If you’re planning to upgrade the exterior of your home, you may be considering External Wall Insulation (EWI) or a new render system. Both options can dramatically improve your property’s appearance, weather resistance, and long-term performance—but they serve different purposes.
This guide explains the differences, benefits, and drawbacks of EWI vs Rendering, helping you understand which option suits your home best.
What Is External Wall Insulation (EWI)?
External Wall Insulation involves fixing insulation boards to the outside walls, then covering them with a reinforced basecoat and decorative render finish.
It improves thermal performance, reduces heat loss, and protects the building envelope.
Best for:
- Cold homes
- Solid-wall properties
- Improving energy efficiency and reducing bills
- Damp or condensation issues
- External refurbishments needing both insulation and a new finish
What Is Rendering?
Rendering is the process of applying a protective and decorative coating to external walls.
It does not add thermal insulation unless combined with an insulation system.
Best for:
- Updating tired or cracked façades
- Improving weather resistance
- Protecting exposed walls
- Achieving modern or traditional finishes
- Homes that already retain heat well
Pros & Cons: External Wall Insulation (EWI)
Pros
- Significantly reduces heat loss and lowers energy bills
- Helps eliminate cold spots and condensation
- Provides a fresh, modern appearance with a wide choice of finishes
- Improves indoor comfort all year round
- Reduces carbon footprint
- Adds an extra protective barrier against wind-driven rain
- Can increase property value
- Ideal for homes without cavity walls (e.g., older solid masonry)
Cons
- Higher installation cost than standard rendering
- Extends the wall thickness (may require adapting sills, soffits, or pipework)
- Planning permission may be required in some areas
- Installation relies on good weather conditions
- Requires a trained EWI installer for correct performance
Pros & Cons: Rendering (Non-Insulated)
Pros
- Great for refreshing the look of the property
- Wide choice of finishes: smooth, textured, dash, roughcast, scratch, etc.
- Silicone and acrylic renders offer excellent weather resistance
- More affordable than EWI
- Less intrusive—does not alter building thickness
- Ideal for repairing damaged or uneven walls
- Faster installation time
Cons
- Does not improve insulation or reduce heating bills
- Offers less moisture control on cold, solid walls
- Won’t solve condensation or damp caused by heat loss
- Some cement-based renders can crack if not correctly applied
- May require repainting unless using silicone or monocouche systems
Which Should You Choose?
Choosing between EWI and rendering depends on your goals, the condition of your property, and your long-term plans. Use the guide below to make the right decision.
Choose External Wall Insulation If:
- Your home is cold and loses heat quickly
- You have a solid-wall or older property
- You want to reduce energy bills
- You want to fix condensation or damp caused by thermal bridging
- You’re undertaking a full exterior renovation
- You plan to stay in the property long-term
Choose Rendering If:
- Your walls already retain heat well
- You simply want to improve the look of your property
- You need to repair cracked, blown, or damaged existing render
- You want a new texture or finish
- You’re working with a smaller budget
- You don’t need insulation but want strong weather protection
Summary
Both External Wall Insulation and Rendering offer huge benefits—but they serve different purposes.
- EWI is the best choice for improving energy efficiency, cutting heating costs, and solving cold-wall or condensation issues. It’s a long-term investment that upgrades both the performance and appearance of your home.
- Rendering is ideal if your main goal is to refresh your property’s exterior, improve weather resistance, or repair worn surfaces—without increasing insulation levels.
If you’re unsure which option suits your home, Complete Render South West Ltd can provide an on-site survey and honest advice tailored to your property.
