Solar panels, heat pumps and insulation in Old Town High Street conservation area
In the Old Town High Street conservation area (Stevenage), 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 Stevenage covers this area but deals with other things (such as changes of use); it does not change the rules below. The area has 87 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. 336 homes inside the boundary have an energy certificate: 18.2% are solid-wall homes with no wall insulation, 55.7% heat with a gas boiler and 38.7% are rated D–G; 0 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
336homes with an energy certificate
18.2%solid walls, no insulation
55.7%heated by a gas boiler
0heat pumps
Article 4: An Article 4 direction published by Stevenage covers this area but deals with other things (such as changes of use); it does not change the rules below. (Stevenage)
What needs planning permission in Old Town High Street
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: 87 in the area (grade I: 0, 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: 74% 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 = 336)
Walls
Homes
Share
Cavity wall, insulated (as built or unspecified)
148
44.0%
Solid wall (brick or stone), no insulation
61
18.2%
Modern wall (U-value from the design)
45
13.4%
Timber frame
36
10.7%
Solid wall, insulated
12
3.6%
Cavity wall, partly insulated
11
3.3%
Other or not known
11
3.3%
Cavity wall, unfilled
5
1.5%
Cavity wall, filled
4
1.2%
Cavity wall, internal or external insulation
1
0.3%
Solid wall, external insulation
1
0.3%
Solid wall, internal insulation
1
0.3%
Heating
Homes
Share
Gas boiler
187
55.7%
Electric (storage heaters, panels, boiler)
148
44.0%
Other
1
0.3%
Loft / roof insulation
Homes
Share
No insulation
23
6.8%
Under 200 mm
47
14.0%
200 mm or more
47
14.0%
Insulated (depth not recorded)
62
18.5%
Flat or other home above
126
37.5%
Other
31
9.2%
Windows
Homes
Share
Double glazed
299
89.0%
Single glazed
31
9.2%
Secondary glazing
5
1.5%
Other
1
0.3%
BCDE
Energy rating: B 32 (9.5%) · C 174 (51.8%) · D 91 (27.1%) · E 37 (11.0%) · G 2 (0.6%). Houses and bungalows: 26% of the homes; solar panels on 0.3% of the certificates. Most common build period on the certificates: 2007-2011. Designated: 24 March 1969.
Compared with Stevenage and England
Share of homes
Old Town High Street
All 7 areas in Stevenage
England
Solid walls, no insulation
18.2%
9.0%
48.7%
Gas boiler
55.7%
74.9%
66.4%
Rated D–G
38.7%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 65% of these are from 2020 or later (latest 18 August 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 Stevenage if in doubt.
Boundary: Stevenage Borough Council via planning.data.gov.uk (entity 44015686, reference CA06, 26.9 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.