Spray Cork vs External Wall Insulation (EWI) — Which Wins in 2026?
External wall insulation works — but it's expensive, invasive and changes how your house looks. Spray cork is the lighter-touch alternative most installers won't mention.
15 March 2026 · 7 min read
External wall insulation (EWI) delivers the biggest thermal uplift available to solid-wall UK homes — but it adds 80–120 mm to the exterior, changes window reveals, and runs £140–£200/m² installed. Spray cork hits roughly 60% of the thermal benefit at about half the cost, with none of the visual changes.
Head-to-head
- Thickness added: EWI 90–120 mm vs spray cork 3–6 mm
- Cost per m²: EWI £140–£200 vs spray cork £75–£120
- Install time (3-bed semi): EWI 4–6 weeks vs spray cork 2–3 days
- Planning: EWI often triggers consent; spray cork rarely does
- Window reveals: EWI needs deepening; spray cork untouched
- U-value improvement: EWI 70–80% vs spray cork up to 30%
When to choose each
Choose EWI when you're targeting deep retrofit (PAS 2035, EnerPHit) or a Solid Wall Insulation grant scheme. Choose spray cork when you want the biggest visible improvement to comfort and exterior appearance for the smallest budget and least disruption — which is most homes.
FAQs
- Can spray cork be used with EWI?
- Yes — spray cork is increasingly specified as the decorative breathable topcoat over mineral-wool EWI systems.
- Does spray cork qualify for ECO4 funding?
- Not currently in its own right, but it can form part of a wider measure where the lead measure does.
- Will spray cork affect house value the way EWI does?
- It improves appearance and EPC notes without altering the elevations, which surveyors generally view favourably.
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