Fire Safety and External Wall Insulation: What Homeowners Need to Know

Fire Safety and External Wall Insulation: What Homeowners Need to Know

When confronted with potential fire threats, appropriate insulation can offer crucial protection, slowing down flame propagation and heat transfer. Thanks to technological advancements and heightened consciousness of fire safety standards, a variety of fire-retardant insulation choices are available.

Whether you're a property owner, builder, or just someone keen on fire safety, this blog is designed to provide you with essential insights into the various degrees of fire-rated insulation prevalent in the UK.

Why is Fire-rated Insulation Important?

Fire-resistant insulation is paramount in safeguarding structures, and it's a vital aspect for homeowners, builders, and designers. Here's why fire-rated insulation holds significant relevance:

  • Safety of Occupants: This is the foremost reason. Insulation that is fire-rated will not ignite easily and will not significantly contribute to the spread of a fire, giving occupants more time to evacuate safely in the event of a fire.
  • Protection of Assets: Fire-rated insulation helps to prevent or slow the spread of fire to other parts of a building, protecting property and valuable assets from fire damage.
  • Maintains Structural Integrity: Fire can compromise the structural integrity of a building. Fire-rated insulation helps preserve the strength of the building's structural components, reducing the risk of collapse during a fire.
  • Limiting Toxic Smoke and Gases: Many fire-rated insulation materials produce limited smoke and fewer toxic gases when exposed to fire. Smoke inhalation is a leading cause of death in fires, so reducing its production can save lives.
  • Compliance with Building Codes and Regulations: British codes have strict requirements for fire resistance, especially in specific types of structures like high-rises, hospitals, schools, and more. Using fire-rated insulation helps ensure compliance with these codes.
  • Reduces Fire Damage Costs: While the primary goal is safety, there's also an economic advantage. Fire-rated insulation can reduce the extent of fire damage, which can potentially lead to lower repair and replacement costs.
  • Insurance Considerations: Many insurance companies might offer more favourable terms or reduced premiums for buildings that incorporate fire-rated materials, including insulation.
  • Peace of Mind: Knowing that a building is equipped with fire-rated insulation can provide peace of mind to occupants, building managers, and owners
  • Environmental Protection: Fires can release harmful pollutants into the environment. By slowing or stopping the spread of fire, fire-rated insulation can help reduce the release of these pollutants.

Is Fireproof Insulation Possible?

Fully fireproof insulation isn't achievable. The terms "fire-resistant" or "fire-retardant" are more precise, and understanding the distinction between them is essential:

  • Fire-resistant: Refers to a material's ability to withstand fire or high temperatures for a specified period without losing its structural integrity. Essentially, fire-resistant materials are designed to resist burning and withstand exposure to direct flame.
  • Fire-retardant: Refers to materials that have been treated (either chemically or through some other means) to reduce their flammability or delay the spread of flames. These materials may eventually burn if exposed to a sustained fire, but they will resist ignition and prevent or slow the spread of fire better than untreated materials.

A Guide to Combustibility

Combustibility refers to a material's propensity to ignite because of fire or a chemical reaction. While a flammable substance can quickly ignite, a combustible one is harder to set alight and might not burn as vigorously. The British Standard outlines classifications for such products. For fire-resistant thermal insulation, you'd ideally seek products with an A1 or A2 rating. Products with lower ratings may, in extreme situations, aid in the spread of flames or even become ignited.

In England, the building regulations related to external wall insulation (EWI) and other building practices are laid out in the Building Regulations. Approved Document B (Fire safety) is particularly crucial given concerns about the flammability of some types of insulation, particularly after incidents like the Grenfell Tower fire. It offers guidelines on the fire performance of building materials, including external wall insulation systems. 


Fire-retardant or Fire-resistant Insulation Materials

Mineral Wool

Mineral wool, which includes both rockwool (derived from basalt) and slag wool (derived from steel mill slag), is inherently fire-resistant due to its mineral-based composition. 

Mineral wool, unlike some other insulation materials, mineral wool doesn't typically need added fire-retardant chemicals, as it is naturally fire-resistant. This is a key advantage of mineral wool over some synthetic insulation materials. 

Here's what makes mineral wool fire-resistant

  • Origin of Materials: Both rockwool and slag wool are made from inorganic materials that inherently have high melting points. These materials are naturally non-combustible.
  • Manufacturing Process: To create mineral wool, raw materials are melted at extremely high temperatures (usually above 1,400°C). The molten material is then spun into a mass of fine fibres. These fibres are then bonded together using a binder to form insulation batts, rolls, or boards. This process ensures that the resulting product can withstand high temperatures without combusting or releasing significant amounts of smoke or toxic gases.
  • Non-Combustible Nature: Mineral wool does not act as a fuel source in a fire. It won't ignite when exposed to an open flame and doesn't contribute to fire spread.
  • Thermal Barrier: Mineral wool can act as a thermal barrier, effectively slowing down the spread of heat and flames in the event of a fire. This provides valuable time for building occupants to evacuate and can help protect structural elements of the building.
  • No Significant Smoke or Toxic Gas Release: In the case of fire, mineral wool doesn't release significant amounts of smoke or toxic gases, two of the primary hazards in building fires.
  • Maintains Integrity: Even when exposed to high temperatures, mineral wool retains its structural integrity and doesn't slump or deteriorate rapidly. This means it continues to act as a barrier during prolonged fire exposure.

Because of these properties, mineral wool is considered an excellent choice for fire safety in building applications, including external wall insulation. When used as part of a properly designed and installed insulation system, mineral wool can significantly enhance a building's overall fire resistance.

However, it's essential to ensure that any external wall insulation system adheres to local fire safety standards and regulations.

Foamed Polystyrene (EPS)

Foamed polystyrene, commonly known as Expanded Polystyrene (EPS), is inherently flammable. However, when used for external wall insulation, EPS often contains fire-retardant additives to help reduce the risk of fire spread.

Fire-Retardant EPS: Most EPS products used in construction, including external wall insulation, are treated with fire-retardant additives to reduce the material's flammability. This means the treated EPS is designed to resist ignition for longer than untreated EPS when exposed to a flame. Fire-retardant EPS will self-extinguish once the ignition source is removed, under controlled conditions.

It's important to note the following:

  • The presence of fire-retardant additives doesn't make EPS non-flammable; it makes the EPS less likely to contribute to the rapid spread of fire.
  • The performance of fire-retardant EPS in an actual fire scenario can depend on several factors, including the thickness of the EPS, the presence of other materials (like external finishes or barriers), and the specific conditions of the fire.
  • For external wall insulation systems incorporating EPS, there are often additional layers, such as protective finishes, render, or cladding, which can also influence the system's overall fire performance.
  • Any external wall insulation system installed in the UK, including those using EPS, must comply with building regulations concerning fire safety. For England, guidance is provided in Approved Document B, which offers details on fire safety requirements for buildings.
  • However, as always it's essential to ensure that EPS, like other combustible insulation materials, is correctly installed and protected with a fire barrier if required by building codes. That's why hiring an experienced insulation company that will professionally install the house insulation with the utmost care and health and safety in mind is the top priority.

Polyurethane Foam

At PD Rendering, polyurethane foam used for external wall insulation is treated with fire-retardant additives to meet building regulations and safety standards. These standards aim to reduce the risk of fire spread across the external facade of a building.

Approved Document B provides guidance on fire safety for buildings in England, and it's crucial to select products that comply with these guidelines.

The fire-retardant coatings on the foam surface don't make the material non-combustible, but they can protect the underlying matrix against thermal degradation and suppress the fire spread without damaging its inherent mechanical properties. 

Polyurethane has the peculiarity that when it comes into contact with the flame, instead of melting, it carbonises, protecting the core of the fire. This causes the structure to remain stable for some time.

For this reason, polyurethane systems are never the origin of a fire. The beginning must be a different one and the isolation, if achieved, will be based on the design of the structural element in which it is integrated, and the time that elapses as the fire develops. The design of the building is key when it comes to fire safety. 

Always ensure that you work with specialists knowledgeable about fire safety regulations relevant to building and insulation. 

Fire-rated insulation is paramount when improving the fire safety of buildings. In order to prevent the spread of flames, minimise smoke production, and protect tenants and property in case of a fire, the consideration of fire performance of insulation materials is crucial. 

Before selecting the fire-rated insulation material, always ensure to consult with an experienced insulation company, review technical specifications, and adhere to local building regulations.

At PD Rendering, our fire safety experts and professionals can provide valuable guidance to ensure the chosen insulation materials meet the required fire ratings and are suitable for the specific application.

Bear in mind, that the information in this article is for general understanding and shouldn't be taken as professional guidance. For specific advice on fire-rated insulation, please get in touch with our fire safety experts.

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