Mechanical services design for commercial kitchens, workshops and buildings. Airflow calculations, fan duties, duct sizing, make-up air and gas interlocks, issued as a calculation note and drawing package that mechanical contractors can price and build from. Designed to AS 1668.2 and AS/NZS 5601.1.
Not ready to brief yet? Read what actually drives the cost of a kitchen exhaust in WA.
Four types of work, one method: real equipment data, cited clauses, calculations you can check line by line.
Restaurants, cafes, bakeries and production kitchens. New fit-outs, or a check on whether the canopies, ducts and fans a previous tenant left behind can be reused.
The other half of every exhaust system, plus the everyday ventilation a building is assessed against.
Kitchens full of ovens and fryers, offices, workshops. How much heat is in the room, and what it takes to take it out.
Workshops and plants where the air carries welding fume, dust or process vapour, drawing on industrial plant engineering practice.
Most problems on site come from designing one part at a time. I design the whole loop so the numbers agree with each other.
Written for the builder, the mechanical contractor and the council officer who each read a different page.
Every firm says its work is checked. Here is what that word bought on a recent commercial kitchen fit‑out in Perth, issued for pricing. Figures are rounded and details withheld, so the job stays private.
Airflow, duct velocity, fan pressure, gas ventilation, noise, support loads. Each quantity was worked a second time from first principles, with its own friction‑factor iteration, so the check could not inherit the first calculation’s mistake. The two were compared line by line: more than 500 rows, zero differences.
The current AS 1668.2 and the older edition named in the local council’s food guideline gave answers about a third apart for the identical canopy. A fan selected on the lower number would have been signed off, installed, and then failed the council check. The higher figure was adopted, with both calculations printed side by side so the choice is auditable.
The obvious fire logic is to stop the supply fan. Run the exhaust without make‑up air, on a tight envelope with the make‑up air path shut, and the room goes a couple of hundred pascals negative. On an ordinary door leaf that is more than double the 110 N opening force AS 1668.1 sets for pressurised stair doors, before any door closer, on the doors people leave through. The design keeps both fans running and a hold point blocks construction until the building’s fire strategy confirms it.
Reusing the old riser as the fresh‑air intake would have saved an entire roof penetration. Six metres was the minimum separation. It was sized, checked, and rejected: the closest discharge came out at under half a metre, and none of them could move, because the appliances fix them. The reasoning is written down, so nobody proposes it again in six months.
Carried forward after issue: a register of hold points and open coordination items, each with a named responsible party and a note on what it blocks. Fabrication, order, construction, commissioning or handover. That register is the difference between a design that is finished and a design that is merely delivered.
Equipment list, floor plan, a few photos of the ceiling and roof. A free call to agree the scope, then a fixed fee.
Canopy sizes, fan positions and budget duties, so the builder and contractors can plan and price early.
Measurements, roof layout and the manufacturer data for the real appliances replace every assumption.
Calc note, drawings, schedules and the compliance matrix, checked independently before it leaves.
Answers to tender questions and RFIs, and review of the contractor's submitted equipment.
Clear on scope: I do the engineering design and calculations as a mechanical engineer (MIEAust NER). The mechanical contractor supplies, installs and commissions the system and issues its compliance certificates, and gas work is done and certified by a licensed gasfitter. Where a job needs certification or sign-off from a registered practitioner, that is coordinated with one, and I tell you upfront when it applies.
Before you price a kitchen job, read what really sets the cost of a kitchen exhaust in WA: seven design decisions from a recent Perth fit-out, with the clauses behind each one.
Typical clients: builders and fit-out companies, restaurant, cafe and bakery owners, mechanical contractors who need a design to price against, and workshops and plants with fume or heat problems. NDA on request. Food trailer or food van with a letter from the council? See food trailer exhaust.
Straight answers, including the ones that might talk you out of hiring me.
Often yes, and it is usually the single biggest saving on the job. But it is a check, not an assumption. What matters is whether the canopy still suits your appliances, whether the filter bank geometry meets the current standard, whether the duct route and riser can carry the airflow your equipment now needs, and whether the roof discharge still clears every air intake. On a recent job the existing canopy was kept, but its filter bank sat outside the prescriptive angle limit, so it needed a documented equivalence case rather than a shrug.
It is the Australian standard for mechanical ventilation. It sets how much air a canopy has to pull for your particular appliances, how ducts and discharges have to be arranged, and how far a discharge must sit from any fresh‑air intake. Your building surveyor and your council environmental health officer will expect the design to meet it. Alongside it sits AS/NZS 5601.1, the gas standard, which governs combustion air and the interlock that stops the burners if the ventilation fails.
The catch is that local guidelines sometimes name an older edition of AS 1668.2 than the one currently published, and the two can give materially different airflows for the same kitchen. That is worth knowing before a fan is ordered.
Plenty of straightforward kitchens get built well by a good mechanical contractor. Where a design earns its keep is when the answer is contested: a council asking which edition of the standard you used, a gas inspector asking how the combustion air figure was reached, an existing canopy you want to keep, a tight roof where discharges and intakes are fighting for space, or two contractors returning prices that are thousands apart because they each guessed at a different scope.
To be straight with you about credentials: I am a member of Engineers Australia (MIEAust) and registered on the National Engineering Register (NER) in Mechanical Engineering. Western Australia’s own registration scheme for building engineers takes full effect on 1 July 2027. If your project needs a particular signature, such as a Chartered engineer or a certifier the council names, say so early and I will tell you plainly whether I am the right fit.
No. I design, you build. I do not sell equipment, so there is no margin riding on which fan gets specified, and no reason to size anything larger than the calculation says. The package is written so your contractor, or three competing contractors, can price the same scope from the same drawings. Installation, gasfitting and commissioning stay with the licensed trades.
A preliminary concept, enough to size the fans, fix the roof penetrations and unblock the builder, usually comes back in days from your equipment list and floor plan. The full package follows once the appliance data sheets are in and I have measured the site. The honest variable is not my drawing time, it is how quickly the equipment supplier sends real airflow figures and how quickly decisions get made on reuse and canopy height.
Fixed fee, agreed in writing before anything starts, after a free scoping call. I do not publish a rate card because the honest range is wide. A reuse check on one canopy and a full kitchen with multiple gas appliances, a gas interlock and a congested roof are different jobs. Send the equipment list and the floor plan and you will have a number and a scope, not an hourly rate that drifts.
If you want to understand what actually drives the cost of the installation, which is the much bigger number, that is written up here.
Send your equipment list and floor plan. Free scoping call, then a fixed-fee design package your contractors can price.
Request a Quote