A new install is a home with nothing ducted in it: a period weatherboard heated by wall units, a renovated brick veneer with splits in two rooms, an extension with the ceiling still open. The roof space is measured for the fan coil, the duct runs are planned so no outlet is starved at the end of a long run, and the outdoor unit goes where it is quiet for you and for the neighbour.
A changeover is a home with a gas ducted heater. The heater comes out of the roof or from under the floor, the gas line is capped by a licensed gasfitter, and the fan coil goes in its place. This is the job with the Victorian Energy Upgrades discount attached, and our replace gas ducted heating page walks through the conditions.
The ducts are the honest part. The program guidance for gas-to-reverse-cycle changeovers recommends new ductwork and fittings, and we agree. Gas heating pushes very warm air through smaller ducts; reverse cycle moves more air at a gentler temperature and wants larger, better sealed runs. We inspect every duct, photograph it and tell you which can stay and which cannot. Underfloor gas ducts in a 1970s brick veneer are the runs we most often end up replacing, and we say so only after looking.
Two other paths belong here. An evaporative to refrigerated conversion takes the roof unit off and assesses the drops for reuse. Add-on cooling puts a cooling coil onto a gas heater you are keeping; it is cooling only, so no VEU discount applies.