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Air conditioning advice

What to consider before installing air conditioning

Plan room selection, system capacity, outdoor-unit placement and permissions for a comfortable, efficient installation.

Reviewed 23 September 2026 6 minute read

At a glance

A good air-conditioning design starts with the rooms you want to condition and their heat gains. Unit size, placement, pipe routes, drainage, noise and building approvals all need to be considered together.

What to have ready

  • Which rooms overheat and at what time of day
  • Room dimensions, glazing and window direction
  • Possible indoor- and outdoor-unit positions
  • A route for refrigerant pipework and condensate drainage
  • Planning, leasehold and building-regulations constraints

Define the comfort problem

Start by identifying the rooms that overheat, when they become uncomfortable and how they are used. Bedrooms, loft conversions, glazed spaces and home offices can have very different cooling loads.

Portable units may help occasionally, but a fixed split system is designed around the room and generally offers quieter, more controlled operation.

Size from heat gain, not floor area alone

Room area is only one input. Glazing, orientation, insulation, occupancy and heat-producing equipment also affect capacity. An oversized system may cycle frequently; an undersized one may struggle on the hottest days.

Plan both sides of the system

Indoor airflow should reach the occupied area without blowing directly onto beds or desks. Outside, the condenser needs airflow, service access and a position that manages noise sensitively. The installer also needs a safe route for power, refrigerant pipes and condensate.

Check permissions and competent installation

Fixed air-conditioning work may need building-regulations approval, and planning or leasehold permission can depend on the property and external-unit position. Refrigerant work should be carried out by appropriately qualified personnel.

Common questions

Independent sources

Guidance can change. Check the latest information before making a decision.

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