Wall systems · The WA brick shortage
Same house. New walls.
WA’s brick shortage is moving builders from double brick to brick veneer and framed construction, in timber and in steel. The house can look the same, but its energy rating can move. We show you how far, and find the route that keeps it compliant.
- Mid-2023 · Cardup closesWA is left with one major brickmaker
- 1 May 2025 · 7 starsNew WA homes must meet the NCC 2022 energy rules
- 2026 · On allocationMidland Brick rations supply as demand outruns capacity
- 29 Sep 2026 · Restart fundedState money to reopen Cardup, with new bricks from 2027
01The wall lab
What changes inside the wall.
Pick a wall system, then change what a builder would: the cavity insulation, the frame and its specification, the batt, stud spacing and noggings, how the cladding is fixed, the cavity and the colour, or an insulated panel’s core and thickness. Then choose its NatHERS climate zone, which way it faces and the day: the hottest or coldest in the zone’s climate file, or an average day in any month. The section shows heat moving through one stud bay, on average over that day, solved in your browser; move across it to read the temperature. The chart follows the wall hour by hour: slide through the day to read the air, the sun and the heat reaching the room.
Cavity masonryReflective foil in the cavity
- Insulation
- Reflective foil blanket
- Total R-value, whole wall
- R1.79No studs to bridge it
- Mass on the room side
- 139kJ/m²K
- Heat delay
- 8 h
- Swing reaching the room
- 32%
Heavy and slow, and one of the two ways most WA double brick is insulated. A reflective foil blanket splits the cavity into two reflective air spaces, and the inner leaf stores heat on the room side, so the afternoon’s heat arrives late at night, much reduced.
Heavy and slow, and the other common WA choice: loose-fill glasswool blown into the 50 mm cavity. The inner leaf stores heat on the room side, so the afternoon’s heat arrives late at night, much reduced.
Heavy and slow, but lightly insulated. More heat gets through over the day, though it still arrives late and damped.
Well insulated, but the brick sits outside the insulation, so its mass does little for the room. The timber studs bridge the batts slightly.
Steel studs carry more heat past the batts than timber, so the whole wall rates below its insulation label. A reflective cavity wins most of it back, and a thermal break on the studs helps too.
The reflective cavity wins back what the steel studs carry past the batts: this wall reaches {pct} of timber brick veneer with a plain cavity ({twin}). The Code aims for steel at 90 to 95% of timber.
Brick veneer doesn’t need a thermal break, but a strip along each stud still trims the heat the steel carries past the batts: this wall reaches {pct} of timber brick veneer with a plain cavity ({twin}). A continuous board across the frame would do more, as it insulates between the studs too.
AAC veneer swaps the brick for 75 mm aerated concrete panels, about a fifth of brick’s weight. AAC insulates over five times as well as brick for its thickness, so the wall rates about R0.5 higher than brick veneer. It stores less heat, so more of the day’s swing reaches the room, but the hot afternoon’s peak is no higher.
Steel studs carry more heat past the batts than timber, so the whole wall rates below its insulation label, though the AAC panel keeps it about R0.5 above steel brick veneer. A reflective cavity wins most of it back, and a thermal break on the studs helps too.
The reflective cavity wins back what the steel studs carry past the batts: this wall reaches {pct} of timber AAC veneer with a plain cavity ({twin}). The Code aims for steel at 90 to 95% of timber.
A strip along each stud trims the heat the steel carries past the batts: this wall reaches {pct} of timber AAC veneer with a plain cavity ({twin}). A reflective cavity does more.
Light and well insulated. With almost no mass, the afternoon’s heat comes through within the hour and nothing is stored for later.
Battens stand the cladding off the frame, adding an air space outside the batts. With almost no mass, the heat still comes through within the hour.
Light and quick. With the cladding and lining both fixed to the steel, the NCC requires a thermal break of at least R0.2, so the lab goes no lower. That takes the edge off the bridging: this wall reaches {pct} of timber with direct-fixed cladding ({twin}). Battens over a reflective cavity do more.
On battens the cladding isn’t fixed to the steel, so no thermal break is required, and timber battens of 20 mm or more count as one in NatHERS anyway. A reflective cavity brings it close to timber with direct-fixed cladding.
On battens over a reflective cavity, this steel wall reaches {pct} of timber with direct-fixed cladding ({twin}), and needs no separate thermal break. The Code aims for steel at 90 to 95% of timber.
On battens no thermal break is required, as the timber battens already act as one, but a strip under them still trims the heat the steel carries: this wall reaches {pct} of timber with direct-fixed cladding ({twin}). The Code aims for steel at 90 to 95% of timber.
Fire-retardant polystyrene runs unbroken through the panel, so no studs bridge it, and its interlocking joints add little. With almost no mass, the afternoon’s heat comes through within the hour, so the core’s R-value does all the work.
PIR insulates almost twice as well as polystyrene for its thickness, so a thinner panel matches a thicker EPS one. Like any panel, it has almost no mass, so the heat that gets through arrives within an hour or so.
A mineral wool core is chosen where a wall must be non-combustible. It insulates about as well as polystyrene for its thickness, and its extra weight slows the heat a little.
At R0.13 the strip is below the R0.2 the NCC sets for a thermal break, so it can’t stand in for one where cladding is fixed direct.
A reflective foil facing the cavity lifts the air space from about R0.17 to R0.61, as long as it stays clean and faces an open gap.
Steel thickness, wall height and noggings move the result by a few per cent either way; the cavity, battens and thermal break matter far more. Where the plans don’t give the frame, NatHERS assumes 90 × 40 mm studs, 0.75 mm thick, with noggings at 1200 mm.
Studs at 450 mm put a third more steel in the wall than at 600 mm, the NatHERS default; where the engineering allows, 600 mm helps.
02What changes
Three things move at once.
Swapping double brick for brick veneer or a frame changes how much the wall insulates, how much heat it stores, and how much leaks through the frame. A rating weighs all three, for the whole house, every hour of the year.
Insulation
A framed wall holds a full batt between the studs, so on paper it insulates better than double brick, even with reflective foil or loose-fill in the cavity.
R-valueThermal mass
Double brick keeps a heavy inner leaf on the room side of the cavity, where it soaks up heat and gives it back hours later. In brick veneer the brick sits outside the insulation, so the room gets little of that.
MassThermal bridging
Studs carry heat past the insulation, steel more than timber. A thermal break, battens or a reflective cavity wins much of it back.
BridgingThe rating
In Perth’s climate, double brick’s mass often gives it an edge in a NatHERS rating, so the same design can lose stars when it is re-rated as a framed home.
Stars
03Steel framing
Steel frames work. The details matter.
Steel frames are straight, light and termite-proof, and as bricks run short, more WA builders are choosing them. Since NCC 2022, NatHERS counts the heat that flows through steel framing, but it measures steel against timber rather than on its own, so the details that close the gap close it in the rating too. In CSIRO’s modelling for the change, steel-framed houses insulated to match timber rated within 0.1 of a star of the timber house. In the table, steel brick veneer with a reflective cavity comes within a few per cent of timber with a plain one.
The Code sets the details, and aims for steel framing to perform at least 90 to 95% as well as timber. Where lightweight cladding is fixed straight to a steel frame along with the lining, or there’s no lining, it needs a thermal break of at least R0.2: timber battens of 20 mm or more and 12 mm polystyrene strips both count. Cladding on battens isn’t fixed to the frame, so it doesn’t need one, and nor does brick veneer, though a thermal break on the studs still helps both. Under the elemental provisions, a steel-framed wall must also reach a set total R-value with the framing counted, or add reflective insulation or a layer of continuous insulation. And when the plans don’t give the frame, NatHERS assessors model 90 × 40 mm studs at 600 mm, 0.75 mm thick, with noggings at 1200 mm, and a medium wall colour. In New South Wales, BASIX sets the requirements instead, with its own measures for thermal bridging in steel frames.
| Wall | Insulation | Total R-value, whole wall | Between the studs | Mass on the room side | Heat delay | Swing reaching the room |
|---|---|---|---|---|---|---|
| Cavity masonryReflective foil in the cavity | Reflective foil blanket | R1.79 | No studs | 139 kJ/m²K | 7 h | 35% |
| Cavity masonry50 mm loose-fill | R1.3 loose-fill | R1.73 | No studs | 139 kJ/m²K | 7 h | 35% |
| Cavity masonryUninsulated cavity | None | R0.62 | No studs | 139 kJ/m²K | 5 h | 47% |
| Brick veneerTimber frame 90 × 45 · R2.5 batt · studs at 600 mm · non-reflective cavity | R2.5 batt | R2.49 | R3.03 | 7 kJ/m²K | 3 h | 70% |
| Brick veneerSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · non-reflective cavity | R2.5 batt | R1.82 | R3.03 | 7 kJ/m²K | 3 h | 70% |
| Brick veneerSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · reflective cavity | R2.5 batt, reflective cavity | R2.41 | R3.47 | 7 kJ/m²K | 3 h | 70% |
| Brick veneerSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · non-reflective cavity · R0.2 thermal break | R2.5 batt, R0.2 thermal break | R1.94 | R3.03 | 7 kJ/m²K | 3 h | 70% |
| AAC veneerTimber frame 90 × 45 · R2.5 batt · studs at 600 mm · on 24 mm top hats, non-reflective cavity | R2.5 batt | R2.98 | R3.50 | 7 kJ/m²K | 3 h | 82% |
| AAC veneerSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · on 24 mm top hats, non-reflective cavity | R2.5 batt | R2.37 | R3.50 | 7 kJ/m²K | 3 h | 82% |
| Lightweight framedTimber frame 90 × 45 · R2.5 batt · studs at 600 mm · direct fixed | R2.5 batt | R2.22 | R2.77 | 7 kJ/m²K | Under 1 h | 98% |
| Lightweight framedSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · direct fixed, R0.2 thermal break | R2.5 batt, R0.2 thermal break | R1.80 | R2.90 | 7 kJ/m²K | Under 1 h | 97% |
| Lightweight framedSteel frame 90 × 40 × 0.75 · R2.5 batt · studs at 600 mm · on 35 mm battens, reflective cavity | R2.5 batt, reflective cavity | R2.15 | R3.38 | 7 kJ/m²K | Under 1 h | 97% |
| Insulated panelEPS-FR core · 100 mm | EPS-FR core, R2.4 | R2.57 | No studs | 2 kJ/m²K | Under 1 h | 98% |
| Insulated panelPIR core · 100 mm | PIR core, R4.5 | R4.71 | No studs | 2 kJ/m²K | 1 h | 94% |
| Insulated panelMineral wool core · 100 mm | Mineral wool core, R2.3 | R2.50 | No studs | 2 kJ/m²K | 1 h | 95% |
Illustrative. From the wall lab, not product data: typical materials with R2.5 batts, studs at 600 mm, one row of noggings, a medium colour and steel studs of 90 × 40 × 0.75 mm, the NatHERS defaults, in walls 2.4 m high, as the NASH tables assume. Insulation is the product’s own R-value. Total R-value counts every layer and the air films; the whole-wall figure adds the studs, the top and bottom plates and the noggings, with a 0.03 contact resistance where steel meets a lining, as NZS 4214 and the NASH tables use. The lab’s steel figures sit within about 10% of the values NASH publishes. Framing around openings adds more bridging in a real wall, in timber and in steel. Air spaces are treated as unventilated. Delay and swing are for Perth’s hottest day in its NatHERS climate file, on a west wall, with the room held at 24 °C. The double brick rows show the two cavity systems most WA builders use; the steel rows show the Code’s thermal break and three common upgrades: a reflective cavity or an R0.2 thermal break behind brick veneer, and cladding on battens over a reflective cavity. The AAC veneer rows use 75 mm panels at R0.6, the figure Hebel gives for its PowerPanelXL, on 24 mm top hats, which bridge only the cavity and are left out. The panel rows compare the three cores at 100 mm, between 0.5 mm steel skins, with the joints treated as continuous; EPS-FR uses Bondor’s declared R-values, and PIR and mineral wool typical ones. A thermal break is modelled as a strip of insulation along the outer face of each stud, the width of the frame.
Sources. NatHERS Technical Note, 23 October 2024 (default steel framing, thermal breaks and wall colour); NatHERS Assessor Handbook, April 2024, chapter 11; CSIRO, Thermal bridging for residential building energy rating, 2020; ABCB, Thermal bridging in residential buildings, 2023; NASH, Technical Note NTN 006, 2023; NCC 2022 Housing Provisions, Part 13.2; NSW Planning Portal, BASIX measures to address thermal bridging; Bondor, BondorPanel® (declared R-values of its EPS-FR panels); CSR Hebel, Hebel PowerPanelXL (75 mm panels on horizontal top hats), with R0.6 for the panel at 4% moisture content from its product flyer and 30.9 kg/m² from its EPD.
04For steel framers
Steel-framed and short of 7 stars? We’ll find the route.
Framing companies bring their steel-framed jobs to us because we know where the stars go, and how to win them back. Often it’s the details: a thermal break or battens, a reflective cavity, studs at 600 mm where the engineering allows. The rating also turns on how the frame is modelled, and we model steel to the letter of the NatHERS rules, so its details get full credit. Where the star band is the wrong test for the design, a Performance Solution under H6V2 tests it against the Code’s own reference house instead, and that often needs fewer upgrades than the star band would.
We agree the brief with your building surveyor before any modelling.
Detail the frame
Battens, a reflective cavity or a thermal break win back much of what the studs carry past the batts. Cheapest when they’re in the plans from the start.
Tune the design
Orientation, glazing and shading, set early. Often cheaper than adding insulation, if it’s done before the plans are fixed.
Test it properly
A Performance Solution against the reference house, when the star band is the wrong test for the design. How it works
05Wall System Check
Rate it before you switch.
For builders, framers and designers. Send a design, or your whole standard range. We rate it in each wall system you’re weighing and show what each needs to comply, including where a Performance Solution is the better route.
- 01
Send the plans
A design or a standard range, the wall systems you’re weighing, and where you build.
- 02
Rate each system
Our accredited assessors rate the design in double brick, brick or AAC veneer and framed construction, in timber and in steel.
- 03
Compare the upgrades
What each system needs to reach 7 stars, side by side.
- 04
Choose the route
NatHERS, the elemental provisions or a Performance Solution under H6V2, all delivered in-house.
06Questions
Straight answers on wall systems.
Will switching from double brick lower my star rating?
It can. A framed wall usually holds more insulation, while double brick keeps heavy mass on the room side. In Perth’s climate that mass often counts for more, so the same design can lose stars in the switch. The only way to know for your design is to rate it.
Can a steel-framed home still reach 7 stars?
Yes. NatHERS counts the extra heat that flows through steel framing, measured against timber, so steel needs details that timber doesn’t: a thermal break or battens under lightweight cladding, and often a reflective cavity or a thermal break behind brick veneer. Detailed properly, a steel-framed wall performs close to a standard timber one. Where the star band is still the wrong test, a Performance Solution under H6V2 can show the design meets the Code.
Does a steel frame always need a thermal break?
No. The NCC requires one, of at least R0.2, where lightweight cladding and the lining are both fixed straight to the steel, or the wall is unlined. Cladding on battens and brick veneer don’t need one, but a strip on each stud still trims the heat the steel carries: try R0.13 to R0.3 in the wall lab. In New South Wales, BASIX applies instead, with its own measures for steel frames.
Does the wall colour matter?
Yes. A dark wall soaks up more sun, which adds heat on a Perth summer afternoon and a little warmth in winter; a rating weighs both. NatHERS models the colour on the plans, or medium where none is given, so it pays to specify it.
Does brick veneer keep the benefits of double brick?
Not the mass. In brick veneer the brick sits outside the insulation, so it protects the wall but stores little heat for the room. Its insulation is usually much better, though.
How does AAC veneer compare with brick veneer?
It insulates better and stores less heat. A 75 mm AAC panel is about R0.6, against about R0.13 for brick, so with the same batts the wall rates about R0.5 higher. Brick’s extra weight evens out more of the day’s swing, though on Perth’s hottest day the peak heat reaching the room comes out about the same. Compare them in the wall lab.
Where do insulated panels fit?
An insulated panel runs its insulation unbroken across the wall, with no studs to bridge it, so its R-value holds up. Like a lightweight framed wall, it has almost no thermal mass. EPS-FR is the usual core; PIR insulates almost twice as well for its thickness, and mineral wool is used where a wall must be non-combustible. Try them in the wall lab.
Which wall system carries the least embodied carbon?
Of the systems in our labs, lightweight cladding on a timber frame carries the least upfront carbon, and double brick, with its brick internal walls, the most. The carbon lab shows how far apart they are, and what else in the home moves the number.
Can you rate our whole range in each system?
Yes. As with a modular range, we set each design up once in each wall system, then rate each job as it comes in. Most home ratings come back within one business day of complete plans.
Wall System Check
Switching walls? Rate it before you build.
Send the plans and the wall systems you’re weighing. We reply within 24 hours.