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Energy efficiency and sustainability in modular homes

From Modular Living Australia — the independent knowledge base Last updated: 8 Oct 2026

In jurisdictions that have adopted NCC 2022, a new home, modular or not, needs a 7-star NatHERS rating, up from 6 stars, and must meet a Whole of Home annual energy budget for fixed appliances.^[1] Tasmania requires 6 stars and the Northern Territory 5 stars, and four modular homes delivered under a Victorian government program rated 7.0 to 7.7 stars.^[2][3][4]

Energy requirements in Australia attach to the dwelling, not to how it was built. A modular home is assessed against the same National Construction Code provisions as a house built on site, using the same software and the same certificates. What differs is where the work happens, and whether that changes the gap between the modelled rating and the finished building. This guide sets out what the current requirements are, which states apply them, and what the available Australian evidence does and does not show about factory-built performance.

Two tests, not one §

NCC 2022 commenced on 1 May 2023, with its new energy efficiency requirements optional until 1 October 2023 and adoption left to each state and territory^[6].

The change introduced two separate hurdles for new houses. The first is a lift in the minimum thermal rating from 6 to 7 stars out of 10. The second is a Whole of Home annual energy budget covering fixed appliances — heating and cooling, hot water, lighting, and pool and spa pumps — which can be offset by rooftop solar, alongside new readiness provisions intended to make later battery installation cheaper^[1].

The distinction matters when reading a builder's claims. A star rating describes the building fabric: how well walls, roof, floor and glazing hold conditions without mechanical assistance. The Whole of Home score describes the equipment installed inside that fabric. A home can be strong on one and weak on the other, and both must be satisfied.

Where the 7-star rule applies §

Adoption was not simultaneous and is not universal.

Two practical consequences follow for anyone buying a factory-built home. First, a builder operating across state lines may quote a specification developed for one jurisdiction; the same design does not automatically comply in another. Second, a Tasmanian or Northern Territory project is not required to reach 7 stars, which does not prevent a buyer specifying it — but it does mean the baseline product on offer may be built to a lower standard than the same builder's mainland range.

A concession that may apply to off-site buildings §

A commercial glazing supplier's 2026 compliance guide reports that the South Australian provisions include a concession for small and irregular allotments, worker accommodation, and off-site manufactured buildings of 70 square metres or less — these being required to meet a 6-star thermal standard while still complying with Whole of Home and condensation management^[9].

If accurate, this is the only Australian provision located for this guide that treats off-site manufactured dwellings as a distinct category for energy purposes, and it is directly relevant to small modular units and secondary dwellings in South Australia. No South Australian government publication confirming the detail has been located here. Anyone relying on it should confirm the current wording with the South Australian planning authority or a registered building certifier before assuming a reduced requirement applies.

What the Australian evidence actually shows §

Claims that factory construction produces better-performing houses are common, but almost all of them come from builders describing their own products, and this site has not located an independent Australian survey comparing measured performance of factory-built and site-built homes. That comparison is not covered by the sources compiled here.

What does exist is a government-published case study. Sustainability Victoria records four prefabricated modular homes delivered under its 7 Star Homes Program, ranging from 99.65 to 168.89 square metres and rating between 7.0 and 7.7 stars, achieved through insulation levels, double glazing and solar passive design, and paired with heat-pump hot water, efficient heating and cooling, efficient lighting, solar photovoltaics, battery storage and rainwater storage^[4]. The ratings were produced using FirstRate5 under NCC 2019^[4].

That establishes something narrower but more useful than the general claim: modular delivery is demonstrably compatible with above-minimum ratings in an Australian program, on ordinary family-house floor areas. It does not establish that modular construction outperforms site construction, and the ratings themselves are modelled design ratings rather than measured post-occupancy results.

What a higher rating is worth §

The star scale is not linear in cost or in benefit, and published estimates of the difference between rating bands vary. A commercial energy assessment firm offers a rule of thumb that a 7-star house requires around 19 per cent less heating and cooling than a 6-star house^[10]. That is a design-model comparison, not a measured bill saving, and the actual difference for any household depends on climate zone, occupancy patterns, appliance choice and how the home is operated.

Where a modular builder offers ratings above the minimum as an upgrade, the question worth asking is which fabric changes deliver it — glazing specification, insulation, air sealing, shading — and whether those changes are made in the factory or added on site. Fabric improvements built into the module are difficult and expensive to retrofit later; equipment covered by the Whole of Home budget is comparatively easy to change.

What happens next §

Building ministers have paused further residential energy efficiency changes to the code until at least mid-2029, and NCC 2025 adds no new residential energy efficiency requirements^[5]. On that basis the 7-star thermal minimum and the Whole of Home budget are expected to remain the framework for the rest of the decade in adopting jurisdictions, which makes a home built to them today unlikely to fall behind the code in the short term.

Questions for a modular builder §

• What star rating does this design achieve in my climate zone, and can I see the assessor's certificate rather than a marketing figure?
• Which software was used, and under which edition of the code was the rating produced?
• What is the Whole of Home result, and which appliances are assumed in it?
• Which fabric elements are fixed in the factory and cannot be changed after delivery?
• If the home is rated above the minimum, which specific components deliver that, and are they standard or an upgrade?
• Does the quoted specification comply in the state where the home will be installed, or in the state where it is manufactured?

References §