Installing air conditioning in a heritage weatherboard home

The streets of Yarraville and Seddon are mostly small single-storey Victorian and Edwardian houses, largely weatherboard with corrugated iron roofs and front verandahs on narrow blocks. Williamstown, set up in the 1840s as Melbourne's first port, adds early basalt houses and timber duplexes, while Newport and Spotswood grew through the Federation and Interwar years.

Those homes share a handful of challenges: a narrow side passage for the outdoor unit, high ceilings that hold warm air up top, roof spaces that can be low and tight under the iron, ornate plaster nobody wants cracked and, in many streets, a heritage overlay that governs what can be seen from the street.

Kingsville, Yarraville and Seddon are in the City of Maribyrnong, while Spotswood, Newport and Williamstown are in Hobsons Bay. Heritage precincts such as the Newport Estate Residential Precinct (HO23) cover whole streets of period homes. Whether an outdoor unit, pipe cover or roof-mounted equipment needs a planning permit depends on the overlay and its schedule, so ask the council before you commit to a position.

A unit at the side or rear, below the fence line and out of view from the street, is the least likely to raise questions. A unit on the front verandah, or a pipe cover running up the façade, is the kind of thing that does. If council wants details, a sketch showing the unit's size, position and colour makes the conversation easier.

On a narrow block, the side passage is often the only spot out of view, and it's often tight. The outdoor unit needs clearance for airflow and room for servicing. A unit wedged between two walls loses capacity and sounds louder, and the neighbour's bedroom window may be a metre away.

The rear yard is usually better: more air, more distance from neighbours and an easy pipe run for rooms at the back. For a front bedroom or lounge, the pipes may need to travel along or under the house to reach it, and the unit still needs a lockable isolating switch beside it.

Weatherboard over a timber frame is one of the easier walls to work with. A hole goes through between studs, the pipes and drain pass straight out, and the outside is finished with a cover duct painted to match the boards. Inside, a wall head sits high but clear of picture rails and cornices.

Solid walls take more care. Basalt and brick need core drilling, and the hole position is chosen to avoid cracking render or damaging original features. Where a room has ornate plaster, or a head on the wall would look wrong, a floor console is often the better choice.

Many period homes sit on stumps with a crawl space beneath. Pipes can often run under the floor to a console near the skirting, then out to a rear outdoor unit, with very little visible inside or from the street. It depends on subfloor height and access, so it's checked on site.

Ducted reverse-cycle needs room for an indoor unit and ducts. Under a low-pitched iron roof that room may not exist, and a large unit may not fit through a small manhole. Some homes have enough subfloor height for ducts underneath with floor outlets; others don't have room either way, and a few well-placed splits or consoles serve them better.

High ceilings change the heating picture. Warm air rises, so a high-wall head in a tall room can leave the floor cool on July nights, while a floor console blows warm air low, where people sit. Melbourne is in the Cold zone of the Zoned Energy Rating Label, so compare heating ratings for that zone.

An older home may have an older switchboard too, and each new air conditioner needs a circuit. Energy Safe Victoria lists air conditioning as non-prescribed electrical work with a Certificate of Electrical Safety, while main switchboard work is prescribed and independently inspected.