Solar panels, heat pumps and insulation in Thornbury conservation area
In the Thornbury conservation area (South Gloucestershire), 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 88 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. 334 homes inside the boundary have an energy certificate: 25.1% are solid-wall homes with no wall insulation, 50.9% heat with a gas boiler and 47.0% are rated D–G; 14 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
334homes with an energy certificate
25.1%solid walls, no insulation
50.9%heated by a gas boiler
14heat pumps
Article 4: South Gloucestershire publishes its Article 4 areas on planning.data.gov.uk and none overlaps this area; a direction can still exist on paper, so check with the council.
What needs planning permission in Thornbury
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: 88 in the area (grade I: 4, II*: 4). 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: 62% 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 = 334)
Walls
Homes
Share
Modern wall (U-value from the design)
107
32.0%
Solid wall (brick or stone), no insulation
84
25.1%
Cavity wall, filled
47
14.1%
Cavity wall, insulated (as built or unspecified)
45
13.5%
Cavity wall, unfilled
30
9.0%
Timber frame
6
1.8%
Cavity wall, partly insulated
5
1.5%
Solid wall, internal insulation
5
1.5%
Solid wall, insulated
3
0.9%
Cavity wall, internal or external insulation
1
0.3%
Other or not known
1
0.3%
Heating
Homes
Share
Gas boiler
170
50.9%
Communal heating
86
25.7%
Electric (storage heaters, panels, boiler)
64
19.2%
Heat pump
14
4.2%
Loft / roof insulation
Homes
Share
No insulation
24
7.2%
Under 200 mm
72
21.6%
200 mm or more
52
15.6%
Insulated (depth not recorded)
28
8.4%
Flat or other home above
78
23.4%
Other
80
24.0%
Windows
Homes
Share
Double glazed
292
87.4%
Single glazed
31
9.3%
Secondary glazing
9
2.7%
Triple glazed
2
0.6%
BCDE
Energy rating: B 85 (25.4%) · C 92 (27.5%) · D 96 (28.7%) · E 52 (15.6%) · F 6 (1.8%) · G 3 (0.9%). Houses and bungalows: 38% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: before 1900. Designated: 31 July 1975.
Compared with South Gloucestershire and England
Share of homes
Thornbury
All 30 areas in South Gloucestershire
England
Solid walls, no insulation
25.1%
41.3%
48.7%
Gas boiler
50.9%
56.2%
66.4%
Rated D–G
47.0%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 44% of these are from 2020 or later (latest 11 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 South Gloucestershire if in doubt.
Boundary: South Gloucestershire Council via planning.data.gov.uk (entity 44006141, reference 20512, 58.9 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.