External Wall Insulation Cost: The 2026 Guide
External wall insulation is one of the biggest fabric upgrades you can make to a solid-wall Scottish home. Here's what it costs in 2026, what you're likely to save, and how funding schemes fit in.
Quick answer
£90–£130 per m² installed; typical semi £8,000–£12,000; detached £12,000–£18,000. EPS systems sit at the lower end, mineral wool higher.
EWI Prices Per m² and Per House
Installed prices normally include insulation boards, reinforcing mesh, base coat, decorative finish and scaffolding. Reveal extensions, new sills, and complex architectural details are priced separately.
| Measure | Typical 2026 range |
|---|---|
| Installed cost per m² | £90–£130 |
| Typical semi-detached | £8,000–£12,000 |
| Typical detached | £12,000–£18,000 |
| Larger / complex homes | £15,000+ |
EPS vs Mineral Wool: Cost vs Performance
EPS (expanded polystyrene) systems offer excellent value and strong thermal performance for most homes. Mineral wool (including Rockwool systems) costs more but adds breathability and fire performance — often preferred on older solid-wall and traditional properties. There's no universal winner; we survey and recommend the system that suits your walls. More on the install process at our EWI service page.
What You'll Save
Realistically, EWI can cut wall heat loss by up to around 35%. For a typical gas-heated semi at current prices, many households see roughly £300–£500 a year off heating — plus comfort gains and less condensation that never show on a bill. Exact savings depend on heating type, occupancy and how poorly insulated the walls were to begin with.
Grants and Funding in Scotland
Funding landscape changes. ECO4 eligibility, Home Energy Scotland loans and cashback, and other schemes open and close over time. We don't pretend a webpage written today is gospel next spring — instead we check what's current when we survey and quote, and help you understand whether your property is likely to qualify.
EWI Over Pebble Dash or Roughcast
This is the common Scottish scenario. Existing dash is assessed; loose material is removed or levelled; the insulation system is fixed through to the substrate. You can finish with a fresh dash or a modern smooth coloured render. Assessment quality matters — shortcuts here cause problems later.
Is EWI Worth It?
On bills alone, payback is measured in years. It looks transformed when your walls needed re-rendering anyway — the render budget effectively subsidises the insulation, and you get warmth and a new exterior from one scaffold. If you're already pricing roughcasting, ask us to price EWI as an option on the same visit.
Free EWI survey and current-funding check — call +44 7473 590709.
Frequently Asked Questions
- What is the cheapest way to insulate solid walls?
- EPS external wall insulation systems usually sit at the lower end of installed cost while still delivering strong thermal performance.
- Does EWI cause damp?
- No — done correctly it moves the cold line outside the wall and helps prevent condensation. Poor detailing is the risk, which is why specification matters.
- Will EWI change how my house looks?
- Yes — you get a new exterior finish, either dashed or smooth coloured render. Many homeowners treat that as a benefit.
- Does EWI need planning permission?
- Usually not for most homes, but conservation areas and listed buildings have restrictions. We'll flag this at survey.
Free EWI survey and funding check
Call +44 7473 590709 for a survey and current-funding check.