NCC 2025 is Here: What's Actually Changed for Ventilation
If you’re a builder, designer or certifier, here’s what’s actually changed, what hasn’t, and why it matters.
Why the changes are happening
Over the past decade, Australian homes have become significantly more airtight and better insulated. That’s a good thing for energy efficiency, but it’s created a new problem: moisture trapped inside wall cavities and roof spaces with nowhere to go.
The result has been a noticeable rise in condensation, mould and structural decay, particularly in cooler and wetter climate zones. The condensation management provisions in NCC 2025 are the industry’s response to that, designed to let buildings breathe again.
Change 1: Mandatory drained and ventilated wall cavities in zones 6, 7 and 8
This is the headline change for ventilation. In climate zones 6, 7 and 8, external walls now generally need a continuous drained and ventilated cavity behind the cladding. Direct-fix cladding, where the cladding is fixed straight onto the frame or sarking, is generally no longer permitted in these zones.
The cavity gives any moisture that gets past the cladding a path to drain down and vent out, instead of pooling against the frame. In practical terms, this means battens installed over the wall wrap before the cladding goes on, creating a clear channel for air and water to move.
There are some exemptions, including certain insulated panel systems and walls that aren’t part of the building envelope, so the requirement won’t apply to every wall on every build. That’s exactly the kind of detail worth confirming early.
Change 2: Clearer provisions for roof construction
The roof ventilation requirements have been restructured to be clearer, with separate provisions depending on whether the insulation runs parallel to the roof plane (think raked or cathedral ceilings) or not parallel (pitched roofs with a horizontal ceiling and an attic space above).
This is more a clarification than a wholesale change. The core roof space ventilation requirements continue to apply in climate zones 6, 7 and 8, as they did under NCC 2022. The restructure simply removes some of the ambiguity that tripped people up previously and gives a cleaner framework to design to.
Change 3: Adoption is staggered across the country
This is where it gets important for anyone working across state lines, because there is no single national start date.
Victoria, the ACT and Western Australia adopted NCC 2025 from 1 May 2026, each with their own transition arrangements. New South Wales and Queensland have deferred adoption until 1 May 2027, so NCC 2022 continues to apply there in the meantime. South Australia has adopted the plumbing provisions but deferred the building provisions. Tasmania and the Northern Territory have taken their own positions on the condensation provisions specifically.
The takeaway is simple: don’t assume. Projects in different states will be working to different versions of the code for at least the next year, so confirm the operative code edition with your building surveyor before you lodge anything.
What’s NOT changing
With this much movement, it’s just as useful to know what you don’t have to worry about.
The residential energy efficiency requirements introduced in NCC 2022, including the seven-star standard, are staying as they are and weren’t revisited in this edition. A number of proposed changes from the draft also did not make the final code. Most relevant for ventilation, the proposed expansion of roof space ventilation into climate zones 4 and 5 was not adopted, so those requirements remain limited to zones 6, 7 and 8.
If you’ve seen that zones 4 and 5 change mentioned elsewhere, that’s why. It was in the draft, but it isn’t in the code you actually have to build to.
What this means for your next project
If you’re designing or building in Victoria, the ACT or WA right now, NCC 2025 is the code you’re working to. If you’re in NSW or Queensland, you’ve got more time, but the direction of travel is clear, and there’s real value in understanding the requirements before they’re mandatory.
The good news is that meeting the new requirements doesn’t have to be complicated. Ventilated battens like the VB10 and VB20 create the cavity needed behind cladding and beneath roofing, with built-in drainage and airflow. And properly specified roof ventilation, combining low-level intake at the eaves with high-level exhaust at the ridge, can be designed to meet or exceed what’s required without reworking the build.
The key is getting it right at the specification stage. Building compliance in from the start is always faster and cheaper than fixing it after the fact.
Where to from here
If you’ve got a project that will be subject to NCC 2025, now or in the next 12 months, and you’re not sure what the changes mean for your design, get in touch with the VENT Systems team. We can walk you through what applies, recommend the right system for your roof and wall types, and help you avoid any surprises at certification.
Or, if you have plans ready to go, you can submit them through our Estimation & Design Service for tailored ventilation recommendations and accurate take-offs. You can even nominate whether your project falls under NCC 2022 or NCC 2025, so your report is built around the code that actually applies to you.
Get in touch with VENT Systems
Or, if you have plans ready to go, you can submit them to our Estimation & Design Servicefor tailored ventilation design and accurate take-offs.