Solar panels, heat pumps and insulation in Spring Grove conservation area
In the Spring Grove 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 7 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. 1,647 homes inside the boundary have an energy certificate: 36.4% are solid-wall homes with no wall insulation, 88.8% heat with a gas boiler and 43.0% 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
1,647homes with an energy certificate
36.4%solid walls, no insulation
88.8%heated by a gas boiler
12heat 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. (Dwellinghouses (C3) to small HMOs (C4) - borough-wide Article 4 Direction)
What needs planning permission in Spring Grove
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: 7 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: 63% 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 = 1,647)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
600
36.4%
Cavity wall, insulated (as built or unspecified)
375
22.8%
Cavity wall, unfilled
254
15.4%
Modern wall (U-value from the design)
145
8.8%
Cavity wall, partly insulated
69
4.2%
Cavity wall, filled
58
3.5%
Timber frame
50
3.0%
Other or not known
41
2.5%
Solid wall, internal insulation
31
1.9%
Solid wall, insulated
15
0.9%
Solid wall, partly insulated
4
0.2%
Solid wall, external insulation
3
0.2%
Cavity wall, internal or external insulation
2
0.1%
Heating
Homes
Share
Gas boiler
1,462
88.8%
Electric (storage heaters, panels, boiler)
162
9.8%
Heat pump
12
0.7%
Communal heating
9
0.5%
LPG
1
0.1%
Other
1
0.1%
Loft / roof insulation
Homes
Share
No insulation
172
10.4%
Under 200 mm
261
15.8%
200 mm or more
153
9.3%
Insulated (depth not recorded)
284
17.2%
Flat or other home above
669
40.6%
Other
108
6.6%
Windows
Homes
Share
Double glazed
1,521
92.3%
Single glazed
63
3.8%
Secondary glazing
51
3.1%
Triple glazed
11
0.7%
Other
1
0.1%
BCDE
Energy rating: A 1 (0.1%) · B 272 (16.5%) · C 666 (40.4%) · D 469 (28.5%) · E 199 (12.1%) · F 30 (1.8%) · G 10 (0.6%). Houses and bungalows: 37% of the homes; solar panels on 0.4% of the certificates. Most common build period on the certificates: 1900-1929. Designated: 18 April 2002.
Compared with Hounslow and England
Share of homes
Spring Grove
All 29 areas in Hounslow
England
Solid walls, no insulation
36.4%
49.9%
48.7%
Gas boiler
88.8%
77.4%
66.4%
Rated D–G
43.0%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 52% of these are from 2020 or later (latest 28 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 44015595, reference HSLCA23, 69.3 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.