Solar panels, heat pumps and insulation in Lewes conservation area
In the Lewes conservation area (South Downs National Park Authority), 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 503 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. 2,261 homes inside the boundary have an energy certificate: 45.7% are solid-wall homes with no wall insulation, 82.1% heat with a gas boiler and 64.7% are rated D–G; 17 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
2,261homes with an energy certificate
45.7%solid walls, no insulation
82.1%heated by a gas boiler
17heat pumps
Article 4: South Downs National Park Authority does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Lewes
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: 503 in the area (grade I: 7, II*: 21). 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: 34% 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 = 2,261)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
1,034
45.7%
Cavity wall, unfilled
290
12.8%
Cavity wall, insulated (as built or unspecified)
280
12.4%
Cavity wall, filled
187
8.3%
Timber frame
169
7.5%
Modern wall (U-value from the design)
112
5.0%
Solid wall, internal insulation
48
2.1%
Solid wall, insulated
42
1.9%
Other or not known
41
1.8%
Cavity wall, partly insulated
31
1.4%
Cavity wall, internal or external insulation
17
0.8%
Solid wall, partly insulated
8
0.4%
Solid wall, external insulation
2
0.1%
Heating
Homes
Share
Gas boiler
1,856
82.1%
Electric (storage heaters, panels, boiler)
370
16.4%
Heat pump
17
0.8%
Communal heating
8
0.4%
Solid fuel (wood, coal)
5
0.2%
Oil
3
0.1%
Other
2
0.1%
Loft / roof insulation
Homes
Share
No insulation
470
20.8%
Under 200 mm
518
22.9%
200 mm or more
327
14.5%
Insulated (depth not recorded)
408
18.0%
Flat or other home above
431
19.1%
Other
107
4.7%
Windows
Homes
Share
Double glazed
1,646
72.8%
Single glazed
441
19.5%
Secondary glazing
169
7.5%
Triple glazed
5
0.2%
CDE
Energy rating: A 2 (0.1%) · B 129 (5.7%) · C 667 (29.5%) · D 910 (40.2%) · E 445 (19.7%) · F 81 (3.6%) · G 27 (1.2%). Houses and bungalows: 66% of the homes; solar panels on 0.5% of the certificates. Most common build period on the certificates: before 1900. Designated: 5 June 1970.
Compared with South Downs National Park Authority and England
Share of homes
Lewes
All 124 areas in South Downs National Park Authority
England
Solid walls, no insulation
45.7%
47.0%
48.7%
Gas boiler
82.1%
54.9%
66.4%
Rated D–G
64.7%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 47% of these are from 2020 or later (latest 26 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 South Downs National Park Authority if in doubt.
Boundary: South Downs National Park Authority via planning.data.gov.uk (entity 44005296, reference 3207, 136.1 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.