Ducted air conditioning

How ducted air conditioning works

In a ducted system, the indoor unit is hidden away in a ceiling void, a loft or a cupboard. It draws air back from the rooms through return grilles, cools or heats it and pushes it out through insulated ducts to supply grilles or diffusers in the ceiling, floor or wall of each room it serves. The outdoor unit and the refrigerant pipework are the same as on any split system.

The only things you see in the room are the grilles, which can be chosen to suit the ceiling and the décor. There is no unit on the wall and no pipework in view, and because the unit is out of the room, what you hear is mainly the gentle sound of air moving.

Where ducted systems suit

• New builds and extensions, where the ducts can be planned into the ceilings and floors before they are boarded.
• Major refurbishments and loft conversions, where ceilings are coming down anyway.
• Living spaces and principal bedrooms where appearance matters most.
• Offices, shops, showrooms and restaurants with suspended or bulkhead ceilings.
• Listed buildings and period interiors, where a wall unit would spoil a room, subject to consent.

In a finished home with solid ceilings and no loft or void to use, ducted can be impractical or disruptive. A multi-split with wall-mounted units is usually the simpler choice there.

What a ducted system needs

Ducted systems need space. The indoor unit needs a void or loft deep enough to hold it, with room to reach the filters and the electrics. The ducts need routes to each room, and the return air needs a path back to the unit. The condensate drain needs a fall, or a pump. Most important of all, there has to be a permanent access panel so the unit can be serviced and the filters cleaned. A ducted unit sealed behind plasterboard becomes very expensive to maintain.

On the survey we look at the ceiling voids, the loft and the structure, check where the ducts can run without cutting through joists, and agree the positions of grilles and access panels with you or your builder.

Zoning and control

A single ducted unit serving several rooms treats them as one zone unless the design says otherwise. That suits an open-plan space, but in a home you may not want to cool every bedroom at once. There are two ways to give rooms separate control. One is to use more than one ducted unit, for example one for the living areas and one for the bedrooms. The other is a zoning system with motorised dampers in the ducts. We explain the options and their costs at the design stage, so you get the level of control you want.

Working with your builder

Ducted air conditioning is best planned early. If you are building, extending or converting a loft, talk to us before the ceilings go up. We can agree the void depths, the duct routes, the grille positions and the access panels with your architect or builder, run the ducts and pipework at first fix and return to fit the grilles, connect the outdoor unit and commission the system at second fix. Our guides to new builds and loft conversions explain the timing.

Grilles, noise and air distribution

The grilles are the only part of a ducted system you see, so their position and style matter. Supply grilles are placed to spread the air across the room without draughts on the bed or the sofa, and return grilles where they can draw air back without short-circuiting it straight into the unit. Slot diffusers, square ceiling diffusers and floor grilles are all possible, depending on the room and the décor. Duct size also affects noise: air moving too fast through a small duct or grille whistles, so we size the ductwork for the airflow each room needs. Getting this right is what makes a ducted system feel calm and quiet.

Commissioning and servicing

A ducted system has to be balanced once it is installed. We set the fan speed and check the airflow at each grille so every room gets its share of air, then commission the system in cooling and heating and hand over the F-Gas records and controls information.

Ducted units need regular filter cleaning just like wall-mounted ones. Because the filter is out of sight, it is easy to forget, and a blocked filter cuts the airflow to every room. An annual service keeps the filter, the coil, the drain and the fan clean, and is the time to check the ducts and grilles too.

Price, planning and warranty

Ducted systems are priced after a survey because the duct routes, the number of rooms and the building work vary so much. You get a fixed-price quote before work starts. For homes, HMRC zero-rates energy-saving materials until 31 March 2027, and we confirm the VAT on your quote (HMRC Notice 708/6). The outdoor unit is subject to the same planning rules as other systems, and listed buildings need listed building consent. Warranty is the manufacturer’s, on its terms, which we explain for the model we quote.