What Is External Solid Wall Insulation
External solid wall insulation (EWI) is a system applied to the outside of a solid wall to improve its thermal efficiency.
Unlike cavity wall houses, solid wall properties have no air gap – meaning they lose up to 45% of heat through the external walls.
Installing an EWI system adds a protective, insulated layer made of EPS, graphite EPS or mineral wool, finished with primer and decorative render.
This method not only boosts energy performance but also protects brickwork and refreshes the appearance of the façade.
👉 Learn more about our dedicated systems for Solid Wall Insulation and Cavity Wall Insulation
👉 Explore full External Wall Insulation Systems including adhesives, mesh, insulation boards and render finishes.
Why Solid Wall Homes Benefit From EWI
Solid brick houses are common across London, Birmingham, Manchester and other older UK cities. These homes were built before insulation standards were introduced, which causes high heat loss and condensation problems.
Benefits of external solid wall insulation include:
- Reduced heat loss and lower heating bills (up to 40%)
- Elimination of damp and cold bridging
- Better thermal comfort throughout the year
- New decorative finish with silicone render
- Higher EPC rating and property value
💡 Fact: The Energy Saving Trust estimates that insulating solid walls can save homeowners £500–£850 per year in heating costs.
Solid Wall vs Cavity Wall – What’s the Difference
Below is a simple comparison showing how solid wall and cavity wall construction differ, and why EWI is the right choice for older homes.
| Feature | Solid Wall | Cavity Wall |
|---|---|---|
| Wall structure | Single layer of brick or stone with no air gap | Two leaves of masonry with an air cavity between |
| Typical build period | Pre-1930s housing stock in the UK | Post-1930s homes and most modern builds |
| Heat loss | High – significant conductive losses through the wall | Moderate – cavity interrupts heat transfer |
| Common issues | Cold bridging, condensation, façade weathering | Moisture ingress if cavity is bridged or poorly insulated |
| Best insulation method | External solid wall insulation with EPS, graphite EPS or mineral wool | Cavity wall insulation with bead or fiber fill |
| Typical external finish | Primer and silicone render system over reinforced basecoat | Usually no change to external leaf after cavity fill |
For a full breakdown of how these systems work, visit our pages on Solid Wall Insulation and Cavity Wall Insulation.
👉 Related reading: EWI vs Internal Wall Insulation – Which is Better for UK Homes?
Types of External Solid Wall Insulation Systems
When insulating solid walls, choosing the right material is essential for performance and durability. Below is a comparison of the most popular EWI materials used in the UK.
| Material | Thermal Efficiency (λ) | Fire Resistance | Durability | Recommended Use |
|---|---|---|---|---|
| EPS (Expanded Polystyrene) | 0.038 W/mK | Low | High | Budget-friendly choice for newer solid brick walls |
| Graphite EPS | 0.031 W/mK | Medium | Very High | Recommended option for most UK homes – combines excellent insulation with long-term durability and weather resistance |
📦 Tip: Always use a complete insulation system (adhesive, insulation board, mesh, primer and render) for best performance.
👉 See all EWI materials and accessories from Penguin BM.
2025 Cost of External Solid Wall Insulation in the UK
The average cost of external solid wall insulation ranges from £95 to £135 per m², depending on insulation type, thickness and render system.
| Property Type | Average Wall Area | Estimated Cost Range (Graphite EPS System) | Notes |
|---|---|---|---|
| Small Terraced House | 80–100 m² | £8,000 – £11,000 | Includes full system with basecoat, mesh, primer and silicone render |
| Semi-Detached House | 120–160 m² | £12,000 – £18,000 | Costs vary by wall condition and access requirements |
| Detached House | 180–220 m² | £17,000 – £25,000 | Larger surface area and complex elevations increase total cost |
| Material Cost Only (Graphite EPS) | Per m² | £45 – £60 | Estimate for DIY or supply-only projects using Penguin BM EWI materials |
🧮 Tip: Use our free External Wall Insulation Calculator to estimate your project cost and required quantities.
Example EWI System Setup for Solid Wall Properties
Penguin BM supplies complete insulation systems compatible with solid wall buildings across the UK. Here’s an example configuration commonly used by professional installers.
Installation Considerations for Solid Wall Insulation
Before installing EWI on a solid wall, make sure to check:
- Wall surface – remove loose paint or damaged render
- Substrate stability – repair cracks and damp patches
- Weather – apply between 5°C and 25°C
- Fixings – required for cement-based systems EWI Fixings Guide
- Primer – always use Lakma Totalgrunt Primer 12kg before applying render
👉 Read more: How to Select the Right Adhesive for EWI
EWI Funding and Grants in 2025
In 2025, UK homeowners can apply for funding schemes supporting energy-efficient upgrades.
The main programs include:
- ECO4 Scheme – up to 100% funding for qualifying households
- Great British Insulation Scheme (GBIS) – partial funding for EPC D–G homes
- Local Authority Delivery (LAD) – regional energy grants managed by councils
🔗 Learn more in our detailed EWI Grants Guide 2025
Calculator FAQs
How accurate is the External Wall Insulation Calculator?
Our EWI Calculator uses UK coverage rates for insulation boards, adhesives, mesh and renders. For most projects the estimate is very close to site reality. We recommend adding a 5-10% waste factor to allow for cuts and site conditions.
Can the calculator work with graphite EPS systems?
Yes. The calculator supports graphite EPS and standard EPS. For higher thermal performance select graphite EPS from the options, then see compatible products in our EWI materials category.
Which render should I choose for a solid wall property?
Silicone render is the most popular choice in the UK thanks to flexibility and water resistance. Read our full comparison in the render guide before ordering.
What adhesive is recommended for brick or solid walls?
For most solid brick substrates we recommend using a cement based EWI adhesive. Start with our guide how to select the right adhesive, then match it with mesh, primer and silicone render from the same system.
Why Choose Penguin BM
- Official UK supplier of Lakma and Tytan EWI materials
- Based in Wembley, London with nationwide delivery
- Full range of adhesives, mesh, insulation boards and silicone renders
- Technical support for installers and trade customers
- Trusted by builders and insulation professionals across the UK
📍 Visit us at 416 Ealing Rd, Wembley HA0 1JQ or shop online.
👉 Contact our team for trade discounts and expert advice.
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