Older homes weren’t built with air conditioning in mind. Rooftop space is tight, electrical capacity is often dated, walls might be solid brick or weatherboard with limited cavity room, and in some cases there’s a heritage overlay constraining what you can do externally. None of this makes a retrofit impossible. It does mean the install needs more thought than dropping a system into a 2020 build.

We retrofit air conditioning across older Sydney suburbs regularly, particularly through Liverpool, Bankstown, Cabramatta, the inner west and the older parts of Parramatta. Here’s what actually matters when you’re planning one.

What “older” means in practice

Different eras of housing present different retrofit challenges, and it’s worth being specific.

Federation and Edwardian homes (roughly 1890s to 1915). Inner west and inner south Sydney suburbs particularly. Ornate ceilings, often pressed metal. Limited or non-existent roof cavity for ducting. Solid double-brick walls. Heritage overlays in places like Glebe, Annandale, Paddington and Balmain often restrict outdoor unit placement and visible external work.

Inter-war and post-war (1920s to 1950s). Common across Bankstown, Strathfield, parts of Liverpool, Marrickville and Earlwood. Single-skin or double-brick construction, low ceilings, modest roof cavities, and electrical systems that have been added to incrementally over decades. The wiring is often the constraint, not the structure.

Mid-century and 60s-70s brick veneer. Covers a lot of suburban Sydney, including older parts of Liverpool, Cabramatta, Granville and Auburn. Reasonable roof cavity, generally workable structurally, but insulation is usually minimal and the original switchboard is often undersized for modern loads.

1980s and 90s builds. Generally retrofit-friendly. Decent roof space, reasonable electrical infrastructure, and few heritage constraints. The main consideration is matching the system to a home that wasn’t designed around aircon distribution.

The age of the home determines which system makes sense, where the constraints sit, and what additional work the retrofit might trigger.

The split system retrofit: usually the simpler path

For most older homes, multi-split is the practical answer.

A multi-split system uses one outdoor unit connected to multiple indoor wall heads. Refrigerant pipes and a small drain line run between them, usually concealed behind external trunking or chased into the wall. No ductwork required, no roof cavity needed, minimal structural impact.

What makes multi-split work for older homes:

The pipe runs are flexible. We can route refrigerant lines along the outside of the home, through eaves, or through limited internal cavities. Federation homes with no roof access at all can still take a multi-split.

The work is mostly external. One penetration per indoor head, typically a 65mm core hole through the wall. Plaster damage internally is minimal.

It works around heritage constraints. Outdoor units can usually be positioned at the rear or side of the home, out of street view, which keeps heritage councils happy in places like Glebe, Annandale and Haberfield.

The honest trade-off: you’ll have a wall head visible in each room, and a multi-split with three or four indoor units typically runs $5,500 to $9,000 supplied and installed depending on capacity and complexity.

The ducted retrofit: harder, but sometimes worth it

Ducted is genuinely possible in some older homes and genuinely not possible in others. The deciding factor is roof cavity space and access.

Where it works:

Mid-century brick veneer with truss roofing usually has the room. So does most 1980s-onwards housing. Some larger Federation and inter-war homes with high pitched roofs have surprising amounts of usable cavity, though access is often tight.

Where it doesn’t work:

Federation and Edwardian homes with low-pitched roofs, heavily timbered roof structures (which prevent running long duct lengths), or pressed-metal ceilings that can’t be cut for vents without serious damage. Single-storey terraces with party-wall construction. Homes with skillion or flat roofs.

A ducted retrofit in a workable older home runs $11,000 to $18,000+ depending on system size, zoning complexity and access difficulty. That’s $2,000 to $4,000 more than the equivalent install in a new build, mostly because of the additional time required to navigate older roof spaces.

The right answer for most older homes ends up being: walk through the house with an installer, look in the roof cavity, and see what’s actually possible. Quote-by-phone-call doesn’t work for these jobs.

The constraints that bite homeowners during a retrofit

A few things consistently catch people off guard.

Electrical capacity. Modern reverse-cycle systems draw real current. A ducted system needs its own dedicated circuit, and many older homes don’t have spare capacity in the switchboard to add one. Switchboard upgrades run $800 to $2,500+ depending on what’s there. Worth getting an electrician to check before you sign for a system.

Asbestos. Anything built before 1990 might contain asbestos in eaves, ceiling sheets, or lagging on hot water pipes. Cutting into these is regulated work requiring a licensed asbestos remover. If your aircon installer doesn’t ask about asbestos before quoting, that’s a red flag. SafeWork NSW has clear guidelines on this and the fines for unsafe handling are substantial.

Heritage constraints. Local councils across Sydney have heritage overlays in older suburbs. The constraint is usually outdoor unit placement (visible from the street), and sometimes external pipe runs. Worth checking with your local council before committing to a particular install layout.

Structural integrity for ducted systems. Older roof trusses weren’t designed to support modern indoor fan coil units, which can weigh 40 to 80kg. A competent installer will assess whether additional bracing is needed, particularly in inter-war and earlier homes.

Insulation and thermal performance. This isn’t strictly a retrofit constraint but it’s one of the most common post-install complaints. An aircon system in a poorly insulated home will run constantly and never quite hit set temperature. Adding ceiling insulation before or alongside the aircon retrofit usually pays for itself in running cost savings within a few years. R5.0 ceiling batts in an uninsulated older home typically cost $2,500 to $5,000 depending on size.

Sizing for older homes specifically

Older homes have different cooling loads than modern builds, and a system sized off a generic kW-per-square-metre rule will usually be wrong.

Things that push sizing up:

Single-glazed windows (almost universal in pre-1990s housing). Minimal wall insulation in older brick veneer. Dark-coloured original tile roofs without sarking, which run hotter than modern Colorbond. Single-skin walls in some Federation and post-war homes.

Things that push sizing down:

Solid double-brick construction in Federation homes has surprising thermal mass and stays cooler than modern brick veneer in steady conditions. Lower ceilings in some post-war housing reduce air volume to condition. Smaller room sizes in original floorplans.

The net effect is that older homes typically need slightly more capacity than a modern equivalent of the same floor area, but the difference is house-specific. Anyone quoting without doing a proper load calculation isn’t accounting for this.

When the retrofit makes sense and when it doesn’t

It makes sense if you’re staying in the home for at least five years, the home is in reasonable structural condition, and you’ve thought through the insulation question alongside the aircon decision. The comfort improvement in an older home with good aircon is dramatic, and it adds resale value in family-home suburbs.

It’s worth thinking twice if you’re planning major renovations within a few years (you’ll likely want to redo the aircon to suit the new layout), if the electrical infrastructure is so old that the upgrade work outpaces the aircon work itself, or if budget constraints would force you into an undersized system that wouldn’t actually keep the home comfortable.

Frequently asked questions

Can I retrofit ducted air conditioning into a Federation home? Sometimes. Depends on roof pitch, ceiling construction and heritage constraints. A site visit is the only way to know for certain. Multi-split is usually the more reliable answer for these homes.

Will retrofitting aircon damage my plaster ceilings or walls? Multi-split installs require one wall penetration per indoor head, usually a 65mm core hole. Damage is minimal and easily patched. Ducted installs require ceiling vents and a return air grille, which involve cutting holes in the ceiling. Both can be done cleanly by a competent installer, but ducted involves more remediation work afterwards.

How long does a retrofit take? A multi-split with three or four indoor heads typically takes 1 to 2 days. A ducted retrofit in an older home runs 2 to 4 days depending on access and complexity. Most installers will quote both timeframes and price separately.

Do I need council approval to retrofit aircon? Usually not in non-heritage areas. Heritage-listed properties or properties in conservation areas often require approval for visible external work, particularly outdoor unit placement. Worth checking with your local council before installation.