One hidden unit, a duct to each room and one unit outside. Here's how ducted air conditioning works, what you see in the house and how zones decide which rooms run.
What is ducted air conditioning?
You'll often hear that ducted air conditioning cools the whole house at once. It can, but it doesn't have to.
Ducted air conditioning is one hidden indoor unit, usually in your ceiling space, that sends cooled or heated air through ducts to a vent in each room. One outdoor unit works with it. Add a zone controller, and you choose which parts of the house get the air.
The seven parts of a ducted system
Daikin's brochure breaks a ducted system into seven parts. The numbers below match the drawing.
| Part | Where it sits | What it does |
|---|---|---|
| 1. Indoor unit | hidden in the ceiling | cools or heats the air and blows it back into the house |
| 2. Outdoor unit | outside | gets rid of the heat or cold the house doesn't need |
| 3. Zone controller | on a wall | turns each zone on or off |
| 4. Refrigerant pipes | out of sight, between the two units | carry heat from one unit to the other |
| 5. Flexible duct | runs from the indoor unit | carries the air around the house |
| 6. Supply air diffusers | in the rooms | let the air out into each room |
| 7. Return air grille | in the house, usually with a filter | takes air from the house back to the indoor unit |
How do ducted air conditioners work?
Ducted air conditioners work by moving your house's air around in a loop:
- Air from your rooms goes back through the return air grille, and a filter catches household dust.
- The indoor unit draws that air over its heat exchanger, which cools or heats it.
- The unit blows the air into the flexible duct.
- The duct carries it to the supply air diffusers, and it comes out in your rooms.
- That air ends up back at the grille, and the loop starts again.
While that runs, refrigerant pipes carry heat between the indoor and outdoor units. That's why ducted still needs a spot outside, even though you can't see the indoor unit.
Does ducted cool the whole house at once?
Only if it has no zones, or you leave them all on. Mitsubishi Electric's ducted brochure describes zoning as the ability to turn off a section of your system when you're not using it.
Daikin and Mitsubishi Electric both offer 4 or 8 zones. So you could run the bedrooms at night and leave the living areas off.
On Mitsubishi Electric's ducted systems, the zone controller is an optional extra, so ask whether your quote includes one. Without zones, there's no section to turn off.
Turning zones off changes the fan speed too. With Daikin's Airside Control, which isn't on every model, the indoor fan slows down as zones close, to between 60% and 100% of its normal airflow. Daikin says that makes it quieter and saves energy.
What you actually see in the house
Not much. The indoor unit, the ducts and the pipes stay out of sight.
You see the diffusers, the return air grille and the controller on the wall. Mitsubishi Electric says diffusers can go in the ceiling, wall or floor, and Daikin offers a choice of diffusers to suit your home.
Outside, you see the outdoor unit.
What ducted needs from your house
- Ceiling space. Daikin says most of its R32 ducted indoor units must go in the ceiling space, not under a floor.
- Well insulated duct. Daikin says your roof can pass 80°C in summer, and up to 30% of the system's capacity may be lost through the duct. So it asks for duct insulated for your climate zone.
- A spot outside. The outdoor unit needs its own space.
- The right power supply. The largest systems can need three-phase power.
Who ducted suits
Ducted suits a whole house with ceiling space to work in, when you'd rather not see a unit in every room. If you only need one room done, it's worth looking at the other types of air conditioners first.
Thinking about it for your place? These guides go further: what size ducted system you need, what moves the price and what it costs to run against splits. The ranges we install are on our ducted air conditioning page.
Send a few photos through our quote form and we'll tell you what your house can take. Sometimes that takes a visit.
Sources
- Daikin Ducted brochure: the seven parts, zones, the fan on Airside Control, roof temperature and duct losses, where R32 indoor units can go
- Mitsubishi Electric ducted brochure 2025: what zoning is, the optional zone controller, where diffusers can go
