Solar panels, heat pumps and insulation in Mortlake Green conservation area
In the Mortlake Green conservation area (Richmond upon Thames), 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. 148 homes inside the boundary have an energy certificate: 74.3% are solid-wall homes with no wall insulation, 88.5% heat with a gas boiler and 55.4% 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
148homes with an energy certificate
74.3%solid walls, no insulation
88.5%heated by a gas boiler
0heat pumps
Article 4: Richmond upon Thames does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Mortlake Green
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), unless an Article 4 direction removes it — check with the council
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), unless an Article 4 direction removes it — check with the council
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)
Prior approval of appearance from the council, unless an Article 4 direction removes it — check with the council
Replacement windows and doors of similar appearance
No permission needed (permitted development), unless an Article 4 direction removes it — check with the council
Part 1 Class A, A.3(a)
Listed buildings: none recorded inside the boundary; on a listed building, solar panels and heat pumps are not permitted development and need listed building consent.
Flats: 73% 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 = 148)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
110
74.3%
Cavity wall, insulated (as built or unspecified)
21
14.2%
Cavity wall, partly insulated
5
3.4%
Cavity wall, unfilled
5
3.4%
Other or not known
2
1.4%
Solid wall, internal insulation
2
1.4%
Cavity wall, filled
1
0.7%
Solid wall, partly insulated
1
0.7%
Timber frame
1
0.7%
Heating
Homes
Share
Gas boiler
131
88.5%
Electric (storage heaters, panels, boiler)
15
10.1%
Communal heating
2
1.4%
Loft / roof insulation
Homes
Share
No insulation
33
22.3%
Under 200 mm
19
12.8%
200 mm or more
5
3.4%
Insulated (depth not recorded)
21
14.2%
Flat or other home above
70
47.3%
Windows
Homes
Share
Double glazed
113
76.4%
Single glazed
22
14.9%
Secondary glazing
13
8.8%
CDE
Energy rating: C 66 (44.6%) · D 65 (43.9%) · E 15 (10.1%) · F 1 (0.7%) · G 1 (0.7%). Houses and bungalows: 27% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: before 1900. Designated: 14 June 1998.
Compared with Richmond upon Thames and England
Share of homes
Mortlake Green
All 85 areas in Richmond upon Thames
England
Solid walls, no insulation
74.3%
63.5%
48.7%
Gas boiler
88.5%
83.6%
66.4%
Rated D–G
55.4%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 61% of these are from 2020 or later (latest 20 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 Richmond upon Thames if in doubt.
Boundary: London Borough of Richmond upon Thames via planning.data.gov.uk (entity 44002463, reference 7396, 4.6 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.