Solar panels, heat pumps and insulation in Chiswick High Road conservation area
In the Chiswick High Road 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 this area but deals with other things (such as changes of use); it does not change the rules below. The area has 2 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. 304 homes inside the boundary have an energy certificate: 57.9% are solid-wall homes with no wall insulation, 78.3% heat with a gas boiler and 50.7% are rated D–G; 4 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
304homes with an energy certificate
57.9%solid walls, no insulation
78.3%heated by a gas boiler
4heat pumps
Article 4: An Article 4 direction published by Hounslow covers this area but deals with other things (such as changes of use); it does not change the rules below. (Change of use or development that would result in new dwellings (Class MA/ZA); Dwellinghouses (C3) to small HMOs (C4) - borough-wide Article 4 Direction)
What needs planning permission in Chiswick High Road
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: 2 in the area. 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: 98% 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 = 304)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
176
57.9%
Cavity wall, insulated (as built or unspecified)
61
20.1%
Timber frame
14
4.6%
Solid wall, internal insulation
11
3.6%
Modern wall (U-value from the design)
10
3.3%
Cavity wall, unfilled
9
3.0%
Cavity wall, partly insulated
7
2.3%
Cavity wall, internal or external insulation
5
1.6%
Other or not known
4
1.3%
Solid wall, insulated
4
1.3%
Solid wall, partly insulated
3
1.0%
Heating
Homes
Share
Gas boiler
238
78.3%
Electric (storage heaters, panels, boiler)
62
20.4%
Heat pump
4
1.3%
Loft / roof insulation
Homes
Share
No insulation
87
28.6%
Under 200 mm
20
6.6%
200 mm or more
9
3.0%
Insulated (depth not recorded)
49
16.1%
Flat or other home above
128
42.1%
Other
11
3.6%
Windows
Homes
Share
Double glazed
261
85.9%
Single glazed
35
11.5%
Secondary glazing
6
2.0%
Triple glazed
2
0.7%
CDE
Energy rating: B 20 (6.6%) · C 130 (42.8%) · D 104 (34.2%) · E 42 (13.8%) · F 4 (1.3%) · G 4 (1.3%). Houses and bungalows: 2% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 1900-1929. Designated: 26 August 2014.
Compared with Hounslow and England
Share of homes
Chiswick High Road
All 29 areas in Hounslow
England
Solid walls, no insulation
57.9%
49.9%
48.7%
Gas boiler
78.3%
77.4%
66.4%
Rated D–G
50.7%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 57% 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 Hounslow if in doubt.
Boundary: London Borough of Hounslow via planning.data.gov.uk (entity 44015580, reference HSLCA28, 7.9 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.