Recommended path
Cavity wall insulation
Indicative cost range
£0
Estimated annual savings
£0
Trade-offs
Planning, building regs, and grants
Methodology
How the wall insulation decision tree works
The recommendation starts with construction type because that is usually the strongest filter. Unfilled cavity walls usually point toward cavity wall insulation first, while solid masonry walls shift the decision toward internal or external wall insulation depending on facade sensitivity and budget. Existing filled cavities and newer, already compliant walls usually reduce the case for further intervention unless there is a known defect or deeper retrofit goal.
Savings are scaled from a baseline of about £295 a year for a gas-heated semi-detached home with unfilled cavity walls, then adjusted for exposed area and property type. Costs, planning notes, and grants are indicative screening values rather than survey-based specifications.
Related guides
Cavity Wall Insulation Cost
Check whether a cheaper cavity route is suitable before heavier retrofit work.
Internal vs External Wall Insulation
Compare the trade-offs between the main solid-wall upgrade routes.
Insulating Old Houses
See the moisture, detailing, and heritage risks that affect older homes.