How Much Does External Wall Insulation Cost?
External wall insulation costs in 2026 range from £80 to £120 per square metre for EPS (expanded polystyrene), £100 to £150 per m² for XPS (extruded polystyrene), and £110 to £170 per m² for mineral wool. Scaffolding, labour and render finish are included in these prices.
External wall insulation (EWI) is the most effective way to improve your home's energy efficiency and cut heating bills. It also refreshes the property's external appearance and extends the life of the building fabric. However, costs vary significantly depending on the insulation material, property size and installation details. In this guide you will find a full 2026 cost breakdown.
Insulation Cost by Material
The insulation material you choose directly affects both price and performance:
| Material | Price per m² | Thermal Performance | Fire Resistance | Moisture Resistance |
|---|---|---|---|---|
| EPS (50 mm) | £80 - £100 | Good | Low | Moderate |
| EPS (80 mm) | £95 - £120 | Very good | Low | Moderate |
| XPS (50 mm) | £100 - £120 | Good | Moderate | High |
| XPS (80 mm) | £115 - £150 | Very good | Moderate | High |
| Mineral Wool (50 mm) | £110 - £140 | Good | Very high | Moderate |
| Mineral Wool (80 mm) | £130 - £170 | Very good | Very high | Moderate |
These prices include scaffolding, adhesive, mechanical fixings, mesh reinforcement, primer and render finish. Architectural details such as window reveals, sills and string courses will add to the cost.
How to Choose the Right Insulation Thickness
The correct insulation thickness depends on your property type, wall construction and location:
- 50 mm: Minimum practical thickness for most UK properties. Suitable where wall thickness constraints apply, such as on terraced houses close to the boundary.
- 80 mm: The most common specification for solid-wall properties in England and Wales. Delivers a good balance between cost and thermal performance.
- 100 mm: Recommended for exposed properties in Scotland, northern England and other colder regions, or to meet Part L Building Regulations for retrofit projects.
- 120 mm and above: Used for Passivhaus-standard builds and deep retrofit projects aiming for maximum energy savings.
Greater thickness increases the per square metre cost but proportionally improves energy savings. A U-value calculation by a qualified energy assessor will confirm the right specification for your property.
The EWI Installation Process
A professional external wall insulation installation follows these stages:
- Surface preparation: Existing paint and loose render are removed and cracks are repaired.
- Scaffolding: Safe scaffolding is erected around the property.
- Adhesive bonding: Insulation boards are bonded to the wall with specialist adhesive.
- Mechanical fixing: Plastic fixings are driven through the insulation into the masonry for additional security.
- Mesh and base coat: Glass fibre reinforcing mesh is embedded into a base coat render.
- Primer: A preparatory primer is applied before the final finish.
- Render finish: A textured or smooth render coat is applied as the final weatherproof layer.
The entire process takes 1 to 2 weeks for a typical house and 2 to 3 weeks for a larger or more complex property.
What to Look Out for When Getting EWI
Installation quality is everything — even the best materials will underperform if fitted incorrectly:
- Choose an accredited installer: Ask to see previous projects and request references. Look for PAS 2030 / TrustMark accreditation.
- Request a guarantee: Reputable firms offer 10 to 25 year guarantees covering both materials and workmanship.
- Timing: The ideal installation temperature is between 5 and 35 degrees Celsius. Avoid installation during freezing weather or extreme heat.
- Window and door details: Reveals, sills and door surrounds must be finished with specialist profiles.
- Ventilation: After insulation, the building envelope is significantly more airtight, so internal ventilation should be reviewed to prevent condensation.
For overall home renovation planning, see our home renovation guide. If you are considering repainting interior rooms after external works, our house painting costs guide will be useful.
Conclusion
External wall insulation in 2026 is an investment ranging from £80 to £170 per square metre. However, with energy savings of 30 to 50 percent on heating bills, the payback period is typically 5 to 10 years. In the long run, EWI benefits both your household budget and your living comfort. The right material, correct thickness and a reputable, accredited installer will ensure you get maximum return from the investment.
On builderquote.co.uk you can compare up-to-date external wall insulation and energy efficiency improvement prices.