Ducted Air Conditioning in Cairns

The roof cavity does most of the damage

A Cairns roof space in the middle of the day sits well above 50 degrees under the sheeting, and through the wet season it is barely cooler and close to saturated. Ducted air conditioning puts cold air and a wet fan coil into exactly that environment, which is why duct specification is not a detail to be left to whoever is cheapest.

Two things follow. The first is insulation value. Thin flexible duct loses a meaningful part of the cooling between the fan coil and the far bedroom, and the room at the end of the longest run is the one that never quite works. The second is the vapour barrier. The outer sleeve of a flexible duct is what stops humid roof air reaching the cold inner core. A torn sleeve, an untaped joint or a duct crushed flat against a batten will sweat, and in February that shows up as a brown ring on a ceiling that everybody blames on the roof.

Zoning, and the airflow floor underneath it

Zoning is the reason most people choose ducted, and it is also where systems get set up badly. A fan coil needs a minimum amount of air moving across it. Close enough zones down and airflow drops below that floor, the coil gets too cold, and you get ice on the fins, water where it should not be, and a system that cuts out.

The answer is either a correctly sized bypass, a constant zone that cannot be closed, or a system with genuine variable capacity that winds back as zones close. Which one applies depends on the equipment, not on preference. Ask how the design handles one small bedroom running at 2am, because that is the condition that finds the fault.

Which homes up here suit it

New slab-on-ground estate homes are the easy case. Truss roofs give clear space, ceilings are a consistent height, and the runs are short.

Rendered block usually works, although a low-pitch roof can leave nowhere to sit a fan coil with the fall the drain needs.

Queenslanders are the hard case and worth being blunt about. High ceilings, shallow pitch, no cavity in the walls, and pressed metal or VJ ceilings nobody wants to cut into. Ducted can be done, but it often turns into bulkheads, and at that point a multi head system usually gives a better result for less disruption and less damage to the house. We would rather say that at quote stage than halfway through.

Power, drainage and commissioning

Most domestic ducted systems here want a dedicated circuit and many want three phase, so the switchboard gets looked at before anything is ordered. Older boards with ceramic fuses and no spare capacity are common through the inner suburbs, and if an upgrade is needed it belongs in the quote rather than in a phone call on install day.

Condensate is the other one. A fan coil in a Cairns roof produces a serious volume of water through the wet season, and the drain needs continuous fall, a trap and an overflow that discharges somewhere safe rather than into the ceiling. We run it and test it with water instead of assuming it works.

If you want to know whether your roof will take ducted at all, call 0489 266 523 and describe the ceiling height and roof pitch first. That answers most of it before anyone drives out.