Why defence HVAC is a different discipline
A commercial office tower HVAC system is a comfort-and-air-quality problem with a fire-life-safety overlay. A defence facility HVAC system is a survivability problem first, a mission-continuity problem second, and a comfort problem only after those two are answered. The same machine room cooling load on a Royal Australian Air Force operations centre and on a corporate data centre might both be 800 kW, but the duct system delivering it is engineered to entirely different criteria.
The defence-specific dimensions that change the design start with operational security. The HVAC contractor cannot simply walk onto a base, take photos for shop drawings and hand the file to a CAD subcontractor in another country. Every drawing, every component country-of-origin, every operator who lays a hand on a spanner inside the facility envelope is part of an audit trail that a Defence Industry Security Programme (DISP) auditor can inspect three years later. SBKJ engineers operate under the same audit discipline whenever we supply duct manufacturing equipment into Australian defence-aligned projects, whether the end facility is a barracks at Robertson Barracks Darwin or a classified ICT block at HMAS Stirling.
The second dimension is hardening. Commercial buildings are designed against natural hazard loads — wind, fire, seismic — not against weaponised threats. A defence command facility may be required to maintain operational capability through a blast event (USACE UFC 3-340-02), through a chemical-biological-radiological-nuclear release (UFC 4-024-01 collective protection), through an electromagnetic pulse (MIL-STD-188-125 hardness), or through a sustained denial-of-services attack on grid power (multi-day generator endurance). Each of those four threats imposes specific demands on the ductwork — heavier gauge, welded construction, sealed penetrations, redundant supply paths, fail-safe damper logic.
The third dimension is environment. Australian Defence Force facilities are deployed across the most demanding climate envelope in the country. RAAF Tindal sits in monsoonal Northern Territory at 35 degrees latitude with summer wet-bulb temperatures that exceed almost any commercial design assumption. HMAS Coonawarra is a tropical naval base on Darwin Harbour with chloride-laden marine air. Puckapunyal is high inland Victoria with frost mornings and 40 degree summer afternoons. Pearce in Perth's hinterland and Edinburgh in Adelaide's north both deliver fine-particulate dust loads that destroy commercial-grade filters in weeks. The materials, the corrosion allowances and the filtration design have to flex across that range without changing the underlying construction discipline.
The fourth dimension is the AUKUS partnership itself. The trilateral agreement between Australia, the United Kingdom and the United States, announced in September 2021, has unlocked the largest defence industrial undertaking in Australian history — a programme valued at more than USD 245 billion through 2055. Every defence facility built in Australia from 2026 onwards exists in that context. Henderson Western Australia and Osborne South Australia are no longer regional shipbuilding precincts; they are now partner nodes in an allied submarine industrial base. The HVAC ductwork in their assembly halls, paint shops, training centres, accommodation modules and ICT facilities is being specified to a different bar than it was a decade ago.
Defence facility types — what each one demands of the duct system
Defence facility design starts with use-class. The HVAC duct demand differs by an order of magnitude across the categories below, and a single defence base usually contains six to eight of them in close proximity.
Military airbase (RAAF)
A typical RAAF base contains: aircraft hangars (deep cathedral bay for fighter aircraft), fuel storage and refuelling apron, weapons storage and bomb-build facility, operations centre, air traffic control tower, communications and radar facility, ground support equipment workshop, accommodation precinct, mess and gymnasium, medical centre, and command and admin block. HVAC duct demand spans hot-dip galvanised lockformed sheet duct in accommodation, 316L stainless in marine-air bases, ATEX/IECEx-rated extract in fuel and weapons buildings, and CBRN-rated supply in the operations centre.
The hangar bay itself is a cathedral-volume problem. A modern fighter-aircraft maintenance hangar at Williamtown for F-35A or at Amberley for the Super Hornet and Growler fleet runs to a clear interior height of 18 to 22 metres, with ducts routed in the roof truss zone above maintenance gantry cranes. The supply-air strategy is typically displacement ventilation with high-volume low-velocity diffusers, because conventional ceiling-supply throws disturb pre-flight ground-runs. AS 1668.2 still governs the baseline outside-air rate but practical outside air is set by the worst-case maintenance activity — paint touch-up, hydraulic fluid handling or fuel-system work — under NFPA 415 jet-fuelling-area logic.
Naval base (RAN)
Royal Australian Navy bases combine working waterfront infrastructure (jetties, dry docks, magazines), shipbuilding and sustainment workshops (paint shop, blast booth, machine shop), ICT facilities, fleet headquarters, accommodation, and training establishments. Marine-atmosphere corrosion governs material selection across the entire site — not just the seaward elevations. SBKJ engineers default to 316L stainless or aluminium-zinc coated steel for outdoor and semi-outdoor duct on RAN sites because the chloride deposition rate at HMAS Stirling, Garden Island and HMAS Coonawarra has degraded standard hot-dip galvanised steel to perforation inside seven years on multiple historical projects.
Army base and garrison
Australian Army bases are the largest by floor area but mechanically the most diverse. Holsworthy and Townsville together exceed 600,000 m² of conditioned space. The HVAC scope mixes accommodation, training simulator buildings (where heat rejection from electronic equipment dominates the load), workshop and motor-pool buildings, classified intelligence facilities, fuel and ammunition, sports and recreation, medical centres, and command facilities. The design approach is to break the base into separately conditioned zones, then specify duct construction by zone use-class rather than basewide.
Training establishment
Training establishments — Royal Military College Duntroon, Australian Defence Force Academy in Canberra, HMAS Cerberus on Western Port, RAAF College Wagga, the Defence Force School of Signals at Watsonia — combine accommodation, classroom, drill hall, simulator, gymnasium and small-scale workshop facilities. The HVAC duct mix is closer to a tertiary education campus than to an operational defence facility, with the addition of secured-zone classroom and simulator buildings that fall under DISP Level 1 or 2 access controls.
Command and control bunker
Hardened command facilities — the Defence Strategic Reserve and the various joint operational headquarters across the country — run the full hardening stack: blast resistance under USACE UFC 3-340-02, CBRN collective protection under UFC 4-024-01, EMP shielding under MIL-STD-188-125 where US-Australia joint operations apply, and TEMPEST emanation control on every classified zone. The duct system in these facilities is the longest-design-cycle, highest-complexity scope on any defence base. Design lead times of 18 to 24 months are typical and the leakage class is set by the most demanding overlay — usually CBRN.
Ammunition magazine and weapons storage
Ammunition magazines and weapons storage are governed by NFPA 495 and the Department of Defense Explosives Safety Board (DDESB) safety distances adopted into Australian Defence policy. Ventilation rates are set by the maximum credible event analysis, ducts are ATEX/IECEx zone-classified with explosion-relief venting where required, and electrical equipment inside the zone is rated to AS/NZS 60079 for the relevant gas group and temperature class. The duct gauge is heavier than commercial because the duct has to maintain integrity through a deflagration event without becoming a fragmentation hazard.
Fuel depot
Defence fuel depots — strategic fuel reserves and tactical aviation fuel storage at airbases — are designed to NFPA 30 with overlays for the specific fuel type (F-44 marine diesel, F-34 jet fuel, F-76 naval distillate). Tank vapour management dictates a continuous-extract duct system on all enclosed pump houses and tank rooms, with leak detection and emergency shutdown integrated into the building management system. The duct material is typically 316L stainless to resist sulphidation from fuel vapours.
ICT facility (classified data centre)
Classified data centres are commercial data centres with a TEMPEST overlay, an EMP overlay where applicable, and a country-of-manufacture audit. The cooling load profile is identical to commercial data centre design (the closest peer document is our data centre HVAC duct manufacturing guide), and ASHRAE TC 9.9 envelope still governs the inlet temperature and humidity. The differences appear at the boundary — every duct penetration through the shielded envelope is engineered for waveguide-below-cutoff attenuation, and every component inside the envelope is logged in a country-of-origin register.
Barracks accommodation
Barracks accommodation HVAC is the largest duct-quantity scope on any base by linear metre. The construction is conventional commercial-grade lockformed galvanised sheet duct under SMACNA Class 6 leakage. The volume is what makes it strategically important: a single brigade-strength accommodation precinct can absorb 8,000 to 12,000 m² of fabricated duct over a 24-month construction window. SBKJ auto duct line machinery is sized to support this volume in a single-shift, single-machine workshop.
The AUKUS partnership and what it means for defence HVAC demand
The AUKUS announcement on 15 September 2021 by the Australian Prime Minister, the Prime Minister of the United Kingdom and the President of the United States set in motion a partnership architecture with two pillars and a timeline running to 2055. For HVAC contractors and specifying engineers in Australia, AUKUS is the dominant demand signal of the next two decades.
Pillar 1 — nuclear-powered conventionally-armed submarines
Pillar 1 commits Australia to operating a fleet of nuclear-powered conventionally-armed submarines. The acquisition pathway runs in three phases. Phase one is the early-2030s acquisition of three to five Virginia-class submarines from the United States, with initial Australian crews already in training in the United States and the United Kingdom. Phase two is the construction of the first SSN-AUKUS class submarines at Osborne South Australia from approximately 2032, with the first boat delivered to the Royal Australian Navy in the early 2040s. Phase three is the steady-state production and sustainment cadence at Osborne and HMAS Stirling.
The HVAC implications appear at the supporting industrial base, not on the submarines themselves. ASC at Osborne is being expanded to take on submarine construction and sustainment in parallel with the Collins-class life-of-type extension. BAE Systems Australia at Osborne is constructing the Hunter-class frigate. Henderson Western Australia is being expanded into the largest naval shipbuilding precinct in Australia, with Civmec, Austal, Luerssen Australia and BAE Systems Australia operating multi-bay assembly halls. HMAS Stirling at Garden Island Western Australia is the operating base for the future submarine fleet and is expanding accommodation, training and ICT capacity.
Each of those facilities carries a substantial HVAC duct scope. A Hunter-class frigate construction hall at Osborne is approximately 110 metres long, 50 metres wide and 35 metres high — a conditioned volume in the order of 190,000 m³. The HVAC duct alone for one such hall runs to 6,000 to 9,000 m² of fabricated sheet, depending on the air-change rate and the diffuser layout. Across the AUKUS-aligned shipbuilding portfolio there are eight to twelve such halls in active construction or planned expansion through 2035.
Pillar 2 — advanced capabilities cooperation
Pillar 2 covers cooperation in artificial intelligence, quantum sciences, hypersonics, cyber capabilities, electronic warfare, undersea capabilities and autonomous systems. The Pillar 2 facilities are smaller in floor area than Pillar 1 but more demanding per square metre. They include test ranges, classified laboratory environments, data centres and integration facilities. For HVAC contractors the Pillar 2 work is concentrated in the DSTG (Defence Science and Technology Group) campuses at Edinburgh South Australia and Fishermans Bend Victoria, in university and CSIRO partner facilities, and at a small number of contractor-owned classified laboratories.
The HVAC duct profile for Pillar 2 facilities skews towards: very tight environmental envelopes (some quantum laboratories require ±0.1 degree C stability over multi-day periods), TEMPEST emanation control on most cyber and electronic warfare facilities, EMP shielding on selected facilities, and a high proportion of stainless-steel duct in laboratory exhaust paths.
Programme scale and timeline
The total programme value of AUKUS through 2055 — including submarine acquisition, construction, infrastructure, sustainment, training and Pillar 2 advanced capabilities — has been published by the Australian Government at more than USD 245 billion. The infrastructure component alone is in the tens of billions of Australian dollars. The HVAC ductwork share of that infrastructure is small in percentage terms (typically 1.5 to 3 per cent of mechanical building services) but, because the absolute infrastructure spend is so large, the resulting duct-fabrication demand is unprecedented in Australian peacetime history.
Australian defence facilities driving HVAC demand through 2040
The map below summarises the Australian Defence Force facilities that are driving HVAC duct demand on AUKUS-aligned and other major defence projects. The list is not exhaustive but covers the highest-density facility groupings.
Royal Australian Air Force bases
RAAF Williamtown New South Wales is the home of the F-35A Lightning II main operating base, with associated weapons system support, simulator and training facilities. RAAF Amberley Queensland operates the Super Hornet, Growler, Wedgetail, KC-30A tanker and C-17A Globemaster fleets, the largest-floor-area RAAF base in Australia. RAAF Tindal Northern Territory is the forward operating base in monsoonal climate, currently being expanded to support US Air Force rotational deployments under the Force Posture Initiative. RAAF Pearce Western Australia operates the pilot training fleet. RAAF Edinburgh South Australia hosts the AP-3C Orion follow-on (P-8A Poseidon and MQ-4C Triton) and is co-located with the DSTG Edinburgh campus. RAAF Williams Point Cook Victoria is the historic training base now hosting Air Force HQ functions. RAAF Richmond New South Wales operates the C-130J Hercules transport fleet.
Royal Australian Navy bases
Garden Island Sydney is the East Coast fleet base, home to the surface combatant fleet (Hobart-class destroyer and Anzac-class frigate). HMAS Stirling at Rockingham Western Australia is the West Coast fleet base, the homeport of the Collins-class submarine fleet and the future SSN fleet under AUKUS. HMAS Coonawarra Darwin is the Northern Territory naval base, supporting Pacific patrol boats and forward operations. HMAS Kuttabul Sydney is the support base co-located with Garden Island.
Army bases and garrisons
Lavarack Barracks Townsville Queensland hosts 3rd Brigade and is the largest Australian Army garrison. Holsworthy Barracks New South Wales hosts the Special Operations Command and 2nd Commando Regiment. Robertson Barracks Darwin hosts 1st Brigade and is being expanded for the US Marine Rotational Force-Darwin. Puckapunyal Victoria is the principal Army training and combined arms training centre. Singleton Army Base New South Wales is the School of Infantry and major arms training establishment.
Training establishments
Royal Military College Duntroon Canberra trains Army officers. Australian Defence Force Academy Canberra is the tri-service degree-awarding institution. HMAS Cerberus Western Port Victoria is the principal RAN training establishment for sailors and junior officers. RAAF College Wagga Wagga New South Wales trains airmen and airwomen. The Defence Force School of Signals at Watsonia Victoria is the principal communications and electronic warfare training establishment.
Defence Science and Technology Group facilities
DSTG Edinburgh South Australia is the principal defence research campus, co-located with RAAF Edinburgh. DSTG Fishermans Bend Victoria hosts maritime, materials and aerospace research. Both campuses contain a high concentration of classified and TEMPEST-controlled laboratory space and are major HVAC duct demand nodes for Pillar 2 advanced capability work.
The standards stack — what defence HVAC ductwork is engineered against
Australian defence facility HVAC is designed against an overlapping stack of civilian Australian standards, NATO standardisation agreements and US military standards. The stack is hierarchical: the most demanding overlay governs in any given location.
Civilian Australian baseline
AS 1668.2 governs mechanical ventilation rates, AS/NZS 4254 governs lockformed and welded ductwork construction, AS 1668.1 governs fire and smoke control, AS 1170.4 governs seismic restraint, AS 4254.2 governs flexible duct, AS/NZS 60079 series governs hazardous-area equipment in fuel and weapons facilities, and AS/NZS 1715 governs occupational atmospheric contaminant control in workshops, paint shops and welding bays. These standards remain active on every defence facility regardless of classification — they are the baseline that the military overlays sit on top of.
NATO standardisation agreements (STANAG)
NATO STANAG 2150 sets military quality criteria for materials and components, including duct and HVAC plant. NATO STANAG 4447 sets CBRN collective protection performance criteria. NATO STANAG 1018 sets compatibility requirements for fuel handling. Although Australia is not a NATO member, NATO STANAG references are used in Australian defence specifications because they harmonise with US, UK and Five Eyes allied requirements. AUKUS-aligned projects routinely reference STANAG documents in their performance specifications.
US military standards (MIL-STD)
MIL-STD-188 series governs military communications standards and is referenced in shared US-Australia communications infrastructure. MIL-STD-188-125 specifically addresses HEMP (high-altitude electromagnetic pulse) protection of fixed ground-based command, control, communications, computer and intelligence (C4I) facilities. MIL-S-901 governs mechanical shock for shipboard equipment and is referenced in submarine and surface combatant interfaces. MIL-STD-167 governs vibration of shipboard equipment. MIL-STD-1310 governs shipboard bonding and grounding. MIL-STD-810 governs environmental engineering considerations for general military equipment.
USACE Unified Facilities Criteria (UFC)
The US Army Corps of Engineers Unified Facilities Criteria documents are the practical engineering rulebook for hardened and secured facilities, and they are routinely adopted in Australian defence specifications. UFC 3-340-02 covers structures to resist the effects of accidental explosions — the foundation document for blast-resistant ductwork. UFC 4-010-01 is the DoD minimum antiterrorism standard for buildings. UFC 4-024-01 governs security engineering, including CBRN collective protection. UFC 3-450-01 governs noise and vibration for buildings. UFC 4-021-01 governs design and Operations and Maintenance of mass notification systems. UFC 3-410-01 governs heating, ventilating and air-conditioning for general military facilities.
NFPA series
NFPA 30 governs flammable and combustible liquids, including the fuel storage and handling facilities at every airbase and naval base. NFPA 33 governs spray application using flammable or combustible materials, applicable to paint shops at all major shipbuilding precincts. NFPA 70 (the National Electrical Code) governs electrical installations on most US-Australia joint facilities. NFPA 415 specifically governs aircraft fuelling ramp drainage and ventilation at airbases. NFPA 495 governs explosive materials, applicable to weapons magazines and ammunition handling. NFPA 90A and 90B govern duct and ventilation system construction and are referenced in NCC pathways.
DSTG and facility-specific specifications
Beyond the published standards stack there is a layer of facility-specific specifications released only to cleared contractors. These are issued by Defence Science and Technology Group, by the Capital Facilities and Infrastructure branch within Defence and by individual facility owners. They are the actual contract performance specifications on most major projects — the published standards above are the public minimum.
Hardened facility HVAC — blast, CBRN and EMP layered
Hardened defence facilities are designed to maintain operational capability through a defined threat envelope. The HVAC ductwork in those facilities carries an order-of-magnitude greater engineering burden than commercial ducts, and the design overlays interact in ways that an unprepared mechanical consultant frequently underestimates.
Blast-resistant ducts
Blast-resistant ductwork is engineered against USACE UFC 3-340-02 and the predicted overpressure envelope at the duct location. Inside a hardened facility envelope the duct is generally not the controlled element — the wall and slab are. But at the boundary, where the duct penetrates the shielded envelope, the duct must hold its integrity through the predicted overpressure pulse. This is achieved using welded heavy-gauge steel construction (typically 3 mm wall minimum, scaling up to 6 mm or 8 mm for high-overpressure penetrations), blast-rated dampers that fail closed under overpressure, and structural support that transfers the impulse load to the building structure rather than back through the duct.
Welded heavy-gauge fabrication of this type is typically beyond standard SBKJ machinery scope. Our auto duct lines, spiral tubeformers and TDF flange formers are optimised for sheet-metal construction in the 0.5 mm to 1.5 mm gauge range characteristic of commercial and accommodation work. Heavy-gauge welded ducts for blast hardening are more economically performed in a specialist welded-fabrication workshop with submerged-arc welding, heat-treatment capability and structural-steel expertise. We refer customers to specialist subcontractors for that scope and supply the surrounding lighter-gauge ductwork that completes the system.
CBRN collective protection
CBRN collective protection allows occupants of a defence facility to operate without individual masks during a chemical, biological, radiological or nuclear event. The engineering control set is the most stringent in defence HVAC and rewrites the duct-construction logic.
Step one is the protected envelope — a definable boundary inside the building, typically a single floor or a contiguous group of rooms, that is sealed against air migration to and from the unprotected zones. Every door is an airlock. Every conduit penetration is sealed. Every plumbing penetration uses water traps with positive displacement.
Step two is the NBC filter bank. This combines a military-grade activated carbon stage for chemical-warfare-agent removal (sarin, VX, mustard, lewisite, blood agents) with a high-efficiency particulate air (HEPA) stage for radiological aerosols and biological agents. Sizing is set by ASHRAE 110 and the relevant collective-protection guidance. Filter banks are bag-in/bag-out for safe replacement under contamination, and they are pressure-monitored continuously.
Step three is overpressure. The CBRN-protected zone operates at 25 to 50 Pa positive overpressure above ambient. The make-up air comes through the NBC filter bank, and exfiltration through any unsealed leak path is outward, never inward. Maintaining 25 Pa across a leakage envelope tighter than commercial SMACNA Class 3 requires welded crevice-free duct construction on the supply side. This is the duct construction class that most clearly distinguishes CBRN-protected facilities from any commercial peer.
Step four is the airlock cascading. Entry through the protected envelope passes through an airlock that has been swept clear of contaminant before the inner door opens. The HVAC control logic manages the airlock pressure cascade automatically, with a fail-safe state that maintains the inner-zone overpressure under any single-failure scenario.
EMP shielding
Electromagnetic pulse hardening protects the facility against high-altitude electromagnetic pulse (HEMP) from a nuclear event, against intentional electromagnetic interference (IEMI) from a radio-frequency weapon and against the long-term consequences of a major geomagnetic disturbance. The protection is implemented as a Faraday cage around the protected envelope.
Every duct penetration through the shielded envelope is a potential antenna. The engineering response is a waveguide-below-cutoff (WBC) penetration: a length of conductive duct (steel or copper) sized so that the cutoff frequency of the duct cross-section exceeds the EMP threat spectrum. For typical EMP threat frequencies up to 1 to 3 GHz, this requires WBC tubes with internal dimensions much smaller than full-flow duct, so the duct cross-section is divided into a honeycomb array of small WBC cells. The honeycomb array passes air with acceptable pressure drop while maintaining shielding effectiveness in the 80 to 100 dB range.
Inside the shielded envelope, ducts are continuous-welded steel construction with bonded flange joints. Every flange joint includes a continuous conductive gasket that maintains shielding integrity. Dampers in the shielded zone are EMP-rated, with conductive blade-to-frame contact maintained through the full damper rotation. Honeycomb assemblies and EMP-rated dampers are specialty products supplied by a small number of approved manufacturers and represent a significant fraction of the EMP-shielded HVAC scope cost.
Australian EMP-shielded facilities are concentrated in the strategic command nodes and a small number of intelligence and Five Eyes facilities. The number of facilities with full EMP hardening is small — under fifty across the country — but each individual project carries a high HVAC engineering content.
Classified facility HVAC — TEMPEST emanation control
TEMPEST is the discipline of preventing electronic emanations from leaking outside a classified facility, where they could be intercepted and reconstructed by an adversary. The threat is well-documented in the open literature and the engineering response is a layered set of physical and electronic controls.
From the HVAC perspective, every conductive penetration through a TEMPEST-shielded enclosure is treated as a potential RF antenna. Duct design responses include four layers of control.
The first control is zoning. Classified-zone HVAC ducts are routed only inside the shielded envelope. Unclassified-zone HVAC ducts never enter the classified envelope. AHU return paths are physically separate between classified and unclassified zones — there is no shared return-air plenum, no shared duct bank and no shared atmospheric-bypass. This zoning is set at architectural concept stage and is non-negotiable in retrofit.
The second control is boundary penetrations. Where ducts must cross the shielded boundary, they pass through waveguide-below-cutoff penetrations identical in principle to the EMP-shielded penetrations described above. The cutoff frequency is set against the TEMPEST threat spectrum, which extends across the radio frequency band relevant to the equipment inside the classified zone.
The third control is component country-of-manufacture. Some classified zones — typically those handling Top Secret or compartmented information — require that every ducted component (fan, damper, sensor, controller) be manufactured in Australia, the United States, the United Kingdom, Canada or New Zealand. The provenance audit is a contracted deliverable. Components without traceable Five Eyes-aligned country of manufacture are not permitted in the controlled zone, regardless of cost or technical merit. This drives a substantial increase in Australian-made content for classified HVAC scope, and it is one of the most consequential AUKUS-era shifts in defence HVAC procurement.
The fourth control is audit trail. Every component installed inside the classified envelope is logged with serial number, country of manufacture, date of installation, the cleared installer's identity and the inspection sign-off. The log is retained for the life of the facility plus a defined records-retention period and is auditable by the Australian Signals Directorate or the equivalent allied agency.
Aircraft hangar HVAC — the RAAF base scope
Aircraft hangars on RAAF bases are the largest single mechanical-load buildings on most defence sites, and the duct scope is correspondingly significant. The principles overlap with civilian aircraft maintenance hangar design (covered in our airport and aviation HVAC duct guide) but with three defence-specific overlays.
Cathedral-bay geometry
Fighter aircraft maintenance hangars at Williamtown, Amberley and Tindal are designed around an interior clear height of 18 to 22 metres to accommodate the F-35A or Super Hornet on jacks with overhead crane access. The supply air strategy is displacement ventilation with floor-level low-velocity diffusers, because conventional ceiling-mounted high-induction supply jets disturb pre-flight ground-runs and wash hydraulic-fluid mist back onto the aircraft. The duct routing follows the roof-truss zone, with vertical drop legs to the floor-level diffusers. Duct lengths in a single fighter hangar typically run to 600 to 900 metres of fabricated sheet across the supply, return and exhaust paths.
Deicing and fuelling exhaust
RAAF bases that operate transport, tanker or maritime patrol aircraft (Amberley, Edinburgh, Richmond) include deicing fluid and fuelling operation areas inside or adjacent to hangars. Both operations create a fugitive vapour load that requires dedicated extract ventilation under NFPA 415 logic. The extract duct material is 316L stainless because the deicing fluid (typically propylene glycol with corrosion-inhibitor additives) and the fuel vapours together create an aggressive corrosion environment for galvanised steel. Sizing is set by the maximum credible fluid release scenario, not the steady-state operating envelope.
Weapons system clean room
Hangars that support weapons-system maintenance — the F-35A external store handling, missile-bay servicing on the Super Hornet, torpedo handling on the P-8A — include dedicated clean-room work areas with controlled environmental envelopes. The clean-room duct scope is small in floor area but high in specification: ISO 14644 cleanliness class, HEPA-filtered supply, AS 1668.2 outside-air rate, and in some cases TEMPEST control where the weapons system contains classified electronics.
Fuel depot and weapons magazine HVAC
Fuel depots and weapons magazines on Australian defence bases are governed by NFPA 30 (fuel) and NFPA 495 (explosives) with overlays from the Department of Defense Explosives Safety Board (DDESB) safety distances. The HVAC ductwork carries a hazardous-area classification and is engineered against AS/NZS 60079 series.
The zone classification depends on the operation. Inside an enclosed fuel pump house, Zone 1 or Zone 2 typically applies depending on the pump type and the ventilation rate. Inside a sealed ammunition magazine the zone may extend to Zone 0 or Zone 1 depending on the explosive material and the ventilation condition. The duct material is 316L stainless to resist sulphidation from fuel vapours and to prevent any spark-generating mechanical contact during a deflagration event.
Ventilation rate is set by the maximum credible event analysis. For a pump house the design rate is typically 6 to 12 air changes per hour with continuous duty fans rated for the zone classification. For an ammunition magazine the design rate is set by the worst-case explosive heating scenario and may include passive ventilation rather than fans, to avoid any electrical equipment in the zone. Explosion-relief venting is engineered into the duct system where the duct geometry could otherwise sustain a pressure rise during a deflagration.
Leak detection is integrated into the duct system with hydrocarbon sensors, smoke detectors and temperature monitors feeding the building management system and the base emergency response. The duct sensors are themselves zone-classified and the cabling is intrinsically safe.
Submarine pen and dock HVAC
Submarine support facilities at HMAS Stirling and the future SSN-AUKUS construction halls at Osborne represent the most demanding HVAC duct scope in the Australian defence base portfolio. The construction hall itself is an oversized assembly building and follows the shipbuilding precinct logic below. The submarine pen — the wet berth where the boat is moored alongside for maintenance — has unique HVAC requirements that no civilian peer matches.
The atmospheric monitoring requirement comes first. A submarine alongside has an internal atmosphere that has to be exchanged with the external atmosphere through controlled ventilation paths. Carbon monoxide, carbon dioxide, hydrocarbon and oxygen sensors monitor the boat's internal atmosphere continuously, and the wet-berth HVAC has interfaces to the boat's air revitalisation system (CO2 scrubber and oxygen generation plant). The duct material is 316L stainless throughout because the marine atmosphere combined with the hydrocarbon and salt loading inside the pen drives accelerated corrosion of any non-stainless construction.
Confined-space ventilation in the submarine pen and in the submarine itself is governed by AS/NZS 2865 with overlays from the relevant defence-specific atmospheric specifications. Ventilation rates are set by the worst-case confined-space activity (typically welding or cutting inside the boat) and the duct system must be capable of rapid increase from steady-state to high-rate operation under operator command.
Air revitalisation interfaces are unique to submarine operations. The boat's onboard CO2 scrubber and oxygen generation plant operate on a closed cycle in the submerged condition, but during alongside maintenance periods the boat draws from shore-supplied conditioned air. The shore-supply HVAC system is engineered to deliver the required volume, temperature, humidity and oxygen partial pressure that the boat's internal atmosphere management plant expects.
Material selection by defence facility type
Material selection on defence projects is driven by environment, security and lifecycle. The default material set we apply across SBKJ-supplied projects is summarised below.
316L stainless steel
316L is the default for all RAN bases (HMAS Stirling, Garden Island, HMAS Coonawarra, HMAS Cerberus), all submarine-related infrastructure (Osborne, HMAS Stirling submarine pen), all marine-air-exposed RAAF bases (Williamtown, Amberley if exposure is significant, Edinburgh), and all fuel and weapons buildings on any base. The grade is 316L (low-carbon variant) for weld-zone corrosion resistance, with surface finish 2B for general construction and 2B-DD or BA for visible architectural duct.
Anti-magnetic 316L is specified in EMI-sensitive electronics rooms because conventional galvanised steel can carry residual magnetism that perturbs precision instrumentation. The anti-magnetic specification requires solution-annealing after forming and a documented permeability test on each batch.
304L stainless steel
304L is used on inland defence facility plant rooms with intermittent humidity, on some kitchen and laboratory exhaust systems, and as a cost-down substitute for 316L where the chloride exposure is genuinely low. It is not used on marine-air bases or submarine infrastructure regardless of cost-down pressure.
Hot-dip galvanised G275 carbon steel
Hot-dip galvanised G275 (275 g/m² zinc coating) is the workhorse for outdoor and indoor duct on barracks accommodation, gymnasium, mess, medical centre, admin block, training establishment and most non-classified ICT facility duct. The coating mass is specified at 275 g/m² minimum (G275 to AS 1397, equivalent to Z275 in the European designation) to give a service life of 30+ years in inland Australian climates.
Aluzinc AZ150 aluminium-zinc coated steel
Aluzinc AZ150 (aluminium-zinc 150 g/m² coating) is used where galvanic compatibility with aluminium structure is required. The Austal aluminium catamaran shed at Henderson is the most prominent example — aluminium-zinc duct in proximity to aluminium hull plates avoids the galvanic-corrosion risk of mixing zinc-only galvanised duct with aluminium structure.
Copper sheet
Copper sheet is reserved for EMP waveguide-below-cutoff penetrations and a small number of TEMPEST-shielded enclosures where copper attenuation properties exceed steel. Copper duct is rare in defence HVAC — it appears as a small fraction of the total duct scope, concentrated at boundary penetrations.
Pre-insulated phenolic and PIR duct
Pre-insulated phenolic and polyisocyanurate panel duct is occasionally specified for accommodation block applications where space and weight constraints are severe. It is not generally permitted in classified zones (because the foam core cannot be country-of-manufacture audited the same way as sheet metal) and is not permitted in CBRN-protected envelopes (because the foam-core construction cannot achieve the leakage class required).
Henderson WA shipbuilding precinct — HVAC scope by tenant
Henderson Western Australia is being expanded into the largest naval shipbuilding precinct in Australia. The precinct hosts Civmec (commercial shipbuilding and offshore patrol vessel work), Austal (aluminium catamaran for the Pacific Patrol Boat programme and US Navy work), Luerssen Australia (offshore patrol vessel) and BAE Systems Australia (frigate and submarine work). The HVAC duct scope across the precinct through 2035 is in the order of 60,000 to 90,000 m² of fabricated sheet duct.
Civmec assembly hall
Civmec operates one of the largest shipbuilding sheds in the southern hemisphere — a multi-bay hall approximately 110 metres long by 50 metres wide by 40 metres high. The HVAC scope covers internal climate control (despite being a shipbuilding shed, the assembly bay is air-conditioned to support precision work and worker comfort), fume extraction over welding stations, paint shop ventilation under NFPA 33 and AS/NZS 1715 and process cooling for thermal cutting equipment. Duct material is hot-dip galvanised G275 for the general supply, 316L stainless for the paint and welding extract, and Aluzinc for any duct in proximity to structural aluminium.
Austal aluminium catamaran shed
Austal's purpose-built aluminium shipbuilding facility carries a unique HVAC profile because the structural material is aluminium throughout. Galvanic compatibility drives Aluzinc AZ150 duct in the production bay rather than zinc-only galvanised. The fume extraction system is sized for aluminium welding fumes, which carry a different particulate signature than steel welding and require dedicated filtration.
Luerssen Australia offshore patrol vessel hall
Luerssen's offshore patrol vessel construction hall at Henderson is a multi-bay assembly hall in the 80,000 to 100,000 m³ range. The HVAC scope mixes accommodation-grade ducts for the office and amenities, hot-dip galvanised supply for the assembly bay and 316L stainless extract for paint and welding.
BAE Systems Australia frigate hall
BAE Systems Australia's expanded Henderson facility supports both surface combatant and AUKUS-aligned submarine work. The HVAC scope is the largest single contract on the precinct, with multi-bay assembly halls, paint shops, training centres, accommodation, ICT facilities and command spaces. Australian Industry Capability content targets are at the higher end of the AUKUS-aligned envelope.
Osborne SA — Hunter-class frigate and SSN-AUKUS construction
Osborne South Australia is the principal east coast counterpart to Henderson WA and is the build location for the Hunter-class frigate (BAE Systems Australia) and the SSN-AUKUS submarine (ASC). The shipbuilding precinct at Osborne is in expansion through 2030 and beyond, with new assembly halls, training facilities, accommodation and ICT infrastructure.
BAE Systems Australia Hunter-class frigate hall
The Hunter-class is the largest surface combatant ever built in Australia. The construction hall is a clean, climate-controlled assembly building approximately 110 metres long by 50 metres wide by 35 metres high. HVAC scope covers internal climate control, fume extraction, paint shop ventilation and process cooling. Duct material is hot-dip galvanised G275 for the general supply with 316L stainless for paint and welding extract.
ASC submarine sustainment and SSN-AUKUS construction
ASC at Osborne is the Collins-class submarine sustainment facility and is being expanded for SSN-AUKUS construction. The HVAC scope is the most demanding in the precinct because submarine construction work is performed in a climate-controlled assembly building with TEMPEST-controlled zones for classified electronics integration. Duct material is 316L stainless throughout the wet-berth and submarine pen areas, with hot-dip galvanised in the general assembly bay and Aluzinc where aluminium structure is in proximity.
Worker comfort in defence environments — barracks, gym, canteen, medical
Defence facility HVAC is not all hardened command and CBRN protection. The bulk of the duct quantity by linear metre is in worker comfort and accommodation systems, which follow commercial Australian standards with defence overlays for security clearance and Australian Industry Capability content.
Barracks accommodation
Australian Defence Force barracks accommodation is built to the National Construction Code Class 3 (residential) with AS 1668.2 ventilation rates and AS 1668.1 fire and smoke control. The duct construction is conventional commercial-grade lockformed galvanised sheet duct under SMACNA Class 6 leakage. The duct fabrication is the largest single scope on most defence accommodation projects and is well-suited to SBKJ auto duct production line machinery for fabrication-shop scale-up.
Gymnasium and canteen
Gym and canteen HVAC follows commercial recreational and food service standards. The duct construction is standard galvanised sheet with a slightly higher outside-air rate than office spaces (AS 1668.2 Table 3.3). Kitchen exhaust duct on canteens follows the same rules as commercial kitchen exhaust — typically 1.2 mm minimum gauge, fully welded construction in the cooking zone, with cleanout access at every change of direction.
Medical centre
Defence medical centre HVAC follows AS 1668.2 with overlays from the Australasian Health Facility Guidelines. Negative-pressure isolation rooms (for infectious disease management) require SMACNA Seal Class A and dedicated extract paths. Operating theatres and procedure rooms require ultra-clean air supply at controlled temperature and humidity. Pharmacy and laboratory exhaust requires 316L stainless construction.
Cyber and ICT facility HVAC — the AUKUS Pillar 2 overlay
Defence-grade data centre HVAC is a specialised overlay on commercial data centre HVAC design. The thermal load profile is identical (ASHRAE TC 9.9 inlet conditions, hot-aisle/cold-aisle physical layout, redundant N+1 or 2N cooling architecture, in-row or perimeter CRAC/CRAH equipment). The defence overlay adds four engineering controls that reshape the duct design.
The first control is TEMPEST emanation control on classified zones. The HVAC duct routing inside a Top Secret or compartmented information zone is contained within the shielded envelope with waveguide-below-cutoff penetrations at the boundary. AHU return paths are physically separate from any unclassified zone.
The second control is EMP shielding on selected facilities. Where the defence ICT facility is also EMP-hardened, the duct construction is welded heavy-gauge with bonded conductive flange joints and EMP-rated dampers throughout the shielded envelope.
The third control is country-of-manufacture audit. Components inside the controlled zone are sourced from Australia, the United States, the United Kingdom, Canada or New Zealand. The audit register is a contracted deliverable and is reviewed at design, fabrication and commissioning stages.
The fourth control is supply chain segregation. The HVAC plant serving the classified zone has no shared infrastructure (chiller, AHU, ductwork, condenser water) with any unclassified zone in the same building. This is operationally expensive — it doubles or triples the plant count compared to a commercial data centre — but is non-negotiable on Protected and above zones.
Counter-UAS facility HVAC — an emerging requirement
The deployment of counter-unmanned aerial systems (CUAS) capability across Australian Defence Force bases is creating a new HVAC duct demand category. CUAS facilities range from radar and electronic-warfare stations at airbases through to dedicated CUAS command nodes at major garrisons and naval bases. The HVAC requirements overlap with classified ICT facility logic but include some category-specific overlays.
The radar and EW emitter cooling load is concentrated in the equipment racks, with high heat-flux densities (5 to 10 kW per rack typical) requiring close-coupled cooling. The duct scope is small in linear metres but high in specification — typically 316L stainless construction with TEMPEST emanation control on the operations and command interface zones.
The CUAS command nodes are classified ICT facilities operating at Protected or Secret level. The duct scope follows the ICT facility logic above with AUKUS-era country-of-manufacture audit applied across the whole component register.
SBKJ machinery selection for defence HVAC fabrication
SBKJ Group's machine portfolio supports the lighter-gauge sheet-metal portion of defence HVAC ductwork — accommodation, admin, training, gymnasium, medical, hangar accommodation, ICT facility outer zones and most worker-comfort scope. Heavier-gauge welded fabrication for blast hardening and EMP shielding is typically beyond standard SBKJ machinery scope and is referred to specialist welded-fabrication subcontractors.
SBAL-V auto duct line — galvanised variant
The SBAL-V auto duct production line in galvanised configuration is the workhorse for barracks accommodation, admin, training establishment and general defence facility duct. Throughput on a single shift exceeds the requirement for a brigade-scale accommodation precinct, with standard SMACNA Class 6 leakage class achievable through TDF flange production. Coil width 1,250 mm or 1,500 mm covers all duct sizes encountered on accommodation and admin work.
SBAL-V auto duct line — stainless variant
The SBAL-V auto duct line in 316L stainless variant is the principal machine for naval shipbuilding accommodation and classified facility duct on RAN sites. The roller and tool assemblies are configured for stainless coil at 0.6 mm to 1.5 mm thickness with adjusted lubrication and run-out speeds. Surface finish is 2B as standard with a 2B-DD upgrade available for visible architectural ducts.
SBTF spiral tubeformer
The SBTF spiral tubeformer supports round duct fabrication for gymnasium, medical, plant room and selected accommodation applications. Diameter range from 80 mm to 1,500 mm covers the full defence facility scope. Coil thickness is configurable for galvanised, 304L or 316L stainless. The four-roller drive section maintains the helical seam quality required for SMACNA Class 6 or Class 3 leakage.
TDF flange former
The TDF flange former produces the integrated flange that gives a TDF joint its characteristic low-leakage performance. For CBRN-protected envelope ducts the TDF joint is supplemented with continuous welded construction beyond the standard sheet-metal scope, but for the standard accommodation and admin work the TDF flange achieves the required leakage class without further intervention.
Heavy-gauge welded fabrication scope
For blast-resistant ducts (UFC 3-340-02), EMP-shielded ducts (MIL-STD-188-125), CBRN-protected envelope ducts requiring continuous welded construction, and submarine pen ducts in 3 mm to 8 mm 316L stainless, the fabrication is performed by specialist welded-fabrication subcontractors with submerged-arc welding capability, post-weld heat treatment and structural-steel expertise. SBKJ does not supply machinery in this gauge range — our machinery scope is the lighter-gauge sheet-metal portion of the same project. We coordinate with welded-fabrication subcontractors as required.
Procurement and security clearance — the DISP framework
Australian defence facility HVAC procurement is governed by the Defence Industry Security Programme (DISP) framework. DISP is administered by the Department of Defence and is the primary vehicle through which industry contractors gain accredited access to defence sites and information.
DISP Member levels
DISP Membership Entry Level is the minimum threshold for any industry contractor working on Defence sites. It requires the contractor to have a security plan, governance arrangements and a security officer in place. Entry Level is appropriate for contractors performing site-survey or project-management work that does not require access to classified information.
DISP Level 1 is required for contractors handling Official information. Most accommodation, training, administrative and commercial-class HVAC work falls in this band. The Level 1 accreditation requires a more substantial security plan, regular reviews and trained security officers.
DISP Level 2 is required for contractors handling Protected information. Most classified ICT facility work, classified training establishment scope and any work touching Protected-classified zones falls here. Level 2 introduces personnel security clearance requirements (typically Baseline Vetting on individual employees).
DISP Level 3 is required for contractors handling Secret information. Hardened command facilities, classified intelligence facilities and selected AUKUS-aligned classified work falls in this band. Level 3 requires Negative Vetting Level 1 (NV1) personnel clearance on the individuals performing the work.
Above DISP Level 3, work touching Top Secret information requires NV2 or PV-cleared personnel through the Australian Government Security Vetting Agency (AGSVA), and the facility itself is accredited as a TS Cleared Facility.
Controlled Goods Order awareness
HVAC work that supports weapons systems may overlap with the Defence Trade Controls Act and the Defence and Strategic Goods List (DSGL). Components that fall under the DSGL — including some specialised filtration, sensors and control systems — require export permits even for shipping between Australian states or to allied partners. HVAC contractors working in weapons-system support zones need DSGL awareness in their procurement chain.
Foreign ownership disclosure
DISP membership requires disclosure of foreign ownership in the contractor and the contractor's supply chain. AUKUS-aligned and major defence projects routinely set Australian Industry Capability content targets that limit the foreign-ownership exposure on any individual scope. SBKJ Group operates as a Box Hill North Victoria Australian-based supplier serving Australian defence customers under the AIC framework.
Australian Industry Capability content
The Australian Industry Capability programme sets a contractually defined Australian content percentage on major defence procurements. The AIC content is calculated across the supply chain — Australian fabrication labour, Australian-supplied raw materials, Australian-installed insulation and Australian-supplied components all count towards the AIC percentage. AUKUS-aligned facility-construction projects routinely target AIC content of 60 per cent or higher on the mechanical building services scope.
For HVAC ductwork the AIC content is dominated by Australian fabricated duct (the labour-intensive portion of the scope), Australian-installed insulation, and Australian-supplied galvanised coil where available. Stainless steel coil, specialised filtration components and EMP-rated dampers are frequently imported from Five Eyes-aligned countries.
How SBKJ supports defence-facility HVAC contractors
SBKJ Group operates from Box Hill North Victoria as the Australian arm of the SBKJ international machine-supply business. We support defence-facility HVAC contractors across four engagement modes.
The first mode is auto duct line and spiral tubeformer machinery supply. We sell, install, commission and maintain the duct fabrication machinery in the contractor's workshop. This is the principal commercial relationship for most contractors and is well-suited to brigade-scale accommodation and admin precincts.
The second mode is engineering consultation on duct specification and material selection. SBKJ engineers have 30+ years of cumulative experience across hardened, marine, hazardous-area and classified facility work. Where a defence specification requires resolution between the SMACNA, AS/NZS 4254, EN 1505 and DW/144 standards, our engineers provide the cross-walk.
The third mode is sub-supply through prime contractors on AUKUS-aligned projects. SBKJ machinery and engineering services are routinely supplied through prime contractors who hold the head DISP accreditation and the contractual relationship with the Department of Defence. This is the dominant mode for AUKUS-aligned shipbuilding precinct and major-base infrastructure work.
The fourth mode is co-ordination with welded-fabrication subcontractors on heavy-gauge scope. For the blast-hardened, EMP-shielded and submarine-pen portions of a project that fall outside SBKJ's machinery scope, we co-ordinate with the contractor's chosen welded-fabrication subcontractor to ensure that the lighter-gauge sheet-metal scope and the heavier-gauge welded scope integrate cleanly at the project boundary.
FAQ
What is AUKUS and how does it drive HVAC duct demand in Australia?
AUKUS is the trilateral security partnership between Australia, the United Kingdom and the United States, signed September 2021. Pillar 1 commits Australia to acquiring nuclear-powered conventionally-armed submarines — initially Virginia-class boats from the US, then SSN-AUKUS class boats built at Osborne SA. Pillar 2 covers cooperation in AI, quantum, hypersonics, cyber, electronic warfare, undersea and autonomous systems. Total programme value through 2055 exceeds USD 245 billion, making it the largest defence industrial undertaking in Australian history. The HVAC scope at Henderson WA, Osborne SA, RAAF bases, RAN bases, Army garrisons, training establishments and DSTG campuses is correspondingly substantial.
What HVAC standards apply to Australian defence facilities?
Civilian baseline AS 1668.2, AS/NZS 4254, AS 1668.1 and AS 1170.4. Military overlays NATO STANAG 2150, MIL-STD-188 series, MIL-S-901, MIL-STD-167, USACE UFC 3-340-02 (blast), UFC 4-024-01 (security and CBRN), UFC 4-010-01 (antiterrorism), UFC 3-410-01 (HVAC). NFPA 30, 33, 70, 415 and 495 for fuel, paint, electrical, hangar fuelling and explosives respectively. DSTG and facility-specific specifications layered on top.
Do defence HVAC contractors need security clearance in Australia?
Yes. DISP Member Entry Level is the minimum, with Level 1 for Official-information work, Level 2 for Protected, Level 3 for Secret. Above that, Top Secret work requires NV2 or PV personnel clearance through AGSVA. Most AUKUS-aligned shipbuilding precinct work requires DISP Level 1 or 2 minimum.
What is CBRN collective protection and how does it change ductwork?
CBRN collective protection lets occupants operate without individual masks during a chemical, biological, radiological or nuclear event. The protected envelope runs at 25-50 Pa positive overpressure, with crevice-free welded ductwork on the supply path, NBC filter banks (carbon plus HEPA), airlock cascading at every entry, and leakage class one to two orders of magnitude tighter than commercial SMACNA Class 3. Reference is USACE UFC 4-024-01 and NATO STANAG 4447.
Why is EMP shielding relevant to defence HVAC?
EMP hardening protects command facilities, classified data centres and selected communications nodes against high-altitude electromagnetic pulse and intentional electromagnetic interference. Every duct penetration through a shielded envelope is a potential antenna and is engineered as a waveguide-below-cutoff penetration with copper or steel honeycomb cells sized so the cutoff frequency exceeds the EMP threat spectrum. Inside the envelope, ducts are continuous-welded with bonded conductive flange joints throughout. MIL-STD-188-125 governs.
What materials are used for defence facility HVAC ducts?
316L stainless for RAN bases, submarine infrastructure, fuel and weapons buildings. 304L for inland defence plant rooms and laboratory exhaust. Hot-dip galvanised G275 for accommodation, admin, training and most worker comfort. Aluzinc AZ150 where galvanic compatibility with aluminium structure matters (Austal aluminium catamaran shed). Anti-magnetic 316L for EMI-sensitive electronics rooms. Copper sheet for EMP waveguide penetrations only.
What does AUKUS mean for HVAC at Henderson WA and Osborne SA?
Henderson WA is the principal western shipbuilding precinct, with Civmec, Austal, Luerssen Australia and BAE Systems Australia operating multi-bay assembly halls. Osborne SA hosts ASC for Collins-class sustainment plus SSN-AUKUS construction and BAE Systems Australia for Hunter-class frigate. HVAC duct demand from AUKUS-aligned facilities through 2040 is conservatively in the hundreds of thousands of square metres of fabricated duct, with strong AIC content targets driving Australian-fabricated content.
How does TEMPEST affect HVAC duct routing?
TEMPEST prevents electronic emanations from leaking outside a classified facility. HVAC ducts are conductive and every penetration through a shielded envelope is a potential RF antenna. Duct design responses are: route classified-zone ducts only inside the shielded envelope, separate AHU return paths from unclassified zones, use waveguide-below-cutoff penetrations at boundaries and audit country of manufacture for fans, dampers and controllers — Top Secret zones often require Five Eyes-aligned country of manufacture only.
