Renovating or adding an extension is exciting. New space, new layout, maybe finally that open plan kitchen you’ve been talking about for years. But here’s the thing most homeowners in the Illawarra forget until it’s too late. Your air conditioning system doesn’t magically adapt to new walls, higher ceilings or a second storey.
I once saw a client finish a beautiful rear extension only to realise their existing split system barely reached the new living area. Doors were left open. Fans were dragged out. Power bills crept up. All avoidable.
Start With the End in Mind
Before builders swing a hammer, sit down and think about how you’ll use the space. Is the extension a light-filled family room that gets smashed by western sun? A home office? A bedroom above the garage?
Each of those uses changes your heating and cooling load. Bigger glass panels look great, but they can turn a room into a greenhouse by 2 pm. High ceilings add volume. Open-plan layouts let conditioned air drift off into spaces you never intended to cool.
The smart move is to factor HVAC planning into your design drawings. Not later. Now. It’s far cheaper to run new ductwork or electrical during framing than after plaster goes up.
Assess Whether Your Existing System Can Cope
Here’s an honest take. Most older systems in Aussie homes are already working hard. Add 30 square metres and expect miracles? Not realistic.
Sometimes we can extend ducting from an existing ducted system. Other times it’s smarter to upgrade the unit entirely. Capacity matters. Undersized systems run constantly, wear out faster and chew through electricity.
The last time I reviewed a renovation in Shellharbour, the homeowners wanted to “just add a vent” to cover the new area. After recalculating the load, we found the system was already at 92 percent capacity on peak summer days. One more room would’ve pushed it over the edge.
Plan for Zoning and Control
Renovations are the perfect time to introduce zoning. Different areas, different needs. Bedrooms cooler at night. Living areas comfortable during the day. Rarely used guest rooms switched off.
Zoning dampers and smart controls give you flexibility without running the whole house flat out. It also helps create a healthier indoor environment because you’re not overcooling one section while another sits stagnant.
Think about future use too. Kids grow up. Spare rooms become offices. Designing flexibility into the system now saves headaches later.
Don’t Ignore Airflow and Vent Placement
This is where small details make a big difference. Supply vents and return air grilles need proper placement. Shoving a vent in the nearest ceiling corner might be easy, but airflow doesn’t work on guesswork.
Good airflow keeps temperatures even and reduces moisture build-up. In coastal NSW, humidity can creep into poorly ventilated spaces and create issues you don’t want to deal with six months after moving back in.
During bigger projects, we’ve coordinated with builders to integrate temporary dust control solutions while ductwork is installed. It keeps debris out of the system before it’s even switched on. Sounds minor. It’s not. Dust trapped in new ducting can affect performance from day one.
Consider Insulation and Building Materials
A new extension isn’t just extra floor space. It’s new insulation levels, roofing materials and window types. All of that changes how heat moves through the home.
If your existing house was built twenty years ago, its insulation standards might be very different from today’s requirements. That mismatch can create temperature imbalances between old and new sections.
Upgrading insulation in connecting areas can dramatically improve overall performance. I’ve seen cooling loads drop noticeably after homeowners added proper ceiling batts and sealed gaps around new joinery.
It’s not glamorous. It works.
Think About Water Management and Ancillary Systems
Most people focus purely on air handlers and outdoor condensers. Fair enough. They’re the obvious components. But renovations often involve plumbing changes too, especially in larger extensions with new bathrooms or laundries.
If your property uses rainwater tanks or integrated systems, maintaining hygiene in stored water is critical. In some cases, contractors specify components like an antimicrobial tank liner to help manage water quality long term. While it’s not directly part of your air conditioner, any system that supports household infrastructure deserves attention during a build.
Overlooking these secondary systems can lead to maintenance issues down the track.
Future-Proof for Efficiency
Energy prices aren’t getting cheaper. Designing your HVAC layout with efficiency in mind is just practical.
That might mean positioning the outdoor unit in a shaded location, allowing adequate clearance for airflow, or ensuring easy access for servicing. I’ve seen condensers boxed in for aesthetics. They overheat. Performance drops. Repairs follow.
Renovations are also a good time to check switchboard capacity. New systems may require dedicated circuits. Sorting this early avoids last-minute electrical upgrades when timelines are tight and tempers shorter.
Coordinate Trades Early
One of the biggest renovation mistakes is treating air conditioning as an afterthought. HVAC needs space in ceilings, roof cavities and wall chases. If those voids fill with lighting, speakers and structural beams before your installer steps in, options shrink fast.
Good communication between your builder, electrician and HVAC technician makes all the difference. I’ve been on sites where a simple 20-minute meeting prevented hours of rework.
Renovating is messy. It’s disruptive. But it’s also an opportunity. Get the planning right and your upgraded home will feel comfortable year-round, not just visually impressive. And that’s the point, isn’t it?