Solar panels, heat pumps and insulation in Old Town West conservation area
In the Old Town West 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 but deals with other things (such as changes of use); it does not change the rules below. The area has 48 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. 286 homes inside the boundary have an energy certificate: 15.7% are solid-wall homes with no wall insulation, 39.5% heat with a gas boiler and 47.2% are rated D–G; 0 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
286homes with an energy certificate
15.7%solid walls, no insulation
39.5%heated by a gas boiler
0heat pumps
Article 4: An Article 4 direction published by Southampton covers this area but deals with other things (such as changes of use); it does not change the rules below. (HMO)
What needs planning permission in Old Town West
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
No permission needed (permitted development)
Part 1 Class A, A.3(a)
Listed buildings: 48 in the area (grade I: 7, II*: 7). 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 = 286)
Walls
Homes
Share
Cavity wall, filled
109
38.1%
Cavity wall, insulated (as built or unspecified)
48
16.8%
Solid wall (brick or stone), no insulation
45
15.7%
Cavity wall, unfilled
33
11.5%
Cavity wall, partly insulated
16
5.6%
Other or not known
13
4.5%
Timber frame
12
4.2%
Solid wall, internal insulation
7
2.4%
Solid wall, insulated
2
0.7%
Solid wall, external insulation
1
0.3%
Heating
Homes
Share
Gas boiler
113
39.5%
Communal heating
91
31.8%
Electric (storage heaters, panels, boiler)
82
28.7%
Loft / roof insulation
Homes
Share
No insulation
19
6.6%
Under 200 mm
42
14.7%
200 mm or more
38
13.3%
Insulated (depth not recorded)
35
12.2%
Flat or other home above
152
53.1%
Windows
Homes
Share
Double glazed
258
90.2%
Single glazed
21
7.3%
Secondary glazing
7
2.4%
CD
Energy rating: B 6 (2.1%) · C 145 (50.7%) · D 115 (40.2%) · E 19 (6.6%) · F 1 (0.3%). Houses and bungalows: 14% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 1976-1982. Designated: 19 October 1972.
Compared with Southampton and England
Share of homes
Old Town West
All 21 areas in Southampton
England
Solid walls, no insulation
15.7%
16.0%
48.7%
Gas boiler
39.5%
42.8%
66.4%
Rated D–G
47.2%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 60% of these are from 2020 or later (latest 15 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 Southampton if in doubt.
Boundary: Southampton City Council via planning.data.gov.uk (entity 44015951, reference 155, 6.9 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.