Solid wall insulation cost, savings and payback

What internal and external solid wall insulation cost for a UK home with no cavity, plus the savings and the trade-offs of each approach.

Homes built before about 1920 often have solid walls with no cavity to fill. These lose more heat than cavity walls, so insulating them can make a large difference, but it is more expensive and more disruptive.

It can be done internally (insulated boards on the inside face) or externally (a render or cladding system on the outside).

Typical UK cost

Cost ranges are indicative and attributed to Energy Saving Trust: Insulation. Prices vary by property, region and installer – always get quotes and check the official source.

Typical saving

The Energy Saving Trust estimates solid wall insulation can save roughly £200 to £600 a year on heating, with the larger savings in bigger, colder homes.

Saving figures are indicative and attributed to Energy Saving Trust: Insulation. Check the official source.

Payback

Because the up-front cost is high, payback is longer than for cavity or loft insulation; it is often chosen alongside other work rather than on cost alone.

What affects the price

• Internal versus external, and the finish specified.
• Wall area, the number of external walls and access (scaffolding).
• Whether the property is listed or in a conservation area.
• Detailing around windows, doors and damp-proofing.