Renovations are one of the cheapest times to add or upgrade air conditioning. Walls are open, ceilings are accessible, electricians are already on site. The retrofit costs that scare homeowners off in a normal year are halved or quartered when the renovation is happening anyway.
The catch: it has to happen in the right order. Get the sequence wrong and you either pay for redo work, or you finish the renovation and find out the aircon you wanted is no longer practical to install.
Before any walls come down
The earliest decision is what type of system the renovation will support. This needs to happen at design stage, before the architect or builder finalises plans.
- If you want ducted, the renovation has to deliver enough ceiling cavity height for ductwork
- If walls are being moved, refrigerant lines and electrical runs can be installed inside them rather than surface-mounted later
- If a new switchboard is being added, sizing it for current and future aircon load saves an upgrade later
Working with a renovation builder who treats aircon as a primary service — not a follow-up trade — is what makes this stage work. The right builder coordinates aircon planning at the same conversation as plumbing, electrical, and structural — not as an afterthought during fit-off. If your builder cannot tell you when the aircon installer will be on site, you have already lost the early-stage cost advantage.
Demolition stage
If you are removing existing walls or ceilings, this is the moment to:
- Inspect the existing electrical capacity (open switchboards before they are reboxed)
- Identify the path the new refrigerant lines will take
- Check the roof cavity height where ducted indoor units would sit
- Plan condenser unit position outside (acoustic implications, line length, neighbour proximity)
None of this work is permanent yet. Decisions made here cost very little. Decisions deferred to later stages cost thousands.
Frame stage (rough-in)
This is when the aircon installer needs to be on site. With walls open, they can:
- Run refrigerant lines inside wall cavities (not pinned to the outside of the wall later)
- Position indoor unit brackets where the framing will support them
- Confirm the dedicated electrical circuit run with the electrician (often the same circuit also supplies adjacent appliances)
- Mark out vent positions on ceilings that have not yet been plastered
Skipping the rough-in visit means a perfectly placed wall stud sits exactly where the aircon installer needed to drill. Now the head goes 200mm to the left of where it was supposed to, the line set has a kink, and the install never quite looks right.
Pre-line stage
Before the plasterer goes in, the aircon installer should be back on site to verify the line set and electrical work are in their final positions. After plaster, those positions are locked. Mistakes from rough-in get found at fit-off, when fixing them means cutting plaster.
This is also the stage to:
- Confirm vent locations align with the planned ceiling layout
- Verify return air pathways are unobstructed (poor return air kills ducted system performance)
- Check the condenser pad outside is built and level
Plaster and ceiling stage
Vents get cut into the ceiling at this stage, not later. The aircon installer typically returns to mount indoor units (for splits) or finalise duct connections (for ducted) after plaster has dried but before painting starts.
Doing it now means the painters paint around clean equipment edges. Doing it later means painters mask off equipment that already has paint near it from previous coats — never as clean.
Final fit-off and commissioning
Last on the trade list. Aircon installer returns to:
- Charge the system with refrigerant
- Test all zones (ducted) or all heads (multi-split)
- Calibrate thermostats and zone controllers
- Walk you through operation
- Issue the certificate of compliance
This stage is quick — usually a single day — but cannot happen until power is on, internet is working (smart thermostats), and the home is otherwise complete enough to test in operating conditions.
The biggest renovation aircon mistake
Treating aircon as a separate project that happens after the renovation is finished. Once walls are closed and ceilings are up, every install option becomes more expensive, slower, and uglier than it would have been three weeks earlier.
If you are planning a renovation in 2026 and you know aircon will be part of it (existing system being upgraded, new system going in, expansion to additional rooms), brief the aircon installer at the same time you brief the renovation builder. Get them coordinated from day one.
A 30-minute coordination meeting at design stage saves more cost and headache than any other decision in the project.
