Solar panels, heat pumps and insulation in Dorchester 1 conservation area
In the Dorchester 1 conservation area (Dorset), 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 Dorset covers part of this area (about 19% of it) and removes permitted development rights for painting the outside, so there these need planning permission too. The area has 241 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. 1,628 homes inside the boundary have an energy certificate: 23.3% are solid-wall homes with no wall insulation, 71.4% heat with a gas boiler and 44.2% 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
1,628homes with an energy certificate
23.3%solid walls, no insulation
71.4%heated by a gas boiler
3heat pumps
Article 4: An Article 4 direction published by Dorset covers part of this area (about 19% of it) and removes permitted development rights for painting the outside, so there these need planning permission too. (Dorchester Conservation Area)
What needs planning permission in Dorchester 1
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: 241 in the area (grade I: 4, II*: 14). 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: 67% 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 = 1,628)
Walls
Homes
Share
Cavity wall, insulated (as built or unspecified)
434
26.7%
Solid wall (brick or stone), no insulation
380
23.3%
Cavity wall, unfilled
249
15.3%
Cavity wall, filled
142
8.7%
Modern wall (U-value from the design)
132
8.1%
Cavity wall, partly insulated
125
7.7%
Timber frame
84
5.2%
Solid wall, internal insulation
31
1.9%
Solid wall, insulated
28
1.7%
Solid wall, partly insulated
15
0.9%
Cavity wall, internal or external insulation
6
0.4%
Other or not known
2
0.1%
Heating
Homes
Share
Gas boiler
1,163
71.4%
Electric (storage heaters, panels, boiler)
446
27.4%
Communal heating
10
0.6%
LPG
4
0.2%
Heat pump
3
0.2%
Oil
1
0.1%
Solid fuel (wood, coal)
1
0.1%
Loft / roof insulation
Homes
Share
No insulation
136
8.4%
Under 200 mm
257
15.8%
200 mm or more
317
19.5%
Insulated (depth not recorded)
220
13.5%
Flat or other home above
603
37.0%
Other
95
5.8%
Windows
Homes
Share
Double glazed
1,354
83.2%
Single glazed
225
13.8%
Secondary glazing
47
2.9%
Triple glazed
2
0.1%
CDE
Energy rating: B 104 (6.4%) · C 805 (49.4%) · D 479 (29.4%) · E 191 (11.7%) · F 38 (2.3%) · G 11 (0.7%). Houses and bungalows: 33% of the homes; solar panels on 0.2% of the certificates. Most common build period on the certificates: before 1900. Designated: 29 April 1970.
Compared with Dorset and England
Share of homes
Dorchester 1
All 311 areas in Dorset
England
Solid walls, no insulation
23.3%
37.3%
48.7%
Gas boiler
71.4%
60.1%
66.4%
Rated D–G
44.2%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 53% of these are from 2020 or later (latest 27 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 Dorset if in doubt.
Boundary: Dorset Council via planning.data.gov.uk (entity 44013814, reference DORC1, 66.1 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.