Solar panels, heat pumps and insulation in Knotty Ash conservation area
In the Knotty Ash conservation area (Liverpool), 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 Liverpool covers part of this area (about 2% of it) and removes permitted development rights for replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), chimneys, flues and soil pipes, painting the outside, so there these need planning permission too. The area has 7 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. 281 homes inside the boundary have an energy certificate: 22.1% are solid-wall homes with no wall insulation, 52.0% heat with a gas boiler and 27.0% are rated D–G; 1 has 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
281homes with an energy certificate
22.1%solid walls, no insulation
52.0%heated by a gas boiler
1heat pumps
Article 4: An Article 4 direction published by Liverpool covers part of this area (about 2% of it) and removes permitted development rights for replacement windows and doors, and other alterations to the house, alterations to the roof (e.g. rooflights), chimneys, flues and soil pipes, painting the outside, so there these need planning permission too. (Land adjacent to St John's Vicarage, Thomas Lane, L14; Land and buildings at Little Bongs , East Prescot Road/Thomas Lane, Liverpool , L14 5NG)
What needs planning permission in Knotty Ash
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
Inside the Article 4 part of the area: planning permission needed; elsewhere: no permission needed (permitted development)
Part 1 Class A, A.3(a)
Listed buildings: 7 in the area. 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: 79% 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 = 281)
Walls
Homes
Share
Other or not known
161
57.3%
Solid wall (brick or stone), no insulation
62
22.1%
Cavity wall, insulated (as built or unspecified)
33
11.7%
Solid wall, internal insulation
10
3.6%
Cavity wall, unfilled
7
2.5%
Timber frame
3
1.1%
Cavity wall, partly insulated
2
0.7%
Cavity wall, filled
1
0.4%
Solid wall, external insulation
1
0.4%
Solid wall, partly insulated
1
0.4%
Heating
Homes
Share
Gas boiler
146
52.0%
Communal heating
106
37.7%
Electric (storage heaters, panels, boiler)
27
9.6%
Heat pump
1
0.4%
LPG
1
0.4%
Loft / roof insulation
Homes
Share
No insulation
18
6.4%
Under 200 mm
28
10.0%
200 mm or more
41
14.6%
Insulated (depth not recorded)
41
14.6%
Flat or other home above
153
54.4%
Windows
Homes
Share
Double glazed
263
93.6%
Single glazed
17
6.0%
Secondary glazing
1
0.4%
BCD
Energy rating: B 26 (9.3%) · C 179 (63.7%) · D 45 (16.0%) · E 22 (7.8%) · F 5 (1.8%) · G 4 (1.4%). Houses and bungalows: 21% of the homes; solar panels on 0.4% of the certificates. Most common build period on the certificates: 1950-1966. Designated: 13 April 2004.
Compared with Liverpool and England
Share of homes
Knotty Ash
All 37 areas in Liverpool
England
Solid walls, no insulation
22.1%
41.6%
48.7%
Gas boiler
52.0%
53.3%
66.4%
Rated D–G
27.0%
—
56.5%
Caveats
Certificates describe a home when it was assessed; 20% of these are from 2020 or later (latest 28 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 Liverpool if in doubt.
Boundary: Liverpool City Council via planning.data.gov.uk (entity 44014310, reference CA015, 23.7 ha). Homes are placed by the coordinates of their UPRN (OS Open UPRN); addresses are not shown.