Start with roof height, not floor area
The first question most people ask is how many square metres they need to cover. It is the wrong starting point. The fan has to hang somewhere, and the mounting height range is what decides which fans are eligible for your building before floor area is even considered.
Each size in the HVLS range has a specific band it can work within:
- 3.7m fan: 3 to 5m mounting height
- 4.3m fan: 3 to 5.5m mounting height
- 5m fan: 3.6 to 6m mounting height
- 6.1m fan: 5 to 12m mounting height
- 6.7m fan: 5 to 14m mounting height
- 7.3m fan: 5 to 12m mounting height
The pattern is simple. The bigger the fan, the higher it needs to hang. A 7.3m fan in a 4m shed is not a compromise, it is a non-starter, because the blades need clearance between their lowest point and whatever happens underneath.
So measure to the underside of the lowest structural member the fan would hang from, not to the roof sheeting. That one measurement will usually cut the list of candidate sizes down to two or three, and then floor area does the rest.
Then match coverage to the floor
Once the height range has filtered your options, coverage picks between them. The published figures, from smallest to largest:
- 2.4m commercial fan: 140 m²
- 3m commercial fan: 210 m²
- 3.7m HVLS fan: 380 m²
- 4.3m HVLS fan: 450 m²
- 5m HVLS fan: 500 m²
- 6.1m HVLS fan: 1,000 m²
- 6.7m HVLS fan: 1,300 m²
- 7.3m HVLS fan: 1,500 m²
Notice the jump between the 5m and the 6.1m. Coverage doubles while the price rises by well under $600, which is why the larger sizes are often better value for anyone with a genuinely open floor. The 6.7m and 7.3m continue that logic, covering 1,300 and 1,500 m² for another $120 and $200 on top of the 6.1m.
The commercial sizes at the top of the list behave differently. The 2.4m and 3m fans are built for lower ceilings and tighter zones, and the coverage figures reflect that. You can browse the full range of industrial ceiling fans with these figures alongside mounting heights and power draw.
Two cautions. First, a coverage figure is not a comfort radius, it is the total floor area the fan will usefully condition. Second, and more important, every figure above assumes an open floor. That assumption is where most sizing mistakes happen.
What breaks the coverage figure
The published coverage for a 6.7m fan is 1,300 m², but only if the air can actually move across that floor. Several common features interrupt it:
- Racking. Tall pallet racking blocks horizontal airflow and splits the space into zones. A fan sized for the full floor may only serve the aisles it can reach.
- Mezzanines. Any intermediate deck cuts the volume in two. The fan above and the space below behave as separate areas.
- Internal partitions. Offices, lunch rooms and stores built inside the main shed wall off sections of floor that the fan cannot service.
- Large machinery. Presses, ovens and big plant interrupt airflow the same way a wall does, and often generate their own heat that needs its own solution.
- Open doors on one side. A big roller door held open all day pushes the airflow pattern off balance and shortens the effective reach.
None of this means the published figures are wrong. It means the honest answer for a subdivided building is usually that the effective area is smaller than the floor plate, and a smaller or additional fan is the right call. This is exactly why every project starts with a site check that maps structure, working height and access before anything is ordered. If your building is long or heavily subdivided, it is worth reading about warehouse ceiling fans before settling on a size.
One big fan or several smaller ones
This is the decision most large buildings come down to, and there is a real trade-off.
One large fan means a single mounting point, a single variable speed controller and one motor to maintain. It is the cleaner install and usually the lower total cost for a genuinely open floor. It also concentrates everything in one place: if that fan is off for service, the space has nothing.
Several smaller fans spread the airflow more evenly, which matters in a long building, a subdivided floor or a space with racking down the middle. They give you redundancy, since one can be off without the whole floor losing airflow, and each covers its own zone rather than fighting the interruptions.
Roof structure often decides it before preference does. A clear span with good steelwork at the right height suits a single large fan. A building with purlins, trusses or a lower section may only have practical mounting points where two mid-size fans would sit. Timber structures can be worked with too, using an engineered mount specified per building after a site check. If you are weighing this up for a workshop, the workshop and shed fans page shows how the mid sizes pair up in practice.
Ceiling height under 5m
Buildings with ceilings under 5m do not need to miss out, they just need the commercial range. The commercial series is rated for mounting heights from 2.5m to 5m, in two sizes:
- 2.4m fan: 140 m² coverage, 2,600 m³/min airflow
- 3m fan: 210 m² coverage, 3,300 m³/min airflow
Both run six blades, are IP55 rated for dust and water, operate at 38dB and draw 300W at the wall. The 2.4m spins to a maximum of 160 RPM with air speeds of 1 to 4.5 m/s, so it suits spaces where people work directly underneath. The 3m tops out at 105 RPM with air speeds of 1 to 3.5 m/s, trading a little velocity for the larger coverage.
Both are hardwired to their own variable speed controller and installed by a licensed electrical contractor, supplied and installed in NSW by Festoon House, an authorised Down Under Fans reseller. For workshops, small factories and retail floors, these sizes cover most needs without the roof height an HVLS fan demands. Production floors with their own process heat are covered on factory fans.
What to have ready before you ask for a quote
A few measurements and details will get you an accurate quote quickly:
- Roof height to the underside of the structure the fan would hang from, not to the roof sheeting.
- Floor area, including a rough sketch if the building is an unusual shape.
- Roof structure material: structural steel, concrete, or timber. Timber triggers an engineered mount, so flagging it early matters.
- What is already suspended: ducting, lighting, chain hoists, pipework. These affect both mount position and clearance.
- What happens in the space: the number of people, the work being done, and whether doors stay open.
Prices are for the fan only and installation is quoted separately, so those details are what turn a rough figure into a firm one.
