Air conditioning in Barnet

The Hampstead Garden Suburb Trust's design guidance says all air conditioning plant needs the consent of both Barnet Council and the Trust. Trust consent is separate from planning permission, and you need both. Units are expected to be inconspicuous and screened where necessary. The conservation area boundary and the area covered by the Trust's scheme of management are not exactly the same, so check which applies to your house. Ask before you order any equipment.

Outside the Suburb and the borough's other conservation areas, a reversible system that also heats can be permitted development on a house if it meets the limits: an outdoor unit up to 1.5 cubic metres, not on a pitched roof, at least 1 metre from the edge of a flat roof, and within the 37 dB(A) noise limit at the neighbour's window. A semi gets one unit, so a multi split covers several rooms. A detached house can have two, which allows a proper whole house design. A unit used only for cooling still needs permission.

Many Barnet homes have gas boilers and radiators. A reversible air to air system can take over heating in the main rooms for much of the year and cool them in summer. If you want to move away from gas entirely, remember most air to air systems do not heat water, and the system must be sized for winter. The Boiler Upgrade Scheme lists a £2,500 grant for eligible air to air installs, but you need an MCS certified installer, and the Energy Saving Trust said in October 2026 that none were yet certified for air to air.

Barnet also has other conservation areas, including Finchley Church End, Finchley Garden Village, College Farm and parts of Mill Hill and Totteridge. In those, an outdoor unit must not face a highway under permitted development, and some areas may have extra controls. Check the council's conservation area pages for your street before planning the unit position, and talk to the council if you are unsure.

For flats and maisonettes in these areas, the usual flat rules also apply: freeholder consent first, then planning, because a single flat has no permitted development right of its own.