Air conditioning units on a house: which rights apply

There is no permitted development class written for an air conditioning unit on a house, which is why the air conditioning unit house planning permission question has no clean yes or no. Part 14 of Schedule 2 to the GPDO 2015 grants rights for microgeneration equipment, including air source heat pumps installed to provide heating. A cooling-only condenser is not that. So the position falls back on whether installing it amounts to development at all under section 55 of the Town and Country Planning Act 1990, and that is a judgement your authority makes.

Why cooling units sit outside the microgeneration rights

Part 14 exists to make domestic renewables easier. Its classes cover solar equipment, ground and water source heat pumps and air source heat pumps, each with limits on size, siting and noise, and the air source heat pump class has been amended more than once. Check the current consolidated text of Part 14 on legislation.gov.uk rather than a summary, because the limits have moved.

A reversible air-to-air system installed to heat the house can sit within the heat pump class, provided the equipment and the installation meet the conditions that apply. A unit installed purely to cool does not, because the class is about generating heat from a renewable source.

That difference is worth pressing with your installer. If the specification and the installation do provide heating, the heat pump route may be available, and it comes with a defined set of limits instead of a judgement call.

Whether a condenser is development

Section 55 defines development to include building operations, and it excludes works which affect only the interior of a building or which do not materially affect its external appearance.

A small condenser on a rear wall, below eaves level, invisible from the street, is often treated as not materially affecting external appearance. The same unit on a front elevation, or a pair of units on a flank wall visible along the street, almost certainly does affect it.

Class A of Part 1 can also assist, because it covers the improvement or other alteration of a dwellinghouse. The difficulty is condition A.3(a), which requires materials used in exterior work to be of similar appearance to the existing exterior, and a grey metal and plastic condenser is not of similar appearance to brick.

Here is the honest position: the law is unsettled for the middle cases, practice varies between authorities, and nobody can tell you from a desk whether your installation is development. The only formal way to confirm that works are lawful is a lawful development certificate under section 192 of the 1990 Act, and on a contested street that is money well spent.

Position, size and visibility from a highway

Whatever route applies, the same design points decide whether the authority is comfortable.

• Put the unit on a rear or concealed flank elevation rather than the frontage.
• Keep it at ground level where possible, because a unit at first floor is both more visible and more audible from neighbouring windows.
• Set it as far as the pipework allows from the nearest neighbouring window and from any boundary with a garden in use.
• Screen it with a louvred timber enclosure that allows the airflow the unit needs, rather than a solid box that causes it to work harder and run louder.
• Avoid mounting on a party wall or on a wall shared with a neighbouring habitable room, where structure-borne noise travels.

Size is relevant for a different reason. Larger systems serving whole-house cooling need bigger external units or several of them, and a bank of three condensers on a suburban flank wall is a different proposition from a single unit serving one bedroom.

Noise and the statutory nuisance position

Noise is where these installations actually go wrong. Planning control, if an application is needed, deals with amenity at the point of decision. Separately and permanently, a unit that causes a noise nuisance can be the subject of action by the authority's environmental health team under the statutory nuisance provisions of the Environmental Protection Act 1990, regardless of whether planning permission was ever needed.

That is worth repeating to clients. A permitted installation is not immune from an abatement notice.

The assessment method authorities recognise is BS 4142, which compares a rating level for the specific sound, with corrections for tonal and impulsive character, against the measured background sound level at the nearest noise-sensitive window. Night-time background levels in a quiet suburb are low, and a unit running at night to cool a bedroom is being assessed against that low background.

Practical steps that help: specify a unit with a published sound power level and a night or quiet mode, use anti-vibration mounts, and avoid siting it where a hard surface reflects sound towards a neighbour. Where the authority asks for evidence, a Noise Impact Assessment sets out the method and the mitigation.

Conservation areas and listed buildings

On article 2(3) land, which covers conservation areas, National Landscapes, National Parks, the Broads and World Heritage Sites, the tolerance for visible external plant drops sharply, and the Part 14 heat pump class carries additional restrictions on designated land.

For a listed building, listed building consent is required for works affecting its character as a building of special architectural or historic interest, and fixing a condenser to an elevation will normally need it. Permitted development rights do not displace that requirement, and carrying out such works without consent is a criminal offence rather than a planning breach to be tidied up later. The case for a discreet installation on a listed building is made through a Heritage Statement that explains the effect on significance and how the work could be reversed.

An Article 4 direction can also remove Class A rights in ordinary residential streets, and a number of authorities have made directions covering frontages. Check before you order the equipment.

Flats and leasehold restrictions

Part 1 of Schedule 2 applies to dwellinghouses. A flat is not a dwellinghouse, so none of the householder permitted development rights are available, and an external condenser on a flat needs planning permission unless the installation does not materially affect external appearance.

And then there is the lease. Most residential leases prohibit alterations to the exterior or to the structure without the landlord's written consent, and many prohibit penetrating the external wall at all. Freeholder consent is a separate permission from planning permission, and neither substitutes for the other.

For a block, the sensible route is a building-wide strategy agreed with the management company, with a single approved location and specification, rather than individual units appearing one at a time.

What an application should include

Where an application is the right answer, keep it tight and make the officer's job easy.

1. Existing and proposed elevations at 1:50 or 1:100 showing the unit in position, with dimensions.
2. A site plan marking the unit, the nearest neighbouring habitable windows and the distances between them.
3. The manufacturer's data sheet, with the sound power level and any quiet mode stated.
4. A short noise statement comparing the predicted rating level with the measured background at the nearest sensitive window.
5. Details of screening, mounts and pipework routing.
6. Photographs of the elevation as existing.

Most refusals on these applications cite noise or visual impact on a frontage, and both are answerable with evidence rather than assertion. The design reasoning belongs in a short Planning Statement, and the equivalent position for commercial premises is set out in air conditioning condensers on commercial buildings.

This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it, and remember that a lawful development certificate is the only formal way to confirm that works are lawful. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.