Solar panels, heat pumps and insulation in Carlton Crescent conservation area
In the Carlton Crescent conservation area (Southampton), 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 Southampton covers this area and removes permitted development rights for solar panels on the house, replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), chimneys, flues and soil pipes, painting the outside, so there these need planning permission too. The area has 38 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. 429 homes inside the boundary have an energy certificate: 26.3% are solid-wall homes with no wall insulation, 38.9% heat with a gas boiler and 40.8% are rated D–G; 8 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
429homes with an energy certificate
26.3%solid walls, no insulation
38.9%heated by a gas boiler
8heat pumps
Article 4: An Article 4 direction published by Southampton covers this area and removes permitted development rights for solar panels on the house, replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), chimneys, flues and soil pipes, painting the outside, so there these need planning permission too. (Carlton Crescent Conservation Area; HMO)
What needs planning permission in Carlton Crescent
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)
Planning permission needed (an Article 4 direction here removes this right)
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)
Planning permission needed (an Article 4 direction here removes this right)
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: 38 in the area. 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: 86% 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 = 429)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
113
26.3%
Modern wall (U-value from the design)
95
22.1%
Cavity wall, insulated (as built or unspecified)
71
16.6%
Cavity wall, partly insulated
48
11.2%
Cavity wall, unfilled
35
8.2%
Timber frame
25
5.8%
Cavity wall, internal or external insulation
18
4.2%
Solid wall, insulated
12
2.8%
Cavity wall, filled
4
0.9%
Solid wall, internal insulation
4
0.9%
Other or not known
2
0.5%
Solid wall, external insulation
1
0.2%
Solid wall, partly insulated
1
0.2%
Heating
Homes
Share
Electric (storage heaters, panels, boiler)
224
52.2%
Gas boiler
167
38.9%
Communal heating
29
6.8%
Heat pump
8
1.9%
LPG
1
0.2%
Loft / roof insulation
Homes
Share
No insulation
37
8.6%
Under 200 mm
32
7.5%
200 mm or more
28
6.5%
Insulated (depth not recorded)
64
14.9%
Flat or other home above
238
55.5%
Other
30
7.0%
Windows
Homes
Share
Double glazed
358
83.4%
Single glazed
68
15.9%
Secondary glazing
3
0.7%
BCDE
Energy rating: B 74 (17.2%) · C 180 (42.0%) · D 126 (29.4%) · E 45 (10.5%) · F 1 (0.2%) · G 3 (0.7%). Houses and bungalows: 14% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: before 1900. Designated: 19 October 1972.
Compared with Southampton and England
Share of homes
Carlton Crescent
All 21 areas in Southampton
England
Solid walls, no insulation
26.3%
16.0%
48.7%
Gas boiler
38.9%
42.8%
66.4%
Rated D–G
40.8%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 53% of these are from 2020 or later (latest 21 September 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 Southampton if in doubt.
Boundary: Southampton City Council via planning.data.gov.uk (entity 44015937, reference 141, 8.6 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.