Planning to insulate your solid wall home? External Wall Insulation is a proven way to improve energy efficiency, cut heating bills, and create a more comfortable living environment, especially in older UK properties with solid walls. But before the work begins, it’s important to understand what the process involves and how to prepare. 

In this blog, we’ll walk you through everything you need to know before installing external wall insulation, from assessing your property to understanding what happens during installation. Whether you are aiming to reduce energy waste, modernise your home’s exterior, or lower your carbon footprint, this checklist will help you make informed decisions at every step. 

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What is External Wall Insulation? 

External Wall Insulation (EWI) is a method of improving a building’s energy efficiency by fixing a layer of thermal insulation to the outside of a property’s walls. This layer is then finished with a protective render or decorative cladding. It forms a thermal envelope around the house, helping to retain heat within the building and reducing heat loss through the walls. 

By upgrading your property with external wall insulation, you can significantly enhance indoor comfort and cut down on heating costs, particularly in older homes with solid walls. 

Key Benefits of External Wall Insulation:

• Lower energy bills and improved energy efficiency 
• Improved indoor comfort year-round
• Reduced risk of damp and condensation
• Increased kerb appeal and property value

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What Types of Properties Are Suitable for EWI?

External wall insulation is ideal for homes with solid walls, which don’t have cavity space for internal insulation. These include:

• Older brick homes (pre-1920s)
• Concrete system-built properties (1930s–1980s)
• Homes with timber or steel frame construction

Checklist Before Installing External Wall Insulation

Installing EWI is a big decision, and it’s important to prepare properly before work begins. Here’s a practical checklist to help you understand what’s involved. 

1. Property Assessment 

Before anything else, your property will need a professional assessment. A full survey helps determine whether your property is suitable for EWI and ensures any issues are addressed early on. 

The survey will cover:

• The condition of the property walls
• Signs of damp or moisture (must be resolved first)
• Wall type (solid, cavity, concrete or mixed)
• Any structural issues like loose render, cracks, or uneven surfaces

Most reputable EWI installation companies will carry out this survey before providing a quote. Always double-check that it’s included in your consultation.

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2. Permissions and Building Regulations

Depending on your location and property type, certain permissions may be required before starting external wall insulation. You may need:

• Planning permission if your home is listed or located in a conservation area.
• Building regulations compliance for insulation thickness, fire safety, and ventilation standards.

A good installer will manage this part for you, including submitting applications and ensuring compliance. Still, it’s worth confirming this during your initial discussions.

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3. Choosing the Right Insulation and Render 

Not all insulation is created equal. The best choice depends on your property, goals, and budget. A knowledgeable installer will guide you, but having an idea of your options helps you make informed decisions.

Insulation options:

• EPS (Expanded Polystyrene): Affordable and widely used
• Mineral Wool: Good for soundproofing and fire resistance
• Phenolic Foam: High performance, ideal for space-limited areas but more expensive

Render finishes:

• Silicone Render: Flexible, water-repellent and long-lasting
• Acrylic Render: Available in vibrant colours, though less breathable
• Mineral Render: Breathable and affordable, but may need repainting over time

Your installer should offer a breakdown of options and recommend a system suited to your property’s structure and needs.

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4. Choosing a Trustworthy External Wall Insulation Installer

The right installer can make or break your project. Look for companies that are fully accredited and have experience working on homes similar to yours.

Check for:

• PAS 2030, TrustMark, Green Deal or UKAS accreditation—these prove the installer meets government standards
• Experience: 10+ years in EWI is a good indicator.
• A solid portfolio of previous projects (great if they’re local to you)
• Warranty: Many offer up to 25-year guarantees on systems.

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5. What to Expect During the EWI Installation Process

EWI installation typically takes 1 to 3 weeks, depending on property size and complexity. Here’s what the process usually looks like:

• Scaffolding setup - For multi-storey homes or buildings with tricky access, scaffolding ensures safe, efficient work.
  
• Surface preparation - The external walls are cleaned and repaired. Old render or flaky paint may be removed, and a bonding primer applied for better adhesion.
  
• Insulation board installation - Insulation boards are fixed securely to your walls. Gaps are carefully avoided to prevent thermal bridging.
  
• Basecoat and mesh layer - A fibre mesh is embedded into a basecoat for strength, weather resistance, and crack prevention.
  
• Coloured render finish - Once cured, a coloured render is applied for a clean finish and added protection.
  
• Final checks and sign-off - The installer conducts a thorough inspection and provides certification, ensuring the job meets UK standards and qualifies for any warranties or schemes.

Installing external wall insulation is a smart upgrade for homeowners looking to reduce energy bills and future proof their properties. While there are a few steps to get right, working with a qualified installer and knowing what to expect ensures your project runs smoothly and brings long-term value. 

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Frequently Asked Questions About Installing External Wall Insulation

1. Can I install external wall insulation myself?

External wall insulation is not a DIY job. It requires proper tools, technical expertise, and industry knowledge to avoid major issues such as damp, thermal bridging, or render cracks. Only certified professionals can ensure it’s installed to meet UK building regulations and deliver long-term energy savings.

2. What’s the difference between external wall insulation and solid wall insulation?

“Solid wall insulation” refers to insulating homes with solid walls (typically built before 1920),  walls that don’t have a cavity. “External wall insulation” is the method used to insulate these solid walls from the outside, by fixing insulation boards to the external surface and covering them with a render.

3. How do I know if my home is suitable for EWI?

The best way to find out is to have a professional assessment. Most homes with solid brick, concrete panel, or non-cavity construction can benefit from EWI. However, the installer will need to check for damp, cracks, or structural issues before confirming suitability.

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Thinking about improving your home with external wall insulation or rendering?

We have over 15 years of experience, are fully TrustMark accredited, and work across the Midlands and the South of England. Contact us today for a free consultation.

📞 Call us on 024 7531 4286 or use our contact form to get started.