Solar panels, heat pumps and insulation in Harefield Village conservation area
In the Harefield Village conservation area (Hillingdon), 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 Hillingdon covers this area and removes permitted development rights for replacement windows and doors, and other alterations to the house, so there these need planning permission too. The area has 24 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. 664 homes inside the boundary have an energy certificate: 25.0% are solid-wall homes with no wall insulation, 85.7% heat with a gas boiler and 60.5% are rated D–G; 10 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
664homes with an energy certificate
25.0%solid walls, no insulation
85.7%heated by a gas boiler
10heat pumps
Article 4: An Article 4 direction published by Hillingdon covers this area and removes permitted development rights for replacement windows and doors, and other alterations to the house, so there these need planning permission too. (Changes of use from commercial, business and service uses to dwellinghouses; Residential extensions)
What needs planning permission in Harefield Village
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
Planning permission needed (an Article 4 direction here removes this right)
Part 1 Class A, A.3(a)
Listed buildings: 24 in the area (grade I: 2, II*: 3). 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: 34% 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 = 664)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
166
25.0%
Cavity wall, insulated (as built or unspecified)
143
21.5%
Cavity wall, filled
121
18.2%
Cavity wall, unfilled
119
17.9%
Modern wall (U-value from the design)
41
6.2%
Cavity wall, partly insulated
27
4.1%
Timber frame
25
3.8%
Other or not known
12
1.8%
Solid wall, internal insulation
4
0.6%
Solid wall, insulated
3
0.5%
Solid wall, external insulation
2
0.3%
Solid wall, partly insulated
1
0.2%
Heating
Homes
Share
Gas boiler
569
85.7%
Electric (storage heaters, panels, boiler)
60
9.0%
Communal heating
17
2.6%
Heat pump
10
1.5%
LPG
5
0.8%
Oil
2
0.3%
Solid fuel (wood, coal)
1
0.2%
Loft / roof insulation
Homes
Share
No insulation
72
10.8%
Under 200 mm
227
34.2%
200 mm or more
112
16.9%
Insulated (depth not recorded)
116
17.5%
Flat or other home above
97
14.6%
Other
40
6.0%
Windows
Homes
Share
Double glazed
617
92.9%
Single glazed
38
5.7%
Secondary glazing
9
1.4%
CDE
Energy rating: A 1 (0.2%) · B 17 (2.6%) · C 244 (36.7%) · D 301 (45.3%) · E 78 (11.7%) · F 15 (2.3%) · G 8 (1.2%). Houses and bungalows: 66% of the homes; solar panels on 0.5% of the certificates. Most common build period on the certificates: 1967-1975. Designated: 4 October 2024.
Compared with Hillingdon and England
Share of homes
Harefield Village
All 32 areas in Hillingdon
England
Solid walls, no insulation
25.0%
25.5%
48.7%
Gas boiler
85.7%
62.7%
66.4%
Rated D–G
60.5%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 44% of these are from 2020 or later (latest 30 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 Hillingdon if in doubt.
Boundary: London Borough of Hillingdon via planning.data.gov.uk (entity 44015533, reference CA-1, 115.8 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.