An air source heat pump installation by Architecture for London.
While gas central heating is fully enclosed inside the building, an air source heat pump (ASHP) – the most common type of heat pump in the UK – requires an outdoor unit.
A frequently asked question by homeowners is, do air source heat pumps require planning permission?
In many cases, they can be installed without planning permission. However, if you live in a historic building or a built-up area, restrictions may apply. Refer to our 3-step guide below to gain a clearer understanding of what might be feasible for your home.
The first step is to determine if your property has permitted development (PD) rights, a national grant allowing certain building work without planning permission.
PD rights generally apply to most domestic properties, including houses and flats. However, in designated areas like Conservation Areas, National Parks, Areas of Outstanding Natural Beauty, the Broads, or World Heritage Sites, additional planning controls known as Article 4 Directions may be in place. These limit development that can be carried out without planning permission.
If you live in a Conservation Area without an Article 4 Direction, you can still install a heat pump under permitted development, only a few additional rules apply – more on these below. Check with your local authority to see if there are any restrictions in your local area.
PD rights do not extend to listed buildings. Here, you will need to apply for Listed Building Consent.
If PD rights apply, the second crucial step is to engage a Microgeneration Certification Scheme (MCS) regulated installer who will conduct a survey of your property and design the heat pump system. This assessment will determine whether the location, size, and performance of the outdoor unit (commonly referred to as the compressor) complies with MCS Planning Standards – a pre-condition for permitted development and the Boiler Upgrade Scheme.
A key factor in locating an ASHP in a built-up area is noise.
MCS document 020 states that an ASHP cannot exceed 42dB at a distance of 1 metre from the centre of a neighbour’s habitable room window, known as the ‘assessment point’. This requirement can make it challenging to find a suitable installation location, as a typical unit produces around 60dB, which may necessitate a significant distance to meet noise limits.
The distance required between the ASHP and the assessment point depends on:
The ideal setup is a quiet unit with only one nearby surface, a solid boundary wall concealing the unit, and no direct line of sight from the unit to the habitable window.
Although a government review has recommended lifting these noise restrictions, they still remain in place at the time of writing. If your ASHP cannot meet MCS noise standards, planning permission will be required.
MCS Planning Standards state that the noise level of an air source heat pump cannot exceed 42dB at 1 metre from a neighbouring window.
Finally, to install a heat pump without planning permission, you will need to meet permitted development guidelines.
In England, heat pump installations fall under Class G of the GDPO, allowing you to install, alter or replace an air source heat pump on a residential property without planning permission.
If your property has PD rights, the rules are as follows:
Conservation Areas and World Heritage Sites
If you live in a Conservation Area or World Heritage Site and Article 4 Directions do not restrict heat pump installations, the heat pump cannot be installed:
Permitted development variations elsewhere in the UK
In Scotland and Northern Ireland, the only size restriction on the external compressor is height; it cannot be taller than 3 metres. All other rules apply.
In Wales, the compressor can be up to 1 cubic metre in volume but must be installed at least 3 metres from the site boundary – a significant constraint in a built up areas.
Permitted development rules for the location of an air source heat pump.
Generally, other types of heat pumps do not require planning permission.
Ground source heat pumps (GSHP) are classed as permitted development. However, in sites of special scientific interest (SSSI) or archaeologically sensitive areas, planning permission may be required for the excavation works.
In Northern Ireland, permitted development rules state that no part of the ground source heat pump can be within 3 metres of a boundary and the external unit must not exceed 4 metres in height.
If you are planning to install a water source heat pump (WSHP), consult your respective environment agencyto ascertain if any licenses are required.
If you're unsure whether your proposed heat pump installation falls under permitted development guidelines, you can seek confirmation from your local authority by applying for a lawful development certificate (LDC).
If your LDC application is deemed 'lawful’, you can proceed with confidence knowing that your plans comply with guidelines. If it’s deemed 'unlawful,' the local authority will detail where your proposals are noncompliant. At this point, you can either modify your plans or apply for planning permission.
Comply with permitted development guidelines whenever you can, as gaining planning permission is usually a lot more onerous.
Understanding the steps outlined above will better prepare you for your heat pump installation.
The information provided in this article is intended for general guidance and educational purposes only. At Designs in Detail, we advise you appoint a skilled residential architect to provide specific expert advice for your project.
About the author
Aron Coates is an architect with over two decades of experience, encompassing projects ranging from the restoration of historic buildings to the design of contemporary homes.
