Solar panels, heat pumps and insulation in The Avenue conservation area
In the The Avenue 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 3 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. 364 homes inside the boundary have an energy certificate: 8.0% are solid-wall homes with no wall insulation, 74.2% heat with a gas boiler and 28.3% 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
364homes with an energy certificate
8.0%solid walls, no insulation
74.2%heated by a gas boiler
0heat 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. (HMO; The Avenue Conservation Area)
What needs planning permission in The Avenue
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: 3 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 = 364)
Walls
Homes
Share
Cavity wall, insulated (as built or unspecified)
126
34.6%
Modern wall (U-value from the design)
75
20.6%
Cavity wall, filled
53
14.6%
Cavity wall, unfilled
48
13.2%
Solid wall (brick or stone), no insulation
29
8.0%
Timber frame
18
4.9%
Other or not known
7
1.9%
Cavity wall, partly insulated
5
1.4%
Solid wall, insulated
3
0.8%
Heating
Homes
Share
Gas boiler
270
74.2%
Electric (storage heaters, panels, boiler)
88
24.2%
Communal heating
6
1.6%
Loft / roof insulation
Homes
Share
No insulation
16
4.4%
Under 200 mm
30
8.2%
200 mm or more
25
6.9%
Insulated (depth not recorded)
39
10.7%
Flat or other home above
202
55.5%
Other
52
14.3%
Windows
Homes
Share
Double glazed
334
91.8%
Single glazed
25
6.9%
Secondary glazing
5
1.4%
BCD
Energy rating: B 90 (24.7%) · C 171 (47.0%) · D 77 (21.2%) · E 21 (5.8%) · F 5 (1.4%). Houses and bungalows: 14% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 2007-2011. Designated: 2 January 1975.
Compared with Southampton and England
Share of homes
The Avenue
All 21 areas in Southampton
England
Solid walls, no insulation
8.0%
16.0%
48.7%
Gas boiler
74.2%
42.8%
66.4%
Rated D–G
28.3%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 48% of these are from 2020 or later (latest 28 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 Southampton if in doubt.
Boundary: Southampton City Council via planning.data.gov.uk (entity 44015945, reference 149, 13.0 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.