Insulation specified for your building — not the system the installer happens to stock.
EWI systems, external cladding, cavity wall insulation and rendered insulation across East London and the Home Counties. BS 8414 compliant, BBA certified systems, Part L compliant throughout.
Most insulation installers sell one system. We specify what your building actually needs.
The insulation industry has a sales problem. Most installers are tied to one manufacturer's system — EPS board with a thin render coat, applied the same way to every property regardless of wall type, exposure rating, or planning constraints. When the system fails — delaminating render, moisture trapped in the wall, thermal bridging at window reveals — the installer has moved on to the next job.
RCB approaches external wall insulation as a building fabric problem, not a product sale. We survey the existing wall construction, assess moisture conditions, check planning constraints, and specify a system that is right for your building. Where BBA-certified products are required — which is most applications — we use only certified systems and follow the certificate's installation requirements precisely.
We also coordinate with ECO4 funding where eligible — many residential properties qualify for partial or full grant funding for external wall insulation. We will assess eligibility as part of the initial survey and handle the application if appropriate.
What's included
External wall insulation can reduce heating bills by up to 40%, improve your EPC rating by two or more bands, eliminate cold bridging, and prevent damp penetration permanently
How It Works
The RCB process for this service.
Building Fabric Survey
We assess your wall construction type, moisture conditions, existing insulation, and planning constraints. We model the thermal improvement each system would deliver and the impact on your EPC rating. ECO4 eligibility is checked at this stage.
System Specification & Quote
We specify the correct insulation system for your building — not the one we prefer to sell. A fixed price covering all materials, installation, scaffolding, and reinstatement of external features. Planning application managed if required.
Scaffold & Preparation
Scaffolding erected to provide safe working access. Existing render cracked, spalled or hollow sections removed. Wall treated for any mould or damp before insulation is applied. Window and door reveals prepared.
Installation & Finishing
Insulation boards mechanically fixed and adhesive-bonded per BBA certificate requirements. Reinforcing mesh embedded in base coat. Finish coat applied to the specified texture and colour. Scaffolding struck and site cleared. Updated EPC issued.
Planning & Regulations
External wall insulation systems installed in the UK must be covered by a British Board of Agrement (BBA) certificate or equivalent European Technical Assessment (ETA). Systems installed on buildings above 18 metres must be tested to BS 8414 (Fire performance of external cladding systems) and comply with the Building Safety Act 2022 — introduced after the Grenfell Tower tragedy — which bans combustible materials in the external walls of residential buildings over 18m. All external insulation work must comply with Building Regulations Part L (Conservation of Fuel and Power). Cavity wall insulation must comply with BS EN ISO 6946. Properties receiving insulation under ECO4 or the Great British Insulation Scheme must meet PAS 2035 requirements for whole-house retrofit assessment. Cladding options include rendered EWI, brick slip systems, composite panels, zinc cladding, timber-effect (fire-rated Class A1/A2), metal rainscreen, and stone-effect systems — each with specific fire rating and planning requirements.
FAQs
Common questions.
How much does external wall insulation cost for a London terrace?
External wall insulation for a standard 3-bedroom mid-terrace (front elevation only, no rear) typically costs £5,000–£10,000 including all materials, scaffolding, and rendered finish. A semi-detached or end-of-terrace treating two or three elevations typically costs £10,000–£20,000. Costs depend heavily on wall area, existing wall condition, system specified, and finish type. RCB provides fixed prices following a site survey.
Will external wall insulation affect my planning permission?
In most cases, external wall insulation is permitted development — no planning permission is required. However, there are exceptions: properties in conservation areas, listed buildings, Article 4 Direction areas, and some new-build estates with covenants. RCB checks planning constraints as part of the initial survey and manages any required application. In conservation areas, a brick slip or timber cladding finish may be more appropriate than render.
What is ECO4 and do I qualify for free insulation?
ECO4 (Energy Company Obligation 4) is a government scheme requiring energy suppliers to fund energy efficiency improvements in low-income and vulnerable households. If your property has an EPC rating of D or below and you receive certain benefits (or your household income is below a threshold), you may qualify for free or heavily subsidised external wall insulation. RCB assesses ECO4 eligibility as part of every insulation survey.
Can external wall insulation cause damp problems?
Incorrectly installed external wall insulation can cause damp — typically when the system is applied to a wall with existing moisture problems without addressing the root cause, when ventilation at eaves and ground floor is not maintained, or when a vapour-impermeable system is used on a wall that needs to breathe. RCB carries out a moisture assessment before specifying any system and will not install insulation on a wall with unresolved damp. We use vapour-open systems on solid brick walls where appropriate.
How much will external wall insulation improve my EPC rating?
For a solid-walled property with no existing wall insulation, external wall insulation typically improves the EPC rating by two to three bands — for example, from an E to a C, or a D to a B. The exact improvement depends on the insulation thickness, the rest of the building's fabric, and the heating system. RCB models the improvement before installation so you know what to expect, and provides an updated EPC on completion.
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