Wall-mounted split units are usually easier to install, easier to maintain and simpler to zone in an existing home. Ducted air conditioning can give a discreet finish and serve several outlets, but it needs adequate ceiling or loft space, carefully designed air paths and good access for maintenance. Neither should be selected before shading, ventilation and other passive cooling measures are assessed.
The practical difference
A wall-mounted system places a visible indoor fan unit high on the room wall. A ducted system conceals the fan unit and distributes conditioned air through ducts and grilles. Both may connect to an outdoor refrigerant unit.
Concealed does not mean space-free. The ducted option needs room for the unit, supply ducts, return air, insulation, dampers where used, a condensate fall and service access. Tight London ceiling voids can make these requirements decisive.
Comfort and control
A wall unit serves its room directly and can respond quickly. Its success depends on avoiding beds, desks and seating in the main air throw. A ducted design can place several grilles for gentler distribution, but poor duct sizing or balancing can cause noise and uneven temperatures.
One ducted zone should not be assumed to give independent control to every bedroom. True zoning requires a designed control and airflow strategy that remains safe when zones close. Ask how return air travels when doors are shut.
Installation and maintenance
Wall units generally require less building work, although pipework and drains still need a neat, durable route. Ducted installations often fit best during a major refurbishment, loft conversion or new extension when ceilings are open.
Filters, drain trays, fans and controls must remain reachable after decoration. An access hatch that cannot accommodate service work is not meaningful access. Duct insulation and airtightness also matter where routes pass through hot or unconditioned spaces.
- Ask for supply and return-air locations on a drawing.
- Confirm access-panel sizes before ceilings are closed.
- Check how each room is controlled with doors shut.
- Keep outdoor-unit planning and noise in the design.
Choosing for London and Essex homes
For a finished terrace or flat, wall-mounted units often offer the least disruptive route. Ducted systems become more attractive where a renovation already provides suitable voids and the discreet appearance justifies the added coordination.
First reduce solar gain, especially through rooflights and west-facing glass. Then commission room heat-load calculations and compare like-for-like proposals for cooling output, sound, access, building work and controls. Check planning and freeholder requirements before ordering.
Frequently asked questions
Is ducted air conditioning silent?
No. Fans and moving air always create some sound. Good unit selection, duct sizing, attenuation and grille design can reduce it, but sound should be assessed explicitly.
Can a ducted system use existing heating ducts?
Do not assume so. Existing ducts may have unsuitable size, insulation, cleanliness or layout. A designer must assess them for the proposed cooling airflow and condensation risk.
Can one wall unit cool the whole floor?
Usually not evenly, especially with closed doors. Design should be based on the rooms requiring comfort rather than hoped-for airflow through halls.
Which system is easier to service?
Wall-mounted units are often more accessible. A ducted system can also be serviceable if properly sized access is designed and kept clear.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.