COVENTRY · THE MIDLANDS · GREATER LONDON
External Wall Insulation for Solid-Wall Homes
External wall insulation is a complete system: insulation boards fixed to the outside of your walls with adhesive and mechanical fixings, a reinforced basecoat, and a weatherproof silicone render finish.
On a solid brick wall it takes the U-value from around 2.1 W/m²K down to 0.30 or better – the standard set by Building Regulations Part L for renovated walls. Around 33% of all heat lost from an uninsulated home goes straight through the walls (Energy Saving Trust).
Graphite EPS from 50mm to 150mm, lambda 0.030-0.031 W/mK
TrustMark registered - Licence No. 3752723
Ceresit systems throughout - BBA Certificate 14/5142
Mineral wool option is Euroclass A1 - non-combustible
25-year insurance-backed guarantee on materials and labour
Trusted by Hundreds of Homeowners Across the Midlands and London
4.7 ★ based on 63 reviews
4.8 ★ based on 49 reviews
5.0 ★ based on 14 reviews
4.7 ★ based on 63 reviews
4.8 ★ based on 49 reviews
5.0 ★ based on 14 reviews
4.7 ★ based on 63 reviews
4.8 ★ based on 49 reviews
5.0 ★ based on 14 reviews
Is My Home Suitable for External Wall Insulation?
Most homes built before 1919 have solid walls - a single skin of brick or stone with no cavity inside. There is nothing in the wall to slow heat down, so it escapes straight through.
External wall insulation - also called outside wall insulation or exterior wall insulation - fixes an insulating layer to the outside face of those walls and finishes it in render. Solid-wall homes are the strongest candidates for it.
Identify Your Walls:
Solid walls have a visible pattern of long and short bricks. Cavity walls only show the long side. If your bricks only show the long side, you have cavity walls - and external insulation is usually not the right answer. We will tell you that at the survey rather than sell you something you do not need.
The Solution:
A layer of insulation on the outside of the wall, finished in render - taking a solid brick wall from around 2.1 W/m²K to 0.30 or better.
Breathable Build-up:
Vapour-open materials let moisture move out of the wall instead of trapping it, which is what stops condensation forming.
What the system is made of:
From the wall outwards: adhesive → insulation board → mechanical fixings → reinforced basecoat with 160 g/m² mesh → primer → silicone render. We use Ceresit systems throughout.
Grey EPS or Mineral Wool
Which System Suits Your Walls?
For most solid brick homes we specify graphite EPS: it reaches the same U-value in less thickness and costs less. For stone or other "breathing" construction, buildings over 18 metres, and anywhere fire performance is critical, we specify mineral wool.
Grey EPS Insulation Boards
Infused with high-quality graphite, these boards provide up to 20% better thermal performance than standard white polystyrene.
✓ Maximised Heat Retention:
Acts as a powerful thermal envelope, cutting heat loss through solid walls from the day it goes on.
✓ Cost-Effective Efficiency:
The most popular choice for modern UK retrofitting, offering the best balance between price and performance.
✓ Moisture Protection:
Correctly installed with our silicone render, it creates a durable barrier against the elements.
Mineral Wool (Rockwool) Systems
Made by melting volcanic rock at around 1,500°C and spinning it into fibres. It is the option we specify where fire performance and breathability matter most.
✓ A1 Fire Resistance:
Completely non-combustible, offering the highest level of fire safety available on the market.
✓ Superior Breathability:
Lets moisture move out of the wall instead of trapping it, which is what stops mould forming.
✓ Acoustic Insulation:
Dense fibrous structure provides an excellent sound barrier, keeping your home quiet and serene.
Expert Material Selection
Our surveyors assess your property to determine the optimal system.
For older stone constructions, we prioritise breathability to reduce the risk of condensation, while for standard solid brick, we focus on thermal density.
Every installation is finished with self-cleaning silicone technology and backed by our 25-year insurance-backed guarantee.
| Feature | Graphite EPS | Mineral Wool |
|---|---|---|
| Thermal conductivity | 0.030-0.031 W/mK | 0.035-0.036 W/mK |
| Thickness for U-value 0.30 on solid brick | ~90 mm | ~100-110 mm |
| Fire classification | Euroclass E | Euroclass A1 (non-combustible) |
| Density | 15-18 kg/m³ | 90-150 kg/m³ |
| Vapour resistance (mu value) | 30-70 | ~1 |
| Acoustic performance | Limited | Good |
| Relative material cost | Baseline | Typically 30-50% higher |
| Best suited to | Solid brick, most domestic retrofits | Stone and "breathing" walls, buildings over 18 m, fire-critical projects |
Typical values for EWI-grade boards. We confirm the specification and U-value calculation for your property before any materials are ordered.
External Wall Insulation Before & After
Four recent projects in Coventry, Birmingham, Leicester and Bedford - solid walls insulated and finished in silicone render.
Drag each slider to compare.
Coventry
Red Brick Terrace
Cold solid brick walls with no cavity
✓ 100mm EPS insulation boards
✓ Kabe silicone render
✓ 25-year insurance-backed guarantee
Birmingham
Pebbledashed Detached
Tired pebbledash over an uninsulated solid wall
✓ Pebbledash covered and walls insulated
✓ Silicate-silicone render finish
✓ Improved EPC rating and weather protection
Leicester
Stained Side Elevation
Algae staining and streaking on an exposed elevation
✓ Solid wall insulation system
✓ 1.5mm coloured silicone render
✓ Algae-resistant finish - no more black streaking
Bedford
Damp-Stained Walls
Staining at the base and cold bridging at the edges
✓ Insulation carried to the edges to stop cold bridging
✓ White Kabe render topcoat
✓ Contrasting protective plinth at ground level
Choosing the Finish for Your Insulated Walls
The insulation does the thermal work. The render on top does everything else – weather protection, breathability, and how the house looks for the next twenty years.
You choose the finish at the design stage, before anything goes on the wall.
Silicone Render Finishes
Every EWI system needs a professional topcoat. Our self-cleaning silicone renders provide a weather-resistant, vapour-open finish that lets the wall dry out rather than trapping moisture, and stays clean for years.
✓ 300+ UV-resistant colours
✓ Self-cleaning technology
✓ Highly breathable & crack-resistant
Traditional Brick Effect Rendering
Want the benefits of insulation without losing the classic look of your home? We specialise in brick-effect render that closely mimics traditional masonry while providing 21st-century thermal performance.
✓ Authentic brick aesthetic
✓ Full thermal benefits of EWI
✓ Far less upkeep than real brick or pointing
Is External Wall Insulation Worth It?
Where Your Heat Goes, and What Insulation Changes
Walls are the single biggest source of heat loss in most solid-wall homes. Insulating them is one of the most effective ways to cut heat loss and improve an EPC rating.
"Around 33% of all heat lost in uninsulated homes escapes through the walls. By insulating your solid walls, you could save energy, lower your heating bill and make your home more comfortable." - Energy Saving Trust
Energy Savings
Insulating solid walls keeps that heat where it belongs - warmer rooms and heating that runs less often.
25-Year Guarantee
Total peace of mind with our comprehensive, 25-year insurance-backed guarantee on materials and labour.
Approved Installers
TrustMark registered and working to PAS standards. Our own teams, on every job - never subcontracted labour.
Value Increase
A completely new exterior in the colour and finish you choose, and a better EPC rating when it comes to selling or letting.
How it Works
How External Wall Insulation is Installed, Step by Step
From the first survey to handing over your guarantee - here is what happens on site, and how long each stage takes.
Free Consultation
We visit your property to measure, discuss your needs, and provide a transparent, no-obligation quote. No hidden costs.
Usually within 7 days of your enquiry
Design & Prep
You choose your perfect colour and finish. We set up safely, carefully protecting your windows, doors, and garden.
Quote provided in 3-7 days;
work starts 2-4 weeks after sign-off
Expert Installation
Our TrustMark registered team installs the insulation and render system, typically over 2 to 4 weeks, with minimal disruption to your daily life.
Typically 2-4 weeks;
up to 20 working days for larger detached homes
Final Sign-Off
We leave your property spotless. We hand over the 25-year guarantee only when you are 100% satisfied with the result.
Immediate upon project completion
0% VAT on External Wall Insulation Until March 2027
Energy-saving materials currently carry zero-rate VAT, so external wall insulation is charged at 0%. On a £15,000 project that is £750 you will not pay if the work is done before the deadline.
From April 2027 the rate moves to 5%.
Rendering without insulation does not qualify - it is standard-rated at 20%.
How Much Does External Wall Insulation Cost?
| Property type | External wall insulation |
|---|---|
| Mid-terrace | £10,000 - £14,000 |
| Semi-detached | £14,000 - £18,000 |
| Detached | £18,000 - £24,000 |
All figures at 0% VAT – energy-saving materials are zero-rated until March 2027. We measure net, not gross: window and door openings come off the square metre count, so you pay for the wall we actually insulate.
Why some quotes come in lower:
- Thinner boards that miss the 0.30 W/m²K target.
- Basecoat without full mesh reinforcement.
- No beading at reveals and corners.
- Guttering and downpipes left where they are rather than moved out to suit the new wall depth – or moved, but not shown anywhere on the quote.
Ask any contractor to put the system name, the board thickness and the U-value in writing. Then the quotes are comparable.
Every quote we give is fixed and in writing after a free site survey, with no hidden costs.
Areas We Cover
Serving the Whole of the Midlands and Greater London
We provide expert solid wall insulation and silicone rendering within a 70-mile radius of Coventry, with a dedicated team serving Greater London.
Not sure if we cover your postcode? While we focus on our core regions, we regularly take on larger projects further afield. Contact us with your project details, and we’ll happily see how we can help.
External Wall Insulation:
Expert Guides & Insights
Everything you need to know about insulating your home, reducing heat loss, and saving on energy bills in the UK.
5 Common External Wall Insulation Mistakes to Avoid
External wall insulation offers many benefits, from lower energy bills to a more comfortable home. However, the benefits only
External Wall Insulation: What’s the Difference Between EPS and Mineral Wool?
External wall insulation is one of the most effective ways to reduce heat loss, cut energy bills, and make
External Wall Rendering: Types of Materials and Finishes for UK Homes
Explore the most popular external wall rendering finishes in the UK, including a range of styles, textures, and materials.
Is External Wall Insulation Worth It?
External wall insulation can significantly improve your home’s energy efficiency and comfort - but is it really worth the
External Wall Insulation for Semi-Detached and Terraced Homes
Learn how external wall insulation works for semi-detached and terraced homes, including its key benefits and what to consider
How Much Does it Cost to Render a House?
Planning rendering work on your house? Learn what affects the price, your finish options, and how to compare quotes
10 EWI & Rendering Projects in the Midlands and Beyond
Real project examples of EWI and render upgrades carried out across the Midlands and London, improving energy efficiency, protection,
Can You Stay at Home During External Wall Insulation or Rendering Works?
Learn how the process works and what level of disruption to expect.
Render Looking Tired? What Causes Cracks, Stains & Green Growth
Learn what causes cracks, stains and algae on external render, how to spot serious issues, and when to repair
Does External Wall Insulation Cause Damp? Risks & Prevention
Learn the real causes of damp after EWI, common risks, and how to prevent moisture issues in your home.
Common Questions
External Wall Insulation – Your Questions Answered
Specification, materials and what happens on site.
How long does external wall insulation last?
The insulation itself does not degrade – it keeps working for as long as it stays dry and intact. What really determines the lifespan of the system is the render and the detailing around windows, the roofline and the base of the wall.
That is why our guarantee covers the whole system, materials and workmanship, for 25 years.
What thickness of insulation will my wall need?
Most solid brick walls need 90 to 100mm of graphite EPS to reach a U-value of 0.30 W/m²K – the standard set by Building Regulations Part L for renovated walls.
We stock boards from 50mm to 150mm, so the thickness is set by your wall and the target U-value rather than by what happens to be on the van.
We confirm the calculation before anything is ordered.
What is an EWI system actually made of?
From the wall outwards: adhesive, insulation board, mechanical fixings, a reinforced basecoat with 160g mesh, a primer, and a silicone render topcoat. Corners and reveals are formed with PVC beads, and the system sits on a 7mm aluminium starter track at the base.
Which insulation systems do you install?
We work exclusively with Ceresit, covered by BBA Certificate 14/5142 – CT16 primer and CT74 silicone render, with the adhesive and basecoat specified to suit the board.
Where a project calls for a different system, we can work to it. Board thickness, fixings and beads are specified to suit your wall.
How much thicker will my walls become?
Around 100mm with a 90mm board plus render. That matters where a wall sits close to a boundary, a pavement or a neighbouring structure. We check clearances at the survey before quoting.
What happens to my gutters, sills and downpipes?
The wall moves out by around 100mm, so guttering, downpipes, window sills, meter boxes and external lights all have to be repositioned to suit the new depth.
We do that work as part of the project, but it is priced separately and itemised on your quote rather than buried in a square metre rate. That way you can see exactly what you are paying for.
Can external wall insulation be installed in winter?
Render needs dry conditions and temperatures above about 5°C to cure properly, so the work is weather-dependent rather than season-dependent.
We install through much of the winter but will pause if conditions turn. Rushing the cure is how cracking starts. The temperature also has to hold for a day or two afterwards while the render cures, which is why we watch the forecast rather than the calendar.
Will I need scaffolding?
Yes, on almost every job. A specialist scaffolding firm erects it, and they handle any pavement or highway permit that is needed – you do not have to arrange anything. It usually stays up for the duration of the works, up to about four weeks.
Do I pay VAT on external wall insulation?
No. Energy-saving materials are zero-rated until the end of March 2027, so insulation is charged at 0%. From April 2027 it goes to 5%. Rendering on its own does not qualify and is charged at 20%.
Does external insulation really stop damp and mould?
Yes – for condensation damp, which is the most common kind. EWI moves the “dew point” to the outside of the wall.
That removes the cold surfaces where condensation forms, which is what allows mould to grow.
Damp caused by rising moisture, failed guttering or leaks needs fixing separately – we check for this at the survey.
What exactly is the "25-Year Guarantee"?
A 25-year insurance-backed guarantee backs every system we install. This covers both materials and workmanship, ensuring your investment is protected long-term.
Can I insulate just my half of a semi or terrace?
Yes, external wall insulation can be installed on just your property.
On a mid-terrace, it is typically applied to the front and rear elevations. On a semi-detached or end-terrace, it also covers the exposed gable side. Where the system meets a neighbour’s wall at the boundary line, our installers form a sealed stop using uPVC stop beads, mesh reinforcement and high-quality sealant. This prevents water ingress and avoids any overhang onto the neighbouring property.
You can find more details in our guide: External Wall Insulation for Semi-Detached and Terraced Homes.
Get Your Free Quote
Leave your details and we'll get back to you within one working day, usually the same day.
Address
Unit L, 34 Bayton Rd, Exhall, Coventry, CV7 9EJ, United Kingdom.
No hard sell. We'll arrange a survey at a time that suits you, and
you'll get a fixed written quote with no obligation.
No hard sell. We'll arrange a survey at a time that suits you, and
you'll get a fixed written quote with no obligation.
Address
Unit L, 34 Bayton Rd, Exhall, Coventry, CV7 9EJ, United Kingdom.