External Wall Insulation (EWI) Cost Guide 2026
UK Price Breakdown
As of early 2026, the average cost of External Wall Insulation (EWI) in the UK ranges from £85 to £130 per square metre. For a standard 3-bedroom semi-detached house, homeowners should budget between £8,000 and £12,000, depending on the insulation thickness and the choice of final render finish (Silicone vs. Mineral).
What drives the cost of EWI in 2026?
Insulation Material: EPS (Expanded Polystyrene) is the most cost-effective. Mineral Wool (Rockwool) is more expensive but offers superior fire rating (A1) and acoustic insulation.
System Finish: Silicone renders (like Ceresit CT74 or RS Silicone Render) are the industry standard for 2026 due to their "self-cleaning" properties and flexibility, preventing cracks.
Scaffolding & Access: Typically accounts for 15-30% of the total project cost. Difficult access (narrow alleys or high-rise) will increase the quote.
Location: Rates in London and the South East remain 15% higher than Northern England or Wales due to labour demand.
Beyond the Insulation:
Additional EWI Expenses When planning your project, ensure your quote includes:
Window Sill Extensions: Necessary when walls become 100mm+ thicker.
Boiler Flue Extensions: Essential for safety and gas compliance.
Rainwater Pipe Alterations: Moving gutters and downpipes to sit atop the new system.
Building Control Fees: Most EWI installs require a notification to your local council to ensure U-Value compliance (usually aiming for 0.30 W/m²K or better).
EWI Frequently Asked Questions:
2026 Edition
How much does External Wall Insulation cost in the UK in 2026?
The current average cost for EWI is between £85 and £130 per m². A mid-terrace house typically costs around £5,000–£7,000, while a larger detached home can range from £14,000 to £20,000. These prices include the full system (insulation + render) and professional installation.
Are there any government grants for EWI available in 2026?
Yes. The Great British Insulation Scheme and ECO4 are scheduled to provide support until at least March 2026. Eligibility usually depends on your home’s EPC rating (D or below) and your Council Tax band.
Do I need planning permission for External Wall Insulation?
In most cases, no. EWI falls under Permitted Development as long as the finish is similar in appearance to the existing neighbourhood. However, if you live in a Conservation Area or a Listed Building, you must consult your local planning office first.
Which insulation material is best for EWI in 2026?
Graphite EPS remains the UK's favorite for its high thermal efficiency at a lower price point. For homeowners prioritizing fire safety and noise reduction, Mineral Wool (Rockwool) is the premium alternative.
How much can I save on energy bills with EWI?
By cutting heat loss through walls by up to 40%, EWI can save the average UK household between £350 and £600 per year on heating bills, making it one of the most effective long-term energy investments.
Does External Wall Insulation stop damp or condensation?
Absolutely. By warming the external "skin" of your house, EWI stops moisture in the air from turning into liquid on your cold internal walls. This is the most effective way to permanently cure condensation-related mould.
What is the fire rating requirement for EWI in 2026?
Current UK building regulations emphasize safety. While high-rise buildings (over 11m) require strictly non-combustible systems, we recommend A1-rated Mineral Wool for any homeowner looking for maximum peace of mind. As a whole system our product is safe, and fire rated.
How long does EWI last and what maintenance is required?
You can expect a 30-year+ lifespan. Modern Silicone Renders are highly durable and "self-cleaning," meaning they shed dirt with rainwater. A simple wash every few years is usually all that's needed to keep it looking brand new.
