Solar panels, heat pumps and insulation in Welwyn conservation area
In the Welwyn conservation area (Welwyn Hatfield), 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 52 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. 188 homes inside the boundary have an energy certificate: 46.8% are solid-wall homes with no wall insulation, 88.8% heat with a gas boiler and 62.8% are rated D–G; 7 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
188homes with an energy certificate
46.8%solid walls, no insulation
88.8%heated by a gas boiler
7heat pumps
Article 4: Welwyn Hatfield does not publish Article 4 areas on planning.data.gov.uk — check with the council.
What needs planning permission in Welwyn
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: 52 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: 12% 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 = 188)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
88
46.8%
Cavity wall, insulated (as built or unspecified)
29
15.4%
Cavity wall, filled
23
12.2%
Modern wall (U-value from the design)
23
12.2%
Timber frame
8
4.3%
Other or not known
6
3.2%
Cavity wall, unfilled
3
1.6%
Solid wall, insulated
3
1.6%
Cavity wall, partly insulated
2
1.1%
Solid wall, external insulation
1
0.5%
Solid wall, internal insulation
1
0.5%
Solid wall, partly insulated
1
0.5%
Heating
Homes
Share
Gas boiler
167
88.8%
Electric (storage heaters, panels, boiler)
13
6.9%
Heat pump
7
3.7%
Communal heating
1
0.5%
Loft / roof insulation
Homes
Share
No insulation
19
10.1%
Under 200 mm
64
34.0%
200 mm or more
54
28.7%
Insulated (depth not recorded)
24
12.8%
Flat or other home above
5
2.7%
Other
22
11.7%
Windows
Homes
Share
Double glazed
149
79.3%
Single glazed
33
17.6%
Secondary glazing
6
3.2%
CDE
Energy rating: B 13 (6.9%) · C 57 (30.3%) · D 83 (44.1%) · E 33 (17.6%) · F 2 (1.1%). Houses and bungalows: 88% of the homes; solar panels on 2.1% of the certificates. Most common build period on the certificates: before 1900. Designated: 6 October 1969.
Compared with Welwyn Hatfield and England
Share of homes
Welwyn
All 9 areas in Welwyn Hatfield
England
Solid walls, no insulation
46.8%
20.8%
48.7%
Gas boiler
88.8%
80.2%
66.4%
Rated D–G
62.8%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 56% of these are from 2020 or later (latest 25 July 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 Welwyn Hatfield if in doubt.
Boundary: Welwyn Hatfield Borough Council via planning.data.gov.uk (entity 44001773, reference 2716, 15.1 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.