Melbourne homeowners undertake more renovations per capita than the national average — kitchen upgrades, bathroom strip-outs, room additions, and the increasingly common whole-house repaint. Most renovation guides cover dust management during the works. Very few mention what to do about the ducted heating and cooling system afterwards.
Renovation work is one of the most common causes of severely contaminated ductwork in Melbourne homes. Plasterboard dust, insulation fibres, and tile cutting debris migrate directly into the duct system during works and settle inside trunk lines and supply runs. Running the system before cleaning distributes this material to every room. This guide explains what happens, which renovations are highest risk, and when and how to clean the system properly afterwards.
What Renovation Dust Does to Ductwork
Return air grilles draw air from the room continuously while the system runs. During a renovation, this includes airborne particles from every nearby trade activity. Even with the system turned off, fine particles settle on and around grille openings and migrate into the duct system through joints, gaps around penetrations, and along duct runs over time.
How particles enter the system
Return air grilles are the primary entry point — they are designed to pull large volumes of room air into the system. Any particle fine enough to remain airborne for more than a few minutes is a candidate for duct entry. Plasterboard dust particles (typically 10 to 100 microns) easily pass through standard filters into the duct network.
Particles also enter through duct joints that open slightly during thermal expansion and contraction, through unsealed penetrations in the ceiling and walls, and through the main system unit if it is in the roof space or a room adjacent to renovation works.
Where the debris settles
Once inside the duct system, heavier particles settle at low points — duct bends, supply register bases, and the main trunk line floor. Fine particles remain airborne longer and deposit throughout the duct network. When the system runs after renovation, settled debris is re-entrained into the airflow and distributed to every supply outlet in the home. The first heating season after a renovation without duct cleaning is typically when occupants first notice unusual dust levels or respiratory irritation.
Highest-Risk Renovation Types
Not all renovation work carries the same duct contamination risk. The following renovation types consistently produce the highest levels of duct contamination in Melbourne homes:
Kitchen and bathroom renovations
Both kitchen and bathroom renovations involve tile removal and replacement (crystalline silica from cutting), plasterboard work (calcium sulphate and silica dust), and trades working in rooms with return air vents. Kitchens are particularly high risk because the return air grille is often located in the ceiling directly above where cutting and demolition occur.
Extension and room addition work
Adding a room or extending an existing space requires cutting into the existing structure — timber framing, plasterboard, sometimes existing brick work. The duct system is often extended as part of the works, meaning duct joints are open and unprotected during the construction phase.
Ceiling insulation installation or replacement
Ceiling insulation work above the duct runs generates glass wool or rockwool fibres that fall directly onto and into ductwork. Even new insulation installation in a roof space with existing duct runs contaminates the duct exterior and can enter at joints. See our guide on how often to clean air ducts for context on how much this accelerates contamination timelines.
Sanding of original paint or timber floors
In Melbourne’s pre-1970 homes — Victorian terraces, Edwardian bungalows, inter-war bungalows — original paint may contain lead. Floor sanding or paint stripping in these homes generates lead-bearing dust that is a serious health hazard if distributed through the duct system. Post-renovation duct cleaning in these properties requires confirmation that the debris being removed does not constitute a hazardous waste stream before using standard vacuum extraction.
Timing Your Post-Renovation Duct Clean
The timing of the duct clean relative to the renovation and occupancy is important for both effectiveness and practicality.
Wait until all trades are finished
Cleaning while any trade work is still underway is pointless — new debris will re-enter the system. Schedule the duct clean after the final trades have completed and the property has received a construction clean. This typically means after floor polishing, tiling, and touch-up painting are complete.
Before resuming system operation
The system must not be run for comfort heating or cooling between renovation completion and the duct clean. Even one day of system operation post-renovation circulates debris throughout the home. If winter falls during this window and heating is essential, use supplementary portable heating until the duct clean can be scheduled.
Booking timeline in Melbourne
FreshDuct can typically schedule post-renovation duct cleaning within 1 to 2 weeks in off-peak periods. If your renovation finishes in April or May — the pre-winter peak demand window — book as soon as you know the renovation completion date to secure timing. See our guide on what to expect from a professional air duct clean for what the service involves.
Why DIY Containment During Renovation Is Insufficient
Many Melbourne homeowners tape over registers during renovation works as a dust management measure. This is a sensible precaution, but it is not sufficient protection for the duct system for the following reasons:
Duct systems are not sealed structures. They have joints, penetrations, and gaps throughout the roof space duct run that are open to the ceiling cavity where renovation dust accumulates. Even with every visible register sealed, fine particles enter the system through these paths.
Return air grilles, which draw air into the system, are typically not taped because doing so creates negative pressure problems if the system runs during works. Even brief system operation with renovation dust in the air is enough to introduce substantial contamination into the return air duct.
The result is that DIY containment reduces but does not prevent duct contamination during renovation. Professional cleaning after works complete is the correct response to what containment does not prevent. See our overview of DIY vs professional duct cleaning for context.