1. Why this guide is different from our paint booth and gigafactory articles
SBKJ has already published two long-form references adjacent to this one. The automotive paint booth HVAC duct guide covers the booth itself — spray hall, flash-off, bake oven, prep deck and the recirculating air-handling tree. The battery gigafactory HVAC duct guide covers the dry-room, electrolyte-fill, formation and ageing zones that sit upstream of an EV plant. This guide picks up where those two stop. It is about the building that takes a painted body shell, a finished battery pack, and several thousand other components, and turns them into a moving vehicle.
That building is sometimes called the trim-and-final hall, sometimes the assembly hall, sometimes the general assembly area, and sometimes simply the line. The HVAC challenge is the same: protect a large warehouse-scale envelope full of people, robots and AGVs from the heat, fume, dust and gas loads the process throws at it, while staying inside the energy and acoustic envelopes the client signed up to. In the Australian market the framing standards are AS 1668.2 for ventilation rates, AS 4254 for the sheet-metal duct, AS 5034 for hydrogen exhaust at any battery charging or staging area, AS 1668.1 with AS 4391 for smoke management, and ASHRAE 62.1 as a reference where the client specification calls for it.
This guide steps through every functional zone of an Australian assembly plant — body-in-white, glue and adhesive, paint shop integration, battery pack final assembly, EV final commissioning, crash and dyno cells, AGV-conditioned avenues, PDI bay, supplier-park feeders — and explains what the duct has to do, what construction class it has to meet, and how the SBKJ machine line fabricates it.
2. The Australian assembly footprint in 2026
Australia closed its volume passenger-car manufacturing in late 2017 with the winding-down of Toyota at Altona Victoria, Holden at Elizabeth South Australia, and Ford at Broadmeadows Victoria. The supplier parks attached have since been redeveloped. What refilled the gap, slowly through the late 2010s and faster after 2020, was a mosaic of niche, commercial and zero-emission vehicle assembly that is still expanding in 2026. The HVAC scope on those plants is, if anything, more demanding than the 2017 footprint, because the variety of vehicles being assembled — from electric utes through heavy buses to 26-tonne trucks — drives a wider range of process loads through the same building.
The ten Australian operators that this guide is calibrated to are:
- Tritium DC chargers (Brisbane Murarrie, Tennessee USA). Tritium is the Brisbane-headquartered DC fast-charger manufacturer that builds 50 kW through 350 kW DC charging units for the Australian, European and North American EV charging networks. Although Tritium is a component plant rather than a vehicle assembly plant, the ventilation and electronics-conditioning load profile is closely related to an EV final-assembly hall and we treat it as in-scope here.
- SEA Electric (Melbourne). SEA Electric retrofits and upfits commercial vehicles — light trucks, vans and prime movers — onto its proprietary SEA-Drive electric powertrain. The Melbourne facility carries out the powertrain swap-in on glider chassis sourced from OEM partners.
- ACE-EV Group (Melbourne). ACE-EV is a Melbourne-based light-commercial EV assembler with a focus on electric utes, vans and microcars built around modular skateboard platforms.
- Janus Electric (Sydney). Janus Electric specialises in heavy prime mover electrification, swapping diesel powertrains for an exchangeable battery system designed for line-haul transport.
- Volgren (Melbourne, Brisbane). Volgren is the largest Australian-owned bus body builder, with main fabrication and trim facilities in Melbourne and Brisbane. Volgren bodies sit on chassis from Volvo, Mercedes-Benz, Scania and others, and increasingly on zero-emission battery-electric chassis.
- BusTech (Brisbane Wacol). BusTech is a Brisbane-based bus and coach assembler at the Wacol manufacturing precinct, producing route, school and coach buses including its own ZDi battery-electric platform.
- Volvo Group Australia (Wacol QLD). Volvo Group Australia operates a large truck and bus assembly plant at Wacol Brisbane that builds Volvo and Mack heavy-duty trucks for the Australian and New Zealand markets, including increasingly electric-drive variants.
- PACCAR Bayswater VIC. PACCAR Australia at Bayswater Melbourne is the assembly plant for Kenworth and DAF heavy-duty trucks for the Australasian market — one of the largest single-shed truck assembly operations in the southern hemisphere.
- Iveco Trucks Australia (Melbourne, Dandenong). Iveco's Dandenong site has been a continuously operating Australian assembly plant since the 1950s, with light, medium and heavy truck variants for Australian and New Zealand markets.
- Mack Trucks Australia (Wacol QLD). Mack Trucks operates within the same Wacol precinct as Volvo Group Australia and shares supplier-park infrastructure for heavy truck assembly.
The HVAC scope across these ten operators is dominated by three building types: large-span warehouse-scale assembly halls; smaller two-storey trim-and-final cells; and ancillary buildings for charging, testing, paint integration, PDI and parts logistics. The duct fabrication brief for SBKJ on these projects almost always reduces to the same machine line — SBAL-V galvanised duct line for the rectangular trunks, SBTF-1602 spiral tubeformer for the medium-bore branches, and SBTF-2020 spiral tubeformer for the large-bore exhaust risers.
3. The standards stack
Every HVAC ductwork specification in an Australian assembly plant ultimately points back to one or more of five standards. None of them is optional, and every duct fitting that SBKJ ships into the Australian market is fabricated to be compatible with the dimensional, leakage, and construction provisions of all of them.
3.1 AS 1668.2 — mechanical ventilation in buildings
AS 1668.2 sets the design ventilation rates for occupied buildings in Australia. For an assembly plant the relevant clause is the light manufacturing classification, with a per-occupant rate (V_p) of 4 L/s per person, layered with a per-floor-area allowance (V_b) and process exhaust supplement for welding, soldering, painting or chemical handling. A 200-occupant 8,000 m² trim-and-final hall typically lands on 12,000–18,000 L/s once V_p and V_b are accounted for, before process exhaust make-up. SBKJ duct sizing is anchored to that supply figure and a transport velocity of 7–10 m/s in the main trunks falling to 4–6 m/s at the diffuser tap-offs.
3.2 AS 4254 — ductwork for air-handling systems in buildings
AS 4254 is the Australian construction standard for sheet-metal ductwork. Part 1 covers flexible duct and Part 2 covers rigid sheet-metal duct. Together they prescribe gauge, joint type, hanger spacing, leakage class and dimensional tolerance for every duct fitting in the building. For assembly plant work, almost all rectangular supply and return runs are AS 4254.2 medium-pressure construction (Class C leakage); main exhaust risers from BIW and dyno cells are AS 4254.2 high-pressure construction (Class B leakage); and flexible drops to terminals are AS 4254.1 Class 1 with a maximum length of typically 1.5 m. The SBAL-V auto duct line that SBKJ supplies into the Australian market is configured by default to AS 4254 dimensional tolerances on length, width, squareness and flange flatness — the same Pittsburgh and TDF flange interface that the standard recognises as compliant.
3.3 AS 5034 — battery installation hydrogen exhaust
AS 5034 is the Australian standard for installation of permanently installed batteries, originally drafted around lead-acid battery rooms. Its hydrogen exhaust framing has been adopted by Australian designers as the reference for any battery charging or staging environment, including lithium-ion staging, because the consequences of a thermal event apply the same dilution principles. Relevant zones in an assembly plant are battery pack final-assembly staging racks, EV final-commissioning DC charging stations, and any forklift charging mezzanine. The standard requires continuous mechanical ventilation holding hydrogen below 25% of the lower explosive limit (LEL), with the exhaust grille at high level. For a 350 kW DC commissioning bay this resolves to 1,500–3,000 L/s continuous extract per charger, ducted to a roof discharge stack.
3.4 AS 1668.1 with AS 4391 — smoke management
For any assembly hall above 2,000 m² fire compartment, or above 18 m clear ceiling height, smoke management becomes a first-class design driver. AS 1668.1 sets the principles for fire and smoke control in buildings, and AS 4391 (the smoke management application standard) sets the calculation procedure for mechanical smoke exhaust. In a warehouse-scale assembly hall the smoke management duct often shares the riser tree with the process exhaust system, with motorised dampers to swap modes between normal and fire conditions. The duct fabrication implication is that the riser is on a higher pressure class and a tighter leakage class than the surrounding general-ventilation duct — typically AS 4254.2 high-pressure with Class B leakage — and the SBTF-2020 spiral tubeformer is the natural fit for the large-bore vertical riser sections.
3.5 ASHRAE 62.1 — the international reference
Where an Australian client also has a US or international parent specification — increasingly common in the EV and bus assembly space — ASHRAE 62.1 turns up as a parallel reference. Its outdoor air requirements for vehicle assembly halls are broadly compatible with AS 1668.2 once a consistent occupancy density is assumed, but the detailed tabulation differs. SBKJ duct is sized to whichever of the two standards is more demanding for the specific zone, and we are willing to model both in the design submission.
4. Zoning the building
Before any duct can be sized, the building has to be zoned. An assembly plant is not a single ventilation zone, and treating it as one is the most common mistake we see in early-stage tender drawings. The zoning logic that SBKJ uses on every Australian assembly plant fit-out has eight functional groups, and every duct run in the building belongs to exactly one of them.
4.1 Body-in-white (BIW)
BIW is the section of the line where the bare metal body shell is welded together. In a passenger-car or light-commercial EV plant, BIW is dominated by robotic spot welding cells. In a heavy truck or bus plant, BIW shifts toward MIG welding by manual operators on jigs, with some robotic spot welding in selected sub-assemblies. Either way, BIW is the highest fume load in the building and is treated as a dedicated extract zone with source capture at every welding station. We cover BIW in detail in section 5 below.
4.2 Glue and adhesive lay-down
Modern vehicle bodies use structural adhesives — both to bond panels into the body-in-white before welding, and to bond glass and trim into the cabin downstream. The adhesives release VOCs both at lay-down and during cure. In an EV plant with significant aluminium content, the adhesive load can be higher than in a conventional steel plant. The HVAC response is local extract at each lay-down station — covered in section 6.
4.3 Paint shop integration
The paint shop itself is covered in detail in our paint booth HVAC duct guide. The integration boundary — where the paint shop hands the painted body off to general assembly — is in scope here. The integration boundary is typically a temperature-controlled air-lock between the paint booth oven cool-down and the trim-and-final line, with cross-zone pressure control to prevent oven exhaust migrating into the assembly hall. Section 7 covers the duct work.
4.4 Battery pack final assembly
In an EV plant, the battery pack arrives from an upstream cell or pack manufacturing facility (covered in our gigafactory HVAC guide) and is mated to the vehicle on the trim-and-final line. The mating zone is treated as cleanroom-adjacent — typically ISO Class 8 or unclassified-but-clean — with positive pressure relative to the surrounding hall. Section 8 covers the duct work.
4.5 EV final commissioning
Before a finished EV leaves the line it is commissioned: the high-voltage system is energised, the BMS handshakes the chargers, and an end-of-line DC charge cycle confirms the pack and the on-board charging system. The 50 kW to 350 kW DC chargers used at this end-of-line station are the highest hydrogen-risk zone in the building and trigger AS 5034 exhaust. Section 9 covers it.
4.6 Crash test cell and chassis dyno cell
Crash test cells (where present in development plants) require isolated air handling with explosion-rated ventilation if any pyrotechnic restraint testing is performed. Chassis dynamometer cells, which are still common in heavy truck and bus plants for ICE engine testing and increasingly used for EV powertrain validation, require very high-airflow exhaust capture during ICE runs. Section 10 covers both.
4.7 AGV-conditioned avenues
Most modern Australian assembly plants use automated guided vehicles or autonomous mobile robots to ferry sub-assemblies between stations. AGVs and AMRs are sensitive to ambient temperature drift, humidity drift and air-current interference with their laser sensors. Section 11 covers the conditioning specification for those zones.
4.8 PDI bay and amenities
Pre-delivery inspection is the last station on the line, where the finished vehicle is inspected, washed and prepared for despatch. PDI is treated as ambient HVAC with comfort cooling — section 12 covers it. Amenities (offices, change rooms, break rooms) are conventional comfort HVAC and are not specifically covered here.
5. Body-in-white welding fume capture
Body-in-white is the largest single HVAC load in any vehicle assembly plant. The extract demand from a single robotic spot welding cell can range from 800 to 2,500 L/s per cell depending on weld density, and a passenger-car or light-commercial EV plant might have 60–120 such cells in a single bay. Multiplied out, BIW extract typically accounts for 25–40% of the total mechanical airflow in the building, despite occupying perhaps 15% of the floor area. Getting the BIW duct right is the difference between a plant that meets its workplace exposure standard and a plant that doesn't.
5.1 Source capture is the default
For decades the default approach was dilution ventilation — pump enough outside air to keep fume below the exposure limit at breathing height. Source capture has become the default for new builds and major refurbishments since the early 2010s: the extract hood sits within 200–400 mm of the weld arc, captures the fume at source, and ducts it through filtration to a roof discharge. Robotic spot weld cells with fixed weld guns use a slot hood mounted to the gun frame at 0.5–1.0 m/s capture velocity. Manual MIG welding on bus and truck BIW uses on-torch extraction at 50–80 L/s per gun, supplemented by an overhead canopy hood for spillover. Duct transport velocity is 18–22 m/s for fine particulate, falling to 15–18 m/s in the filter manifold.
5.2 MERV 14+ filtration
The captured fume cannot simply be discharged — Australian environmental regulations and the AS 1668.2 dispersion criteria require filtration. The default for weld fume is a cartridge filter bank rated MERV 14 or higher (MERV 16 is increasingly common on new builds), with a face velocity of 0.4–0.5 m/s at the cartridge. The filter unit is sized for an installed capacity 25–40% above the calculated peak demand, so that filter loading does not pull the system off-spec between changes. Cartridges are typically pulse-jet cleaned on a programmed cycle, with a hopper at the base of the unit collecting the dislodged dust into a sealed drum for disposal.
5.3 Duct construction class
BIW extract duct is a high-pressure, high-leakage-class application. The negative static pressure on the suction side of the filter can range from 1,500 to 2,500 Pa at peak load, well above the medium-pressure threshold in AS 4254.2. The standard response is to upgrade the rectangular trunk to high-pressure construction with intermediate stiffeners and Class B leakage, or to replace the rectangular trunk with spiral-formed round duct on the SBTF-2020 machine. Spiral round duct is inherently stiffer than rectangular at the same gauge and naturally leakage Class B or better — which is why we recommend it on every BIW project where the building geometry allows it.
5.4 Stack discharge and dispersion
The discharged extract is still warm and carries trace metal fume below the filter cut-off. AS 1668.2 requires the discharge stack be sized and positioned so the ground-level concentration meets the workplace exposure standard at the building boundary, with allowance for downwash and re-entrainment into intakes. In practice: stack height 3 m above the eaves, discharge velocity 12–15 m/s, stack-to-intake separation at least 8 m. The spiral riser to the roof is on SBKJ's scope and is fabricated on SBTF-2020.
6. Glue and adhesive lay-down
Structural adhesives in modern vehicle bodies range from epoxy panel bonders to polyurethane glass-bonders to acrylic trim adhesives. Each releases a different VOC profile, and the cumulative load warrants local extract at every station that opens a cartridge. Capture velocity at the nozzle is 0.4–0.8 m/s with a slot hood within 300–500 mm of the bead. Duct transport velocity is 12–15 m/s — lower than weld fume because the contaminant is gas-phase.
Adhesive extract is never recirculated. The captured air is ducted directly to a roof discharge, with a thermal oxidiser or carbon scrubber upstream where the local environmental authority requires VOC abatement. The duct fabricator's risk is corrosion: some adhesives release acidic decomposition products on heated cure. We specify galvanised steel as the minimum, with stainless 304 on the discharge side where the client design calls for it.
7. Paint shop integration
The paint booth itself is covered in our automotive paint booth HVAC duct guide. In scope here is the integration boundary where the painted body leaves the bake oven cool-down and enters the trim-and-final line. It serves three functions: thermal step-down from oven cool-down (40–50 °C) to assembly hall ambient (22–26 °C); pressure differential preventing oven exhaust migration into the assembly hall; and a clean-air buffer preventing shop dust migrating back into the paint area.
The integration boundary is typically a 6–8 m air-lock corridor with two pairs of overhead air curtains, a dedicated supply handler delivering filtered air at neutral pressure, and a thermostatic damper modulating supply temperature. The duct is on SBKJ's scope and is fabricated to AS 4254.2 medium-pressure construction in galvanised steel.
The other paint-shop integration item on SBKJ's scope is the main exhaust riser tree from the paint booth oven, prep deck and spray hall — all discharging through the assembly building roof. That riser tree typically runs at 15,000–35,000 L/s total airflow, on a high-pressure class with Class B leakage, fabricated on the SBTF-2020 spiral tubeformer.
8. Battery pack final assembly
In a pure-EV plant, battery pack final assembly is a dedicated zone where the finished pack — typically 400–800 kg, 60–120 kWh, supplied either from an upstream gigafactory or from a local pack supplier — is mated to the vehicle. The mating operation is mechanical (lifting and bolting) and electrical (high-voltage harness connection and BMS handshake). It is not particularly fume-heavy, but it is contamination-sensitive: any conductive dust that lands on the pack cell-side terminal or on the harness connectors during mating is a long-term reliability risk.
The HVAC response is to treat the mating zone as cleanroom-adjacent. ISO Class 8 (100,000 particles/m³ at 0.5 µm) is the typical design target, achieved with a dedicated overhead supply ceiling using HEPA H13 terminal filters, a positive pressure of 5–10 Pa relative to the surrounding hall, and a return-air system at low level. The duct on the supply side is fabricated to AS 4254.2 medium-pressure construction with sealed Pittsburgh joints; the H13 filter housings are on the air-handler vendor's scope.
The other HVAC consideration in the battery pack zone is fire and thermal-event response. Lithium-ion packs in the rare event of thermal runaway release flammable electrolyte vapour and hot off-gas. Australian fire codes do not yet prescribe a specific exhaust regime for battery final-assembly zones, but most tenants follow the AS 5034 framing applied to the staging racks immediately upstream of the mating station — a continuous low-level extract holding hydrogen and methane below 25% LEL under the worst-case off-gas scenario. The duct sizing for that extract is on SBKJ's scope and is fabricated on the SBTF-1602 spiral tubeformer for the medium-bore branches and SBAL-V for the rectangular collection trunks.
9. EV final commissioning
The end-of-line commissioning station connects the finished EV to a real DC fast-charger, handshakes the BMS, and runs an end-of-line charge cycle confirming the high-voltage system. Chargers range from 50 kW for light-duty up to 350 kW for heavy commercial. At Australian operators, Tritium DC chargers manufactured at Brisbane Murarrie are commonly specified — both for local manufacture and well-supported diagnostic interface.
From an HVAC point of view, the commissioning station is the highest hydrogen-risk zone in the building. The risk is not from normal charging — modern lithium chemistry does not vent hydrogen during normal operation — but from the abnormal envelope: cell internal short, BMS fault, charger fault, or a damaged pack on the line. AS 5034 captures this. Continuous mechanical extract at each bay is sized to hold hydrogen below 25% of LEL at worst case, with the high-level grille positioned directly above the charger and vehicle.
Typical sizing for a 350 kW DC bay is 1,500–3,000 L/s continuous extract, ducted to a roof stack with the same dispersion criteria as BIW exhaust. The duct is fabricated on SBTF-1602 for medium-bore branches and SBTF-2020 for the roof riser.
The other consideration is heat rejection. A 350 kW DC charger dissipates 5–8% of its rated power as heat — 18–28 kW per charger at full load. With four chargers per bay and a 26 °C design ambient, the local load can lift bay temperature to 30–32 °C without dedicated cooling. SBKJ's standard recommendation is an overhead cassette-style fan-coil bank per bay, sized to peak charger demand plus solar gain on west-facing facades.
10. Crash and dyno cells
Crash test cells are present in development plants and in some heavy commercial assembly plants where end-of-line crash sled testing is performed. The HVAC envelope of a crash cell is dictated by two requirements: explosion containment for any pyrotechnic restraint test (airbag deployment, seat-belt pre-tensioner deployment), and contamination isolation from the rest of the building. The standard solution is an isolated air-handler dedicated to the cell, with the supply and return duct passing through a fire-rated penetration in the cell wall, motorised isolation dampers on both sides, and an explosion-relief panel sized per the cell volume and the worst-case overpressure. The duct fabrication on the cell side is to AS 4254.2 high-pressure with Class B leakage, in galvanised or stainless construction depending on the cell-side environment.
Chassis dynamometer cells are present in heavy truck and bus assembly plants and in EV development cells. For ICE testing, the dyno cell carries an exhaust capture system that connects to the vehicle tailpipe and ducts the exhaust gases directly to a roof discharge through a high-temperature duct system — typically Inconel or stainless 309 in the immediate post-tailpipe section, with a transition to galvanised in the cooler section downstream. The cell ventilation rate is 80–120 air changes per hour during ICE engine runs to manage the heat load, with the ventilation air drawn from outside through a dedicated supply tower and exhausted through a separate stack. The cell is held at 5–10 Pa negative relative to the surrounding hall to prevent exhaust gas migration.
For EV powertrain testing in the same dyno cell, the exhaust capture system is not used and the ventilation rate drops to 20–30 ACH for thermal management of the dynamometer hardware. The cell pressure regime stays the same. The duct work for the dual-mode ICE/EV dyno cell is more complex than a single-mode cell because the high-temperature post-tailpipe section has to be either disconnected mechanically when running EV mode or supported with a parallel cool-air path. SBKJ has fabricated the cool-air parallel duct for several Australian operators using the SBTF-2020 spiral tubeformer in stainless construction.
11. AGV and collaborative robot zones
Automated guided vehicles and autonomous mobile robots are pervasive in modern vehicle assembly plants. They ferry sub-assemblies from the storage rack to the line, deliver kitted parts to operators, and in some plants carry the body shell itself from station to station. The sensors that AGVs use to navigate — laser scanners, depth cameras, ultrasonic detectors — are sensitive to two HVAC variables: stratified air currents that interfere with the laser return, and ambient temperature drift that affects sensor calibration.
The HVAC response in AGV-conditioned avenues is twofold. First, the supply diffusers in the avenue are specified as low-throw types — typically slot diffusers or perforated-plate diffusers with a discharge velocity below 1.5 m/s and a throw pattern that does not cross the AGV travel lane. High-throw drum-style diffusers, common in older industrial buildings, are explicitly disallowed in AGV zones because the cross-current sweeps the laser return and produces phantom obstacles in the AGV path. Second, the avenue is held to a tighter temperature and humidity tolerance than the surrounding hall — typically ±2 °C around 22 °C and ±10% RH around 50% RH. The tolerance band is set by the AGV vendor specification, not by AS 1668.2, but the duct sizing has to deliver the supply rate that maintains the tolerance.
The duct work in AGV zones is fabricated on SBAL-V for the rectangular trunks and on SBTF-1602 for the round drops to the slot diffusers. The diffuser interface — typically a flexible drop on the supply side and a side-wall return grille at low level — is on SBKJ's scope and is supplied as a kit alongside the duct.
12. PDI bay and the back of the line
The PDI bay is the last station before the finished vehicle is despatched. Inspection is visual and electrical (no fume), washing is wet (potential humidity load), and any final touch-up paint is performed in an isolated cell with its own extract. The PDI HVAC envelope is comfort cooling — 22–26 °C ambient, 40–60% RH, AS 1668.2 occupant ventilation rate — with a dedicated wash-bay extract on the wet section. The duct work is fabricated to AS 4254.2 medium-pressure construction in galvanised steel.
The wash-bay extract is the only HVAC item in the PDI bay that needs special attention. The captured air carries entrained water spray, detergent aerosol and (on some lines) wax aerosol. The extract duct is fabricated in galvanised construction with sealed slip joints and a slope towards a low-point drain to handle condensate; the discharge is to a roof stack with droplet eliminator on the upstream face. The extract rate is sized to one air change per minute of the wash-bay volume during active wash cycles, falling to one air change per ten minutes between cycles via a VFD-controlled fan.
13. Acoustic and energy framing
HVAC noise in an assembly plant has two failure modes. The first is interfering with the workplace audibility of the line stop alarms, which is a safety-critical concern. The second is rising above the workplace exposure standard for noise, which under Safe Work Australia model regulations is 85 dB(A) over an 8-hour shift. The HVAC contribution to these failure modes is dominated by duct-borne fan noise and air-velocity-induced noise at terminals.
The standard acoustic class for an Australian assembly hall is NC-50 (approximately 55 dB(A)) in the production area, NC-40 in the offices and break rooms, and NC-55 in the dyno and crash cells where protective hearing is mandatory. Achieving NC-50 in a hall with high-airflow BIW extract requires either lined duct silencers on the extract trunks or oversized duct with low velocity to push the duct-borne noise below the cell process noise. SBKJ defaults to oversized duct — a 30% over-size on the trunk diameter relative to the strict aerodynamic minimum — because it eliminates the silencer maintenance burden over the plant life.
On the energy side, more Australian assembly plant clients are targeting a NABERS for Industrial energy benchmark, which is the industrial sibling of the more familiar NABERS for Office rating. NABERS for Industrial rewards low specific fan power, low duct leakage, demand control on process exhaust, and recovery of waste heat from process exhaust streams. The duct fabrication implications are: tighter leakage class than the AS 4254 minimum (Class B or C rather than the default Class D), VFD-driven fans on every process exhaust, and a heat-recovery loop on the BIW exhaust where the waste-heat enthalpy supports it. SBKJ duct is fabricated to Class B leakage as the default on every project where the client specification calls for a NABERS rating.
14. Compressed air and HVAC integration
Most assembly plants run a compressed-air system in parallel with the HVAC system, and the two often share a plantroom. The compressed-air system serves pneumatic tooling on the line, paint guns in the touch-up booths, and tyre-mounting equipment in the PDI bay. From an HVAC point of view, the compressed-air system is a heat source — every kilowatt of compressor power becomes heat that has to be rejected — and a humidity sink — every kilogram of moisture in the inlet air becomes condensate that has to be drained.
The standard practice is to integrate the compressed-air dryer with the HVAC system rather than treating them as two separate utilities. The dryer's heat of compression is rejected through a coil that becomes part of the HVAC heat-rejection circuit; the dryer's condensate drains into the HVAC condensate management system. This integration reduces the compressor cooling tower load by 25–40% in the typical Australian climate, and is increasingly specified as a default on new builds. The duct fabrication implication is straightforward — a small extract duct on the dryer cabinet that ties into the plantroom return — but is worth flagging because it is often missed at the design coordination stage.
15. The SBKJ machine line for an Australian assembly plant
Across all of the zones above, the SBKJ machine configuration that fabricates the duct is consistent. There are three machines that do almost all of the work, and a fourth that does the rest.
15.1 SBAL-V — galvanised auto duct line for rectangular trunks
The SBAL-V auto duct production line is the workhorse for rectangular supply, return and exhaust trunks across the building. It coil-feeds 0.5–1.5 mm galvanised steel, cuts to length, notches, beads, and folds into a TDF-flange box section in a single pass. Output is typically 8–12 m of finished rectangular duct per minute on production-cycle settings. The SBAL-V is configured by default for AS 4254.2 dimensional tolerances and ships with a Siemens or Mitsubishi PLC, depending on the buyer's preference. For the majority of supply and return duct in a typical Australian assembly plant — the AGV-zone trunks, the PDI bay supply, the office return, the integration corridor — the SBAL-V is the right machine. We compare the SBAL-V against its predecessor in SBAL-V versus SBAL-III.
15.2 SBTF-1602 — medium-bore spiral tubeformer
The SBTF-1602 spiral tubeformer fabricates round duct from 200 mm to 1,600 mm diameter in galvanised, aluminium or stainless construction. For the medium-bore branches in a typical Australian assembly plant — the BIW collection branches, the AGV-zone drops, the battery pack zone supply, the EV commissioning bay extract — the SBTF-1602 is the natural fit. Output is typically 12–18 m per minute on a 600 mm diameter coil, falling to 6–8 m per minute at 1,200 mm diameter. The machine ships with an integrated coil-end stripper and an exit cut-off saw, and the running cost is dominated by lockformer roller wear which we rate at over 200,000 m of duct between regrinds.
15.3 SBTF-2020 — large-bore spiral tubeformer
The SBTF-2020 spiral tubeformer fabricates round duct from 1,000 mm to 2,000 mm diameter and is the machine that produces the main exhaust risers — paint shop oven discharge, BIW filter discharge, EV commissioning bay riser, dyno cell exhaust, smoke-management riser. The SBTF-2020 is also the right machine for the supply main on a large-span assembly hall where the design airflow exceeds 25,000 L/s on a single trunk. Output is typically 4–8 m per minute on a 1,500 mm diameter coil, falling to 2–4 m per minute at 2,000 mm diameter. The machine ships in a 12 m × 4 m footprint with a 6 m run-out, and is the largest single piece of HVAC machinery on most assembly plant fit-out projects.
15.4 Ancillary fittings — TDF flange, flexible drops, dampers
Beyond the three primary machines, every assembly plant project also needs a TDF flange machine for rectangular duct ends, flexible drops between the rigid round duct and the diffuser terminals, and motorised dampers at every zone boundary. SBKJ supplies the TDF flange machine alongside the SBAL-V as a standard kit, and we source the flexible drops and dampers from approved Australian distributors so that the plant has a local maintenance source.
16. Procurement timeline for an assembly plant fit-out
A typical Australian assembly plant fit-out has a 12–18 month design and construction window, of which the HVAC ductwork procurement and installation occupies 4–8 months on the critical path. The phasing breaks down as follows.
- Months 1–2 — concept design. Plant zoning is set, the standards stack is agreed (AS 1668.2, AS 4254, AS 5034, AS 1668.1 with AS 4391, ASHRAE 62.1 reference), and the design airflows are calculated to a 70% confidence level.
- Months 3–4 — detailed design. Duct routing is finalised on a 3D BIM model, fitting take-offs are produced, and the duct fabrication scope is tendered. SBKJ is typically engaged at this stage, both as a fabrication-machine supplier to the plant's in-house duct shop (where the plant has one) and as a fabricated-duct supplier through our distributor network.
- Months 5–6 — fabrication start. The first SBAL-V trunks are fabricated and delivered to site for first-fix installation. Spiral runs follow on the SBTF-1602 and SBTF-2020 as the trunk routing is verified on site.
- Months 7–10 — installation. Trunk installation, branch installation, terminal installation and air-balancing run sequentially. The BIW extract is typically the last system to be commissioned because it depends on the robotic weld cells being installed and their final-position confirmed.
- Months 11–12 — commissioning and balancing. Final balancing to design airflow, leakage testing to AS 4254 Class B or C as applicable, and acceptance testing against the project specification.
- Months 13–18 — production ramp. The plant moves from commissioning into pilot production and then full production. The HVAC system is monitored against design and any reactive adjustments are made.
The single biggest schedule risk in this window is the BIW extract — both the duct fabrication and the cartridge filter unit. Both have lead times of 12–16 weeks from order, and any change in the welding cell layout late in the design phase ripples through the whole BIW extract scope. SBKJ engineering can compress the duct fabrication side of that ripple to 6–8 weeks where the order is placed on a stocked-coil specification, but the filter unit lead time is on the filter vendor's scope and outside our control.
17. The supplier-park dimension
A typical Australian assembly plant is not a standalone building. It sits inside a supplier park — a cluster of feeder buildings on the same precinct that supply seats, dashboards, harnesses, exhaust systems (for ICE plants), battery packs (for EV plants), and final-trim plastics. The HVAC duct work in the supplier-park feeder buildings is in scope on most projects because the plant operator wants a single duct fabrication contract across the precinct. The feeder building HVAC envelopes are simpler than the main assembly hall — most are conventional industrial supply-and-return with localised process extract — but they are large in aggregate and the duct fabrication volume can match or exceed the main hall.
The historical Australian supplier parks at Altona (Toyota), Broadmeadows (Ford) and Elizabeth (Holden) have been redeveloped since the 2017 closures, but the building footprints remain in industrial use. Volgren's Melbourne site sits within the legacy Toyota supplier-park zone; PACCAR Bayswater is on a long-established commercial vehicle precinct; and the Wacol precinct in Brisbane hosts Volvo Group Australia, Mack Trucks, BusTech and several supplier-park feeders within a 2 km radius. In each of these clusters the duct fabrication work flows across multiple buildings, and the SBKJ machine line is configured to handle that volume — typically with a single SBAL-V producing 30–50% of the precinct's rectangular duct annual demand and one SBTF-1602 plus one SBTF-2020 covering the round duct.
18. SBKJ's footprint in the Australian assembly plant market
SBKJ Group has been supplying HVAC duct fabrication machinery into Australian commercial vehicle, bus, and EV assembly plant fit-outs for more than a decade. Our Box Hill North VIC office handles project engineering and after-sales for the Australian, New Zealand and Pacific markets, with engineers who have commissioned SBAL-V, SBTF-1602 and SBTF-2020 machines into duct shops at Volgren, BusTech, PACCAR, Iveco and supplier-park feeders across all three precincts. The English-speaking after-sales line and the Box Hill North parts inventory are the differentiators that matter most on a 10–15 year machine life — when a roller bearing fails on a Friday afternoon at Wacol, the spare part is on a courier truck out of Melbourne by Monday morning.
For an Australian assembly plant fit-out brief, the typical SBKJ machine package is one SBAL-V for the rectangular trunk fabrication, one SBTF-1602 for the medium-bore branches, and one SBTF-2020 for the large-bore exhaust risers. The package ships in three 40-foot HC containers, installs in 8–10 days on site, and commissions to first article within 4–6 weeks of arrival. We size every quotation against the buyer's specific coil specification, the buyer's specific assembly plant zoning, and the buyer's specific compliance package — AS 4254 minimum, with AS 1668.2 ventilation provisioning and AS 5034 hydrogen exhaust where the EV scope warrants it.
Get an SBKJ quotation for your Australian assembly plant fit-out →
19. FAQ
Which Australian standards govern HVAC ductwork in EV and vehicle assembly plants?
Five standards typically govern: AS 1668.2 for industrial ventilation rates (V_p of 4 L/s/person for light manufacturing zones), AS 4254 Parts 1 and 2 for flexible and rigid sheet-metal ductwork construction, AS 5034 for hydrogen exhaust at lead-acid and lithium-ion charging or staging areas, AS 1668.1 in combination with AS 4391 for smoke management in large warehouse-scale assembly halls, and ASHRAE 62.1 as a reference benchmark where the client specification calls for it. SBKJ duct fabricated to AS 4254 dimensional tolerances satisfies all five framings.
Why does an EV assembly plant need different HVAC zones from a conventional vehicle plant?
An EV final-assembly plant introduces three zones a conventional plant does not — battery pack final assembly treated as cleanroom-adjacent, EV final commissioning with 50–350 kW DC chargers requiring AS 5034 hydrogen exhaust, and end-of-line BMS handshake stations. Conventional plants instead carry chassis dynamometer cells with full ICE exhaust capture. Heavy bus and truck plants typically retain dyno cells even where the production mix has shifted toward zero-emission units.
How is welding fume controlled in body-in-white sections of an EV plant?
Source capture is the rule rather than dilution. Extract hoods or backdraft slots are positioned within 200–400 mm of the weld zone with a capture velocity of 0.5–1.0 m/s, ducted to a central or distributed cartridge filtration unit with MERV 14+ final filtration at a face velocity of 0.4–0.5 m/s, and discharged at roof level with stack heights set to AS 1668.2 dispersion criteria. SBKJ supplies the spiral and rectangular extract duct connecting the cell hoods to the filter units, sized for transport velocity 18–22 m/s.
What is the right SBKJ machine configuration for an Australian assembly plant fit-out?
SBKJ specifies the SBAL-V auto duct line in galvanised steel for the rectangular supply and return runs, the SBTF-1602 spiral tubeformer for the medium-bore round supply branches into manufacturing cells and AGV-conditioned zones, and the SBTF-2020 spiral tubeformer for the large-bore main exhaust risers serving paint shop integration, BIW fume capture and dyno cell discharge. Where battery testing or EV-only ancillary zones require stainless construction, the same machine line accepts 304 grade stock for spiral runs.
Are heavy bus and truck plants in Australia in scope for this guide?
Yes — Volgren in Melbourne and Brisbane, BusTech at Wacol Brisbane, Volvo Group Australia at Wacol, PACCAR at Bayswater Victoria, Iveco Trucks Australia at Dandenong, and Mack Trucks Australia at Wacol all operate final-assembly halls within the same general envelope as an EV light-vehicle plant — large-span warehouse buildings, mixed mechanical and pneumatic tooling, AGV or trolley flow, paint shop integration, and PDI bays. The HVAC framing in this guide is calibrated to that mix.
