Most exhaust fans that fail to clear a room are not faulty. They are choked by the ducting behind them, or ducted nowhere at all. Getting the fan right is the easy half of this job.
Pricing agreed before we start. We usually reply the same day.
Kitchens, bathrooms and laundries all produce moisture and odour faster than a closed room can shed them, and the consequence is mould, mildew and that persistent damp smell that no amount of cleaning fixes. An exhaust fan is the answer. A badly installed one is not.
Two things decide whether a fan actually works. The first is whether it moves enough air for the room, which the NCC now sets a floor under. The second, and the one that gets ignored, is the ducting behind it. Every metre of duct and every bend adds resistance, and resistance costs airflow. The number printed on the box is measured with nothing attached to the fan at all.
Then there is where the air ends up. A very large number of Sydney homes have an exhaust fan whose duct simply stops in the roof space, or has no duct on it whatsoever. The fan runs, the mirror clears, and the moisture goes straight into the roof to condense on the underside of the roofing and soak the insulation. That is no longer permitted, and it never should have been.
So when we quote a fan we are really quoting a system: the right unit for the room, the right duct diameter for the run, and a proper discharge to outside air.
Both of these look identical from inside the room. The fan runs, the noise is the same, the steam clears off the mirror. Only one of them is actually getting the moisture out of your house.
Scroll to see both →
How to read it: on the left, the duct stops inside the roof space, so every shower pushes warm wet air into the roof where it condenses on cold roofing and soaks the insulation. On the right, the duct rises steadily and seals to a cowl, so the moisture leaves the building. Under NCC 2022 exhaust must discharge directly or via a duct to outdoor air, which rules the left-hand version out.
Two separate questions. The room sets the minimum airflow. The duct run decides which type of fan can actually deliver it.
| Room | Minimum flow | Usual mounting | Worth knowing |
|---|---|---|---|
| Bathroom | 25 L/s | Ceiling | Needs a run-on timer and light interlock if there is no window |
| Sanitary compartment | 25 L/s | Ceiling | Often a small, sealed room, so the timer matters more than the fan size |
| Laundry | 40 L/s | Ceiling or wall | Higher than a bathroom, and frequently under-specified in older homes |
| Kitchen | 40 L/s | Wall, ceiling or rangehood | A recirculating rangehood filters odour but removes no moisture at all |
A standard axial ceiling fan is fine here, and it is what most homes have. Cheap, quiet enough, and perfectly adequate when the duct is short, straight and actually connected to something.
Put the same fan on a long run and it will barely move air at all.
A centrifugal ceiling unit holds its airflow far better against resistance than an axial one. This is the sensible choice for a bathroom in the middle of a house, where the nearest outside wall or eave is some distance away.
It costs more up front and it is the difference between a fan that clears a room and one that hums.
An inline centrifugal fan sits in the duct away from the ceiling rather than in the grille above your head. It will hold useful airflow over runs that would defeat anything else, and it is dramatically quieter in the room because the motor is not directly overhead.
The usual answer for apartments, long duct paths and anyone who hates fan noise.
Manufacturers quote free air, with nothing attached. Add duct and the delivered figure drops, roughly in proportion to length, diameter and the number of bends. As a rule of thumb each bend costs about as much as an extra metre of straight duct.
We size for what will actually be delivered at the grille, which sometimes means a bigger fan or a bigger duct than the brochure implies.
The heaviest moisture load in the house, concentrated into short bursts. Ceiling mounting near the shower works best, ducted the shortest sensible route to outside. Where the room has no window the fan must be interlocked with the light and run on for ten minutes.
If you are also chasing warmth, a combined unit covers heat, light and exhaust in one cut-out.
Cooking swings the room from cold to hot quickly and puts both steam and grease into the air. A ducted rangehood is far more effective than a recirculating one, which filters smell but returns every gram of moisture to the room.
Wall mounting is the most common, though ceiling units suit island cooktops.
Small, usually kept shut, and full of appliances producing warm damp air. It carries the same 40 litres per second minimum as a kitchen, which surprises people, and it is the room we most often find with no fan at all.
Wall or ceiling mounting both work depending on the layout and where the duct can run.
The mirror still fogs and the room stays damp
Either the fan is undersized for the room or the duct is defeating it. A collapsed, kinked or disconnected duct is extremely common, and a fan can sound perfectly healthy while moving almost nothing.
Worth checking before replacing the unit, because a new fan on the same bad duct performs the same.
There is mould or damp in the ceiling above
Nearly always an exhaust discharging into the roof space. The moisture condenses on the underside of the roofing, drips onto the insulation and sits there.
The fix is ducting the fan properly to an eave vent or a roof cowl, which is a straightforward job once someone is up there.
The fan has become noticeably louder
Bearings on the way out, or a restricted duct making the fan work against pressure it was never meant to see. Undersized ducting is the usual cause of a whine.
If noise is the main complaint, an inline fan mounted away from the ceiling solves it outright.
Cold air blows back down when it is off
No backdraft damper, or one that has stuck open. The duct is behaving as a chimney in reverse and feeding outside air straight into the room.
A simple fix, and worth doing because it is quietly costing you heating in winter.
The unit itself spans an enormous range, from around eighty dollars for a basic fan to well over three thousand for a high-end system with heating, lighting and controls. We buy through wholesalers we have dealt with for years, which usually lands better pricing than retail.
Labour is the variable. A straightforward swap in an accessible ceiling with sound existing wiring and a usable duct route is a short job. What stretches it is the awkward stuff: no existing duct, a tight or inaccessible roof space, cutting into tiled or plastered surfaces, an apartment where the discharge has to be worked out rather than assumed, or old wiring that needs replacing before anything new goes on it.
That last one comes up more than you would think. Wiring colour codes in Australia changed over the years and plenty of homes carry a mixture of old and new, so identifying what is what before disconnecting anything is part of the job rather than an optional extra.
We would rather look at the room and give you a fixed price than guess over the phone, and we will tell you honestly when the existing duct can be reused and when it cannot.
An exhaust fan connects to your wiring, which puts it firmly outside what an unlicensed person may do in NSW. It also involves cutting into ceilings and walls with cables running through them, and severing one you did not know was there turns a cheap job into an expensive one.
Once the work is done your electrician lodges a Certificate of Compliance for Electrical Work confirming it was tested and complies with the Gas and Electricity (Consumer Safety) Regulation 2018 and the relevant standards, within 7 days of testing. Since 1 July 2026 that is lodged through the BCNSW eCert portal.
Keep the certificate. It is what you produce for an insurer, a buyer or a building inspector when they ask who did the work.
It is set by the room, not by preference. NCC 2022 sets a minimum of 25 litres per second for a bathroom or sanitary compartment and 40 litres per second for a kitchen or laundry. The catch is that the figure printed on the box is usually free air, measured with nothing attached. Once the fan is pushing through several metres of duct and a couple of bends, real delivered airflow can be well under the rating, so the fan has to be chosen for the duct run rather than for the room alone.
No. Exhaust from a bathroom, kitchen, rangehood, sanitary compartment or laundry must discharge directly or via a duct to outdoor air. Venting into the roof is not compliant and never was a good idea, because warm moist air hitting cold roofing condenses on the underside and soaks the insulation and timbers. It is the single most common fault we find, and it is usually invisible until something starts to smell or sag.
Yes. Every metre of duct and every bend adds resistance, and a rough flexible duct adds far more of it than smooth rigid duct at the same diameter. As a rule of thumb each bend costs roughly the same as an extra metre of straight duct. A sagging run is worse again, because the dips collect condensate and choke the airflow. Short, straight, properly supported and gently rising is what makes a fan perform.
If the bathroom or sanitary compartment has no window or other natural ventilation, yes. The exhaust has to be interlocked with the light switch and keep running for 10 minutes after the light goes off. Even where it is not required we usually suggest it, because the moisture is still in the room when you walk out and switch the light off.
Often it is not the fan, it is the duct. Undersized or restricted ducting makes a fan work harder and whine. Choosing a larger diameter, straightening the run or moving to an inline fan mounted away from the ceiling usually solves it. Cheap axial fans on a long duct run are the usual culprit.
Attending your job is a chargeable callout. We confirm what it costs when you book, and the price for the work itself is agreed before we start, so there are no surprises on the invoice.
Based in Castlecrag, covering all of Sydney. A few of the suburbs we work in most:
Covering all 48 North Shore suburbs. See the full list of locations we service.
Upfront pricing, with the price agreed before we start. Call before 11am for same-day service.
