External Wall Insulation
Wrap your home in warmth and slash energy bills
External wall insulation typically costs £8,000–£15,000 for a semi-detached home, cuts wall heat loss by up to 70%, and can lift an EPC by two or more bands. ECO4 funding covers some or all of the cost for qualifying East Anglia households — we check eligibility at the free survey.
About External Wall Insulation
External wall insulation (EWI) is one of the most effective ways to reduce heat loss from solid-walled properties common across East Anglia. Many Victorian and Edwardian homes in Cambridge, Bury St Edmunds, and Norwich have solid brick walls with no cavity, losing up to 35% of heat through their walls. By wrapping your home in insulation and protective render, we can cut that heat loss by up to 70% and improve your EPC rating by two or more bands.
Key Benefits
Heat Pump Costs (After BUS Grant)
Insulation is the essential first step before installing a heat pump. These heat pump costs show the savings you unlock once your walls are insulated.
| Property | Heat Pump Size | HP Net Cost | Annual Running |
|---|---|---|---|
| 1-2 bed | 5-6 kW | £0 - £2,500 | £610 - £720 |
| 3-bed semi | 8-10 kW | £500 - £5,500 | £610 - £720 |
| 4-bed detached | 10-12 kW | £3,500 - £10,500 | £610 - £720 |
Helpful Guides
Our Installation Process
Property Assessment
We survey your property, assess wall construction, check for damp issues, and measure all elevations for accurate quoting.
System Selection
We recommend the optimal insulation thickness and render finish based on your wall type, budget, and aesthetic preferences.
Installation
Scaffolding is erected and insulation boards are mechanically fixed and adhesive-bonded to external walls, followed by mesh reinforcement and render application.
Finishing
Final render coat is applied in your chosen colour and texture. We remove scaffolding, clean up, and update your EPC certificate.
Typical Timeline
Works Well With
Insulate first, then install a smaller, cheaper heat pump. The correct order saves thousands.
Airtight insulated homes need mechanical ventilation to maintain fresh air quality.
Insulation reduces total energy demand, meaning solar can cover a larger share of your bills.
Financing
EWI costs £90-£150/m². Mid-terrace £6,000-£10,000; semi £8,000-£15,000; detached £18,000-£30,000. ECO4 may cover full cost (ending 31 Dec 2026). Warm Homes Local Grant (up to £15,000) from 2027. U-value improves from 2.1 to 0.29 W/m²K (86% improvement).
Warranty
- 25-year system warranty
- 10-year workmanship guarantee
- BBA certified EPS, mineral wool, or phenolic systems
- Range of render finishes available
Popular Combinations
Combine services for greater savings. All figures based on typical East Anglia households.
Insulation + Heat Pump
Insulate first, then a smaller heat pump works harder for less. The correct upgrade order.
Insulation + Heat Pump + MVHR
The complete fabric-first retrofit. Airtight, insulated, ventilated, and efficiently heated.
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Frequently Asked Questions
What is external wall insulation?
EWI involves fixing insulation boards (typically 90-150mm thick) to the outside of your walls, then covering with a protective render finish. It is particularly effective for solid-walled properties that cannot have cavity wall insulation.
How much can I save with external wall insulation?
Depending on your property size and current insulation levels, EWI can save £200-£500 per year on heating bills. Combined with a heat pump, the savings compound significantly. Many properties also improve by 2+ EPC bands.
Does EWI require planning permission?
Most EWI installations are covered under permitted development. However, listed buildings, conservation areas, and significant changes to appearance may require permission. We check planning requirements during our initial assessment.
What is the ECO4 scheme and do I qualify?
ECO4 (Energy Company Obligation) provides free or heavily subsidised insulation for eligible households. You may qualify if you receive certain benefits (Universal Credit, Pension Credit, Child Tax Credits) or live in a low-EPC-rated property (D, E, F, or G). We can check your eligibility and handle the application process as an ECO4 approved installer.
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