Heat pumps in flats: planning, noise and shared services
A heat pump in a block has to clear Class G limits, a noise assessment to habitable rooms in the same building, and a licence to alter from the freeholder.
Heat pump flats planning is a different problem from fitting a unit to a semi. The outdoor unit has to go somewhere that is not someone's balcony, the noise is received by habitable rooms in the same building as well as next door, and the person who wants the installation often does not own the wall it would be fixed to. Permitted development rights can help, but they help less often in a block than people expect, and the lease usually bites before planning does.
Settle three questions before drawing anything. Who owns the external fabric, where can a unit sit without a habitable room window within a few metres, and is the building served by one plant room or 30 individual systems.
Why a block of flats is harder than a house
A house has a rear garden, a flank wall and a single owner. A block has a demise line that usually stops at the internal face of the external wall, a management company with an alterations covenant, neighbours above and below rather than beside, and a roof that may already carry tanks, lift motors and a communal aerial.
The acoustic geometry changes too. A unit on a rear elevation of a house points at a garden. A unit on a balcony in a block points at the glazing of the flat next door, three metres away, and the sound reflects off the soffit and the balustrade back into the receiving room. Reverberant build up in a recessed balcony or a lightwell is the single most common reason a flat installation fails a noise assessment.
Then there is the question of 30 units all doing the same thing. One heat pump on one balcony may be unobjectionable. Thirty, with no coordinated position or specification, changes the appearance of the building and the background sound level in the courtyard.
The permitted development position
Air source heat pumps on domestic premises sit in Schedule 2 Part 14 of the Town and Country Planning (General Permitted Development) (England) Order 2015, under Class G. That class has been amended more than once in recent years, including changes to the volume limit for the outdoor unit and to the siting restriction near a boundary, so read the current consolidated text on legislation.gov.uk before advising anyone. The position stated here is general and the detail should be checked as at the date you are working.
The conditions that matter in a block are consistent across versions. The right is exercisable in relation to a dwellinghouse or a block of flats, so a flat above a shop in a mixed use building is usually outside it. The installation must be used solely for heating purposes. The unit must be sited so as to minimise its effect on the external appearance of the building and on the amenity of the area. And it must be installed in accordance with the MCS planning standard, which sets a sound limit assessed one metre from the nearest habitable room window of a neighbouring property, calculated at 42 dB.
Permitted development rights fall away in several situations that are common in blocks: a listed building, a flat created by a prior approval conversion where the approval removed rights, an Article 4 direction over a conservation area, and any site where a planning condition on the original permission restricts external plant. On a flat roof the practical restriction is often the condition about the pitched roof slope and the height above the eaves rather than the roof itself.
Siting options and what each one costs you
| Position | Planning difficulty | Usual objection |
|---|---|---|
| Communal grounds, screened enclosure | Lower, but needs landlord consent and pipe routes | Loss of amenity space and pipework through the structure |
| Flat roof, set back from the parapet | Moderate | Visibility from the street and structure borne noise to the top floor |
| Balcony, floor standing | Higher | Reverberant noise and loss of usable amenity area |
| Wall bracket on a rear elevation | Higher | Appearance and vibration transmission into the wall |
| Shared ground array with a plant room | Lowest in planning terms | Capital cost and the space the plant room occupies |
The two options that survive scrutiny most often are the screened ground enclosure and the plant room serving a shared system. Both involve the freeholder, which is why the planning conversation and the lease conversation have to run together.
Balconies deserve particular caution. A floor standing unit eats into a minimum amenity area that the original permission probably conditioned, and in buildings where material restrictions apply to balconies the enclosure specification is constrained as well. Unit selection matters here too, and our note on refrigerant choice and global warming potential in planning explains why the specification sheet is worth reading before the position is fixed.
Noise to the nearest habitable room
Where the installation falls outside permitted development, the authority will want an assessment against BS 4142 for the rating level and BS 8233 for internal levels in the receiving rooms. The sensitive receptor in a block is frequently in the same building, which means structure borne transmission has to be considered alongside airborne sound.
The measures that make a scheme work are specification rather than screening. Anti-vibration mounts sized for the unit, flexible pipe connections, a bracket detail that does not bridge directly to a party structure, acoustic louvres on an enclosure, and a unit selected for its night time sound power rather than its headline figure. Night time is the test that matters, because heating demand and sleep overlap.
A Noise Impact Assessment for a communal system should model the plant as a single source with its enclosure, not as a catalogue figure. Where individual units are proposed across a building, model the cumulative case as well as the single unit case, because an officer will ask what happens when every flat takes up the option.
Illustrative example: a 24 flat block proposes a roof mounted cascade behind a 1.8 metre acoustic screen set back 2 metres from the parapet, with the nearest habitable room window being a top floor bedroom four metres below. The assessment models the cascade at full output at night, applies a correction for the tonal character of the fans, and specifies spring isolators under the frame. Figures are illustrative only.
Communal plant against unit by unit systems
A communal system gives one planning application, one acoustic case, one set of conditions and one maintenance contract. It also gives one point of failure, a Heat Network billing obligation, and a service charge line that leaseholders will scrutinise. Where the block has an existing communal boiler and risers, it is usually the better route, and the existing plant room space is the reason.
Individual systems give each leaseholder control and let the building convert gradually. The planning cost is that the first application sets a precedent the authority has to live with, so officers often prefer to deal with a building wide strategy even when each installation would be permitted development. Offering a strategy document voluntarily, with a drawing showing the approved position and specification for every flat, usually gets a better outcome than 30 separate conversations.
Where a district heating connection is a realistic prospect, consider whether the building should be designed to accept it later. Our note on safeguarding a future heat network connection covers the plant space and pipe route reservations that make that possible.
Leases, service charges and who owns the wall
Most long leases demise the internal surfaces and reserve the external walls, roof and structure to the landlord. A leaseholder therefore has no right to fix a unit to the outside of the building without a licence to alter, however favourable the planning position is. Section 20 consultation obligations can also apply where the landlord carries out works recharged through the service charge above the statutory threshold.
Get the licence to alter and the planning position resolved in the same month. An installer who has been paid a deposit and has a delivery date will push for a start, and a unit fitted without a licence is a forfeiture risk that no planning consent cures. Say this in writing to the client early.
Conditions and commissioning evidence
Expect conditions requiring approval of the unit make and model, the enclosure or screen details, the anti-vibration specification, and a post-installation verification report demonstrating the predicted rating level has been achieved. Build the verification into the contract so the commissioning engineer attends with the acoustician rather than six weeks later.
Keep the file. The documents that matter two years on are the approved drawings, the acoustic report, the commissioning certificate, the MCS certificate where permitted development was relied on, and the licence to alter. An Energy Statement prepared for the application should reference them so the consent, the lease and the plant all describe the same installation.
Start with the ownership plan and the lease, then the acoustics. Browse all 66 PlanScope report types to see which documents a plant installation in a block typically needs, and have any draft reviewed before submission. PlanScope provides AI-assisted draft reports for planning applications. We do not guarantee planning approval. This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
Frequently asked questions
Do permitted development rights cover heat pumps on flats?
Class G of Schedule 2 Part 14 of the General Permitted Development Order can apply to a block of flats as well as a house, but the class has been amended more than once, so read the current consolidated text. Rights commonly fall away for listed buildings, Article 4 areas, mixed use buildings and conversions whose prior approval removed them.
What noise limit applies to a permitted development installation?
The MCS planning standard referenced by Class G sets a calculated sound limit of 42 dB assessed one metre from the nearest habitable room window of a neighbouring property. Where the installation needs planning permission instead, the authority will normally want a BS 4142 rating assessment with internal levels judged against BS 8233 for the receiving rooms.
Can I put a heat pump on my balcony?
Sometimes, but it is the hardest position to defend. A recessed balcony reflects sound off the soffit and balustrade into neighbouring glazing, a floor standing unit reduces the minimum amenity area the original permission conditioned, and buildings with material restrictions on balconies limit what enclosure you can build. Check the lease as well.
Is a communal system better than individual units?
In planning terms usually yes. One application, one acoustic case and one set of conditions beat thirty separate conversations, and an existing plant room and risers make retrofit easier. The trade offs are capital cost, heat network billing obligations and a service charge line that leaseholders will examine closely.
Does the freeholder have to agree?
Almost always. Long leases typically demise internal surfaces only and reserve external walls, roof and structure to the landlord, so a leaseholder needs a licence to alter before fixing anything outside. Planning permission does not override that, and an installation without a licence creates a forfeiture risk that no consent resolves.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.