The Installer's Guide to Ducted AC in Heritage Homes

Heritage homes are everywhere across Victoria. Victorian terraces in Fitzroy. Federation bungalows in Shepparton. Edwardian semis along the Dandenong corridor. They are beautiful, they are sought-after, and they are genuinely difficult to work with.

The problem isn't the homes themselves. The problem is that most of the HVAC industry still reaches for a standard catalogue solution when these jobs need something smarter. The result? Installers either walk away, or they shoehorn in a bulky bulkhead that ruins the room and the client relationship.

At Vic Air Supplies, we've spent over 30 years helping installers across Victoria tackle exactly these kinds of jobs. This guide breaks down the real constraints of heritage home installations, the right toolkit to address them, and why the "too-hard basket" is where the best margins actually live.

Table of Contents

1. What Makes Heritage Homes So Difficult for Ducted AC?
2. The Heritage Overlay: What Installers Actually Need to Know
3. The Right Toolkit: How Vic Air Approaches These Jobs
4. Compact Comfort: Built for Tight Spaces
5. Light Weight Duct: Your Best Friend in a Low Ceiling
6. iZone: Wireless Control That Protects the Plaster
7. The Design & Estimation Shortcut
8. Why "Too Hard" Is Where the Margin Is
9. Frequently Asked Questions
   
   

1. What Makes Heritage Homes So Difficult for Ducted AC? 

When installers pop the manhole on a heritage property, they usually find a combination of problems that simply don't appear in newer builds.

Minimal ceiling void.
Flat or near-flat roof extensions, common in Victorian and Edwardian additions, may leave as little as 200mm to 250mm of usable clearance. A standard residential ducted unit typically sits around 320mm to 400mm in height. That's a non-starter.

Fragile internal fabric.
Original lath-and-plaster ceilings crack easily. Running data cables down old walls by chasing through plaster is expensive and risky. Vibration alone can cause damage that turns a straightforward rough-in into a costly repair job.

No wall space for risers.
Floor-to-ceiling windows, heritage joinery, and original cornices are common features that leave no obvious vertical path for duct runs.

Heritage planning controls.
Visible external changes, including outdoor condenser placement, require careful navigation of local planning rules. Getting this wrong can mean permit applications, delays, and unhappy clients.

None of these constraints are insurmountable. But addressing all of them requires you to be specifying from the right range of air conditioning supplies before you've even picked up a tape measure.

2. The Heritage Overlay: What Installers Actually Need to Know 

Under the Victorian Planning Scheme, properties within a Heritage Overlay require a planning permit for works that are visible from a public street or park. This primarily concerns the placement of outdoor service units, including condensers.

Key points for installers:

• Indoor units that are fully concealed don't typically trigger the heritage overlay. A ducted indoor unit hidden above a laundry or service cavity, for example, falls entirely within the structure and creates no planning permit issue.
  
  
• Outdoor condensers are the main concern. If the condenser is visible from the street, a planning permit is almost certainly required. The solution is strategic placement: behind fencing, garden beds, or in a side passage not visible from the street frontage.
  
  
• Internal alterations generally don't require a permit unless the heritage schedule specifically applies internal alteration controls, which is relatively rare.
  
  
• Always verify by checking the relevant council's planning scheme or contacting their heritage planning team. The City of Melbourne, Yarra City Council, and others all offer guidance specific to their Heritage Overlay schedules.

The practical takeaway: with the right indoor unit and careful condenser placement, a full ducted system is achievable on most heritage properties without triggering the permit process.

3. The Right Toolkit: How Vic Air Approaches These Jobs 

Vic Air Supplies is Melbourne's only HVAC wholesaler with an in-house sheet metal shop. That matters enormously on heritage projects, where our experienced fabrication team works alongside our Design & Estimation team to spec jobs where every millimetre counts. When a standard solution won't fit, we can custom-fabricate something that will.

Beyond fabrication capability, the three products that consistently make the difference on tight heritage jobs are:

1. Compact Comfort for the indoor unit
2. Light Weight Duct for the duct runs
3. iZone wireless controls for room sensors and zoning

Here's what each one brings to the job.

4. Compact Comfort: Built for Tight Spaces 

Compact Comfort is an Australian-owned, designed, and manufactured brand specialising in high static ducted air conditioning with inbuilt multi-zone temperature control. It's not a slimmed-down version of a standard unit. It has been engineered from the ground up for the kind of installs where standard units simply don't fit.

Why it works for heritage homes:

Low profile.
Compact Comfort is purpose-designed to fit in minimal ceiling voids, including flat roof cavities where a traditional roof cavity doesn't exist. For precise height specifications on individual models, speak with our team. The range has been specifically developed to address the clearance constraints that make heritage homes difficult.

High static pressure.
This is the critical spec that gets overlooked when installers reach for a "slim" unit. High static pressure means the fan can push air through restrictive duct runs: the kind you're forced to fabricate around heritage beams, joists, and structural elements that can't be moved. A unit with weak fan grunt will simply underperform once the ductwork starts bending and narrowing around obstacles.

VAV technology.
Compact Comfort uses Variable Air Volume (VAV) technology to adjust airflow based on real-time demand across zones. This means the system isn't dumping full airflow into a room that's already at temperature. It responds precisely, which is both more comfortable and more energy-efficient. It also reduces unnecessary strain on the system, extending its lifespan.

Inbuilt multi-zone control.
Zone control is built into the Compact Comfort platform rather than bolted on as an afterthought, which simplifies the install and reduces the number of components required.

Wi-Fi connectivity.
The system supports remote control via smartphone app, a feature that resonates strongly with the kind of homeowners who invest in heritage properties.

For heritage jobs, Compact Comfort is consistently the indoor unit specification we recommend. It turns a "can't be done" conversation into a genuine opportunity. Browse the Compact Comfort range.

5. Light Weight Duct: Your Best Friend in a Low Ceiling 

Once you've got the indoor unit sorted, the duct runs are where heritage installs live or die. Standard R1.0 flex duct is bulky, awkward to route in tight spaces, and adds up quickly when you're navigating between joists.

Vic Air's Light Weight Duct, manufactured in-house at our Keilor Park and Dandenong South branches, is a pre-insulated rigid board made from high-density polyurethane. Here's what makes it the right tool for heritage jobs:

• It's roughly one-seventh the weight of equivalent sheet metal. That means less OH&S risk, faster handling, and significantly reduced installation time.
  
  
• It's rigid, which means it holds its shape. You can fabricate wide, flat rectangular sections: the kind of low-profile runs that slide between floor joists or navigate tight offsets without collapsing or kinking.
  
  
• R2.0 board is just 42mm thick. Compare that to 75mm of insulation required to achieve the same R-value with sheet metal. Every millimetre matters in a tight void.
  
  
• The material can withstand pressures up to 2,000Pa and has an operating temperature range well beyond residential requirements.
  
  
• It can be cut and fabricated on-site. For heritage jobs where no two obstacles are in the same place, this is a genuine advantage over ordering pre-made steel runs that may not fit when they arrive.
  
  
• Available in silver or black exterior finish. When ductwork runs in visible areas, the black-finish option allows for a more discreet result.

Our in-house manufacturing team can also pre-fabricate unit-specific V-boxes, supply air transitions, cushion boxes, and return air plenums to suit Compact Comfort units, meaning the entire duct system is engineered to work together before it reaches site. See our full Light Weight Duct range.

6. iZone: Wireless Control That Protects the Plaster

The biggest hidden risk in a heritage install isn't the unit clearance or the duct routing. It's the cabling. Chasing data cables through old lath-and-plaster walls is genuinely destructive. The vibration from cutting can fracture plaster that's been intact for a century, and the resulting repair bill can easily dwarf the cost of the rough-in itself.

iZone is an Australian-engineered Wi-Fi home automation system that eliminates this problem entirely.

The iSense wireless temperature sensors are battery-operated and pair wirelessly with the main bridge. No data cables required through the walls. The client gets per-room temperature control without a single wall being chased.

For heritage rooms that cannot be disturbed, this is not a workaround. It's the right solution. The original cornices, plaster walls, and joinery remain completely untouched. The only physical control element the client typically sees is the main touchscreen or app interface in a modern section of the home.

Additional iZone capabilities worth noting for clients:

• Compatible with Google Assistant and Amazon Alexa (iZone Nova and Nova Mini)
• Smartphone app control from anywhere
• Programmable scheduling for automated temperature management
• Zone-by-zone control to avoid heating or cooling unused heritage rooms

iZone integrates natively with Compact Comfort's control platform, making it a clean, coherent system rather than a mix of components from different manufacturers. Browse the full iZone range.

7. The Design & Estimation Shortcut

The biggest mistake on heritage jobs isn't specifying the wrong product. It's guessing on the static pressure calculation.

With Compact Comfort's high-static fan, you have genuine headroom to work with. But that headroom isn't unlimited, and the friction losses through flat, rectangular runs navigating around heritage beams add up quickly. Underestimate the equivalent duct length or miss a bend, and you'll commission a system that delivers disappointing airflow. The blame always falls on the installer.

Vic Air's Design & Estimation team exists specifically to take this calculation off your plate. Send us your floor plans, and we'll overlay the duct design, calculate the static pressure, and confirm the specification fits before you order anything. This service is available to our trade customers across all three branches: Keilor Park, Dandenong South, and Shepparton.

Getting the design right upfront means fewer surprises on site, faster commissioning, and a stronger foundation for the premium price point these jobs command.

8. Why "Too Hard" Is Where the Margin Is

When you say yes to a heritage job that your competitors have walked away from, you're not competing on price against every other installer in town. You're competing on capability. The client has already been told it can't be done, and you're the person who's found a way.

That shift in positioning changes the entire conversation. It's no longer a race to the cheapest ducted quote. It's a custom solution to a genuine problem, with a premium to match.

The combination of Compact Comfort, Light Weight Duct, and iZone wireless control is exactly the toolkit that makes those jobs achievable. And because Vic Air manufactures the ductwork in-house and stocks the full Compact Comfort and iZone range across three Victorian branches, you're not waiting on imported components or managing multiple supplier relationships.

The "too-hard basket" is where the best margins are. It's also where repeat referrals come from, because clients who got the install that couldn't be done tell everyone they know.

Ready to Quote a Heritage Job?

Don't guess on the static pressure. Send your plans to our Design & Estimation team and let us map out a Compact Comfort solution that fits before you commit to a quote.

Keilor Park: saleswest@vicair.com.au | 03 9365 1900
Dandenong South: saleseast@vicair.com.au | 03 8770 2800
Shepparton: salesshep@vicair.com.au | 03 5833 4700

Contact Our Team Today

FAQs

Q: Do I need a planning permit to install ducted AC in a heritage property?

Generally, the indoor unit doesn't require a permit as it's fully concealed. The outdoor condenser may require one if it's visible from the street or a public park. Check with your local council to confirm what applies to your specific Heritage Overlay. Our team can also advise on slimline side-discharge condenser options that are easier to conceal.

Q: What clearance does Compact Comfort require in a ceiling void?

Compact Comfort is purpose-designed for minimal ceiling voids, including flat roof extensions. Contact our sales team for unit-specific height requirements, and remember to allow additional clearance for condensate drain fall and suspension.

Q: Why use Light Weight Duct instead of standard flex duct on tight jobs?

Light Weight Duct is rigid, so you can fabricate wide, flat rectangular runs that navigate between joists without collapsing. It's also pre-insulated: R2.0 board is just 42mm thick, which saves critical space in tight voids. It can be cut on-site, which is essential when every obstacle is in a slightly different position.

Q: Can iZone be installed without running new cables through heritage walls?

Yes. iZone's iSense sensors are battery-operated and communicate wirelessly with the main bridge. No wall chasing required. This is the standard approach we recommend for heritage properties where protecting original plaster is a priority.

Q: How does Compact Comfort handle long or restrictive duct runs?

Its high static pressure capability means the fan can push through the friction losses created by flat duct runs, multiple bends, and tight offsets. The exact run lengths achievable depend on your specific duct layout, which is why we recommend using our Design & Estimation team before finalising your specification.

Q: Can I get a duct design for a heritage job before quoting?

Yes. This is exactly what our Design & Estimation team is there for. Send us your floor plans and we'll map out a system, calculate the static pressure, and confirm the specification fits. It's a free service for our trade customers and it takes the guesswork out of quoting tight jobs.