Solar panels, heat pumps and insulation in Westerham conservation area
In the Westerham conservation area (Sevenoaks), 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. The area has 104 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. 285 homes inside the boundary have an energy certificate: 57.2% are solid-wall homes with no wall insulation, 90.2% heat with a gas boiler and 67.0% are rated D–G; 1 has 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
285homes with an energy certificate
57.2%solid walls, no insulation
90.2%heated by a gas boiler
1heat pumps
Article 4: Sevenoaks does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Westerham
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), unless an Article 4 direction removes it — check with the council
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), unless an Article 4 direction removes it — check with the council
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)
Prior approval of appearance from the council, unless an Article 4 direction removes it — check with the council
Replacement windows and doors of similar appearance
No permission needed (permitted development), unless an Article 4 direction removes it — check with the council
Part 1 Class A, A.3(a)
Listed buildings: 104 in the area (grade I: 2, II*: 9). 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: 37% 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 = 285)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
163
57.2%
Cavity wall, insulated (as built or unspecified)
39
13.7%
Modern wall (U-value from the design)
29
10.2%
Timber frame
21
7.4%
Cavity wall, unfilled
15
5.3%
Solid wall, internal insulation
7
2.5%
Cavity wall, partly insulated
6
2.1%
Solid wall, insulated
4
1.4%
Cavity wall, filled
1
0.4%
Heating
Homes
Share
Gas boiler
257
90.2%
Electric (storage heaters, panels, boiler)
23
8.1%
Oil
3
1.1%
Heat pump
1
0.4%
Solid fuel (wood, coal)
1
0.4%
Loft / roof insulation
Homes
Share
No insulation
51
17.9%
Under 200 mm
78
27.4%
200 mm or more
45
15.8%
Insulated (depth not recorded)
52
18.2%
Flat or other home above
35
12.3%
Other
24
8.4%
Windows
Homes
Share
Double glazed
216
75.8%
Single glazed
36
12.6%
Secondary glazing
33
11.6%
CDE
Energy rating: B 5 (1.8%) · C 89 (31.2%) · D 119 (41.8%) · E 55 (19.3%) · F 16 (5.6%) · G 1 (0.4%). Houses and bungalows: 63% of the homes; solar panels on 0.4% of the certificates. Most common build period on the certificates: before 1900. Designated: 1 January 1973.
Compared with Sevenoaks and England
Share of homes
Westerham
All 41 areas in Sevenoaks
England
Solid walls, no insulation
57.2%
46.7%
48.7%
Gas boiler
90.2%
77.7%
66.4%
Rated D–G
67.0%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 48% of these are from 2020 or later (latest 21 October 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 Sevenoaks if in doubt.
Boundary: Sevenoaks District Council via planning.data.gov.uk (entity 44016735, reference CA18, 52.0 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.