Air conditioning in Barnet and Hampstead Garden Suburb

Barnet is mostly houses

Unlike inner London, where most people live in flats, much of Barnet is houses with gardens. Finchley, Hendon, Mill Hill, Edgware and Whetstone are dominated by 1920s and 1930s semis and detached houses, with Edwardian homes in East Finchley and Chipping Barnet and purpose built flats along the main roads such as the High Road and Finchley Road. That makes air conditioning simpler here, because the permitted development rules for heat pumps are designed around houses.

When it is permitted development

In England, Class G of the planning rules allows an air source heat pump on a house without planning permission if it meets every condition (Planning Portal). After the changes on 29 May 2025, the key points are:

Condition	Detail
Use	must not be used solely for cooling
Number	one on a semi or terrace, two on a detached house
Size	outdoor unit up to 1.5 cubic metres on a house
Noise	MCS 020 calculation of 37 dB(A) or less at the neighbour’s window
Roofs	not on a pitched roof; at least 1 metre from the edge of a flat roof
Front walls	outside conservation areas, only at ground floor level if facing a highway
Conservation areas	not on a wall or roof fronting a highway
Listed buildings	not permitted development

So a reversible system installed to heat and cool, with the outdoor unit at the back of a Finchley semi and the noise calculation done, is often lawful without an application. A cooling only air conditioner always needs permission.

Detached houses: two units

The May 2025 change allowing two heat pumps on a detached house is useful in Barnet, where there are many larger detached homes in Mill Hill, Totteridge and parts of Finchley. It allows, for example, one outdoor unit serving the bedrooms and another serving the ground floor living spaces, each as a multi split. That gives better resilience and more flexible zoning than one large unit. Our guide to whole house air conditioning explains how that design works.

Hampstead Garden Suburb: two consents

Hampstead Garden Suburb, in the south of the borough around NW11 and N2, is a planned early 20th century suburb with its own controls. The Hampstead Garden Suburb Trust’s design guidance says all air conditioning plant needs the consent of both Barnet Council and the Trust. The Trust operates a scheme of management that controls changes to properties, and its consent is separate from planning permission. You need both.

Barnet Council notes that the conservation area boundary and the area covered by the Trust’s scheme of management are not exactly the same. Check which applies to your house before you plan anything. In practice, units are expected to be inconspicuous and screened where necessary, which usually means a rear position, low down, behind planting or a screen, with quiet operation.

Flats in Barnet

Flats along the main roads and in converted houses follow the same rules as anywhere in London. A single flat has no permitted development right of its own: the right applies to a whole block of flats, allows one unit for it and does not apply where the building also contains commercial premises, such as shops on the ground floor. Freeholder consent comes first. Our air conditioning for flats page covers that process.

Heating as well as cooling

Many Barnet homes have gas boilers and radiators. A reversible air to air system can heat the rooms you use most for much of the year and cool them in summer, taking load off the boiler. A full switch away from gas is possible with good insulation and a separate hot water solution, because most air to air systems do not heat water.

The Boiler Upgrade Scheme lists a £2,500 grant for eligible air to air heat pumps in homes in England and Wales (gov.uk). The system must replace the existing fossil fuel or electric heating, be sized for the full heating need and be installed by an MCS certified installer. As of 20 October 2026, the Energy Saving Trust says there are no MCS certified air to air installers yet. Our guide to air to air heat pump running costs shows how to compare it with gas.

Quiet units for close neighbours

Even in suburban Barnet, the neighbour’s window can be close. On a semi, the side passage is often the obvious place for an outdoor unit, but it may sit a short distance from the attached neighbour’s kitchen or the other side’s bedroom window. The MCS 020 calculation checks every neighbouring habitable room window, at ground and upper floors, against the 37 dB(A) limit. Distance, a solid fence or wall in the line of sight and avoiding tight corners all help.

Next steps

Tell us whether your home is a semi, detached house or flat, whether it is in Hampstead Garden Suburb or another conservation area, and which rooms you want cooled. Our Barnet area page and home air conditioning page explain how the survey and install run.