Solar panels, heat pumps and insulation in Marlow conservation area
In the Marlow conservation area (Buckinghamshire), 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 164 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. 1,070 homes inside the boundary have an energy certificate: 38.8% are solid-wall homes with no wall insulation, 78.8% heat with a gas boiler and 54.9% are rated D–G; 12 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
1,070homes with an energy certificate
38.8%solid walls, no insulation
78.8%heated by a gas boiler
12heat pumps
Article 4: Buckinghamshire 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 Marlow
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: 164 in the area (grade I: 2, II*: 18). 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: 43% 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 = 1,070)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
415
38.8%
Cavity wall, insulated (as built or unspecified)
198
18.5%
Modern wall (U-value from the design)
189
17.7%
Cavity wall, filled
85
7.9%
Cavity wall, unfilled
76
7.1%
Timber frame
32
3.0%
Solid wall, internal insulation
28
2.6%
Cavity wall, partly insulated
24
2.2%
Solid wall, insulated
11
1.0%
Cavity wall, internal or external insulation
5
0.5%
Other or not known
5
0.5%
Solid wall, external insulation
1
0.1%
Solid wall, partly insulated
1
0.1%
Heating
Homes
Share
Gas boiler
843
78.8%
Electric (storage heaters, panels, boiler)
174
16.3%
Communal heating
36
3.4%
Heat pump
12
1.1%
Solid fuel (wood, coal)
3
0.3%
LPG
1
0.1%
Oil
1
0.1%
Loft / roof insulation
Homes
Share
No insulation
140
13.1%
Under 200 mm
253
23.6%
200 mm or more
147
13.7%
Insulated (depth not recorded)
195
18.2%
Flat or other home above
191
17.9%
Other
144
13.5%
Windows
Homes
Share
Double glazed
935
87.4%
Single glazed
85
7.9%
Secondary glazing
50
4.7%
BCDE
Energy rating: A 1 (0.1%) · B 118 (11.0%) · C 364 (34.0%) · D 359 (33.6%) · E 184 (17.2%) · F 32 (3.0%) · G 12 (1.1%). Houses and bungalows: 57% of the homes; solar panels on 0.7% of the certificates. Most common build period on the certificates: 1900-1929. Designated: 10 March 1969.
Compared with Buckinghamshire and England
Share of homes
Marlow
All 186 areas in Buckinghamshire
England
Solid walls, no insulation
38.8%
45.4%
48.7%
Gas boiler
78.8%
64.7%
66.4%
Rated D–G
54.9%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 51% of these are from 2020 or later (latest 29 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 Buckinghamshire if in doubt.
Boundary: Buckinghamshire Council via planning.data.gov.uk (entity 44010553, reference 9065, 78.6 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.