Why whole-store HVAC matters more than the kitchen hood alone
If you have already read our commercial kitchen exhaust HVAC duct guide, you know the canopy hood, the grease duct riser and the pollution control unit are the loudest engineering decisions in a cafe or quick-service restaurant. But the canopy is only one of seven distinct ventilation systems in a modern QSR, and the others — dining area conditioning, service counter air balance, drive-thru pressure control, customer toilets, cool room and freezer venting, make-up air, and toilet exhaust — are where projects quietly fall over after they open. Customers complain about smelly air. Operators complain about doors that slam open from pressure imbalance. Owners complain about energy bills that drift 18-25 percent over the franchise template. The root cause is usually the whole-store HVAC package that was bolted around the kitchen as an afterthought.
This guide is written from the duct fabricator's perspective — the people who fabricate the rectangular and round duct sections, flanges, elbows and spiral round risers that the mechanical contractor installs. After 30 years of fabricating duct for Australian retail food projects, we have a strong view on what the design package needs to look like before it lands on the fabrication floor. Use it as a procurement brief, a fabricator's reality check, or a fit-out manager's pre-flight checklist before signing a head-contract package for a 200-store rollout.
The Australian cafe and QSR sector is one of the most concentrated retail-food markets in the world. McDonald's Australia operates roughly 1,000 restaurants; Hungry Jack's around 430 stores as the local Burger King licensee; KFC Australia approximately 720 stores under the Yum! Brands franchise; Domino's Pizza Enterprises (ASX:DMP) over 700 stores across Australia and New Zealand; Subway Australia around 1,200 outlets; Red Rooster around 360; Oporto around 200; Guzman y Gomez (ASX:GYG) approximately 190; Mad Mex around 80; Grill'd Healthy Burgers around 140; Pizza Hut Australia around 250; Zambrero (TQ Funds) roughly 250. Cafe chains include Coffee Club (Minor International, around 340 stores), Gloria Jean's Coffees, Zarraffa's Coffee (Queensland-origin, around 95 stores), Muffin Break (Foodco Group), Michel's Patisserie, Donut King, Brumby's Bakery, Bakers Delight, Black Star Pastry, and the premium cafe chains Industry Beans, ST. ALi and Campos. Across those operators there are well over 7,000 individual store sites in Australia, and the duct fabrication brief from a premium operator (Soul Burger, Mary's, Burger Project, Schnitz, Roll'd, Boost Juice, Sumo Salad) looks materially different from a legacy QSR brief — tighter acoustic targets, more aggressive outdoor-air rates and more visible architectural ducting.
The Australian compliance stack — four documents you cannot skip
Every QSR or cafe fit-out in Australia is governed by a four-document compliance stack. None of them are optional, all of them are referenced in the building permit and most of them are audited during commissioning by either the local council environmental health officer or the franchise compliance manager. The four documents are the National Construction Code, AS 1668.2, AS 4674 and the FSANZ Food Standards Code.
The National Construction Code (NCC) sets the building classification framework. A typical street-front cafe or QSR with under 300 m² of dining floor area is normally classified Class 6 (retail). A larger dine-in QSR with assembly seating may also trigger Class 9b classification thresholds, which add stricter egress, smoke control and fire compartmentation provisions. The classification mix matters because it determines whether the duct runs need fire dampers at every level penetration, what smoke-spill duct work is required, and whether the kitchen exhaust riser needs a fire-rated shaft enclosure all the way to the roof. The franchise template you start with may have been engineered for a Class 6 stand-alone box and need to be reworked for a Class 6 / Class 9b combined tenancy when the same store goes into a shopping centre food court. Reworks of this kind are common at shopping centre rollouts where the template was originally designed for a drive-thru pad site.
AS 1668.2 — The use of mechanical ventilation in buildings is the primary mechanical ventilation standard. It sets the outdoor air rate formula, the kitchen exhaust requirements (Section 4 in the current edition), the contaminant categories and the minimum exhaust rates for amenities. For dining areas the relevant numbers are a per-person component V_p of 5 L/s/person, a per-area component V_a of 1.0 L/s/m² of net occupiable floor area, and an occupant diversity factor that adjusts the design from worst-case to expected operation. For a 120-seat suburban QSR with a 200 m² dining footprint at peak occupancy, this means roughly 900-1,100 L/s of outside air through the dining diffusers — before adding the make-up air for the kitchen exhaust hood. The 25 L/s per WC fixture and 10 L/s per urinal fixture in the toilet exhaust calculation come from the same standard.
AS 4674 — Design, construction and fit-out of food premises is the construction-detail standard. It governs how the kitchen surfaces, joinery, plumbing and ductwork are detailed to be cleanable and hygienic. For ductwork it matters in three ways: (1) the requirement that exposed duct surfaces in food preparation areas are smooth, non-porous and cleanable, which drives joint and seam choices; (2) the requirement that grease ducts have access panels at every change of direction and at minimum 3-metre intervals on horizontal runs, which drives the panel and gasket specification; and (3) the requirement that pipework and ductwork penetrations are sealed in a way that prevents pest entry and water ingress, which drives the boot, flange and fire-stopping detail. Most fabrication briefs we see specify "AS 4674 compliant fabrication" without ever giving the fabricator the actual access panel spacing schedule. Resolve that ambiguity at quotation stage, not on the fit-out floor.
FSANZ Food Standards Code — particularly Standard 3.2.2 (Food Safety Practices and General Requirements) and Standard 3.2.3 (Food Premises and Equipment) — sets the operating hygiene rules that drive how the HVAC system has to behave during trading. The condensate must not drip onto food preparation surfaces. The make-up air supply diffuser positions must not blow contaminants onto exposed food. The cool room evaporator drains must discharge to a tundish, not to an open drain. The kitchen exhaust must remove cooking effluvia at the rate required to keep food preparation surfaces below the prescribed temperature gradient. These rules do not change the cubic metres of duct that gets fabricated but they do change the diffuser positioning, the condensate routing and the access panel spacing. They are inspected by the local council environmental health officer, not by the building certifier, and a single failed inspection delays opening by a week.
For grease exhaust specifically, two additional documents are commonly referenced even though they are not strictly part of the Australian compliance stack. The first is AS 1668.1 — The use of ventilation and air conditioning in buildings — Fire and smoke control, which governs fire-rated duct work, fire dampers and smoke spill ducts. The second is NFPA 96 — Standard for Ventilation Control and Fire Protection of Commercial Cooking Operations, the US standard widely referenced by international QSR franchisors for grease duct construction, joint sealing, access panel spacing and clearance to combustibles. Most national franchisors require their grease duct package to meet NFPA 96 even when an Australian-only project could technically be built to AS 1668.1 alone. Where there is a conflict between the two, NFPA 96 is normally the stricter document and is the one fabricated to. This is why our SBKJ kitchen exhaust riser packages are quoted to NFPA 96 even on Australian-only projects — it is what the franchisor's specification will ask for in 80 percent of cases.
Zone 1 — Dining area conditioning
The dining area is the longest-duration occupied space in a cafe or QSR. The HVAC target is comfort, low noise and steady humidity — 22-24°C dry bulb, 50 percent ±10 percent relative humidity, NC-40 at the loudest diffuser face. Premium cafes push the acoustic target down to NC-35 in seating zones and NC-45 in service zones, with a slightly cooler 21-22°C setpoint.
The dining area is normally served by a rooftop packaged AC unit (standard franchise approach), a ducted split system (suburban shopping centre cafes), or a chilled water FCU off a base-building reticulation (food court tenancies). Each has different duct sizing implications — packaged units want short, large-section trunks with low pressure drop; ducted splits want carefully laid-out VAV-trimmed branches; FCU systems want individual zones with return-air strategies that do not short-circuit.
Material is almost always galvanised steel (Z275 zinc coating) fabricated to AS/NZS 4254.1 or 4254.2. Pittsburgh lock seam for rectangular with TDF flanges every 1.2-3.0 m; 0.7-1.0 mm wall spiral round for diameters under 800 mm. The galvanised finish gives 25-year+ service life because the airstream is conditioned, low-humidity and not grease-laden. Most franchise templates specify 25 mm internal acoustic lining for the first 3-5 m downstream of the rooftop unit; we prefer external wrap insulation over a bare galvanised interior for cleanability where the noise budget allows.
Diffusers, take-offs and volume dampers must be specified at fabrication brief, not at site, because the take-off geometry is cut before the diffuser arrives. Return air strategy is either a dedicated return duct or, in some templates, the ceiling void as a return plenum — the latter is cheaper to fabricate but forces every other service in the void to be rated for plenum use, which is rarely favourable on the full bill of materials.
Zone 2 — Service counter and front-of-house
The service counter is the pressure-regime interface — kitchen negative, dining slightly positive, outdoor neutral. Managing that pressure change cleanly is what stops cooking smells migrating into the seating area and dust from outside being drawn into the kitchen prep zone.
Two duct details matter. First, supply diffusers should not blow directly across the food display or order point at velocity; set them at least 1.5 m from the food line with throw directed away from the customer face. This often requires a 90-degree elbow with a turning vane and a manual volume damper at the service counter take-off — the fabricator needs this detailed in the brief, not added at site. Second, air curtains over the kitchen-to-dining door (common in upscale dine-in and cafe-bakery hybrids) sit on their own duct connection with sizing set by door width, not room load.
The pressure relationship is managed through transfer grilles from dining to kitchen — undercut doors, fixed-louvre transfers in the service counter bulkhead, or door-mounted grilles. Specify location and free area in the duct package, not the door schedule, because they are part of the air balance and easy to forget.
Zone 3 — Drive-thru window pressure and isolation
Drive-thru is a separate HVAC zone for one reason: vehicle exhaust gases. When the order window or the pickup window opens, the air pressure inside the drive-thru zone determines whether vehicle exhaust drifts inside or whether conditioned air spills outside. The correct answer is the second one. A small amount of conditioned air spilling out of the window is cheap (a few hundred dollars a year in extra cooling). A small amount of vehicle exhaust drifting in is a customer complaint, a staff health complaint and, in rare cases, a council compliance notice. The cost of getting the pressure direction wrong is much higher than the cost of getting it right.
Drive-thru transactions are roughly 50-65 percent of total transaction volume at major QSR chains in Australia. McDonald's, KFC, Hungry Jack's, Red Rooster, Oporto and Zambrero all run drive-thru as a primary channel. Some chains (Guzman y Gomez, Grill'd) run drive-thru at selected pad sites only. The drive-thru window is therefore not a minor service-counter variant — it is one of the highest-traffic and highest-visibility customer touchpoints in the store, and the air quality at the window matters to the customer experience score in the franchise's mystery shopper audits.
The duct design for the drive-thru zone is: a dedicated air handling unit (a rooftop split or a small dedicated package) serving only the drive-thru window area; a high-efficiency outside air filter (MERV 11 minimum, MERV 13 preferred); a pressurisation target of 30-50 Pa positive relative to outside, measured at the window when closed; and a separate return air loop that does not cross-mix with the dining area zone. The duct work for this zone is short — usually less than 15 metres of trunk between the AHU and the window — but it has to be sized for the design pressure and air change rate, which is typically 6-8 air changes per hour in the window zone.
A vestibule-style isolation is the gold standard where site geometry allows it. The drive-thru window sits inside a small vestibule with two doors — one to outside, one to the kitchen — and the vestibule has its own supply diffuser at a slight positive pressure. The kitchen door is always closed except during transactions, and the vestibule's positive pressure prevents back-flow from outside. From a fabrication brief, the vestibule is a small supply diffuser with a dedicated take-off and a separate volume damper. It adds maybe 30 metres of branch ductwork to the package but it eliminates one of the most common QSR customer complaints — the drive-thru smell — at a cost of well under one percent of the fit-out budget.
For sites without a vestibule, the drive-thru window relies on direct pressurisation of the order-and-pickup zone. The duct routing here is straightforward but the air balance is sensitive. Commission the pressure with the window closed first, then again with the window open at typical transaction duration, to verify that even with the window open the indoor pressure stays positive relative to outside. The pressure-test results should be in the commissioning report — not as a one-time check but as a setpoint that operations can verify monthly with a simple smoke pencil at the window face.
Zone 4 — Kitchen exhaust and make-up air integration
The kitchen exhaust system is the topic of our dedicated commercial kitchen exhaust HVAC duct guide. We will not repeat the canopy sizing, grease duct construction, fire wrap or pollution control unit specifications here — they are covered in that document with the full detail. What we want to address in this whole-store guide is the integration between the kitchen exhaust system and the rest of the store HVAC, because that is where most whole-store designs fail.
The kitchen exhaust pulls a defined air volume out of the kitchen through the canopy hood. For a typical QSR with 4-6 burners, two fryers and a grill, that volume is 4,500-7,000 L/s at the canopy. The air pulled out has to be replaced by air coming in. The make-up air strategy delivers 80-90 percent of the exhaust volume back into the kitchen as tempered outside air through a dedicated rooftop make-up air unit (MUA). The remaining 10-20 percent comes through transfer grilles from the dining area, which keeps the dining area at a slight positive pressure relative to outside and the kitchen at a slight negative pressure relative to dining. The negative pressure differential keeps cooking smells from migrating into the dining area when the kitchen door opens.
The duct fabrication for the MUA path is: a roof intake plenum with a weatherhood and a bird screen; a filter section (MERV 11 minimum); a heating coil (gas-fired direct or indirect, electric, or heat-recovery from the exhaust riser); a fan section sized for the design volume and the duct pressure drop; and a duct distribution network that delivers the tempered air into the kitchen above or adjacent to the canopy face, but not directly into the canopy capture zone (which would short-circuit the make-up air back out through the canopy without doing any conditioning work on the kitchen space).
For an Australian climate, the MUA temperature setpoint is normally 18-22°C, which is below the kitchen's elevated background temperature (the canopy captures most of the cooking heat, but radiant heat still pushes the kitchen air several degrees above dining) but warm enough not to chill the cook staff. In Melbourne and Sydney winter conditions, the heating coil works hard for 4-5 months of the year; in Brisbane and Perth, the coil is largely inactive and the MUA mostly delivers ambient air through a filter. The duct sizing is the same in both climates — what changes is the heating coil capacity and the energy bill.
From a fabrication perspective, the MUA duct package is galvanised, rectangular for the trunks (because they are wide and short), and spiral round for the branches into the kitchen ceiling. Insulation requirement is exterior wrap to prevent condensation on the cold duct walls during summer (when the ambient OA is humid and the duct interior is air-conditioned) and to keep the heated air warm in winter. Internal lining is not normally specified on MUA ducts because the airstream is filtered and clean, and acoustic attenuation at the fan is handled with a packaged silencer instead.
The single biggest installation error we see on MUA systems is short-circuiting — the MUA discharge diffuser is too close to the canopy face, and the make-up air goes straight up through the canopy without conditioning the kitchen. The fix is to position the MUA diffusers at least 1.5-2.0 metres laterally from the canopy face, on the opposite side of the canopy from the prep bench, so the air sweeps across the kitchen toward the canopy rather than into it. This is a layout decision, not a fabrication decision, but the duct package has to support it with the right branch routing.
Zone 5 — Customer toilet exhaust
Customer toilet exhaust is governed by AS 1668.2 with a minimum exhaust rate of 25 L/s per WC fixture and 10 L/s per urinal fixture. For a typical QSR with two unisex WCs and one accessible WC plus a urinal in the male amenity, the design exhaust rate is roughly 75-100 L/s. The exhaust fan runs continuously during trading hours — not on occupancy sensor control alone — because the AS 1668.2 minimums are continuous-operation numbers, not on-demand numbers.
The duct fabrication for toilet exhaust is short, simple and almost always overlooked in the franchise template detail. Galvanised rectangular or spiral round, 0.6-0.8 mm wall thickness, with a single fan on the roof or in the ceiling void discharging through a roof cowl or wall louvre. The duct is normally 200-300 mm diameter for a single-amenity toilet block, with branch take-offs to each WC compartment and the urinal recess. Routing matters more than sizing — the exhaust grille has to be located above or adjacent to each fixture to capture odour at source, and the take-off from the trunk to the grille has to be ducted, not just a hole in the ceiling.
Two compliance details to verify at fabrication brief: (1) the toilet exhaust must not discharge into the same plenum or duct system as the kitchen exhaust, because mixing food-area and amenity-area airstreams is prohibited under both AS 1668.2 and the FSANZ Food Standards Code; (2) the toilet exhaust roof termination must be at least 3 metres from any outside air intake (the MUA intake or the dining area OA intake), because the negative pressure at the intake will otherwise draw amenity air back into the conditioned spaces.
Staff amenity ventilation runs to the same standard. The staff WC, the change room and any back-of-house lockers are normally on a single exhaust loop at 25 L/s per WC and 10 L/s per shower. The staff room itself is usually conditioned by extending a dining-area diffuser branch, which is fine for comfort but does not give the staff room an independent control zone. For sites where staff comfort during peak summer days is a recruitment issue, consider a small dedicated split AC for the staff room and zone it off the main HVAC trunk.
Zone 6 — Cool room and freezer storage
Cool rooms (2-4°C) and freezers (-18 to -25°C) are refrigerated boxes with their own evaporator, condensate drain and pressure relief vent. Three details bridge to the building duct system. First, the cool room pressure relief vent — typically 100 mm diameter with a low-flow check damper, 1-2 m of galvanised section ducted to the kitchen ceiling void, sitting between the cool room manufacturer's package and the building duct package. Second, the compressor exhaust — cool room and freezer compressors reject 4-8 kW into the back-of-house and need a dedicated exhaust hood or transfer grille feeding either the kitchen exhaust or a dedicated back-of-house extractor. Freezers need more aggressive compressor ventilation and a pressure-equalisation valve on the relief vent. Third, condensate routing — plumbing, not duct, but the duct package has to leave clearance for the drain from evaporator to tundish to floor waste.
The cool room door cycle creates a small pressure pulse in the kitchen every opening. For high-traffic QSR sites with frequent cool room access, size the kitchen exhaust with 10-15 percent margin over calculated minimum to absorb the pulses without dragging dining pressure down.
Zone 7 — Service voids and routing
The service void above the ceiling dictates duct depth, maximum aspect ratio and routing. Australian QSR and cafe tenancies typically have 300-600 mm of void, with higher-end tenancies running 400-500 mm. The duct package shares space with sprinkler reticulation, water services, electrical, data and (in some tenancies) the kitchen extract riser. The brief should give the fabricator available void depth at each section, maximum duct depth allowed, and the locations of any obstructions.
A typical galvanised rectangular dining trunk is 200-350 mm deep by 400-700 mm wide; spiral round branches are 200-400 mm diameter. Take-offs over 250 mm diameter are normally 45-degree saddle-tap with turning vanes. AS 4674 requires access panels at every change of direction and minimum 3-metre intervals on horizontal kitchen exhaust runs. Specify panel location and free area in the fabrication brief — the fabricator has to build them in from the start, and panel locations need internal stiffeners to maintain structural rigidity.
Material selection — when galvanised, when stainless
The material selection rule for cafe and QSR duct work is simple in principle and slightly more nuanced in practice. Galvanised steel (Z275 zinc coating, AS/NZS 4254 fabrication) is the default for all retail HVAC duct — dining, service counter, drive-thru, customer toilet, cool room pressure relief, staff amenity, and back-of-house exhaust below the kitchen extract. Stainless steel (304 grade typically, 316 in coastal or aggressive environments, continuous welded longitudinal seams) is mandatory for the grease-laden cooking exhaust path from the canopy hood to the roof termination, per NFPA 96 and AS 1668.1.
Galvanised duct is acceptable in the retail HVAC zones because the airstream is dry, conditioned, low-temperature and non-corrosive. The Z275 zinc coating on the steel coil gives 25-30 year service life with no internal corrosion, and the fabrication seam (Pittsburgh lock for rectangular, spiral lock for round) is reliable for the design pressures (under 1,000 Pa at the trunk) typical in retail HVAC. SBKJ fabricates galvanised duct on the SBAL-III auto duct production line, which integrates the coil decoiler, levelling, notching, folding, Pittsburgh seaming and TDF flange forming in a single pass. The output is a finished rectangular duct section in lengths up to 1,200 mm at the line, longer for custom orders.
Stainless duct is required in the grease exhaust path because the airstream is hot (cooking effluvia at 80-150°C at the canopy face), wet (water vapour from cooking), grease-laden (which oxidises and accelerates corrosion on galvanised), and subject to fire load. NFPA 96 specifies welded construction, no Pittsburgh lock seams, no riveted joints, no flange-and-gasket joints with combustible gaskets. The seam has to be continuous, welded and inspected. SBKJ fabricates stainless grease duct on the SBAL-V production line, which is configured for stainless coil handling, continuous longitudinal welding (typically TIG or plasma), and the higher edge-finishing tolerances required for welded duct. The output is a finished grease duct section ready for flange welding at the joint, with NFPA 96-compliant construction throughout.
The cost differential is significant — stainless raw material is roughly 4-5 times the cost of galvanised per kilo, and the welded construction takes longer to fabricate per metre. For a typical QSR store, the dining and amenity duct package is around 80-120 metres of galvanised, costing a relatively modest portion of the HVAC budget; the kitchen exhaust riser is 15-25 metres of stainless, costing a disproportionate share. Understand the split before you brief the fabricator, because the stainless component cannot be cheapened by substituting galvanised — that substitution would breach NFPA 96 and would not pass commissioning.
One subtle exception: in some shopping centre tenancies where the kitchen exhaust riser is shared between multiple food court tenants and the riser is owned and maintained by the centre management, the tenant only fabricates the in-tenancy section from the canopy to the riser connection. That in-tenancy section is still stainless, but the volume is lower and the fabrication brief is correspondingly simpler. Confirm at lease stage who owns and fabricates which sections of the riser.
Energy disclosure — NABERS, Climate Active
The Australian energy disclosure framework for commercial buildings is in active evolution and the QSR and cafe sector is starting to feel it. NABERS (National Australian Built Environment Rating System) is well established for office, hotel and retail shopping centre buildings but is only emerging as a rating tool for standalone QSR pad sites. No formal scheme is yet mandatory but the trend is clear — energy disclosure for QSR sites will follow the trajectory of office and shopping centre buildings.
Climate Active certification is the other framework moving through the sector — a voluntary federal government certification for carbon neutrality at the business or product level. A number of listed and franchise QSR operators have already started Climate Active certification for their head office operations; the next step is store-level certification, which requires energy data at the individual store level and a reduction-and-offset strategy that the HVAC system materially affects.
From a duct fabrication perspective, energy disclosure does not change the duct itself. What it changes is the fan motor, the heating coil, the VSD, the controls strategy and the way the system is commissioned. A well-fabricated duct package with low pressure drop, tight joints (low leakage) and good insulation (low conduction loss) helps the system achieve a better energy rating regardless of which scheme it is rated under. Tight joints — a leakage rate under 1 percent of design air volume at trunk pressure — is the single biggest fabrication-side contribution to energy performance.
Acoustic and indoor air quality targets by store type
Different store types have different acoustic and IAQ targets. The franchise template sets the headline numbers but the local fit-out has to verify them against the actual tenancy noise environment (which can be quiet suburban or noisy shopping centre food court) and the actual customer expectation (a premium cafe customer expects quieter conditions than a quick-counter takeaway customer).
Premium cafe and dine-in — NC-35 in seating zones, NC-40 in service zones, supply air filtration MERV 11-13, outdoor air rate 8-10 L/s/person (above AS 1668.2 minimums to support the boutique feel). Examples: Industry Beans, ST. ALi, Campos premium outlets, Black Star Pastry.
Cafe chain and bakery — NC-40 in seating, NC-45 in service, MERV 8-11 filtration, outdoor air rate at AS 1668.2 minimums. Examples: Coffee Club, Gloria Jean's Coffees, Zarraffa's Coffee, Muffin Break, Michel's Patisserie, Donut King, Brumby's Bakery, Bakers Delight.
QSR dine-in — NC-40 in seating zones, NC-45 in service zones, MERV 8 filtration, AS 1668.2 minimums for outdoor air. Examples: McDonald's, Hungry Jack's, KFC, Red Rooster, Oporto, Nando's, Guzman y Gomez, Mad Mex, Zambrero, Grill'd, Schnitz, Roll'd, Pizza Hut dine-in.
QSR takeaway only — NC-45 in counter zones (no seating), MERV 8 filtration, AS 1668.2 minimums. Examples: Domino's Pizza, Crust Gourmet Pizza, Pizza Capers, Salsa's Fresh Mex takeaway, Boost Juice, Sumo Salad takeaway counters.
Premium burger — NC-38 to NC-40 in seating, MERV 11 filtration, outdoor air rate at AS 1668.2 plus 20 percent margin. Examples: Soul Burger, Mary's, Burger Project.
The fabrication implication of these tiers is mostly about pressure drop and duct sizing. Lower NC targets force larger duct cross-sections (lower velocity, less aerodynamic noise) and more aggressive silencer treatment. The duct package for a premium cafe is typically 15-25 percent larger by cross-section than the duct package for a comparable QSR takeaway counter, even though the air volume is similar. Specify the acoustic target at brief stage so the fabricator can size the trunks correctly the first time.
Procurement model — franchise template vs site-specific
QSR and cafe HVAC procurement runs on two distinct models. The first is the franchise template — the franchisor (head office) standardises the HVAC package across all stores, runs the design through a single mechanical consultant, and rolls it out store by store with minor site-specific adjustments. McDonald's, Hungry Jack's, KFC, Domino's, Subway and most of the large chains run on this model. The second is the site-specific model — each store is designed individually, often by a different mechanical consultant, with the operator giving the architect a generic brief and letting the consultant size the system from first principles. Premium cafes, smaller chains and independent operators run on this model.
The duct fabrication brief is materially different under the two models. Under the franchise template, the duct package is a near-replica of the previous 10-50 stores fabricated for that operator, with site-specific adjustments only at the trunk routing (where it has to fit the specific tenancy void) and the diffuser locations (where it has to match the architectural ceiling layout). The fabrication brief is therefore quick to produce, the cuts are well understood, and the fabricator can quote based on the historical bill of materials. Lead times are short (4-8 weeks from order to delivery) and pricing is competitive because the fabricator is producing a near-standard product at scale.
Under the site-specific model, each store is a custom fabrication. The brief takes longer to produce because the cuts and quantities are derived from scratch, the bill of materials varies by site, and the fabricator has to quote each project individually. Lead times are longer (6-12 weeks from order to delivery) and pricing is per-project rather than at fleet rate. For premium cafe operators, the trade-off is acceptable because the site-specific design supports the boutique architectural intent. For large QSR chains, the franchise template is the only way to control rollout cost across hundreds of sites.
SBKJ supports both models. For franchise template work, we run a dedicated production cell with the franchisor's standard duct sizes pre-loaded into the auto duct line's CNC controller, and we maintain a rolling spare parts and fitting buffer that lets us turn around a site-specific adjustment within the same production week. For site-specific work, we run each project as a one-off with full pre-fabrication review, 3D site coordination if requested, and bespoke fitting fabrication for custom diffusers and trunk geometries. Both lanes use the same SBAL-III galvanised auto duct production line for the retail HVAC portion and the SBAL-V stainless production line for the kitchen exhaust portion — the equipment is the same, what changes is the production planning and the brief detail.
Drive-thru economics and the duct case
We mentioned earlier that drive-thru transactions are 50-65 percent of total transaction volume at major QSR chains in Australia. The economic implication for HVAC is that the drive-thru window is a higher-priority air quality zone than the counter inside the store — more customers experience it, the experience is shorter and more sensory, and the air quality at the window is a direct contributor to the customer experience score in mystery shopper audits. For franchise operators with national footprints, a 5-point improvement in drive-thru customer experience scores correlates with a measurable lift in same-store transaction count over a 12-month window.
The duct fabrication case for investing in the drive-thru zone is therefore not just compliance — it is brand equity. A drive-thru that smells of vehicle exhaust costs the chain real money in repeat-visit attrition. A drive-thru that smells of clean conditioned air gets a positive halo on the same audit. The marginal duct cost of getting the drive-thru pressurisation right — a dedicated AHU, a high-efficiency filter, a vestibule if site geometry allows, and 30-50 Pa positive pressure relative to outside — is well under one percent of the total fit-out budget. The marginal customer experience lift is much higher than that.
For chains running a national rollout, the duct fabrication brief for the drive-thru zone should be standardised across all sites, even when the rest of the store template is being site-adapted. The same MUA model, the same filter spec, the same trunk size, the same vestibule layout (where geometry allows). Standardisation here means the fabricator can build a buffer of pre-fabricated drive-thru duct kits that ship directly to site without per-store fabrication time. SBKJ has built drive-thru duct kits for several Australian QSR rollouts and the lead-time saving is typically 2-3 weeks per store on the drive-thru portion.
Franchise Code of Conduct compliance
The Australian Franchise Code of Conduct, administered by the ACCC, touches the duct package in two indirect ways. First, the Code requires franchisors to disclose the standard fit-out cost to prospective franchisees including HVAC, so franchisors generally want fixed-price fabrication commitments from preferred duct fabricators to keep the disclosure accurate over the rollout. SBKJ supports franchise duct procurement with fixed-price duct schedules over rolling 12-month periods. Second, the Code prevents franchisors from mandating a single supplier without commercial justification, so the approved fabricator list typically carries 2-4 alternatives and franchisees choose on price, lead time and service. SBKJ sits on the approved fabricator list for several Australian QSR and cafe operators.
Group ownership and how procurement flows
The Australian QSR and cafe market is more concentrated than it appears — a handful of corporate groups own many of the operating chains and standardise specification across them. Retail Food Group (ASX:RFG) owns Crust Gourmet Pizza, Pizza Capers, Salsa's Fresh Mex, Gloria Jean's Coffees, Michel's Patisserie and Donut King — procurement is consolidated at group level. Yum! Brands is the global franchisor for KFC Australia and Pizza Hut Australia, with regional procurement driven by global engineering standards adapted to NCC, AS 1668.2 and FSANZ. Minor International owns Coffee Club. Domino's Pizza Enterprises (ASX:DMP) runs a heavily standardised small-format template (80-150 m², mostly takeaway-only). Guzman y Gomez (ASX:GYG) operates both dine-in and drive-thru formats. TQ Funds owns Zambrero. Foodco Group owns Muffin Break. For independent operators and the premium cafe chains — Industry Beans, ST. ALi, Campos, Soul Burger, Mary's, Burger Project — procurement is site-specific and runs through the consulting mechanical engineer for each project.
Climate adjustments by Australian capital
The duct fabrication is the same nationally, but design loads and MUA heating capacity vary by climate. Melbourne, Adelaide, Hobart — cool temperate; MUA heating coils run 5-7 months; standard external wrap insulation. Sydney, Perth — warm temperate; cooling dominant; galvanised with standard wrap. Brisbane, Gold Coast — humid subtropical; cooling and dehumidification dominant; humidity-resistant external insulation recommended. Darwin, Cairns, northern Australia — tropical; closed-cell external insulation to prevent exterior condensation; 316 stainless preferred for coastal-exposed roof termination sections within 1 km of the coast.
Commissioning, balancing and witness testing
Commissioning is where the fabrication meets the real world. A duct package that was fabricated to spec, installed to drawing and connected correctly still has to be balanced, tested and signed off before opening day. The commissioning sequence for a typical cafe or QSR is:
1. Visual inspection — confirm every duct section, joint, flange, gasket, access panel, support, hanger and insulation wrap is installed to drawing. Check that the kitchen exhaust riser is stainless throughout the grease-laden portion and that the joint welds are continuous. Check that the make-up air unit, the dining AHU, the drive-thru AHU and the toilet exhaust fan are all installed and connected.
2. Pressure test — pressure-test each duct branch at the design pressure plus 50 percent margin. Leakage should be under 1 percent of design air volume at trunk pressure. Anything above 3 percent is a fail. SBKJ duct fabrication typically achieves under 0.5 percent leakage on a clean installation, which gives margin for site-installed flange and gasket issues.
3. Air balance — set each diffuser and grille to design air volume within ±10 percent. Adjust manual volume dampers as required. Document the as-balanced air volumes on the balance certificate.
4. Pressure balance — verify the dining area is slightly positive relative to outside (5-10 Pa), the kitchen is slightly negative relative to dining (3-5 Pa), and the drive-thru window zone (where present) is positive relative to outside (30-50 Pa). Use a calibrated micromanometer at each measurement point.
5. Smoke test — smoke-test the kitchen exhaust canopy face to verify capture velocity. Smoke should be drawn cleanly into the canopy from at least 300 mm below the canopy edge. Smoke escaping the canopy face indicates the make-up air balance is wrong or the canopy is undersized.
6. Acoustic test — measure noise at the loudest occupied position with the system running at full design air volume. NC level should be at or below the design target. Adjust silencer settings if required.
7. Indoor air quality test — measure CO2 at peak occupancy. CO2 should remain under 1,000 ppm with the system at design outside air rate. Anything above 1,200 ppm indicates the outside air rate is below AS 1668.2 minimum.
8. Documentation — issue the commissioning report, the balance certificate, the pressure-test certificate, the as-built drawings and the operator's manual. These documents go to the building certifier for the occupation permit and to the local council environmental health officer for the food premises certificate.
Common failure modes at fit-out
A small number of failure modes recur across the cafe and QSR fit-outs we supply duct for. (1) MUA short-circuiting back through the canopy — fix: move the MUA diffuser at least 1.5-2.0 m laterally from the canopy face. (2) Drive-thru window running negative pressure — fix: oversize the drive-thru AHU by 15-20 percent, specify a lower-pressure-drop MERV 13 filter, commission with the window both open and closed. (3) Toilet exhaust discharge too close to OA intake — fix: relocate the cowl to at least 3 m from any intake. (4) Galvanised substituted for stainless in the grease exhaust path — fix: never substitute; SBKJ stamps each stainless section for traceability. (5) Access panels not fabricated to AS 4674 spacing — fix: include the access panel schedule in the fabrication brief. (6) Pressure imbalance after seating capacity increases — any seat count change above 20 percent should trigger an AS 1668.2 recalculation and air rebalance.
What the SBKJ fabrication package looks like
For a typical Australian QSR or cafe fit-out, the SBKJ fabrication package includes the following:
Retail HVAC duct package — galvanised steel (Z275 zinc coating) fabricated on the SBAL-III auto duct production line. Includes rectangular trunks for dining and back-of-house, spiral round branches to diffusers, transverse duct flanges every 1.2-3.0 metres, Pittsburgh lock longitudinal seams, external wrap insulation specified at quotation. Lead time 4-8 weeks for franchise template work, 6-12 weeks for site-specific work.
Kitchen exhaust duct package — 304 stainless steel (316 stainless on coastal or aggressive environments) fabricated on the SBAL-V production line. Includes continuous longitudinal welded seams, NFPA 96 compliant construction, flanged joints with high-temperature gaskets, access panels at every change of direction and 3-metre intervals on horizontal runs. Fire wrap specified separately. Lead time 6-10 weeks.
Make-up air duct package — galvanised rectangular trunks for the MUA distribution from the rooftop unit to the kitchen ceiling. External wrap insulation to prevent condensation in summer humid conditions and heat loss in winter. Lead time 4-8 weeks.
Drive-thru duct package — galvanised, optionally pre-fabricated as a standard drive-thru kit for chain rollouts. Includes the AHU connection, the OA filter housing, the trunk and branch ducts to the window zone, and the vestibule supply diffuser take-off where applicable. Lead time 3-6 weeks as a standard kit.
Toilet exhaust duct package — galvanised, small-diameter spiral round and rectangular sections, with the exhaust fan typically supplied by others. Lead time 3-5 weeks.
Cool room and freezer ventilation interface — short galvanised sections for the pressure relief and compressor exhaust between the refrigeration package and the building HVAC. Lead time 3-5 weeks.
Documentation included with every fabrication package: shop drawings reviewed and signed before production, mill certificates for the steel coil, fabrication QA records for each duct section, ISPM-15 fumigated crating for the delivery, and a section-by-section installation manual for the mechanical contractor. SBKJ also provides on-site fabrication support during installation for franchise template rollouts at no extra cost.
How to brief SBKJ for a cafe or QSR fit-out
If you are a franchisor, a fit-out manager or a mechanical contractor looking to brief SBKJ on a cafe or QSR duct fabrication package, the following information accelerates the quotation:
- NCC classification mix (Class 6, Class 9b, or combined)
- Net floor area (dining, kitchen, drive-thru, back-of-house)
- Peak occupancy (design seat count, plus standing customer allowance)
- AS 1668.2 outside air rate calculation (or seat count and area for us to calculate)
- Kitchen canopy exhaust rate (or canopy width and burner duty)
- Make-up air rate (or 80-90 percent of canopy exhaust if not yet calculated)
- Drive-thru pressurisation requirement (if applicable)
- Customer and staff WC count (for toilet exhaust sizing)
- Cool room and freezer count and size (for pressure relief and compressor exhaust)
- Acoustic target (NC level by zone)
- Service void depth and any routing constraints
- Site climate band (capital city or specific climate adjustment)
- Construction programme (target site mobilisation date and project completion date)
For franchise rollouts, we also need the master specification document from the franchisor, the standard duct schedule from previous stores in the same template, and the procurement panel arrangement (whether SBKJ is a sole supplier, a panel supplier or an approved alternative). For site-specific work, we need the mechanical consultant's design drawings at IFC (Issued for Construction) revision and the architectural ceiling and floor plans showing the diffuser positions and the duct void.
FAQ
What is the difference between cafe and QSR ventilation and a full commercial kitchen?
A commercial kitchen exhaust article covers the canopy hood, grease duct riser and pollution control unit only. A whole-store cafe or QSR design adds the dining area conditioning (22-24 degrees Celsius, 50 percent relative humidity, NC-40 acoustic target), service counter air curtain, drive-thru window pressure control, customer toilet exhaust at AS 1668.2 minimum 25 L/s per WC fixture, cool room and freezer condensate-controlled vents, and the make-up air strategy that ties all of these together at 80-90 percent of the kitchen exhaust volume.
Can galvanised steel duct be used in a QSR or must it be stainless?
Galvanised steel duct is acceptable for retail dining-area HVAC, drive-thru pressure ducts, customer toilet exhaust and cool room evaporator runs. Stainless steel duct, typically 304 grade with continuous welded longitudinal seams, is mandatory for the grease-laden cooking exhaust path under NFPA 96 and AS 1668.1. SBKJ machine configurations reflect this split — SBAL-III galvanised lines for retail HVAC, SBAL-V stainless-capable lines for kitchen exhaust risers.
What ventilation rate does AS 1668.2 require in a QSR dining area?
AS 1668.2 requires a per-person component (V_p) of 5 L/s/person for dining areas plus a per-area component (V_a) of 1.0 L/s/m squared of net floor area, multiplied by the occupant diversity factor. For a typical 120 seat suburban QSR at peak occupancy, this works out to approximately 900-1,100 L/s of outside air, before adding the kitchen exhaust make-up air requirement.
How is drive-thru ventilation different from the rest of the store?
The drive-thru order window and pickup window must be on a separate air handling zone with a slight positive pressure relative to the outside vehicle queue, so that vehicle exhaust gases cannot migrate inside when the window opens. Best practice is a dedicated air handling unit serving the drive-thru window zone with a 30-50 Pa pressurisation target, vestibule-style isolation if site geometry allows, and a high-efficiency filter on the OA path.
What standards apply to cafe and QSR fit-outs in Australia?
The four-document compliance stack is: National Construction Code Volume One Class 6 retail and Class 9b assembly provisions; AS 1668.2 mechanical ventilation; AS 4674 design construction and fit-out of food premises; and the FSANZ Food Standards Code Chapter 3 hygiene and Chapter 4 design requirements. For kitchen exhaust the additional documents are AS 1668.1, AS 1668.2 Section 4 and NFPA 96 commonly referenced for grease duct standoff and access door spacing.
What is the make-up air volume for a typical QSR kitchen?
Industry practice is 80-90 percent of the kitchen exhaust volume delivered as tempered make-up air, with the remaining 10-20 percent drawn through transfer grilles from the conditioned dining area to maintain a slight negative pressure in the kitchen relative to the public space. For a typical QSR with 6,000 L/s of canopy exhaust, this means roughly 5,000-5,400 L/s of dedicated make-up air through a rooftop MUA unit.
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