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Is External Wall Insulation Safe?

Last modified: 21.09.2023

External Wall Insulation (EWI) systems are designed to improve the thermal performance of a building's envelope by applying insulating materials to the exterior walls and then finishing with a weather-resistant layer, such as a render, cladding, or brick slips. When designed, installed, and maintained properly, EWI is safe and offers various benefits. However, there are certain factors and potential risks to consider. So is external wall insulation safe?

External Wall Insulation (EWI) offers numerous benefits. Firstly, it significantly improves a building's thermal performance, creating a more comfortable interior and reducing energy costs. This insulation reduces drafts and cold spots, ensuring even warmth distribution inside the building. Aesthetically, EWI can revitalise older structures and enhance the appearance of newer ones. Various finishes, from modern renders to traditional brick slips, allow the building's exterior to be customised. Beyond aesthetics, EWI provides an essential protective layer. It defends the structure against weather extremes, extending its lifespan and minimising maintenance needs. Additionally, by increasing the internal surface temperature of walls, EWI reduces the risk of surface condensation and the associated mould growth, promoting a healthier living environment. In short, EWI effectively blends functionality, protection, and efficiency for buildings.

Fire safety is paramount

when considering any building material or system, including External Wall Insulation (EWI). Ensuring that EWI systems are fire-resistant is essential to protect both the building's inhabitants and the structure itself.

    • Non-combustible Materials: It's essential to use insulation materials that are either non-combustible or have a very low contribution to fire. Mineral wool, for instance, is a commonly used non-combustible insulant.
    • Fire Barriers: Incorporating fire barriers within the insulation system at different levels can prevent the spread of flames and maintain compartmentalisation in case of a fire.
    • Large Scale Tests: It's not enough to test individual materials for fire safety. The entire EWI system, including insulation, fixings, and finishes, should be subjected to large-scale fire tests to evaluate its performance in real-world scenarios.
    • Certification: Only EWI systems with recognised fire performance certifications should be selected, ensuring they've passed stringent tests and meet established safety standards.
    • Clearance from Openings: EWI should be carefully detailed around openings like windows and vents. Proper installation can prevent fire spread via these potential weak points.
    • Proper Fixing: Using the correct fixings and ensuring they are appropriately spaced is vital. This prevents the system from collapsing prematurely in a fire, which could expose combustible layers beneath.
    • Regular Checks: Over time, any damages or wear and tear on the external facade could compromise its fire resistance. Regular inspections and prompt repairs are essential.
    • Avoid Penetrations: After installation, drilling or penetrating the system without proper guidance could compromise its integrity and fire performance.
    • Building Codes: In the UK, fire safety in buildings is primarily governed by the Building Regulations, specifically through Approved Document B (Fire Safety). This document split into two volumes, offers guidance on various fire safety aspects, including means of warning and escape, internal and external fire spread, and provisions for the fire service. Volume 1 pertains to dwellinghouses, while Volume 2 addresses buildings other than dwellinghouses. The regulations emphasise the use of appropriate materials, compartmentation to prevent fire spread, adequate escape routes, and alarms. Beyond the Building Regulations, the Regulatory Reform (Fire Safety) Order 2005 plays a pivotal role, especially for commercial and multi-occupancy residential buildings. It mandates regular fire risk assessments and the implementation of necessary fire safety measures by responsible individuals, such as building owners or managers. Furthermore, the Building (Amendment) Regulations 2018 introduced post-Grenfell, specifically restrict the use of combustible materials in the external walls of certain tall residential buildings.
    • Fire Breaks: Some regulations require the incorporation of fire breaks at regular intervals, especially in multi-story buildings, to prevent the vertical spread of flames.
    • Occupant Education: Building occupants should be made aware of the EWI's features related to fire safety and be given guidance on what (and what not) to do to maintain the system's integrity.

Moisture and dampness in buildings can have multifaceted origins and serious implications. Externally, driving rain, inadequate drainage, and poor construction can introduce water into building structures. Internally, everyday activities like cooking, bathing, and drying clothes produce moisture. If not appropriately managed, this moisture can condense on colder surfaces, leading to interstitial or surface dampness. Moreover, ground moisture can rise through capillary action in walls without proper damp-proof courses, resulting in rising dampness. All these manifestations of dampness can degrade building materials, lead to mould growth, and create an unhealthy indoor environment. Managing and preventing dampness requires a holistic approach. Proper ventilation is crucial to allow moist air to escape, preventing condensation, especially in high-humidity areas like kitchens and bathrooms. Good building design and maintenance, which includes intact damp-proof courses, adequate roof overhangs, and well-maintained gutters, prevent water intrusion. Furthermore, materials chosen for the building should be suitable for the local climate, and barrier systems should be installed to protect against ground moisture. Regular inspections can identify potential moisture issues early, mitigating the risks of structural damage and health hazards.

Regular upkeep of External Wall Insulation (EWI) is vital for its longevity and optimal performance. This entails periodic inspections for damages or wear, ensuring that the protective layer remains intact against external elements. Issues like cracks, peeling, or water ingress should be addressed promptly. Furthermore, any signs of mould or algae growth on the surface may require cleaning or treatment, ensuring the system not only functions properly but also maintains its aesthetic appeal.

The addition of EWI increases the overall thickness of a building's external walls. This has implications for the building's footprint, potentially reducing external space or encroaching on boundaries, especially in properties with tight constraints. Moreover, the augmented thickness can alter the appearance and proportions of windows, doors, and architectural details, potentially changing the building's overall aesthetic and character.

Implementing EWI often requires adherence to specific planning permissions and regulations, especially in conservation areas or on listed buildings. Local planning authorities may have guidelines on aesthetics, materials, and methods to ensure any changes align with the character of the locality. Furthermore, building regulations dictate performance standards. This includes thermal efficiency and fire safety, ensuring that any EWI system installed meets the prescribed safety and efficiency benchmarks.