Guide
Is external wall insulation worth it?
External wall insulation is usually worth it on solid-walled and concrete houses that are hard to heat, especially when the outside needs re-rendering anyway. It's less worthwhile on well-insulated cavity walls, on homes where planning won't allow a change in appearance, or where the main heat loss is elsewhere, such as an uninsulated loft.
When EWI makes most sense
- Solid brick, stone or concrete walls with no cavity to fill
- Walls that need re-rendering or covering anyway — scaffold and preparation are already paid for
- Homes with cold, damp-prone walls and condensation on inside surfaces
- When you don't want to lose room space or disturb the inside of the house
When to look at other options first
- The loft isn't insulated — usually cheaper and quicker to fix first
- The cavity is empty and suitable for filling
- Planning won't allow the appearance to change (consider internal insulation or brick slip)
- The wall has an unresolved damp or structural problem
What about payback?
Payback depends on the home, the heating system, energy prices and how the house is used, so we don't promise a figure. Comfort benefits — warmer walls, fewer draughts, less condensation — are immediate. Where EWI replaces render that needs doing anyway, the extra cost of insulation is what should be weighed against the savings.
What are the downsides?
EWI changes the look of the house, needs scaffolding for a few weeks, and must be detailed carefully at eaves, cills and the base of the wall. Done poorly, it can cause damp problems. Done well, it's one of the most effective upgrades for a solid-walled home.
Questions
Does EWI add value to a house?
It can improve the EPC rating and kerb appeal, which buyers notice, but we don't claim a specific value increase.
Will EWI improve my EPC?
On solid-walled homes it's usually one of the measures with the biggest effect on the rating, because walls are a large heat-loss area.
Is EWI worth it on a cavity wall?
Usually only if the cavity can't be filled or the outside needs re-rendering anyway.