Air conditioning in a London conservation area: what is allowed

Why this matters so much in central London

In much of central London, a conservation area is the normal case, not the exception. The council figures speak for themselves:

Borough	Conservation areas	Share of borough
Kensington and Chelsea	38	nearly three quarters (RBKC)
Westminster	56	over 76% (Westminster)
Camden	40	about half (Camden)
Hammersmith and Fulham	44	about half (LBHF)
Islington	42	around half (Islington)

So if you live in South Kensington, Chelsea, Notting Hill or Holland Park, assume you are in one until the council map says otherwise.

The street facing rule

The key rule comes from Class G of the permitted development order. On land in a conservation area, an air source heat pump must not be installed on a wall or roof which fronts a highway, and must not sit nearer to the road than the house itself. The Planning Portal sets this out alongside the other limits.

In practice, that rules out the front of the house, the front basement area facing the pavement, and the front roof slope. On a corner plot, a side wall facing the second street counts as fronting a highway too.

The rest of the limits still apply

A conservation area adds the street rule on top of the normal Class G limits. The unit must:

• also be used for heating, not only cooling
• meet the MCS 020(a) noise calculation of 37 dB(A) at a neighbour’s habitable room window
• be no bigger than 1.5 cubic metres on a house, 0.6 cubic metres on a block of flats
• be the only unit on a terraced or semi detached house (two on a detached house)
• not be on a pitched roof, and be at least 1 metre in from the edge of a flat roof
• not be at a listed building

An Article 4 direction can also remove permitted development rights in particular streets, so check with the council’s planning team.

Positions that usually work in Kensington and Chelsea

Kensington and Chelsea’s housing is mostly stucco and brick terraces, garden squares, mansion blocks and mews. Each has its own likely spots.

Stucco terraces

Many have a rear closet wing with a flat roof and a basement lightwell at the back. A unit on the closet wing roof, set back from the edge, or at the back of the lightwell often keeps it out of public view. The pipes can run inside to rooms at the front, so a front drawing room can still be cooled.

Mansion blocks

These are blocks of flats, so the one unit per block limit applies, and almost every lease needs freeholder consent. Most mansion block jobs end up as planning applications. Our freeholder consent guide covers what managing agents ask for.

Mews houses

Mews houses often front the cobbled mews itself, which is a highway, and have little or no rear space. The roof may be the only option, and only if it is flat and not visible. A planning application is common.

Noise rules in the Royal Borough

Kensington and Chelsea takes plant noise seriously. Its Local Plan says applications for noise generating plant, including air conditioning units and heat pumps, with an unacceptable noise and vibration impact will be resisted. Committee reports show the council approving roof units with acoustic enclosures where the numbers work. In a tight lightwell, sound bounces off the walls, and the MCS 020 method says a unit boxed in by more than three reflecting surfaces cannot meet the standard at all. Position is the whole game.

If you need an application

A clear application in a conservation area normally includes:

1. Photos of the rear elevation and the proposed position.
2. The unit’s make, model and dimensions, with a manufacturer’s image.
3. A plan showing the distance to neighbours’ windows.
4. The noise calculation, and details of any enclosure.
5. The pipe route, showing it is kept inside or in a painted cover on rear walls.

Councils are much more relaxed about a small, dark coloured unit tucked behind a parapet than a white box on a visible wall.

Listed buildings are different again

Many Kensington and Chelsea homes are also listed. Class G does not apply at a listed building at all, and you will need listed building consent for drilling through historic fabric, as well as planning. Our guide to air conditioning in a listed building explains how to keep the work reversible and discreet.

Colour, size and pipe covers

Small details change how a conservation officer sees a scheme. A compact outdoor unit is easier to hide behind a parapet or inside a lightwell than a large one, and some makers offer darker casings that sit better against London stock brick than bright white. Pipe covers on a rear wall can be painted to match the render or brick. Where pipes would cross a visible elevation, running them inside the building, through a ceiling void or a cupboard, is usually worth the extra work. None of this replaces the planning rules, but it often decides whether neighbours and the council are comfortable with the result.

What we do at the survey

We check the council map, look for an Article 4 direction, find positions out of public view, and run the noise numbers before recommending anything. Then we tell you plainly whether we think it is permitted development or an application. The Kensington and Chelsea area page covers the local housing in more detail, and the home air conditioning page shows how a job runs from survey to handover.