The short answer
A ceiling cassette is a split system's indoor unit set into the ceiling, with only a flat panel showing. It suits larger and open-plan rooms with space above the ceiling, but in most houses fitting one means building work.
On this page
Cassettes are a familiar sight in shops, offices and restaurants, where suspended ceilings leave plenty of room above. In homes they turn up mostly in extensions, basements and new builds, where space above the ceiling can be planned in from the start.
How a ceiling cassette works
The body of the unit hangs above the ceiling on threaded rods fixed to the structure, and a square or rectangular panel sits flush with the ceiling below it. On a typical four-way cassette, air is drawn in through the middle of the panel, passes through a filter and over the coil, and is blown out through slots along the edges, with louvres setting the direction.
Like any split system, it connects to an outdoor unit through refrigerant pipes, a cable and a condensate drain, all running through the space above the ceiling. Most cassettes have a built-in condensate pump that lifts the water high enough for the drain pipe to run downhill through the void. Depending on the range, a cassette can share a multi-split outdoor unit with wall-mounted units in other rooms.
A cassette is a middle ground. It keeps most of the unit out of sight, like a ducted system but without the ductwork, though it involves more building work than a wall-mounted split.
Types of cassette
| Type | Blows air | Often suits |
|---|---|---|
| Four-way | In four directions | The middle of a large or open-plan room |
| Compact four-way | In four directions | Smaller rooms, or a 600 mm ceiling grid |
| Two-way | To two opposite sides | Long, narrow rooms |
| One-way | In one direction | Near a wall, or narrow spaces |
Some models let you close off individual outlets, which helps when a cassette sits near a wall or would otherwise blow towards a sofa or desk.
What fitting one involves
- Depth above the ceiling for the body of the unit. This varies by model, and slimmer cassettes are made for shallower voids.
- A large, accurately cut hole in the ceiling, lined up with the panel.
- Working around joists. In a house, joists are often closer together than a cassette is wide, so fitting one may mean trimming joists. That's structural work that needs to be designed and carried out properly.
- Routes for the pipes and drain through the void to an outside wall.
- A lowered ceiling where there's no usable void, such as in a downstairs room with another room above. That takes away some ceiling height.
- Access for servicing. The filter sits behind the panel and is reached from below, and engineers may need to get at the pipes and drain above.
In an upstairs room with a loft above, the unit and its pipes can sit in the loft, which is often simpler than working between two floors.
What it does well
- Discreet. It sits flush with the ceiling and leaves the walls free for furniture, pictures and windows.
- Coverage in larger rooms. Air goes out in several directions from near the middle of the room, which can suit an open-plan space better than a wall unit at one end.
- Flexible drainage, thanks to the built-in pump.
- Out of the way, so furniture can't block it and it isn't easily knocked.
The drawbacks
- Building work. Cutting the ceiling, working around joists or lowering a ceiling is more disruptive than fixing a unit to a wall.
- Space above. Without enough depth over the ceiling, a cassette may not be possible at all.
- The pump. It's one more part that can fail, and it can sometimes be heard in a quiet room. A blocked drain can leak onto the ceiling, and condensate drainage covers the signs.
- Cleaning from a stepladder. Filters usually need cleaning every few weeks while the system is in regular use.
- Looks. The panel is much larger than a light fitting and can look out of place in some rooms.
- Heating in tall rooms. Warm air tends to rise, so in a room with a high ceiling, heat delivered from above can collect near the top.
Related guides
- Ducted air conditioningDucted air conditioning hides the indoor unit in a loft, ceiling void or cupboard, and ducts carry the air to grilles in the rooms. Only the grilles are visible, but it needs space and usually more building work than a wall-mounted system.
- Wall-mounted split systemsA wall-mounted split system pairs an indoor unit fixed high on a wall with an outdoor unit outside, joined by refrigerant pipes. It is a common choice for fixed air conditioning in UK homes, and most models heat as well as cool.
- Where the water goes: condensate drainageWater that condenses in the indoor unit as it cools runs through a drain hose to a suitable outlet, with a small pump where it can't fall naturally. In heating mode the outdoor unit produces water too.