Solar panels, heat pumps and insulation in Downton conservation area
In the Downton conservation area (Wiltshire), 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 101 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. 290 homes inside the boundary have an energy certificate: 39.0% are solid-wall homes with no wall insulation, 63.4% heat with a gas boiler and 73.8% are rated D–G; 3 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
290homes with an energy certificate
39.0%solid walls, no insulation
63.4%heated by a gas boiler
3heat pumps
Article 4: Wiltshire 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 Downton
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: 101 in the area (grade I: 3, II*: 2). 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: 21% 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 = 290)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
113
39.0%
Cavity wall, insulated (as built or unspecified)
69
23.8%
Cavity wall, unfilled
37
12.8%
Cavity wall, filled
30
10.3%
Solid wall, insulated
15
5.2%
Solid wall, internal insulation
8
2.8%
Cavity wall, partly insulated
7
2.4%
Modern wall (U-value from the design)
4
1.4%
Timber frame
4
1.4%
Solid wall, partly insulated
2
0.7%
Cavity wall, internal or external insulation
1
0.3%
Heating
Homes
Share
Gas boiler
184
63.4%
Electric (storage heaters, panels, boiler)
87
30.0%
Oil
10
3.4%
Solid fuel (wood, coal)
4
1.4%
Heat pump
3
1.0%
Communal heating
2
0.7%
Loft / roof insulation
Homes
Share
No insulation
19
6.6%
Under 200 mm
91
31.4%
200 mm or more
83
28.6%
Insulated (depth not recorded)
57
19.7%
Flat or other home above
29
10.0%
Other
11
3.8%
Windows
Homes
Share
Double glazed
249
85.9%
Single glazed
22
7.6%
Secondary glazing
19
6.6%
CDE
Energy rating: A 1 (0.3%) · B 4 (1.4%) · C 71 (24.5%) · D 137 (47.2%) · E 58 (20.0%) · F 17 (5.9%) · G 2 (0.7%). Houses and bungalows: 79% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: before 1900. Designated: 31 December 1973.
Compared with Wiltshire and England
Share of homes
Downton
All 244 areas in Wiltshire
England
Solid walls, no insulation
39.0%
42.5%
48.7%
Gas boiler
63.4%
45.5%
66.4%
Rated D–G
73.8%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 50% of these are from 2020 or later (latest 13 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 Wiltshire if in doubt.
Boundary: Wiltshire Council via planning.data.gov.uk (entity 44015352, reference CA/S/21, 62.6 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.