What it is
Insulation boards — EPS, mineral wool or PIR — fixed to the outside of the walls and finished with render or cladding. The whole wall becomes warm, cold bridges disappear, and the inside of the house is untouched. Typically 60–120mm thick.
Suitability
- Solid-walled homes, or cavity homes where cavity fill is unsuitable
- Detached, semi-detached and end-terrace where the walls are accessible
- Not usually possible on listed buildings, and planning permission may be needed in conservation areas or where the appearance changes materially
Details that matter
Roof overhang at the eaves, window sills extended, services moved, drainage and the damp-proof course level respected. A poor EWI job shows at the windows first.
Solid walls, thinking big?
Check my homeTell us the property and we will show whether external, internal or neither makes sense.
Cost and funding
£8,000–£20,000 for a typical semi, including scaffold. External wall insulation is a funded measure under whole-house schemes for eligible households. Current routes.
Questions homeowners ask
Does external wall insulation need planning permission?
Not usually for a house outside a conservation area, provided the appearance is similar. Always check with the council first.
Sources and when they were last checked
- Energy Saving Trust — Roof and loft insulation — checked 2 September 2026