Air conditioning is easy to forget when you’re deep in a renovation. It’s not as visible as a new kitchen bench or a fresh coat of paint, so it tends to get pushed to the end of the list — right up until the first hot, humid week of the build, when everyone’s suddenly asking why the ceiling isn’t sorted yet.
If you’re renovating an established Brisbane home and considering ducted air conditioning, the process is genuinely different to installing it in a new build. Here’s what actually changes, what it costs to plan for, and where it fits into your renovation timeline.
Why Retrofitting Is a Different Job to a New Build
In a new build, ducted air conditioning gets designed in from the start. The roof trusses, ceiling cavity, and wall cavities are all planned around where the ductwork needs to run. In an established home, none of that exists yet. The system has to work with a roof space, ceiling height, and wall layout that were never designed with air conditioning in mind.
That doesn’t rule ducted air conditioning out. Most established Brisbane homes, from Queenslanders to post-war brick, single or double storey, can support it with the right design. But a few things need closer attention.
The roof space and ceiling cavity is where the indoor unit and the bulk of the ductwork sits, and a flatter roofline or minimal cavity can limit duct sizing and run length, which in turn affects how many zones are practical. Existing ceiling and wall finishes matter too, since a retrofit usually means cutting register points into an existing ceiling. And access can be a genuine constraint: getting equipment into the roof space of an older home isn’t always straightforward, particularly with lower pitch roofs, raked ceilings, or limited manhole access, which is common in older Brisbane housing stock.
None of this rules ducted air conditioning out on its own. It’s just why a retrofit quote should always start with someone getting into your roof space, not a phone estimate.
The Best Time in Your Renovation Timeline to Plan It
The single biggest mistake we see in renovations is treating air conditioning as a “nice to have” decided after the ceiling is already closed up. If ducted air conditioning is even a possibility, it needs to be discussed at the same stage as electrical and lighting, before ceilings, cornices, and fresh paint go in.
Ideally, a ducted air conditioning specialist gets into the roof space alongside your builder at the early design and quoting stage, before layouts are locked in. From there, register positions, return air placement, and any bulkheads for duct runs need to be finalised before ceiling and wall linings go up. And because the system needs power run to the right location, it’s far easier to coordinate this before final electrical fit-off, while walls are still open, than to chase it up afterwards.
Bringing your AC installer in after the plasterers isn’t impossible, but it usually means compromises: fewer zoning options, more visible ductwork, or extra cost to work around finishes that are already done.
Single-Storey vs Double-Storey Homes: What Changes
Single-storey homes are generally the more straightforward retrofit. The indoor unit sits in the roof space above, and ducts run relatively short distances to each room.
Double-storey homes add a genuine engineering challenge: getting ducting from the roof space down to ceiling level on the ground floor. This usually means routing ducts through cupboards, service risers, or purpose-built bulkheads, which needs to be planned with your builder rather than squeezed in afterwards. It’s very achievable, but it’s a conversation that needs to happen at the design stage, not once the ground floor ceiling is already framed.
Zoning: Getting More Out of a Retrofit
If you’re already going to the effort of a retrofit, zoning is worth building in from day one rather than treating it as an upgrade for later. Zoning splits your home into independently controlled areas, so a nursery, a home office, or a rarely-used guest room isn’t cooled to the same setting as the main living area around the clock.
It’s worth thinking about early because it’s a duct layout decision, not a control panel decision — each zone needs its own motorised damper and duct run planned into the design, and adding zones after the ductwork is installed generally means reopening ceilings, the exact disruption a retrofit is trying to avoid the second time around.
It also tends to pay off more in a Brisbane climate than people expect: long cooling seasons and big day-to-night temperature swings mean a lot of energy gets wasted cooling rooms nobody’s using, and zoning is one of the more effective ways to bring running costs down without downsizing the system.
Zoning Suits How Renovated Homes Actually Get Used
A renovation often changes room function, with a bedroom becoming a home office or a rear extension becoming an open-plan living zone, and zoning gives you the flexibility to adjust as those living patterns change rather than locking in one temperature setting for the whole house.
Modern systems pair zoning with app or wall-panel control, so adjusting individual areas day to day doesn’t mean walking around the house or calling a technician back. The extra cost of wiring in three or four zones during a retrofit is minor compared to the cost of doing it as a standalone job later, once ceilings and walls are finished and painted.
Cost Factors Worth Understanding
Retrofit pricing varies more than new-build pricing, because every established home presents different roof access, duct run lengths, and existing infrastructure. Rather than quote a flat figure, which would be misleading, it’s more useful to understand what actually drives the cost up or down.
Roof access and duct run length matter most: a single-storey home with generous roof space and short runs to each room is the most cost-effective retrofit scenario, while double-storey homes, low-pitch roofs, or homes with limited manhole access add labour time and materials. The number of zones plays a similar role, since each one adds a motorised damper and additional control wiring. Building zoning in from the start is far cheaper than adding zones to an already-installed system.
Finishes, Existing Infrastructure, and Timing
Ceiling and wall repair is another factor worth planning around: cutting register points into finished ceilings means patching, sanding, and repainting afterwards, and if your renovation timeline allows the AC install before final ceiling finishes, this cost largely disappears. System capacity and brand also come into it, since larger homes or homes with poor insulation need higher-capacity units, which cost more upfront but should be sized correctly through a proper heat load calculation rather than guesswork.
In some retrofits, existing infrastructure, like electrical circuits, external unit pads, or even partial ductwork from a previous system, can be reused to reduce costs, though that’s something only an on-site assessment can identify. And as covered above, timing within the renovation matters just as much as any of these: an install coordinated before ceilings and walls are closed up avoids the rework costs that get added when it’s squeezed in afterwards.
Because of how much these factors vary, a reliable quote should always follow a physical site inspection — treat any fixed “per room” price quoted over the phone with some caution.
Questions Worth Asking Before You Commit
Before signing off on a ducted retrofit as part of your renovation, it’s worth asking your installer:
- Has someone physically inspected the roof space, or is this quote based on floor plans alone?
- How many zones is the roof space realistically able to support?
- What happens to ceiling and wall finishes that are already complete? Will anything need to be reopened?
- How does the install schedule fit around your other trades (particularly ceiling, electrical, and painting)?
- What’s the realistic timeframe, and does it need to happen before or after other renovation works?
A retrofit that’s planned properly, at the right stage of the renovation, tends to be far less disruptive — and far less costly — than one squeezed in as an afterthought.
When Ducted Might Not Be the Right Call
Ducted air conditioning isn’t automatically the best answer for every renovation. If your roof space is genuinely restrictive, or you’re only conditioning one or two rooms, a well-placed split system can be a more cost-effective option than forcing a ducted retrofit into a space that doesn’t suit it. A good installer should be willing to tell you this rather than pushing ducted regardless of the site conditions.
This is exactly why it’s worth working closely with both a trusted local air conditioning installer and your home renovator or contractor, rather than treating the decision as something to figure out alone. They’re the ones who deal with these trade-offs on every project, and bringing them into the conversation early means you get advice grounded in what your specific home and budget can actually support.
A good installer will walk your roof space, talk through zoning and system options honestly, and provide a detailed quote that accounts for your home’s quirks; your renovator or contractor can then coordinate that work against the rest of the build so nothing gets undone or reopened later. Leaning on their combined expertise is generally how renovators end up with a system, and a renovation timeline, that actually works.