What Affects the Cost
Wall construction. Double-brick walls, the norm across Melbourne's inner and middle suburbs, require core drilling ($150–$250) for any external wall penetration. This is slower and more expensive than cutting through timber frame. The cavity between brick layers also needs proper sealing to prevent drafts and water ingress.
Fans venting into the roof cavity. Many Melbourne homes built before the mid-1990s have bathroom fans that exhaust into the roof space rather than outside. In Melbourne's cold, damp winters, this causes severe condensation on the underside of roof tiles and on timber framing. Correcting this by adding ducting to an external point is one of the most common and most valuable ventilation jobs in the city.
Ducting condition and length. Replacing a fan using existing, well-routed ducting is quick. Running new ducting through a roof space with low clearance, around obstacles, and with multiple bends takes much longer. Old flexible foil ducting ($8–$12/m) that has sagged or kinked should be replaced with rigid or semi-rigid duct ($15–$25/m).
Number of fans and rooms. A single bathroom is straightforward. Adding extraction to a second bathroom, ensuite, and laundry multiplies duct runs and penetration points.
Roof access. Many period homes in Melbourne have low-pitch roofs with limited crawl space. Cathedral ceilings in renovated homes eliminate roof space entirely, requiring alternative ducting routes or wall-mounted fans.
Electrical work. A new fan on an existing circuit with a nearby switch is simple. Running a new circuit from the switchboard, adding a timer switch, or wiring a humidity sensor adds to the electrical scope.
Roof ventilation. Replacing passive whirlybirds with powered roof ventilation (solar or mains) involves larger penetrations and more robust mounting. Solar-powered units like the
Solar Whiz range ($700–$1,000 installed) move 10–15 times more air than a whirlybird.
A simple like-for-like bathroom fan swap with working ducting sits toward $200. Installing exhaust fans in multiple rooms with new ducting, core-drilled wall vents through double brick, and new switched circuits in a period home with limited roof access pushes toward $1,500.
Melbourne-Specific Considerations
Melbourne's cold winters make proper ventilation more important here than in most Australian cities. A hot shower in a 5 degree C ambient temperature produces far more condensation than the same shower in Brisbane's mild 20 degree C winters. Without effective extraction, that moisture sits on walls, ceilings, windows, and inside roof cavities, feeding mould growth that is very difficult to eliminate once established. The NCC 2022 condensation management provisions now specifically address this risk in new builds, but existing Melbourne homes need retrofitted solutions.
The inner suburbs of Fitzroy, Carlton, Brunswick, Richmond, and Northcote are dominated by Victorian-era homes and Edwardian cottages. Many of these have had bathrooms added or upgraded over the decades, but the exhaust fan installation was often an afterthought. Fans venting into the roof cavity are extremely common, and the resulting moisture damage to sarking, roof timbers, and insulation is a recurring issue at building inspections. If your bathroom fan does not have visible ducting running to a roof cowl or external wall vent, it is almost certainly dumping moisture into the ceiling space. An inline fan like the Fantech Rapid Response ($170–$290) mounted in the roof space with rigid ducting to a roof cowl is a reliable fix.
In Melbourne's middle ring, suburbs like Kew, Camberwell, Malvern, and Glen Iris have predominantly double-brick housing stock from the 1920s through the 1970s. Any new external wall vent requires core drilling through both layers of brick. This adds $150–$250 to the job and must be done by an experienced installer who can seal the brick cavity properly to prevent moisture and drafts.
A humidity-sensing fan is particularly worthwhile in Melbourne's climate. Rather than running on a fixed timer, the fan continues operating until moisture levels actually drop. This prevents the common problem of residents switching the fan off too early on a cold morning, leaving moisture trapped in the bathroom. Fantech's silent series models with built-in humidity sensors start at around $290.
For kitchen ventilation, Melbourne's terrace renovations and period home extensions frequently feature open-plan kitchen-living areas. Ducting a rangehood externally through a brick wall or up through the roof adds $300–$1,000 depending on complexity. If you have a gas cooktop, the National Construction Code requires external ducting, so a recirculating rangehood is not compliant. Schweigen silent rangehoods, which place the motor in the roof space for near-silent kitchen operation, are increasingly popular in Melbourne renovation projects.
Dark-coloured roofs on period homes absorb significant heat in summer, making upper floors uncomfortably hot. Powered roof vents are far more effective than passive whirlybirds, which rely on wind and do very little on Melbourne's still, hot days. Solar-powered units operate at peak output precisely when heat buildup is worst.
Hiring a Licensed Air Conditioning Technician in VIC
In Victoria, all hardwired electrical work must be performed by a licensed electrician registered with Energy Safe Victoria. The electrician must issue a Certificate of Electrical Safety (CoES) on completion, which is your proof the work meets Australian Standards. A good installer will provide this on the day, not promise to send it later.
Ventilation work in Melbourne typically involves an electrician for wiring and a ventilation specialist or air conditioning technician for ducting design and installation. Many installers hold both qualifications. If separate tradespeople are involved, confirm who is responsible for the overall system performance.
Worth checking:
Current Victorian electrical licence (verify on the Energy Safe Victoria website)
Certificate of Electrical Safety issued on completion
Fan extraction rate specified in the quote (minimum 25 L/s for bathrooms per AS 1668.2)
Ducting route and discharge point confirmed as external, not into the roof cavity
For double-brick homes, core drilling and cavity sealing included in the scope
How We Calculate
Estimates are based on surveyed trade rates for licensed electricians and air conditioning technicians in the Melbourne metro area, adjusted for property age. All prices include GST. Figures cover standard residential exhaust fan and ventilation work. Commercial extraction systems and ducted air conditioning are not included.