Solar panels, heat pumps and insulation in St Marys conservation area
In the St Marys conservation area (Lewisham), external wall insulation needs planning permission, and so does an air source heat pump on a wall or roof facing the road; one at the back or side, internal and loft insulation and solar panels on a roof slope normally do not. An Article 4 direction published by Lewisham covers this area and removes permitted development rights for replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), painting the outside, so there these need planning permission too. The area has 10 listed buildings; on a listed building solar panels and heat pumps are not permitted development at all and need planning permission and listed building consent. 183 homes inside the boundary have an energy certificate: 47.5% are solid-wall homes with no wall insulation, 57.9% heat with a gas boiler and 41.5% are rated D–G; 32 have a heat pump. EPC register November 2026; rules as at 21 October 2026.
Data: EPC register November 2026 (latest certificate per home), conservation area boundaries 3 November 2026, permitted development rules as at 21 October 2026 · calculated 5 November 2026 · Methodology and sources
183homes with an energy certificate
47.5%solid walls, no insulation
57.9%heated by a gas boiler
32heat pumps
Article 4: An Article 4 direction published by Lewisham covers this area and removes permitted development rights for replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), painting the outside, so there these need planning permission too. (Lewisham Major Centre; Small HMO Northern Extension; St Mary's Conservation Area Article 4 Direction)
What needs planning permission in St Marys
Work (house, not listed)
In a conservation area
Rule
Air source heat pump on a wall or roof facing the road, or nearer the road than the house
Planning permission needed
Part 14 Class G, G.1(j)
Air source heat pump at the back or side (outdoor unit up to 1.5 m³, MCS Planning Standards, one per house — two on a detached house)
No permission needed (permitted development)
Part 14 Class G
Solar panels on a pitched roof (up to 0.2 m proud, not above the ridge)
No permission needed (permitted development)
Part 14 Class A, A.2(c)
Solar panels on a wall, balcony or roof enclosure facing the road
Planning permission needed
Part 14 Class A, A.2(e)
Solar panels on a flat roof (up to 0.6 m above the roof)
Replacement windows and doors of similar appearance
Planning permission needed (an Article 4 direction here removes this right)
Part 1 Class A, A.3(a)
Listed buildings: 10 in the area (grade I: 0, II*: 2). The table is for houses that are not listed: on a listed building, solar panels and air source heat pumps are not permitted development at all (they need planning permission), and any of these works needs listed building consent.
Flats: 87% of the certified homes here are flats or maisonettes. Homes in a block of flats have no householder rights for alterations; heat pumps and solar have their own, tighter rules for blocks of flats.
The homes in the area (latest certificate per home, n = 183)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
87
47.5%
Modern wall (U-value from the design)
33
18.0%
Other or not known
27
14.8%
Cavity wall, insulated (as built or unspecified)
14
7.7%
Solid wall, internal insulation
10
5.5%
Solid wall, insulated
6
3.3%
Timber frame
5
2.7%
Cavity wall, unfilled
1
0.5%
Heating
Homes
Share
Gas boiler
106
57.9%
Electric (storage heaters, panels, boiler)
37
20.2%
Heat pump
32
17.5%
Communal heating
8
4.4%
Loft / roof insulation
Homes
Share
No insulation
37
20.2%
Under 200 mm
16
8.7%
200 mm or more
4
2.2%
Insulated (depth not recorded)
17
9.3%
Flat or other home above
87
47.5%
Other
22
12.0%
Windows
Homes
Share
Double glazed
156
85.2%
Single glazed
15
8.2%
Secondary glazing
12
6.6%
BCDE
Energy rating: B 36 (19.7%) · C 71 (38.8%) · D 56 (30.6%) · E 19 (10.4%) · F 1 (0.5%). Houses and bungalows: 13% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 1900-1929. Designated: 1 January 1976.
Compared with Lewisham and England
Share of homes
St Marys
All 31 areas in Lewisham
England
Solid walls, no insulation
47.5%
69.0%
48.7%
Gas boiler
57.9%
85.5%
66.4%
Rated D–G
41.5%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 54% of these are from 2020 or later (latest 3 August 2026). “No insulation (assumed)” is the assessor's default for older walls.
The rules are England's national permitted development rules (General Permitted Development Order 2015, Schedule 2, as at 21 October 2026). They do not cover building regulations or a council's own conditions. This is not a planning decision: ask Lewisham if in doubt.
Boundary: London Borough of Lewisham via planning.data.gov.uk (entity 44014980, reference LEWCA16, 7.2 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.