Solar panels, heat pumps and insulation in Plympton St Maurice conservation area
In the Plympton St Maurice conservation area (Plymouth), 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 59 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. 175 homes inside the boundary have an energy certificate: 61.7% are solid-wall homes with no wall insulation, 79.4% heat with a gas boiler and 73.1% 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
175homes with an energy certificate
61.7%solid walls, no insulation
79.4%heated by a gas boiler
0heat pumps
Article 4: Plymouth 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 Plympton St Maurice
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: 59 in the area (grade I: 1, II*: 6). 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 = 175)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
108
61.7%
Cavity wall, filled
22
12.6%
Modern wall (U-value from the design)
12
6.9%
Cavity wall, insulated (as built or unspecified)
7
4.0%
Cavity wall, partly insulated
7
4.0%
Cavity wall, unfilled
6
3.4%
Timber frame
5
2.9%
Solid wall, internal insulation
4
2.3%
Solid wall, partly insulated
3
1.7%
Solid wall, insulated
1
0.6%
Heating
Homes
Share
Gas boiler
139
79.4%
Electric (storage heaters, panels, boiler)
33
18.9%
Solid fuel (wood, coal)
3
1.7%
Loft / roof insulation
Homes
Share
No insulation
29
16.6%
Under 200 mm
49
28.0%
200 mm or more
37
21.1%
Insulated (depth not recorded)
20
11.4%
Flat or other home above
28
16.0%
Other
12
6.9%
Windows
Homes
Share
Double glazed
138
78.9%
Single glazed
25
14.3%
Secondary glazing
12
6.9%
CDE
Energy rating: B 7 (4.0%) · C 40 (22.9%) · D 75 (42.9%) · E 39 (22.3%) · F 12 (6.9%) · G 2 (1.1%). 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: 29 January 2008.
Compared with Plymouth and England
Share of homes
Plympton St Maurice
All 16 areas in Plymouth
England
Solid walls, no insulation
61.7%
44.9%
48.7%
Gas boiler
79.4%
69.8%
66.4%
Rated D–G
73.1%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 42% of these are from 2020 or later (latest 22 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 Plymouth if in doubt.
Boundary: Plymouth City Council via planning.data.gov.uk (entity 44012309, reference CON13, 41.5 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.