External Wall Insulation
Where a wall has a narrow cavity, it is not advised to use standard cavity wall insulation. Instead, it may be appropriate to insulate this type of wall externally, in a similar way to how a solid wall could be externally insulated.
*Figures are taken from Energy Saving Trust and are based on fuel prices as of October 2023. Estimates are based on insulating a three bed, semi-detached, gas-heated home.