (DEMIRS) administers the Building Act 2011 and the WA NCC adoption. WA continues to use the NatHERS pathway through accredited assessors, with no WA-specific star variation; the elemental DTS option remains available under ABCB Housing Provisions Part 13.

SA

South Australia adopted the NCC 2022 livable housing and energy efficiency provisions on 1 October 2024, administered by PlanSA (Department for Trade and Investment) under the Planning, Development and Infrastructure Act 2016 and the Building Code transposed via the Ministerial Building Standard. New Class 1 dwellings must achieve 7 NatHERS stars plus WoH 60; Class 2 SOUs must average 7 stars (no unit below 6) with WoH 50 (PlanSA: Liveability and energy efficiency NCC 2022 in SA, verified 2026-05-09). SA does not run a separate scheme: compliance is via a NatHERS certificate from an accredited assessor, or the NCC 2022 elemental DTS path. Section J still applies as drafted to Class 2 SOUs above the 5-storey threshold and to common areas.

TAS

Tasmania has not adopted the NCC 2022 7-star NatHERS or Whole-of-Home provisions for residential buildings. The minimum thermal requirement remains at 6 NatHERS stars under the Director of Building Control determinations, administered by Consumer, Building and Occupational Services (CBOS) within the Department of Justice (CBOS: Energy efficiency for new homes, verified 2026-05-09). Tasmania did adopt the NCC 2022 condensation mitigation provisions from 1 October 2023, but kept the residential energy bar at the NCC 2019 6-star level pending review. Builders working in Tasmania still use NatHERS-accredited assessors and the Specification 42 software; the only difference is the lower star target and no WoH 60 obligation.

NT

The Northern Territory has its own variation to NCC 2022 Part H6, in force from 1 October 2023, administered by the NT Department of Lands, Planning and Environment through Building Advisory Services. NT requires a minimum 5-star NatHERS rating for Class 1 buildings (not 7-star), with two compliance pathways: NatHERS modelling, or NT-specific elemental DTS provisions in NT Part 13.2 to 13.6 of the Housing Provisions (NCC: NT Part H6 Energy efficiency, NT Government: NCC 2022 Northern Territory variations, verified 2026-05-09). The national 7-star and Whole-of-Home requirements do not apply in the NT. R-value tables in NT Part 13.2 are calibrated to climate zone 1 tropical conditions, so the elemental path is materially lighter than the national baseline.

ACT

The ACT commenced the NCC 2022 livable housing, energy efficiency, and condensation provisions on 15 January 2024, administered by the ACT Building Regulator (Access Canberra) under the Building Act 2004 and the Building (General) Regulation 2008. New Class 1 dwellings must meet 7 NatHERS stars plus WoH 60; Class 2 SOUs average 7 stars (no unit below 6) with WoH 50 (HIA: Commencement of NCC 2022 in the ACT, verified 2026-05-09). The ACT Appendix to NCC 2022 includes modified application of Part H6 to alterations of existing buildings, and the ACT separately mandates EV charging and solar PV pre-provisioning in new Class 2 to 9 buildings. The Energy Efficiency (Cost of Living) Improvement Act 2012 runs in parallel as a retailer obligation scheme but is not part of building approval; NatHERS-accredited assessors remain the standard path for Class 1 compliance.

Source link

NCC 2022 Part H6: https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h6-energy-efficiency (verified 2026-05-09)
ABCB Housing Provisions Part 13: https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/13-energy-efficiency (verified 2026-05-09)
NCC 2022 Section J: https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-one/j-energy-efficiency (verified 2026-05-09)

References

Australian Building Codes Board, NCC 2022 Volume Two, Part H6 Energy efficiency. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h6-energy-efficiency (verified 2026-05-09).
Australian Building Codes Board, NCC 2022 Specification 42, House energy rating software. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/42-house-energy-rating-software (verified 2026-05-09).
Australian Building Codes Board, ABCB Housing Provisions Standard 2022, Part 13.3 External glazing. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/13-energy-efficiency/part-133-external-glazing (verified 2026-05-09).
Australian Building Codes Board, Energy efficiency performance in NCC 2022. https://ncc.abcb.gov.au/news/2022/energy-efficiency-performance-ncc-2022 (verified 2026-05-09).
Australian Building Codes Board, New whole-of-home energy efficiency. https://ncc.abcb.gov.au/news/2022/new-whole-home-energy-efficiency-whats-it-all-about (verified 2026-05-09).
Australian Building Codes Board, NCC 2022 Volume One, Part J1 Energy efficiency performance requirements. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-one/j-energy-efficiency/part-j1-energy-efficiency-performance-requirements (verified 2026-05-09).
NSW Department of Planning, Housing and Infrastructure, BASIX standards (increase to standards). https://www.planningportal.nsw.gov.au/BASIX-standards (verified 2026-05-09).
Australian Building Codes Board, NCC 2022 NSW Part H6 variation. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/5-new-south-wales/h6-energy-efficiency (verified 2026-05-09).

NCC 2022 Volume Two: what’s in it for residential builders: the full Section H overview including Part H6 context
NCC version transitions: which NCC edition applies to your CC lodgement date
ABCB Housing Provisions Standard: the companion document with the DTS numbers used for compliance
Insulation: where to use it and which type to choose: R-value tables, product selection, and installation rules for Part 13.2
NatHERS: what the star rating scheme is and how accredited assessors run models
Whole-of-Home energy rating: the WoH score, what it covers, and how hot water and HVAC choices affect it
BASIX: the NSW energy and water compliance pathway for Class 1 and 2
Energy report: the NatHERS certificate produced by the assessor