Solar panels, heat pumps and insulation in Isleworth Riverside conservation area
In the Isleworth Riverside conservation area (Hounslow), 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 Hounslow covers part of this area (about 26% of it) but deals with other things (such as changes of use); it does not change the rules below. The area has 57 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. 1,413 homes inside the boundary have an energy certificate: 33.1% are solid-wall homes with no wall insulation, 70.3% heat with a gas boiler and 39.9% are rated D–G; 23 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
1,413homes with an energy certificate
33.1%solid walls, no insulation
70.3%heated by a gas boiler
23heat pumps
Article 4: An Article 4 direction published by Hounslow covers part of this area (about 26% of it) but deals with other things (such as changes of use); it does not change the rules below. (Dwellinghouses (C3) to small HMOs (C4) - borough-wide Article 4 Direction)
What needs planning permission in Isleworth Riverside
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: 57 in the area (grade I: 6, II*: 5). 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: 55% 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 = 1,413)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
467
33.1%
Modern wall (U-value from the design)
311
22.0%
Cavity wall, insulated (as built or unspecified)
301
21.3%
Cavity wall, filled
129
9.1%
Cavity wall, unfilled
82
5.8%
Cavity wall, partly insulated
48
3.4%
Timber frame
28
2.0%
Solid wall, internal insulation
17
1.2%
Solid wall, insulated
12
0.8%
Other or not known
9
0.6%
Cavity wall, internal or external insulation
7
0.5%
Solid wall, partly insulated
2
0.1%
Heating
Homes
Share
Gas boiler
994
70.3%
Communal heating
231
16.3%
Electric (storage heaters, panels, boiler)
162
11.5%
Heat pump
23
1.6%
LPG
3
0.2%
Loft / roof insulation
Homes
Share
No insulation
177
12.5%
Under 200 mm
236
16.7%
200 mm or more
121
8.6%
Insulated (depth not recorded)
231
16.4%
Flat or other home above
459
32.5%
Other
188
13.3%
Windows
Homes
Share
Double glazed
1,277
90.4%
Single glazed
66
4.7%
Secondary glazing
43
3.0%
Triple glazed
27
1.9%
BCDE
Energy rating: A 3 (0.2%) · B 312 (22.1%) · C 534 (37.8%) · D 421 (29.8%) · E 124 (8.8%) · F 17 (1.2%) · G 2 (0.1%). Houses and bungalows: 45% of the homes; solar panels on 0.2% of the certificates. Most common build period on the certificates: before 1900. Designated: 11 November 1972.
Compared with Hounslow and England
Share of homes
Isleworth Riverside
All 29 areas in Hounslow
England
Solid walls, no insulation
33.1%
49.9%
48.7%
Gas boiler
70.3%
77.4%
66.4%
Rated D–G
39.9%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 43% 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 Hounslow if in doubt.
Boundary: London Borough of Hounslow via planning.data.gov.uk (entity 44009063, reference 1215, 155.8 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.