A home renovation is one of the best opportunities you’ll ever have to get air conditioning right. Walls are open. Trades are on site. The ceiling is accessible. Everything lines up for a smooth, cost-effective install.
Yet time and again, homeowners finish a beautiful renovation only to realise they didn’t plan for air conditioning. And by then, the job that could have been straightforward during the build becomes a far more complicated and expensive project.
The good news is that most of these mistakes are easy to avoid once you know what to look for. Here are the most common renovation decisions that create headaches when it’s time to install air conditioning, and what to do instead.
Closing Up Walls Without Running Ductwork First
This is the big one. During a renovation, there’s a window of time when wall frames are exposed and ceiling cavities are wide open. It’s the perfect moment to run ductwork, refrigerant lines, and electrical cabling for a ducted system.
Once the plasterboard goes up, that window closes. Retrofitting ductwork into a finished space means cutting into walls and ceilings that were only just completed, then patching, plastering, and repainting. You end up paying twice for the same surface.
Even if air conditioning isn’t in the budget right now, it’s worth asking your builder about roughing in the infrastructure while the walls are open. Running conduit and leaving access points costs a fraction of what it takes to open everything up again later.
Choosing Ceiling Types That Block Access
Not all ceilings are equal when it comes to installing ducted air conditioning. Flat plasterboard ceilings with a decent cavity above them are ideal. But some renovation choices make things much harder.
Raked or cathedral ceilings look stunning, but they reduce or eliminate the ceiling cavity entirely. Exposed beam designs have the same issue. If there’s no space between the ceiling lining and the roof, there’s nowhere to run ducts.
Ornate plaster ceilings and heritage features also add complexity. Nobody wants to cut into a restored ceiling rose or decorative cornice to fit a supply grille.
If you’re set on a design that limits ceiling cavity space, talk to your HVAC installer early. There are slim duct systems and alternative configurations that can work in tight spaces, but it’s best they are planned into the design, rather than an afterthought.
Building Bulkheads That Block Duct Runs
Bulkheads are a popular way to conceal range hoods, downlights, and plumbing. They look neat, they add a contemporary feel, and they solve a lot of visual problems. But they can also create physical barriers that block the path ductwork needs to follow.
A bulkhead running across a hallway ceiling, for example, can cut off the route between the indoor unit and the bedrooms at the other end of the house. If ducts can’t pass through or around it, the installer has to find a longer, less efficient path, or the bulkhead has to come down.
The fix is simple: before any bulkheads are framed up, get your air conditioning installer to review the plans. They can identify where ducts need to run and make sure the bulkhead design allows for that. You can also install slimline vents in bulkheads during the building phase. That’s why it’s important to incorporate air conditioning into your renovation planning.
Skipping Insulation (or Getting It Wrong)
Insulation and air conditioning work as a team. A well-insulated home needs a smaller, less expensive system to keep comfortable. A poorly insulated home forces the system to work harder, run longer, and use more energy.
During a renovation, insulation is easy to upgrade. Batts can go into open wall frames, ceiling insulation can be topped up, and old, compressed insulation can be replaced. But once the walls are sealed, upgrading becomes disruptive and expensive.
It’s also worth thinking about where the ductwork will sit. If ducts run through a scorching hot roof space with no insulation around them, the cooled air inside those ducts warms up before it ever reaches the room. Insulating the duct runs and the surrounding roof cavity makes a measurable difference to comfort and running costs.
Undersizing the Electrical Supply
A ducted air conditioning system needs a dedicated electrical circuit, and the outdoor unit typically requires a decent amount of power. If your renovation includes a switchboard upgrade or new electrical work, it’s the perfect time to make sure there’s capacity for an AC system, even if you’re not installing one right away.
Homeowners who skip this step often find out later that their switchboard is full, or that running a new circuit from the board to the outdoor unit location means chasing cables through freshly finished walls and ceilings.
Ask your electrician to allow for a dedicated AC circuit and make sure the switchboard has space for it. It’s a small addition during a renovation, but a significant cost saving down the line.
Not Thinking About Where the Outdoor Unit Will Go
Every ducted system needs an outdoor unit, and it needs to go somewhere with good airflow, reasonable proximity to the indoor unit, and minimal noise impact on living areas and neighbours.
Renovations often change the layout of outdoor areas. New decks, extensions, landscaping, or fencing can eat up the spots where an outdoor unit would normally sit. If the only remaining option is a long pipe run to a distant corner of the property, the install becomes more expensive and the system less efficient.
When you’re planning outdoor spaces as part of your renovation, mark out a potential location for the outdoor unit. It doesn’t need to be locked in, but having a workable spot earmarked saves a lot of problem solving later.
Designing an Open Plan Layout Without Zoning in Mind
Open plan living is one of the most popular renovation goals, and it looks great. But from an air conditioning point of view, a large open space behaves very differently to a series of smaller rooms.
A big open kitchen, dining, and living area needs careful zone planning. Without it, the system either overcools some areas while undercooling others, or it runs at full capacity all the time, which drives up energy bills.
If your renovation involves knocking out walls and opening up the floor plan, bring your HVAC installer into the conversation early. They can design a zoning layout that matches the new floor plan, with separate zones for the open living area, bedrooms, and any home office or media room, so you get even comfort throughout the house without wasting energy on empty rooms.
The Bottom Line: Plan for Air Conditioning Before the Walls Go Up
You don’t necessarily need to install air conditioning during your renovation. But you do need to plan for it. The decisions you make about ceilings, bulkheads, insulation, electrical, and outdoor spaces will either make a future install smooth and affordable, or turn it into a project that costs twice as much and disrupts a home you’ve only just finished.
The best time to have this conversation is before construction starts. A quick consultation with an experienced HVAC installer at the planning stage can save thousands down the track and protect the investment you’re making in your renovation.
