Why broadcasting HVAC is a category of its own
Most commercial HVAC engineering targets occupant comfort — 22 °C, AS 1668.2 outdoor air, NC-35 to NC-40 so conversation is not effortful. A broadcasting facility breaks that template in three ways. First, the noise target inside a recording booth or on-air studio is NC-15 to NC-25 — quieter than a hospital operating theatre, and one of the quietest occupied spaces in any building type. Second, the heat loads in a TV studio can spike from 200 W/m² base up to 500–800 W/m² as soon as the lighting grid is energised, forcing the cooling plant to absorb a 4× thermal swing inside ten seconds. Third, the consequences of an HVAC misstep are measured in failed retake budgets, on-air pops, and viewer complaints about background hum during the 6 pm news.
A facility-wide HVAC design has to deliver four different room types simultaneously: large-volume TV studios with lighting heat dominance, small acoustic booths for radio and podcast, open-plan newsrooms with continuous occupancy, and mission-critical master control rooms that cannot lose cooling for a single minute of a live transmission window. The ductwork that connects this network is not interchangeable from one zone to the next — branch by branch, the construction class, velocity ceiling, attenuator strategy and vibration isolation specification shifts as the duct crosses from one acoustic class into the next. This guide is the working reference SBKJ engineers use when our customers are quoting a duct package for a broadcasting refit or new build, covering AS 1668.2, AS/NZS 2107, ASHRAE Applications Handbook Chapter 8, duct fabrication options for NC-15 acoustic measurement, layout problems unique to broadcasting, and a directory of major Australian broadcasters.
The standards stack: AS 1668.2, AS/NZS 2107 and ASHRAE Chapter 8
Three documents anchor the engineering for any Australian broadcasting HVAC scope, and an experienced engineer keeps all three within reach of the design desk.
AS 1668.2 — The use of ventilation and airconditioning in buildings, Part 2: Mechanical ventilation in buildings. AS 1668.2 sets the outdoor air rates that govern minimum supply volumes for every zone in the facility. For office and newsroom occupancy the rate is 7.5 L/s per person, and the same rate applies to crew and on-air talent in production studios. For studios with audience seating — large TV studios for talk shows or live audience comedies — the auditorium rate of 5 L/s per audience occupant applies, plus the 7.5 L/s per crew occupant in technical positions. The standard also dictates minimum exhaust and makeup volumes for green rooms, makeup rooms, kitchens and lavatories that surround the production space, and these auxiliary ventilation loads add up to a meaningful fraction of the air-handling plant on a campus-scale facility.
AS/NZS 2107 — Acoustics: Recommended design sound levels and reverberation times for building interiors. AS/NZS 2107 is the source document for room-by-room NC targets in an Australian acoustic specification. For broadcasting it tightens the noise envelope significantly relative to general office use. Recording booths, radio studios and audio post-production rooms sit at NC-15 to NC-20. Television studios sit at NC-20 to NC-25. Control rooms, video post-production and audio mixing rooms sit at NC-25 to NC-30. Newsrooms, open-plan editorial and admin offices sit at NC-30 to NC-35. Corridors, plant rooms and machine spaces sit at NC-40 and above. The mechanical engineer's job is to deliver an HVAC system whose contribution at each occupied position is at least 3 dB below the NC target — not equal to it — to leave headroom for cumulative noise from the lighting grid, camera robotics, prompters and audience.
ASHRAE Applications Handbook, Chapter 8 — Communications Centers. ASHRAE Chapter 8 is the most detailed international reference specifically for broadcast and recording facility HVAC. It covers television studio cooling load profiles (including the lighting-grid duty cycle problem), radio studio and audio booth acoustic ventilation, master control room redundancy, equipment room and server room cooling, satellite and broadcast tower base-station cooling, and the practical issues of supply diffuser concealment and stratified return through lighting grids. Chapter 8 is the reference Australian engineers cite when their AS 1668.2 calculations need to be reconciled with the harder edge of broadcast-specific design: zoned redundancy, very low duct velocities, and the specific octave-band attenuation required to keep duct-borne noise out of microphone pickup.
Beyond these three, supporting references include AS/NZS 4254 (Ductwork for air-handling systems in buildings) for the duct construction itself, SMACNA HVAC Duct Construction Standards as a parallel reference for international suppliers, AS/NZS 4859 for thermal insulation of ductwork, and the local building code provisions for fire dampers and smoke spill arrangements. The integration of fire and life-safety ductwork into an acoustically tuned environment is its own design problem and we cover it in a dedicated section below.
Zoning a broadcasting campus by acoustic class
The single most useful early design step on any broadcasting project is a campus-wide acoustic zone plan. Every room is colour-coded into one of five classes, and the duct package follows from the zoning rather than the floor plan.
Class A — On-air and recording studios (NC-15 to NC-25). The most aggressive acoustic envelope. Includes radio on-air booths, podcast production rooms, audio recording booths, audio post-production rooms (Foley, dialogue replacement, music mixing), and the on-air zone of a television studio. Duct construction is welded longitudinal seam, with integrated attenuators at every penetration, internal acoustic lining where required for octave-band attenuation, and vibration-isolated hangers throughout. Branch velocity is capped at 2–3 m/s, and supply diffusion is displacement or low-velocity ceiling cassette at no more than 0.15 m/s at face level.
Class B — Control rooms and technical operations (NC-25 to NC-30). Audio mixing rooms, vision mixing rooms (production control room or PCR), audio control rooms (ACR), video edit suites, and master control room (MCR) operator positions. The acoustic target is looser than Class A but still well below a typical office. Duct construction may be welded seam or carefully sealed standard-construction with double-skin lining around the room boundary. Branch velocity 4–5 m/s. Diffusers are typically swirl or perforated face at face-level distance to maintain comfort without compromising consoles or operator headsets.
Class C — Newsrooms and open-plan editorial (NC-30 to NC-35). The newsroom is the operational hub of a broadcaster and runs on a high computer heat load (workstations, multiviewer monitor walls, edit terminals) and continuous occupancy. The acoustic target is conventional commercial office, but the heat load is two to three times higher than a typical floor. Galvanised AS/NZS 4254 duct is acceptable, with conventional swirl diffusers and ceiling void return. Branch velocity 6–8 m/s.
Class D — Back of house and corridors (NC-35 to NC-40). Green rooms, makeup rooms, wardrobe, dressing rooms, prop stores, set construction workshops, server rooms (except MCR-adjacent server racks which are Class B), kitchens, cafeterias, atria and lobbies. Standard commercial HVAC practice applies. The only specific risk is duct-borne noise transmission from these zones back into Class A studios through shared shafts — which is why the duct routing strategy across the facility matters as much as the construction class of any single piece.
Class E — Machine rooms and plant (NC-50+). The chiller plant rooms, AHU rooms, pump rooms, fan rooms, generator rooms and fuel storage rooms are noisy by nature and are isolated from the rest of the campus by acoustic-rated walls, doors and floor slabs. The ductwork inside these rooms is conventional, but every duct that crosses the wall out of a plant room toward an occupied zone must include a properly sized attenuator and a vibration-isolated penetration.
Television studio HVAC: lighting heat dominance
A modern television studio is a thermal challenge masquerading as an acoustic one. Typical studio volumes range from 600 m² for a regional news set up to 3,000 m² or more for a major drama or talk-show stage in Pyrmont, Docklands or South Yarra. Lighting heat loads are the single largest sensible load and have changed character in the last decade as LED retrofits replaced tungsten and fluorescent rigs.
A traditional tungsten-lit studio ran at 400–600 W/m² with the rig fully energised, and the cooling system was sized for the peak. An LED-rigged studio can run at 200–350 W/m² for the same illumination output and colour temperature, which represents a meaningful reduction in installed chiller capacity for a new build or refit. But the catch is that even LED rigs spike to 500–800 W/m² in high-key talk show, news set or game show configurations where the rig is dense and the camera angles demand bright fill. The cooling system has to handle the peak, not the average, because the studio is unforgiving when an air-handling unit lags the lighting cue by even thirty seconds: talent skin tone shifts visibly under-camera and audio condensation rings start dropping out of the microphones if humidity wanders.
Three design strategies dominate Australian TV studio HVAC. First, oversize the chiller and AHU plant to handle the peak rig load with at least 15% margin, and use variable-speed fan drives that ramp up cleanly without inducing duct rumble. Second, deliver air at low velocity and high volume — typically 8–12 air changes per hour at design conditions — to keep the bulk room temperature stable as the lighting load cycles. Third, return air through the ceiling void above the lighting grid so that the heat plume rising from the rig is captured directly and does not stratify down to talent face level. Floor-level return is rare in TV studios because the cable and infrastructure trenches in the floor make return ductwork impractical.
Diffuser placement is the most visible part of a TV studio HVAC design. The cinematographer does not want to see a register grille in the master shot, the gaffer does not want a diffuser dumping cold air into the spot of the lead key light, and the sound mixer does not want a microphone to pick up the swirl signature of a swirl diffuser one metre below it. The standard answer is to conceal the supply terminals behind the lighting grid itself, using ceiling slot diffusers that align with grid beams and project air upward and outward in a pattern that does not collide with the camera angles. Alternative arrangements include displacement diffusion through a perimeter plenum at low level (used in some drama-style studios where talent stays in fixed positions), and integrated supply through the lighting catwalk soffit (used where the grid is deep and there is room to combine air and lighting infrastructure on the same superstructure).
Noise inside the TV studio is constrained to NC-20 to NC-25. That sounds permissive next to a radio booth at NC-15, but with a sensible air volume of 12,000–25,000 L/s and the requirement to keep diffuser face velocity under 1.5 m/s, the duct velocity in the studio branches has to remain under 3 m/s and the attenuator package is substantial. Most Australian TV studios fitted in the last decade have used welded-seam spiral or rectangular duct with internal acoustic lining on the last 10–15 metres of every branch before entry into the studio, plus a primary attenuator at each AHU outlet sized for the dominant fan tone (typically in the 250 Hz and 500 Hz octave bands).
Radio studio HVAC: the NC-15 problem
A radio studio is the inverse of a TV studio. The room is small (often 15–30 m²), the thermal load is modest (a few people, a small audio console, headphone amplifiers, a couple of computer monitors — perhaps 60–100 W/m² total), but the noise target is the most aggressive in the entire building: NC-15 to NC-20.
At NC-15, the integrated sound pressure level from HVAC inside the studio is around 25–30 dBA across the speech-frequency bands. That is two to three times quieter than a typical living room at night, and well below the threshold at which a condenser microphone picks up duct-borne noise as a continuous floor in the recording. The implication for HVAC design is severe. Outdoor air supply through AS 1668.2 occupancy rates is small in absolute terms (3 people × 7.5 L/s = 22.5 L/s for a typical on-air booth), but that small volume has to be delivered through a duct system whose contribution at the microphone position is essentially inaudible.
The standard SBKJ design pattern for an NC-15 radio booth is as follows. Supply ductwork is welded longitudinal seam spiral or rectangular, fully sealed with no detectable air leakage. A primary attenuator close to the AHU suppresses fan tone propagation. A secondary attenuator within 2 m of the studio penetration suppresses regenerated noise from upstream dampers and turning vanes. Duct velocity is capped at 1.5 m/s in the last 5 m of branch before the studio. Supply terminal is a low-velocity perforated-face diffuser or a linear slot in the ceiling, with face velocity under 0.5 m/s. Return is through a ceiling-void plenum with a parallel attenuator path back to the central system. All penetrations through the studio acoustic envelope are sealed with double-leaf isolation, and any rigid duct hanger crossing a studio wall is replaced with a spring isolator. The fan plant feeding the studio is on a separate, vibration-isolated AHU dedicated to the Class A acoustic zone, not shared with the office or newsroom side of the facility.
The cost penalty of this specification is real — an NC-15 booth might add 30–50% to the per-square-metre HVAC cost relative to a general office target — but the cost of failing the NC target after commissioning is far higher. Reworking ductwork inside a finished studio means demolishing acoustic wall lining, refabricating duct branches with welded seams and integrated attenuators, and re-commissioning. We have seen this happen on facilities that tried to save 15% on the original duct package and then spent 4–5× that figure on rectification.
Podcast studio HVAC: the new acoustic market
Podcasting has grown from a fringe radio cousin to a major content category over the last decade, and Australia now has a dense network of dedicated podcast production studios across both the public broadcasters (ABC's podcast factory in Ultimo, SBS podcast spaces in Artarmon) and the commercial podcast networks (Acast Sydney, LiSTNR studios in multiple cities, Mamamia Podcast Network, Audioboom Australia). Many large workplaces also operate in-house podcast booths for executive interviews, internal-comms shows and B2B content series.
Acoustically, a podcast studio is essentially a small radio studio. The NC target sits at NC-15 to NC-20, the room volume is small (10–25 m²), the occupancy is low (one to four people), and the recording chain is dominated by large-diaphragm condenser microphones with sensitivity profiles that ruthlessly print any continuous noise into the master. The HVAC design pattern follows the radio studio template — welded longitudinal seam supply duct, twin attenuators, low velocity throughout, displacement-style ceiling diffusion, isolated return through ceiling void — and the cost premium over a general office build-out is comparable.
The differences between a podcast studio and a traditional radio studio are practical rather than acoustic. Podcast studios are often retrofitted into existing commercial office floor plates rather than purpose-built from the slab up, which means the HVAC designer is working with existing risers, existing AHU plant, and an existing return air path that was never designed for an NC-15 envelope. Three retrofit patterns recur. The first is a self-contained variable-refrigerant-flow (VRF) cassette serving the booth directly with a heavily attenuated supply, decoupled from the central building HVAC. This works for very small booths but limits outdoor air delivery and is hard to keep below NC-20 in summer when the cassette fan ramps. The second is a dedicated outdoor air system (DOAS) running to a low-velocity supply terminal inside the booth, with a separate sensible cooling element either ceiling-mounted (chilled water cassette) or in a secondary AHU above the suite. This is the gold-standard retrofit and is the SBKJ recommendation for any new podcast studio inside an existing building. The third is a shared central supply with a custom attenuator package added just before the booth penetration — a low-cost option that often fails the NC target on first measurement and has to be rectified.
Livestreaming studios — the YouTube and Twitch-format spaces that have proliferated in Sydney and Melbourne over the last five years for influencer production, podcast video, esports and corporate streaming — sit between podcast and TV in their HVAC profile. Lighting heat loads are higher than a podcast booth because the streaming format uses key, fill and back lighting for camera-quality video. Noise targets are looser than a radio booth (NC-25 is usually acceptable because the microphone is closer to talent and the streaming audience tolerates more room tone than a podcast listener). The HVAC pattern looks like a small TV studio: ceiling slot diffusion, double-attenuator supply, ceiling-void return through any lighting grid, and a sensible cooling allocation in the 250–400 W/m² range.
Newsroom HVAC: open-plan computer heat
The newsroom is where the broadcaster spends most of its time. It is a continuously occupied open-plan editorial floor with high workstation density, multiple monitor walls, edit suites along the perimeter, and direct feeds from the operations and master control rooms. From an HVAC perspective, the newsroom is a high-density office with two specific complications: the computer heat load is two to three times a typical commercial office (300–400 W/m² is common during peak production hours), and the acoustic envelope must protect the adjacent Class A and Class B rooms from any open-plan noise leakage back into the studios.
The NC target inside the newsroom itself sits at NC-30 to NC-35, comparable to a high-end office. Duct construction is conventional galvanised to AS/NZS 4254, with the supply system sized for the high sensible load. Air change rates of 8–12 per hour are typical, with chilled water cooling delivered through ceiling cassettes or ducted supply to swirl diffusers across the open floor. Return air through ceiling void is standard, and a portion of the return is filtered through the central AHU to support outdoor air conditioning and humidity control.
The complication unique to broadcasting newsrooms is the interface between the newsroom and the adjacent studios. The newsroom often opens directly onto a control room or studio entrance, with glazed walls that look from the newsroom floor into the production environment so editorial staff can see the live broadcast happening. Those glazed interfaces are an acoustic weak point — both sound transmission and HVAC noise transmission cross the interface unless the ductwork on both sides is carefully isolated. The SBKJ recommendation is to feed the newsroom and the studio from separate AHU plant, with no shared duct trunk, and to route any shared corridor or ceiling-void duct path with attenuated transitions at every zone boundary.
A second complication is 24-hour occupancy. News programming runs around the clock for major broadcasters (the ABC, SBS World News, Sky News Australia and Nine's continuous news operations all maintain night editorial staff), and the HVAC needs to run reliably through low-occupancy periods without short-cycling the plant or losing humidity control. Variable-air-volume (VAV) terminals with minimum set-point flow rates are standard, and night-mode operation is often a fully separate control sequence that drops chilled water flow and increases outside air to take advantage of cooler overnight air temperatures.
Control rooms and master control: redundancy
Control rooms are the technical nerve centres of any broadcaster — the audio control room (ACR) and production control room (PCR) for each studio, the central master control room (MCR) that manages on-air switching and transmission to the broadcast tower, and the network operations centre (NOC) that monitors and manages the IT and broadcast IP infrastructure. From an HVAC perspective these rooms share three attributes: high equipment heat load from racks, consoles and monitor walls; tight NC targets in the 25–30 range; and a redundancy requirement that escalates to mission-critical for the MCR.
For a typical PCR or ACR, the design pattern is a sensible cooling allocation of 250–400 W/m² (driven by audio and vision equipment racks, monitor walls and continuously occupied operator positions), supplied through a dedicated AHU branch with twin attenuators and welded-seam ductwork. The acoustic target is met by the same low-velocity, integrated-attenuator approach used in the studios, with the additional requirement that the ductwork must not transmit audio cross-talk between adjacent control rooms (a real risk where two PCRs share a ceiling void and the duct between them carries airborne sound from one console to the other). The remediation is double-skin duct, separated risers, and acoustic baffles between the two ceiling-void zones.
For the MCR, the redundancy requirement steps up. The MCR is the broadcaster's transmission control centre — the room that handles on-air playout, transition between programmes, advertising insertion, emergency broadcast switching and the link to the broadcast tower. An MCR outage during a live transmission window is a catastrophic event for the broadcaster, and the HVAC has to be designed against it. Industry standard for Australian MCRs is N+1 redundancy on chillers, AHUs and pumps; dual-path supply ductwork from two independent AHUs with automatic changeover dampers; concurrent maintenance capability so that any single component can be taken offline for service without affecting cooling continuity; and 24/7 monitoring with automatic alarm escalation to the facilities team.
The duct package for an MCR therefore looks more like a data centre than a studio. Two independent supply risers feed the room from two AHUs in separate plant rooms, each sized for full load. The supply joins inside the room at a manifold with automatic isolation dampers, and either path can carry the full design flow if the other is offline. Return is similarly dual-path. The MCR also typically has a separate close-control air-conditioning (CRAC) unit serving the broadcast server racks directly with a chilled-water or DX coil, providing local backup if the central plant fails entirely. Quarterly changeover testing under a documented procedure is essential — the redundancy is only real if it has been proven within recent memory.
Outside broadcast (OB) infrastructure
Outside broadcast vans sit outside the main facility HVAC scope and are essentially mobile broadcast environments with their own dedicated air-conditioning plant — typically a packaged DX system with a ducted supply manifold delivering air to gallery operator positions, the audio booth and the equipment rack space. The interface with the broadcaster's facility HVAC is at the OB compound, where vans plug into facility power, fibre and water. The HVAC engineer's main consideration is to ensure vehicle exhaust and generator emissions from the compound do not contaminate outdoor air intakes, which means locating intakes on the opposite façade or upwind based on prevailing wind direction. Sports OB at major Australian venues — the MCG, Melbourne Park, Allianz Stadium, Suncorp Stadium, Optus Stadium — sometimes uses semi-permanent commentary boxes that warrant a permanent attenuated supply matching a small radio booth (NC-20 to NC-25), fed from a dedicated AHU within the venue's plant space.
Acoustic ductwork construction: galvanised, welded seam, lined
The choice of duct construction is the most consequential single decision in a broadcasting HVAC package. The three options used in practice are conventional galvanised, welded longitudinal seam, and acoustically lined, and the boundary between them is set by the acoustic class of the room the duct is serving.
Conventional galvanised AS/NZS 4254 duct. Standard commercial HVAC fabrication. Pittsburgh seam rectangular, snap-lock or roll-formed spiral round, transverse joints sealed with TDC, TDF flange or slip-and-drive. Suitable for all Class C, D and E rooms — newsrooms, corridors, back-of-house and machine rooms. Branch velocity up to 10 m/s. Standard sealant class typical (Class B or C). Acceptable noise contribution at the diffuser is achieved through diffuser selection and attenuator placement rather than duct construction.
Welded longitudinal seam duct. The longitudinal seam is continuously welded, creating an air-tight tube with no detectable air leakage at operating pressure. Used for all Class A and Class B supply ductwork — studios, control rooms, audio booths and any duct branch where pinhole leakage or break-out noise from the seam would be unacceptable. The construction is more expensive than standard Pittsburgh or snap-lock duct but is the only practical option for NC-15 to NC-20 spaces. SBKJ supplies welded-seam spiral duct from our SBTF-1602 platform configured with welded longitudinal seam tooling, and welded-seam rectangular duct from custom configurations of our SBAL-V auto duct line for projects requiring rectangular cross-section.
Acoustically lined duct. Internal acoustic lining (typically 25–50 mm fibre-board or fibre-blanket bonded to the inner duct surface) provides additional octave-band attenuation, particularly in the mid-frequency range (250 Hz to 2 kHz) where most fan noise and regenerated noise concentrates. Acoustic lining is specified on Class A supply duct from the last attenuator to the supply terminal, on duct sections crossing acoustically sensitive walls, and on the return duct from studio plenum back to the central return riser. Lining adds thickness and pressure loss to the duct, both of which must be accounted for in the fabrication and the system pressure calculations.
In practice, a single broadcasting facility uses all three duct construction classes within the same project: galvanised AS/NZS 4254 for the newsroom and back-of-house, welded longitudinal seam for studio and control room branches, and acoustically lined sections at the supply terminals into Class A spaces. The SBKJ machine configuration recommended for a multi-class fabrication shop is the SBAL-V galvanised auto-line for the high-volume Class C/D/E ductwork, paired with the SBTF-1602 spiral tubeformer set up for welded longitudinal seam for the Class A/B branches, plus an integrated attenuator fabrication cell for the in-line silencers. This three-cell configuration covers the entire fabrication scope for a broadcasting project from a single facility footprint.
Attenuator sizing and placement
Attenuators (duct silencers) are inline components consisting of a parallel array of acoustically absorptive splitters that reduce sound power propagating down the duct in each octave band. Selection is by required insertion loss in the dominant frequency bands, balanced against the silencer's pressure loss.
Primary attenuators sit close to the AHU fan, suppressing fan tone and broadband noise before it propagates into the building duct system. Sizing is driven by the fan sound power spectrum and the cumulative insertion loss required to bring duct-borne noise below the lowest NC target served by that AHU. Typical primary attenuators for broadcasting are 1.5–2.5 m long, with splitter spacings selected for the 125–500 Hz octave bands where fan tones dominate. Secondary attenuators sit close to the supply terminal, typically within 2–5 m of the room penetration, suppressing regenerated noise from upstream dampers, transitions and balancing devices. Cross-talk attenuators are added to duct branches serving two acoustically sensitive rooms in series, where airborne sound can travel through the ductwork from one room to the other.
Attenuator placement is as important as selection. A correctly sized attenuator in the wrong location does not suppress noise reliably — an attenuator downstream of a balancing damper allows damper-regenerated noise to travel straight to the diffuser. The design rule: attenuators always go downstream of the noise source they suppress, with no significant noise-generating element (damper, elbow, transition) between the attenuator and the room.
Vibration isolation and structural detail
Vibration is the silent killer of broadcasting HVAC acoustic performance. A perfectly sized attenuator suite delivers nothing if the AHU is bolted rigidly to the structure or if the duct is hung on rigid rod hangers crossing into the studio ceiling. Three isolation layers are essential. First, the AHU and fan plant: every air-handling unit serving Class A or B zones sits on an inertia base (concrete-filled steel frame, 2–4× AHU operating weight) on spring isolators sized for at least 95% isolation efficiency at the dominant fan tone, natural frequencies in the 4–6 Hz range. Second, duct connections: flexible canvas or rubberised collars at every fan inlet and outlet break the rigid path from fan to duct, replaced on a 5–10 year maintenance cycle — a failed flex connector is a common cause of progressive duct rumble months after commissioning. Third, duct hangers: where ductwork crosses into a Class A or B ceiling void, rigid rod hangers are replaced with spring isolators, natural frequencies 4–8 Hz. Even a small section of rigid hanger crossing the studio acoustic envelope can short-circuit the entire isolation scheme.
Beyond the three core layers, structural detail at every penetration matters. Where ductwork crosses an acoustically rated wall, the wall is built with double-leaf isolation (separate stud frames each face, no rigid connection between them) and the duct passes through isolated sleeves that maintain the acoustic seal. The penetration is detailed with two layers of resilient lap (mineral wool packing plus elastomeric sealant each face) so airborne noise cannot pass around the duct through the wall annulus.
Displacement diffusion and stratified return
Air distribution geometry inside a broadcasting studio is its own design discipline. The cinematographer, the gaffer, the sound mixer and the talent each have opinions, and the HVAC engineer's job is to satisfy them all while delivering AS 1668.2 outdoor air at NC-20.
The standard supply approach in a Class A studio is displacement diffusion or low-velocity ceiling cassette. Displacement diffusion delivers air at a low temperature differential (typically 2–4 K below room temperature) at low velocity (under 0.15 m/s at the face) into a low-level perimeter plenum. The cool air spreads across the floor in a stable layer, rises gently as it absorbs heat from occupants and equipment, and is drawn off at the ceiling. The advantage of displacement diffusion is that air movement at face level is essentially zero — talent never feels a draft, microphones never pick up wind noise, and the lighting key shots are not disturbed by visible air currents. The disadvantage is that displacement requires generous floor area for the perimeter plenum and a careful balance between supply temperature and stratification height.
Where the studio layout does not support displacement, the alternative is low-velocity ceiling cassette diffusion, with supply terminals concealed behind the lighting grid. The diffusers are sized for face velocities under 1.5 m/s and air patterns that project upward and outward to mix with the rising heat plume from the rig, rather than downward into talent zones. Diffuser concealment behind the lighting grid is a coordination exercise: every diffuser position needs to align with the grid beam pattern, the lighting plot must not block diffuser throw, and the camera angles must not show the diffuser face.
Return air is almost always through the ceiling void above the lighting grid, with the void itself acting as a stratified plenum that captures the warm air from the rig and conveys it back to the AHU. Stratified return offers two advantages: the temperature differential between supply and return is maximised (which improves the AHU coil efficiency), and the contaminant load from set materials, fog effects and human emissions is captured at the ceiling rather than recirculated through the breathing zone. The return penetration through the ceiling is detailed with an acoustic plenum to maintain the NC target — the ceiling void is part of the acoustic envelope, not separate from it.
Fire, smoke and life safety integration
Australian building code provisions for fire dampers, smoke spill ductwork and emergency ventilation must be integrated into a broadcasting HVAC scheme without compromising the acoustic envelope. Any duct crossing a fire-rated wall requires a fire damper rated to the wall's fire resistance level, and for Class A studios the damper is selected for low pressure loss and minimum acoustic signature, with additional acoustic detailing on both sides. Large TV studios with audience seating are often classified as places of public entertainment and require dedicated smoke spill ductwork sized for high temperature operation (300 °C for 60 minutes per AS 4254 fire-rated duct provisions), routed independently of the comfort HVAC. Smoke spill fans are typically roof-mounted and activated by fire alarm in coordination with the building fire trip sequence. Refuge zones with pressurised stairs and lobbies interface with the general HVAC at AHU plant level, through dedicated emergency fans drawing outdoor air through standalone duct risers separate from the comfort system. All dampers and isolated components are tested at commissioning and re-tested on the maintenance cycle in line with AS 1851.
Major Australian broadcasters and their facilities
Understanding the addressable market for broadcasting HVAC fabrication starts with the facility footprint of the major Australian broadcasters. Each of the broadcasters below operates a metropolitan-scale campus or multiple campuses with the full mix of studio, control room, newsroom and back-of-house environments described in the preceding sections.
ABC — Australian Broadcasting Corporation. The public broadcaster maintains major campuses at Ultimo (Sydney) and Southbank (Melbourne), with smaller regional hubs in every state capital. The Ultimo campus is the largest broadcasting facility in Australia by floor area and includes multiple TV studios (drama, news, light entertainment), a substantial radio operation across multiple networks (ABC Radio National, ABC News Radio, ABC Local Radio, Triple J, ABC Classic FM), podcast production studios (the ABC has been a major podcast publisher for over a decade), the central newsroom, master control, broadcast servers and outside broadcast facilities. The Southbank campus mirrors the Ultimo functional mix at smaller scale. State hubs in Brisbane, Adelaide, Perth, Hobart and Darwin operate smaller TV and radio facilities with local news production.
SBS — Special Broadcasting Service. The multicultural public broadcaster operates its main campus at Artarmon (Sydney) with TV studios for SBS, SBS World News, NITV and the multilingual program slate, radio studios for the extensive SBS Radio language services (more than 60 languages), podcast production and the central newsroom. SBS also has facilities in Melbourne. The Artarmon facility was substantially refurbished in the 2010s and is one of the better-instrumented broadcasting HVAC installations in Australia for reference purposes.
Seven Network. Seven operates the Pyrmont (Sydney) campus, the Docklands (Melbourne) campus and the Mt Coot-tha (Brisbane) hill-top facility. The Pyrmont campus combines major TV studios with the central news and weather operation. Docklands serves as the Melbourne production hub for Seven News, AFL coverage and other Melbourne-originated content. Mt Coot-tha is the long-established Brisbane facility, originally built for the analogue era and substantially refurbished for digital and HD production.
Nine Entertainment. Nine operates a North Sydney headquarters, Docklands (Melbourne) production facility and Mt Coot-tha (Brisbane) operation. North Sydney is the central headquarters with newsroom, master control and a major TV studio cluster. The Docklands facility houses Melbourne-originated production. The Brisbane operation at Mt Coot-tha mirrors the Seven facility on the same hill. Nine also operates the metropolitan talk radio stations 2GB (Sydney), 3AW (Melbourne), 4BC (Brisbane) and 6PR (Perth) through its Nine Radio division, with studios in each city.
Network 10 (Paramount ANZ). Ten operates the Pyrmont (Sydney) campus and the South Yarra (Melbourne) facility, with a smaller Brisbane studio. The Pyrmont site sits in proximity to Seven and other Sydney media operations. South Yarra is the Melbourne production base. Ten's parent group also operates Paramount+ streaming services from the same infrastructure.
Foxtel and Sky News. Foxtel operates its primary broadcast facility at North Ryde (Sydney), with the technical operations centre and the bulk of Sky News Australia's production. Foxtel's facility was purpose-built for satellite and IPTV distribution and is one of the most technically sophisticated broadcasting plants in Australia.
Commercial radio networks. The Australian commercial radio market is consolidated into three major network groups. ARN (Australian Radio Network) operates the KIIS, GOLD and WSFM brands across metropolitan Australia, with studios in Sydney, Melbourne, Brisbane, Adelaide and Perth. SCA (Southern Cross Austereo) operates the Hit Network and Triple M Network, with metropolitan studios in each capital city and regional studios across more than 80 regional Australian markets. Nine Radio operates the talk format stations 2GB, 3AW, 4BC and 6PR as noted above. Pacific Star Network operates SEN and other Melbourne-based sport and talk formats. Community radio includes 2SER (Sydney), RRR and PBS (Melbourne), FBi (Sydney), 3RRR (Melbourne) and a substantial network of regional community stations.
Podcast networks. Australian podcast production is increasingly organised around dedicated networks: Acast Australia, LiSTNR (the SCA podcast division), Spotify Australia studios, Mamamia Podcast Network, Audioboom Australia, and a long tail of independent producers with in-house studios. ABC Podcasts and SBS Audio are the public broadcaster equivalents. The total Australian podcast studio inventory has grown rapidly over the last five years and now represents a meaningful share of the small-studio HVAC market.
Streaming infrastructure. The major streaming services in Australia — Foxtel Group services (Binge, Kayo, Flash), Stan, Paramount+, Disney+ AU, Amazon Prime Video Australia and Netflix — operate origin and edge servers across the Equinix and NextDC carrier-neutral data centre footprints in Sydney and Melbourne. The HVAC scope for streaming infrastructure is data centre HVAC (covered separately in our data centre HVAC ductwork guide) rather than broadcasting facility HVAC, but the broadcaster's master control room and broadcast server rooms increasingly resemble small data centre halls and apply the same redundancy and cooling continuity standards.
Camera robotics, LED retrofit and contemporary studio loads
Two trends have reshaped broadcasting studio HVAC over the last decade. The first is the LED lighting retrofit: most major Australian broadcasters have replaced tungsten and fluorescent rigs with LED, reducing peak studio sensible heat loads by 30–50%. This frees cooling capacity on existing facilities and allows downsizing of replacement AHU plant on refurbishment. The implication for HVAC engineers on a refurbishment is that the heat load survey must be done with the new LED rig in place, not the legacy rig — sizing chiller plant on legacy loads after retrofit leads to oversized plant that short-cycles in shoulder season.
The second trend is camera robotics and remote production. Robotic camera mounts (Vinten, Telemetrics, Egripment) allow operators in a central control room to frame cameras without a physical operator on the studio floor. The thermal impact is small but the implication for layout is that camera positions are more flexible and HVAC diffuser placement must accommodate a wider range of camera frames, pushing diffuser concealment further into the lighting grid and increasing use of ceiling slot diffusion. Remote production also shifts more technical activity from the studio floor to control rooms and master control, increasing equipment heat load there while reducing it in the studio. Recent Australian refurbishments have responded by relocating chilled water plant closer to the control room cluster and increasing cooling allocation in MCR and PCR zones.
SBKJ machine configuration for a broadcasting fabrication scope
A duct fabricator quoting a broadcasting project needs to deliver three duct construction classes from a single workshop: high-volume galvanised AS/NZS 4254 for the Class C, D and E rooms; welded longitudinal seam spiral or rectangular for the Class A and Class B branches; and integrated attenuator fabrication for the silencer package. SBKJ's recommended machine configuration for this scope is built around three cells.
Cell 1 — SBAL-V galvanised auto duct line. The SBAL-V is the workhorse for high-volume galvanised rectangular ductwork from coil. It handles the newsroom, corridor, back-of-house and machine room ductwork at output rates that comfortably cover a 10,000–25,000 m² broadcasting campus on a single-shift basis. The machine includes coil decoiling, levelling, longitudinal seam roll-forming, transverse end-forming for TDC or TDF flange, and inline cut-to-length. PLC integration allows direct nesting from CAD without manual sheet metal preparation.
Cell 2 — SBTF-1602 spiral tubeformer configured for welded seam. The SBTF-1602 spiral tubeformer is the platform for round spiral ductwork from 80 mm up to 1,600 mm diameter, configured with welded longitudinal seam tooling rather than the standard mechanical seam. The welded-seam configuration produces airtight tube suitable for Class A and Class B branches into studios, control rooms and audio booths. SBKJ supplies the welding integration as a factory option, including welding power source, seam tracking, gas shielding and inline weld inspection. The same SBTF-1602 base machine can be reconfigured back to mechanical seam for non-acoustic work, which protects the fabricator's investment across multiple project types.
Cell 3 — Attenuator fabrication. Integrated attenuators (duct silencers) can be fabricated in-house using a combination of the SBAL-V rectangular line for the silencer outer casing, a dedicated splitter assembly bench for the acoustic splitter array, and a mineral fibre cutting and bonding workstation for the absorptive infill. SBKJ engineers can specify the attenuator dimensions, splitter spacing, absorption thickness and end conditions to match a given acoustic insertion loss target, and the fabrication can be integrated into the project ductwork delivery from the same shop.
The three-cell configuration covers approximately 95% of the duct fabrication scope for a typical Australian broadcasting project. The remaining 5% — exotic transitions, custom architectural plenums, very large rectangular boxes — is typically handled as bench fabrication using the same coil stock and the same fabrication standards. A fabricator setting up for the broadcasting market with this machine configuration can quote a complete facility duct package competitively against any specialist acoustic ductwork supplier.
Commissioning and acoustic measurement
Commissioning is where the HVAC design meets reality, and broadcasting commissioning is more demanding than most building types. Four measurement protocols are essential. First, NC measurement at every studio operating position — with HVAC at design flow and the studio in operational lighting configuration, an acoustic engineer measures sound pressure level in octave bands from 63 Hz to 8 kHz at each microphone and operator position, compared against the NC curves and acoustic specification. Any band exceeding target requires investigation and remediation before sign-off. Second, duct-borne noise spectrum at the supply diffuser via close-microphone measurement, separated from room reverberation to identify attenuator deficiencies or regenerated noise from upstream dampers. Third, vibration measurement at the AHU and at duct hangers crossing acoustic boundaries, with accelerometers verifying inertia base isolation efficiency (typically 95% or better). Fourth, thermal and humidity stability over a 4-hour live broadcast simulation at full lighting and occupant load, with HVAC maintaining set-point within 0.5 K and humidity within 5% RH across the test window. Drift outside these bounds during a real broadcast leads to visible camera issues and audio artefacts. The commissioning report becomes part of the facility's permanent acoustic certification and is referenced at every subsequent maintenance or refurbishment activity.
Maintenance and lifecycle
Broadcasting HVAC maintenance is more demanding than commercial office maintenance because the acoustic performance of every component degrades on a known schedule and must be refreshed before the degradation becomes audible on-air. Flexible duct connectors at fan inlets and outlets fail in 5–10 years through ozone exposure and thermal cycling, and a failed flex connector transmits fan vibration directly into the duct and produces a low-frequency rumble that prints into recording. Attenuator splitter material absorbs moisture and particulate over decades and loses absorption coefficient — inspection and replacement on a 5–7 year cycle maintains insertion loss at design. Spring isolators under AHU plant settle and shift natural frequency; re-adjustment on a 10–15 year cycle restores design performance. Duct sealant at Class A penetrations dries and cracks over decades, creating pinhole leaks that allow noise break-out into ceiling voids. VAV control loops drift over years of operation and can develop audible hunting that requires periodic re-tuning. The annual maintenance budget for a major broadcasting HVAC installation is typically 4–6% of installed capital value, higher than the 2–3% typical for commercial office.
How SBKJ supports broadcasting fabricators
SBKJ Group, headquartered in Box Hill North VIC, supplies HVAC duct fabrication machinery to fabricators across 100+ countries and has supported broadcasting and acoustic-sensitive projects across the Australian market and internationally. For fabricators quoting broadcasting work specifically, our engineering team provides three layers of support.
First, the SBAL-V galvanised auto duct line and the SBTF-1602 spiral tubeformer with welded longitudinal seam configuration are both deliverable as turn-key fabrication cells from our Australian operation, with the welded-seam tooling supplied as a factory option from the original quotation. Lead times for either platform are typical of large industrial machinery — 12–20 weeks from order — and our Box Hill North office handles commissioning and Australian installation directly.
Second, our engineering team supports project quoting with specific guidance on duct construction class, attenuator integration and the practical fabrication tolerances required for NC-15 to NC-25 acoustic envelopes. We have provided this support on a range of acoustic-sensitive projects from broadcasting through to performing arts (see our concert hall and performing arts centre HVAC ductwork guide), cinema and theatre entertainment venues (see our cinema and theatre entertainment HVAC ductwork guide), and high-density technical environments (see our data centre HVAC ductwork manufacturing guide).
Third, we maintain a deep reference library on the acoustic duct lining and attenuator specifications used in Australian broadcasting and acoustic-sensitive work, which is published openly in our acoustic HVAC duct lining and attenuator guide. Combined with our AS 1668.2 Australian ventilation code reference, this gives a fabricator the technical underpinning to quote and deliver broadcasting work with confidence.
Discuss a broadcasting duct package with an SBKJ engineer →
FAQ
What NC rating is required inside a radio studio?
Radio recording booths and on-air studios target NC-15 to NC-20 — among the quietest occupied spaces in any building type. Achieving this requires very low duct velocity (under 3 m/s in branch runs), generous attenuator sizing, vibration-isolated fan plant and welded-seam acoustic-rated duct construction.
How is a TV studio different from a radio studio for HVAC design?
Television studios are large-volume rooms (1,000–3,000 m³) with extensive lighting heat loads of 200–500 W/m² (up to 800 W/m² in high-key talk show or news sets). The dominant design challenge is removing sensible heat without disturbing camera framing, talent comfort or microphone pickup. Radio studios are small acoustic booths where thermal loads are modest but the noise target is far more aggressive — NC-15 to NC-20 versus NC-20 to NC-25 in a TV studio.
Why does a podcast studio need bespoke HVAC?
Podcast studios are condenser-microphone environments where any continuous HVAC noise prints into the recording. Bespoke HVAC means low velocity supply (under 2 m/s at terminals), integrated attenuators, vibration-isolated AHU plant and ductwork built to suppress break-in noise from adjacent mechanical spaces.
What is the master control room (MCR) HVAC redundancy standard?
Master control rooms run 24/7 and are mission-critical for broadcast continuity. Industry standard is N+1 redundancy on chillers, AHUs and pumps, dual-path supply ductwork from independent AHUs with automatic isolation dampers, and quarterly changeover testing under a documented procedure.
Can galvanized duct be used in a broadcasting facility?
Yes for back-of-house — corridors, newsrooms, machine rooms and admin offices use standard galvanized rectangular duct to AS/NZS 4254. For studios, control rooms and audio booths, the duct must be acoustically rated with sealed welded longitudinal seams to prevent break-out noise and pinhole air leakage. SBKJ supplies galvanized SBAL-V auto-line ductwork for office areas and welded-seam spiral SBTF-1602 for studio supply branches.
