BASIX in 2024: The Higher Energy and Thermal Standards Explained

If you build homes in NSW, BASIX in 2024 is a different animal to the scheme you knew a couple of years ago. On 1 October 2023, the NSW Government lifted the Building Sustainability Index (BASIX) standards to align with the energy efficiency provisions of the National Construction Code (NCC) 2022 — the biggest step change in the scheme since it launched two decades ago. Thermal performance requirements jumped to the equivalent of 7 stars under NatHERS for most new dwellings, energy targets rose, and a new requirement to record embodied emissions of building materials appeared alongside.

Ten months on, the industry has moved through the shock phase, but plenty of builders are still working out what the new standards mean for their standard designs, their specification lists and their budgets. And one deadline matters right now: the transition arrangement that allowed some projects to use the old standards ends on 30 September 2024. This article, from the assessors at NathersPRO — the energy assessment consultancy within the Rouse Hill–based Contrive group — explains what changed, who it applies to, and how to design for the new standards without panic-buying performance you do not need.

A quick refresher: what BASIX is and where it applies

BASIX applies to all new residential dwellings in NSW and to alterations and additions above the relevant cost threshold. Rather than adopting the NCC energy provisions directly, NSW delivers residential sustainability through the BASIX certificate lodged with your development application or complying development certificate. Every BASIX certificate addresses three areas:

Water — a reduction target for potable water use, met through fixtures, rainwater tanks and landscape choices.
Thermal comfort — the performance of the building shell, demonstrated either through a NatHERS simulation (“Thermal Comfort – Simulation” pathway) or, for some dwellings, the deemed-to-satisfy style DIY pathway.
Energy — a greenhouse gas reduction target covering hot water, heating and cooling systems, lighting, pools and other fixed equipment.

The October 2023 changes left the water target alone. The thermal and energy standards are where everything moved.

What changed on 1 October 2023

Thermal performance: the 7-star era

The headline change is thermal. Before the update, BASIX thermal requirements sat, on average, around the 5.5 to 6 star NatHERS mark depending on dwelling type and location. The new standards lift most new dwellings to the equivalent of 7 stars, aligning NSW with the NCC 2022 residential energy efficiency provisions adopted around the country.

In practice, BASIX expresses this through capped heating and cooling loads for your climate zone, verified by a NatHERS simulation of your actual design. That distinction matters: two 7-star homes in different parts of NSW face different load caps, and a design that sails through in one climate zone can miss in another. It also means the assessment is design-specific — orientation, glazing, insulation, shading and floor construction all feed the result, which is why early engagement with your assessor now pays for itself.

Energy: higher greenhouse gas targets

The BASIX energy targets also increased for most new homes, with the size of the increase varying by dwelling type and location. Meeting the new targets generally pushes specifications toward efficient electric equipment — heat pump or efficient electric hot water, higher-efficiency air conditioning, LED lighting throughout — and, on many projects, rooftop solar. Gas appliances and resistive electric hot water, which once scraped through, now make the energy target hard to reach on many dwelling types.

Embodied emissions: measure and record

The update also introduced a requirement to quantify and record the embodied emissions of construction materials — the carbon associated with manufacturing and transporting what you build with — as part of the BASIX/planning process. At this stage the obligation is to measure and report rather than to meet a target, but it signals clearly where NSW policy is heading, and it adds a documentation task your consultant team needs to own.

Who the higher standards apply to — and the exceptions

The increased standards apply to most new residential development across NSW, but not uniformly:

Most houses, dual occupancies, townhouses and low-rise dwellings — full higher standards apply.
Certain climate zones in north-eastern NSW — concessions apply in a small number of milder climate zones where the cost-benefit of the full increase did not stack up.
Apartment buildings up to five storeys — smaller increases were applied to some mid-rise residential flat buildings, recognising their different cost structures.
Alterations and additions — continue under their own BASIX settings rather than the full new-dwelling standards.

The other carve-out is temporal. Projects with a building contract signed before 1 October 2023 could, if eligible, continue under the previous standards during a 12-month transition period. That transition ends on 30 September 2024. If you are holding older BASIX certificates or part-lodged applications relying on the old standards, now is the time to confirm where you stand — after the deadline, revised applications will be assessed against the new standards, and a design optimised for 6 stars will usually need genuine rework, not just a re-run of the certificate.

What 7-star-equivalent means for your standard designs

The jump from around 6 to 7 stars sounds incremental. Thermally, it is a meaningful tightening — and it exposes design habits that the old standards forgave. Based on the projects crossing NathersPRO’s desks since the change, expect pressure on:

Glazing. Large west-facing windows with standard aluminium single glazing are the single biggest star-killer. Most 7-star designs in Sydney’s climate use improved glazing — double glazing or high-performance units — at least on the worst orientations.
Orientation and layout. Living areas facing north with bedrooms buffered to the south is worth a lot of free performance. Mirrored “handed” designs that ignore orientation now show their cost.
Insulation and construction detail. Ceiling and wall insulation upgrades are cheap performance; slab-edge treatment, roof colour and sarking choices all move the dial.
Shading. Eaves, awnings and pergolas sized to block summer sun while admitting winter sun are among the most cost-effective compliance tools available.
Sealing and ventilation. Draught sealing, quality door seals and ceiling fans improve both simulated loads and real comfort.

The encouraging news: the gap is nearly always closable with design intelligence rather than expensive products. A pre-design or concept-stage assessment — testing the design in NatHERS software before the DA drawings are finalised — routinely finds a compliant path that costs a fraction of the brute-force approach of upgrading every window in the house.

Practical workflow for builders and developers

Under the new standards, the sequencing of energy assessment has changed from an end-of-documentation formality to a design input:

Concept stage: get preliminary NatHERS modelling on your floor plan and siting, especially for repeated designs. Fix orientation and glazing problems while they are lines on paper.
DA/CDC stage: lodge the BASIX certificate with a specification you can actually build — over-promising in the certificate (and value-managing later) creates compliance failures at occupation certificate stage.
Construction: keep the BASIX commitments schedule on site. Certifiers check the commitments — insulation values, glazing specs, hot water systems, tank sizes — against what is installed.
Any design change: re-check before you build it. Window changes, facade swaps and appliance substitutions can all invalidate the certificate.

Frequently asked questions

Does every new home in NSW now need 7 stars?

Most new dwellings must meet thermal standards equivalent to 7 stars under NatHERS, but there are exceptions — concessional settings apply in some north-eastern NSW climate zones, and some apartment buildings up to five storeys received smaller increases. BASIX applies the standard as heating and cooling load caps for your climate zone, so the precise requirement is always design- and location-specific. An accredited assessor can tell you exactly what your site must achieve.

My building contract was signed before October 2023 — do the old standards still apply?

Eligible projects with contracts signed before 1 October 2023 could use the previous standards during the transition period, but that period ends on 30 September 2024. If your project has not yet secured its approvals under the transition arrangements, act immediately — from October 2024 the higher standards apply.

How much more does a 7-star home cost to build?

It depends almost entirely on how early the energy assessment enters the design process. Designs optimised from concept stage — orientation, window placement, shading, sensible glazing — often reach compliance with modest specification changes. Designs finalised without energy input and “fixed” afterwards pay much more, because the only remaining levers are expensive ones like whole-of-house high-performance glazing. There is no single dollar figure; the honest answer is that early assessment is the cheapest compliance strategy.

What is the embodied emissions requirement — do I have to reduce them?

The current requirement is to calculate and record the embodied emissions of the materials in your development as part of the BASIX process; there is no reduction target yet. Treat it as a reporting task your assessor or consultant team completes from your specification — and as advance notice of where NSW sustainability policy is heading.

Get your BASIX sorted early

NathersPRO (natherspro.com.au) provides NatHERS assessments, BASIX certificates and design-stage energy advice for builders and developers across NSW, as part of the Contrive group in Rouse Hill — so your energy assessment, architecture, civil and planning inputs stay coordinated. Explore the group’s services or contact us to talk through your next project: +61 497 848 111 or info@contriveconsultants.com.au.