Where to put an outdoor air conditioning unit

Basic clearances and airflow

Outdoor units need space around them to draw in air and expel it without recirculating warm exhaust air back into the intake, which reduces efficiency and can cause the unit to work harder than necessary. Most manufacturers specify minimum clearances from walls, fences and other obstructions, typically measured in hundreds of millimetres on each side and above the unit.

Cramming a unit into a tight alcove or hard against a fence might look tidy, but it's one of the most common causes of underperforming systems we're called out to investigate, and it's entirely avoidable at the design stage.

Noise and neighbours

Outdoor units run continuously while the system is operating, and even a quiet modern unit produces some noise, so position relative to your own and neighbouring bedroom windows matters. Mounting a unit directly beneath a neighbour's bedroom window, or in a narrow gap between buildings that amplifies sound, is a common source of complaints that's easily avoided with better positioning.

It's good practice to consider likely noise-sensitive rooms on both sides of a boundary, not just your own layout, and to check a unit's stated noise output before committing to a tight position. Anti-vibration mounts and careful bracket choice also reduce transmitted noise into a building's structure, which matters particularly on end-of-terrace and semi-detached properties.

Roof mounting vs ground mounting

• Ground mounting on a slab or frame is usually the simplest and cheapest option where garden or side-return space allows, and it keeps the unit easily accessible for servicing.
• Roof mounting suits flat-roofed commercial buildings or properties with no usable ground space, but it needs a structurally suitable roof, safe access for engineers, and weatherproofing around any roof penetrations.
• Wall-bracket mounting above ground level is common where there's no ground space but a suitable external wall, though it needs a wall capable of taking the unit's weight and vibration without transmitting noise indoors.
• Roof and high wall-bracket positions generally cost more to install and service safely due to access requirements, so this should be factored into any comparison of siting options.

Flats and shared buildings

In flats and other shared buildings, outdoor unit siting often needs freeholder or management company permission before installation, particularly where the unit will sit on a shared wall, roof or communal area. It's worth checking your lease and getting written permission before committing to a purchase, since retrofitting a unit into a different position after installation is far more costly than agreeing the position upfront.

Shared buildings also raise noise considerations for more neighbours than a standalone house, so positions away from other residents' windows and away from shared amenity spaces are usually preferred, even if it means a slightly longer pipe run.

Getting the position right first time

A site visit before any quote is finalised is the best way to weigh up all of these factors together, since the ideal position on paper isn't always the ideal position once pipe run length, access for future servicing and neighbouring windows are all considered. We'll always talk through the options with you rather than defaulting to whatever's quickest to fit.

If you're planning a new air conditioning installation and want the outdoor unit sited properly from the outset, get in touch for a free quote and we'll assess your property in person.