Solar panels, heat pumps and insulation in Derngate conservation area
In the Derngate conservation area (West Northamptonshire), 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. 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. 713 homes inside the boundary have an energy certificate: 22.0% are solid-wall homes with no wall insulation, 45.3% heat with a gas boiler and 24.8% are rated D–G; 3 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
713homes with an energy certificate
22.0%solid walls, no insulation
45.3%heated by a gas boiler
3heat pumps
Article 4: West Northamptonshire does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Derngate
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: 24 in the area (grade I: 0, II*: 1). 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: 86% 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 = 713)
Walls
Homes
Share
Cavity wall, insulated (as built or unspecified)
187
26.2%
Modern wall (U-value from the design)
157
22.0%
Solid wall (brick or stone), no insulation
157
22.0%
Other or not known
90
12.6%
Solid wall, insulated
53
7.4%
Solid wall, internal insulation
34
4.8%
Cavity wall, unfilled
13
1.8%
Cavity wall, filled
12
1.7%
Timber frame
5
0.7%
Cavity wall, partly insulated
3
0.4%
Cavity wall, internal or external insulation
2
0.3%
Heating
Homes
Share
Electric (storage heaters, panels, boiler)
386
54.1%
Gas boiler
323
45.3%
Heat pump
3
0.4%
LPG
1
0.1%
Loft / roof insulation
Homes
Share
No insulation
32
4.5%
Under 200 mm
25
3.5%
200 mm or more
66
9.3%
Insulated (depth not recorded)
63
8.8%
Flat or other home above
448
62.8%
Other
79
11.1%
Windows
Homes
Share
Double glazed
620
87.0%
Secondary glazing
65
9.1%
Single glazed
25
3.5%
Triple glazed
3
0.4%
BCD
Energy rating: A 1 (0.1%) · B 167 (23.4%) · C 368 (51.6%) · D 157 (22.0%) · E 15 (2.1%) · F 3 (0.4%) · G 2 (0.3%). Houses and bungalows: 14% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 1996-2002. Designated: 25 June 1986.
Compared with West Northamptonshire and England
Share of homes
Derngate
All 118 areas in West Northamptonshire
England
Solid walls, no insulation
22.0%
55.0%
48.7%
Gas boiler
45.3%
62.9%
66.4%
Rated D–G
24.8%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 49% of these are from 2020 or later (latest 22 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 West Northamptonshire if in doubt.
Boundary: West Northamptonshire Council via planning.data.gov.uk (entity 44002557, reference 4805, 9.6 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.