Photo by Architecture for London
While gas central heating is fully enclosed inside the building, an air source heat pump – 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 Areas without an Article 4 Direction limiting heat pump installations, you can still carry out the works 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.
According to MCS document 020, for a unit with a typical sound level of 60dB, where it is mounted on the ground within 1 metre of a wall, or on the wall within 1 metre of the ground, the minimum distance it can be to the nearest assessment point (a point 1 metre from the centre of your neighbour’s window) is 8 metres.
The distance can reduce to 1 metre if your unit does not have a line of sight from the assessment point and exceed 42dB.
These standards can be challenging to meet in built-up areas. Although a government review has recommended removing these noise restrictions, they remain in place until at least the summer of 2024. If you cannot meet MCS planning standards you will require planning permission.
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 where Article A 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 sensitive areas such as Areas of Outstanding Natural Beauty (AONBs) or sites of special scientific interest (SSSI) or archaeological interest, 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 aligns with permitted development guidelines, you can seek confirmation by applying to your local authority 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.
It is usually recommended to align with permitted development guidelines for your heat pump installation whenever feasible, as obtaining planning permission can be significantly more onerous.
Understanding the steps outlined above will better prepare you for your heat pump installation.
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.
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.
