External air conditioning condensers and air source heat pumps: planning permission, noise management, and alternative options

Rod Mclean
Design Consultant

Are you looking to install a new comfort cooling system or replace your boiler with a heat pump but are unsure whether you need planning permission for the external unit?

At Calibre we have an experienced design team to assist you with all the issues surrounding planning permission, and noise levels.

External air conditioning condensers

More building owners are installing air conditioning for the benefits of comfort and indoor air quality. Air conditioning works by transferring heat from inside to outside using a liquid refrigerant. This requires an external unit called a condenser which must be installed somewhere near the building with access to plenty of fresh air.

External air source heat pumps

An air-source heat pump is an alternative way to heat your home and has an important role to play in achieving Government targets on reducing CO2 emissions. It absorbs heat from the outside air within an external heat pump and releases this into the building. They look similar to air conditioning condensers and their size depends on how much heat they need to generate, the more heat, the bigger the heat pump.

Will I need planning permission?

Planning permission is an approval that is needed by your local planning authority before construction, extensions, or even demolition can begin. You will probably need it if you build something new or make a major change to your building such as changing the use of your building or building an extension.

If you are looking to upgrade your building by installing air conditioning or a heat pump you should first check out whether you need planning permission for the external unit.

If your building project requires planning permission and you carry out the work without it you can be served an enforcement notice either ordering you to undo the work you have done or to apply for planning permission retrospectively.

What are my permitted development rights?

Some types of heating and cooling installations do not need planning permission under permitted development rights. These include the installation of air-source heat pumps in residential properties in England and Scotland up to a volume of 0.6 cubic metres. They must be installed at least one metre from the property boundary, must not be installed on a pitched roof and if installed on a flat roof must be at least one metre from the edge of the building. In addition, they must not be installed on a wall that fronts a highway.

You should check with your local planning authority what permitted development rights you have on your property as there are exclusions in listed buildings and buildings in protected areas, and permitted development rights can be removed within a planning condition if some major work has already been undertaken on the property. Gov.uk has a useful website that will help you find your local council https://www.gov.uk/find-local-council and where guidance on local planning laws may be found.

Noise levels and planning permission

The other consideration when installing an air conditioning unit or air source heat pump is the noise the external unit may generate. This noise may be deemed to be an issue for neighbours, particularly in city areas. Most manufacturers provide noise level data which typically will be between 40 – 60 decibels at a 1m distance, although this will depend on how intensely the unit is operating. By means of comparison a standard modern domestic fridge will run at around 45 decibels and a typical busy London borough during the daytime may exceed 60 decibels.

However, your unit may run during the quiet times of the evening or night time and consideration should be given to close neighbours. If you are thinking of sitting the external condenser or heat pump near a neighbouring property you may need to consider an acoustic enclosure. If you have had to apply for planning permission, noise levels may be one of the planning conditions you have to comply with.


What are acoustic enclosures?

External acoustic enclosures for silent air conditioning concealed behind a secondary fence in a London conservation area

Acoustic enclosures for external air conditioning condensers and air source heat pumps will help to reduce noise pollution without reducing the airflow or affecting the efficiency of their operation. They will also provide additional visual screening and maybe polyester powder painted to any standard BS or RAL colour. They will also provide additional weatherproofing and security.

The main components are acoustic panels and louvres, attenuators and access panels for maintenance. They are generally designed specifically for the project and can accommodate virtually any make or size of unit on the market today.

The only disadvantage is that they are quite bulky and will increase the footprint of your unit by at least three times and have a price range from £1,500 to £8,000 depending on the size and noise level reduction you require so you will need to consider this in your project budget.

An alternative option for air conditioning

An alternative option for air conditioning that will not require any planning consideration or cause any external noise issues is a water-cooled condenser unit. They are ideal for installation in apartments, listed buildings, and properties with limited space. They operate differently from standard comfort cooling systems as the condenser unit is installed within the property and uses mains water to absorb the heat drawn from the space within the refrigerant pipework.


Chelsea, I Terrace Mews

Rod Mclean

Rod just loves a finished project. Because it means he can re-tell to the industry what Calibre does, why, and how we do it. Being closely involved in all main areas of the business during his career has given him a holistic view of how Calibre approach new and existing customers, communicate with the market, and which new ideas to get excited about.

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