Solar panels, heat pumps and insulation in Old Hatfield conservation area
In the Old Hatfield 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. 266 homes inside the boundary have an energy certificate: 25.2% are solid-wall homes with no wall insulation, 75.9% heat with a gas boiler and 51.1% are rated D–G; 8 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
266homes with an energy certificate
25.2%solid walls, no insulation
75.9%heated by a gas boiler
8heat 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 Old Hatfield
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: 2, 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: 55% 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 = 266)
Walls
Homes
Share
Solid wall (brick or stone), no insulation
67
25.2%
Cavity wall, filled
59
22.2%
Modern wall (U-value from the design)
49
18.4%
Cavity wall, insulated (as built or unspecified)
31
11.7%
Cavity wall, unfilled
26
9.8%
Cavity wall, partly insulated
22
8.3%
Timber frame
9
3.4%
Solid wall, insulated
1
0.4%
Solid wall, internal insulation
1
0.4%
Solid wall, partly insulated
1
0.4%
Heating
Homes
Share
Gas boiler
202
75.9%
Electric (storage heaters, panels, boiler)
49
18.4%
Heat pump
8
3.0%
Communal heating
6
2.3%
Solid fuel (wood, coal)
1
0.4%
Loft / roof insulation
Homes
Share
No insulation
23
8.6%
Under 200 mm
55
20.7%
200 mm or more
45
16.9%
Insulated (depth not recorded)
33
12.4%
Flat or other home above
81
30.5%
Other
29
10.9%
Windows
Homes
Share
Double glazed
200
75.2%
Single glazed
47
17.7%
Secondary glazing
18
6.8%
Triple glazed
1
0.4%
CDE
Energy rating: B 21 (7.9%) · C 109 (41.0%) · D 96 (36.1%) · E 34 (12.8%) · F 6 (2.3%). Houses and bungalows: 45% of the homes; solar panels on 0.0% of the certificates. Most common build period on the certificates: 1976-1982. Designated: 1 January 1968.
Compared with Welwyn Hatfield and England
Share of homes
Old Hatfield
All 9 areas in Welwyn Hatfield
England
Solid walls, no insulation
25.2%
20.8%
48.7%
Gas boiler
75.9%
80.2%
66.4%
Rated D–G
51.1%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 66% 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 Welwyn Hatfield if in doubt.
Boundary: Welwyn Hatfield Borough Council via planning.data.gov.uk (entity 44001774, reference 2720, 11.5 ha); the council's appraisal or map. Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.