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For energy assessors

Eight arguments energy assessors have with builders, settled with the clause

The builder says sarking makes up for the thinner batts. The exhaust fan has always vented into the roof space. The plumber is on a different edition from the builder on the same bathroom. Energy assessors spend a surprising share of the week being told how it has always been done.

These are eight real questions assessors asked DatumDesk, answered with the verdict, the clause and the page. Five are the ones where the assessor was right and could not find the page fast enough. Three are about the edition, where the honest answer is that the national table does not decide it.

Sarah-Jane Kavanagh, DatumDesk · Updated 13 October 2026

How to read each one. The question as it was asked, the verdict, and the citation in the form Document, Clause, Page. Every item links to the full published answer with all of its sources. Adoption differs by state, so confirm with your state building authority.
  1. 01

    Cutting insulation for downlights lifts the R-Value the rest of the ceiling must reach.

    Twenty downlights in an insulated ceiling is a real rule, not an assessor's preference. Where insulation is cut back for fittings, the remaining insulation has to be lifted to the R-Value in Table 13.2.3w, set by the percentage of ceiling left uninsulated. The twist in Western Australia is the compliance path, because alterations to existing homes can use a different route, so settle the path before you settle the batts.

    WAClass 1NCC 2025 (NCC 2022 electable)
    The questionOur Perth renovation adds 20 downlights to an insulated ceiling. The energy assessor says we now need thicker insulation to make up for the gaps. Is that a real requirement, and how is the loss worked out?

    The answer. It is a real rule: where ceiling insulation is cut back for fittings like downlights, the remaining insulation must be lifted to the R-Value in Table 13.2.3w, set by the percentage of ceiling left uninsulated. Whether that table binds a Perth renovation depends on the compliance path, because WA lets alterations to existing homes use a different route.

    ABCB Housing Provisions Standard (NCC 2025), 13.2.3(5) Roofs and ceilings, p. 347

    Read the full answer with every source
  2. 02

    In Tasmania the national zone 7 ceiling table does not apply, so neither side of the R5 argument can use it.

    This one is a trap for both sides. In Tasmania the schedule replaces Housing Provisions Section 13 with BCA 2019 Part 3.12, so neither the assessor's R5.0 nor the builder's R4.0 can be argued from the national zone 7 table. The dispute has to be settled against BCA 2019, clause by clause. Being the person who knows that is worth more than being right about the number.

    TASClass 1aNCC 2022 with BCA 2019 Part 3.12
    The questionOur energy assessor specified R5.0 ceiling insulation for a climate zone 7 build, but the builder insists R4.0 is enough because the roof has sarking. Who is right?

    The answer. In Tasmania neither side can rely on the national zone 7 ceiling table. The Tasmanian schedule replaces Housing Provisions Section 13 with BCA 2019 Part 3.12, so the dispute has to be settled against BCA 2019, clause by clause.

    ABCB Housing Provisions Standard (NCC 2022), Tasmania schedule, TAS Parts 13.1 to 13.7, p. 547

    Read the full answer with every source
  3. 03

    An ensuite exhaust fan has to discharge outdoors, not into the roof space.

    It has never been how it is done, whatever the builder says. A bathroom or sanitary compartment exhaust must discharge to outdoor air at not less than 25 litres a second. It was not compliant under NCC 2022 either, and a fan approved under the Victorian Energy Upgrades program does not change that. Duct it out.

    VICClass 1aNCC 2025
    The questionOur Ballarat build has the ensuite exhaust fan venting into the roof space. The builder says that's how it's always been done, but the energy assessor disagrees. Do exhaust fans have to duct outside now, and what flow rates apply?

    The answer. The assessor is right. A bathroom or sanitary compartment exhaust must discharge to outdoor air, not into the roof space, at not less than 25 L/s. The practice was not compliant under NCC 2022 either, and a Victorian Energy Upgrades approved fan does not make it compliant.

    ABCB Housing Provisions Standard (NCC 2025), 10.8.2, p. 294

    Read the full answer with every source
  4. 04

    Brick veneer in climate zone 6 has a condensation rule of its own, and the assessor is reading it correctly.

    The assessor is right, and the reason surprises builders: the drained and ventilated cavity in climate zone 6 comes from condensation management, not the energy provisions. At least 12 mm deep, with 1,000 square millimetres of openings per metre. It is a durability rule wearing an energy assessor's hat.

    VICClass 1aNCC 2025
    The questionI'm building brick veneer in Melbourne and my energy assessor says the walls need a drained and ventilated cavity. Is that right, and what exactly does it involve?

    The answer. The assessor is right: in climate zone 6 a masonry veneer wall must have a drained and ventilated cavity at least 12 mm deep with 1,000 mm2 per metre of openings, and the requirement comes from condensation management, not the energy provisions.

    NCC 2025 Volume Two, ABCB Housing Provisions, 10.8.1 and Table 10.8.1, p. 293

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  5. 05

    A new Brisbane home still needs a thermal performance rating under NCC 2022, whatever the client has heard.

    Seven stars is one deemed-to-satisfy pathway, not the only one, and it comes with separate heating and cooling load limits. In climate zones 1 and 2 a covered outdoor living area brings the minimum down to 6.5 stars, or 6 with a ceiling fan, and the whole-of-home requirement applies on top. Tell the client the number is a floor with options, not a slogan.

    QLDClass 1aNCC 2022
    The questionWe're designing a new home in Brisbane and the client has heard it has to hit 7 stars. Is that right, and is there any concession for a Queensland climate?

    The answer. Seven stars, with separate heating and cooling load limits, is one Deemed-to-Satisfy pathway, not the only one. In climate zones 1 and 2 a covered outdoor living area brings the minimum down to 6.5 stars, or 6 stars with a ceiling fan, and a separate whole-of-home energy requirement applies on top.

    NCC 2022 Volume Two, H6D2 Application of Part H6, p. 136

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  6. 06

    A builder on NCC 2022 and a plumber on NCC 2025 can both be right in the same bathroom.

    Both trades are right, which is the strangest answer on this page. South Australia is in a split adoption: building work follows NCC 2022 while plumbing and drainage follow NCC 2025. Your rating sits on the building side. The plumber's work does not. Adoption differs by state, so confirm with your state building authority.

    SAClass 1aNCC 2022 + 2025 (split)
    The questionWe're renovating a bathroom in Adelaide. The builder is working to NCC 2022 but the plumber says his work falls under NCC 2025. Can both be right on the same job?

    The answer. South Australia is in a split adoption: building work follows NCC 2022 while plumbing and drainage follow NCC 2025, so a builder and a plumber can each be on a different edition of the same renovation.

    NCC 2025 Volume Three, Plumbing Code of Australia, Part A6, scope of Volume Three; volumes adopted independently by each State/Territory, p. 18

    Read the full answer with every source
  7. 07

    In WA you can elect the earlier edition until 1 May 2027, and the regulation says exactly how.

    A Perth permit application lodged in March 2027 can still elect NCC 2022, because regulation 31A lets an applicant use the edition in effect 12 months before the application. The option ends for applications made from 1 May 2027. Put the lodgement date in the rating report so nobody re-argues the edition later.

    WAClass 1NCC 2025 (NCC 2022 electable to 30 April 2027)
    The questionOur Perth duplex permit application goes in around March 2027. Can we still elect NCC 2022, and what should we watch as the 1 May 2027 cutoff approaches?

    The answer. Yes: WA reg 31A(2)(b) lets a permit applicant use the edition in effect 12 months before the application, which for a March 2027 lodgement is NCC 2022, but the option runs out for applications made from 1 May 2027.

    Building Regulations 2012 (WA), compilation as at 1 May 2021, Reg 31A(1), (2)(a)-(b) and (2A), p. 31

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  8. 08

    A Tasmanian approval granted in the five-week NCC 2025 window sits in a genuine gap.

    Approvals granted in Tasmania between 1 May and 4 June 2026 sit in a genuine gap, because the reinstating Act carries no savings clause. Neither edition can be assumed. Written confirmation from CBOS is the only safe course, and a rating that names its edition without it is a rating that may be done twice.

    TASClass 1aNCC 2022
    The questionOur Hobart project got its building approval on 20 May 2026, while NCC 2025 was briefly in force in Tasmania. Which edition applies to our project now?

    The answer. Approvals granted in Tasmania between 1 May and 4 June 2026 sit in a genuine gap: the reinstating Act has no savings clause, so neither edition can be assumed and written CBOS confirmation is the only safe course.

    NCC 2025 Volume Two, Schedule 18, TAS operative date, p. 21

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The pattern

What these have in common.

Five of the eight end with the assessor right and the builder wrong. The other three end with the edition, and those are the ones that will cost a re-rating if they are guessed. Section 13, the state schedule and the lodgement date decide more arguments than the batts do.

Carry the clause, not the recollection. The builder has done it that way for twenty years. The page number has not changed its mind.

Where these came from

Every answer above was produced by DatumDesk.

DatumDesk answers Australian National Construction Code (NCC) compliance questions with clause citations, drawing on NCC 2022 and NCC 2025, state and territory variations, and ABCB handbooks. The commentary on this page is ours. The question, the verdict and the citation on each item are the published answer, verbatim, and the full answer with every source is one click away.

Browse all published answersCheck which edition applies in your state
Questions energy assessors ask

Before you rely on any of this.

Does DatumDesk cover the energy efficiency provisions and the state variations?

Yes. Housing Provisions Section 13, Volume One Section J, the Livable Housing Design Standard and every state and territory schedule are in the corpus, including the Tasmanian schedule that swaps Section 13 for BCA 2019 Part 3.12.

Did an exhaust fan have to duct outside under NCC 2022 as well?

Yes. The answer above sets out that discharging into the roof space was not compliant under NCC 2022 either. The outdoor discharge requirement and the 25 litres a second minimum are in both editions.

Which NCC edition applies in my state right now?

It depends on the state and, in some, on the lodgement date. Victoria and Western Australia are on NCC 2025, with Western Australia allowing an election for NCC 2022 until 30 April 2027. The ACT allows either edition until the same date. New South Wales, Queensland, South Australia (for building work) and Tasmania move on 1 May 2027. The Northern Territory has disapplied NCC 2025 until the next edition. DatumDesk keeps a per-state status page at datumdesk.ai/ncc-2025 and every answer leads with the edition operative in your jurisdiction. Adoption differs by state, so confirm with your state building authority.

How are DatumDesk answers checked?

Answers are generated only from an indexed corpus of the NCC volumes, the Housing Provisions, state and territory variations, ABCB handbooks and referenced regulation. Every numeric value is cited to a document, clause and page. Practice notes are labelled as interpretive. Licensed Australian Standards are named and deferred to, never reproduced. Where the corpus does not hold the answer, DatumDesk says so instead of guessing.

Does DatumDesk replace a building surveyor or certifier?

No. The certifier makes the call and carries the authority. DatumDesk makes sure you arrive at that conversation with the clause, the edition and the page already in hand, and that your question is on the record.

What does DatumDesk cost?

DatumDesk Pro is AU$19 a month or AU$190 a year, per practitioner, with every feature on both. The first 14 days are free. Cancel any time from your account.

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