Enhancing Fire Safety in Building Facades

M. Abdullah Quadri, Effisus

A high-rise building standing tall amidst a bustling cityscape, a marvel of modern engineering and architectural design. But beneath the surface, there is a silent guardian at work, shielding occupants from potential disasters: the building’s facade. This crucial element is the first line of defense against fire spread, ensuring the safe evacuation of occupants in case of an emergency. Are we doing enough to ensure fire safety in building facades?

Recent research has uncovered that the incidence of façade fire in a high-rise building has dramatically increased over the last 30 years, with an average of 4.8 occurrences per year worldwide; this highlights the dire need for stakeholders like architects, consultants developers etc. to prioritize fire safety in their designs. Fire Safety is no longer an option, but a responsibility we hold as designers of spaces where people live, work, and gather. With the stakes this high, let’s challenge ourselves to not only create buildings that stand tall but also stand safe.

External cladding is a crucial element of any façade system, providing both insulation and protection against the elements. However, it is essential to note that good fire resistance is not the same as fire reaction, and considerations must be made for both.

The choice of cladding material, such as Aluminium Composite Panels (ACP), High-Pressure Laminates (HPL), Glazing, windows, curtain walls, and Fibre-Reinforced Plastic (FRP), can significantly impact a building’s fire safety.

For instance, ACP with a polyethene core has a limited fire performance, with fire spread occurring rapidly across the surface and potentially leading to collapse within 60 minutes, according to British Standard BS 8414.

The fire performance of Continuous Insulation (CI) materials is tested according to EN ISO 13501-1, which

Gallery of UNStudio designs the new UIC building ‘V on Shenton’ in Singapore provides a standardized methodology for the fire classification of construction products and building elements. XPS and PIR foams, for example, are considered combustible and have lower fire performance than non-combustible materials like mineral wool.

Phenolic foam has a high fire performance and is classified as a B-s1, d0 material, meaning it has low smoke production and does not produce flaming droplets.

For Weather/Water-Resistive Barrier (WRB) materials, testing is typically done according to ASTM E84, which measures surface burning characteristics of building materials. However, there are more complete and application-related testing or certification like BS 8414 or NFPA 285 as well as EN 13501 that test for fire performance in the context of the entire façade system. The lack of alignment and standardization in the testing requirements in the different markets is a challenge when protecting our buildings.

It is important to note that the fire resistance of these materials is not the same as fire reaction. While fire resistance refers to the ability of a material to withstand fire for a specified period of time, fire reaction refers to how a material contributes to the spread and intensity of a fire. Therefore, when evaluating the fire safety of façade systems, consideration must be given to both fire resistance and fire reaction properties of the materials used.

Finding the perfect facade solution that meets the project’s functional and aesthetic needs while maintaining adequate fire resistance can be a daunting task for architects and builders. With a variety of membranes and materials to choose from, striking the right balance between flexibility, function, and fire resistance is a delicate compromise that cannot be taken lightly. Ultimately, the safety of building occupants should always be a top priority, and incorporating fire-resistant materials and systems into facade design is essential to mitigate potential risks.

As stated before designers play a crucial role in ensuring the safety of buildings from fire hazards. Building components and materials that do not comply with fire safety standards can be a red flag for designers. The fire incidents in commercial & industrial properties can also be attributed to construction defects. These defects include a lack of fire resistance testing and the use of non-compliant materials, such as those that do not meet the BS 8414 fire safety standard or the EN ISO 13501-1 standard for cladding and other complementary materials. Therefore, considering fire safety at the design stage is essential to prevent devastating building fires and protect the lives of those within its walls.

While internal fires can often be managed with the help of automatic sprinkler systems or firefighters, external fires pose a significant threat to building safety. According to the Fire Protection Research Foundation (FPRF), the spread of fire from the building interior to the exterior facade is one of the most significant challenges in modern building fires. The phenomenon known as “leapfrog” effect occurs when a fire breaches the interior compartment of the building and jumps to the exterior facade. This effect can happen when floor slab fire stopping is missing or not installed to standards or when the curtain wall is not listed. Flames can penetrate gaps in the building and quickly reach upper floors, even propagating downwards if the facade material is flammable. This highlights the importance of preventing the spread of fire to the exterior of the building and reinforces the need to design and construct fire-resistant buildings.

As a fire grows, the temperature within the fire chamber can reach extreme levels. The heat flux - the rate of heat energy transmitted through a unit area - can exceed 120-150kW/m2, according to the National Institute of Standards and Technology (NIST). This intense heat can break window glazing, allowing hot gases to escape from the top of the opening. Hot gases that do not burn inside the room due to limited air can ignite when they reach the exterior where there is enough air to sustain combustion. Flames produced by these gases can reach a temperature of over 500°C, and at a height of 1m, they can produce a heat flux of 50-100kW/m2. These figures illustrate the need for buildings to be designed and constructed to withstand the extreme temperatures and heat fluxes produced by a fire, preventing its spread to other parts of the building.

The spread of fire on the exterior of a building can have devastating consequences. As intense heat builds up behind the facade, flames can begin to delaminate the panels, exposing more combustible materials to the fire. This can result in the rapid engulfing of large areas of the building and multiple storeys of the facade. In addition to the use of flammable materials, other factors that contribute to the rapid spread of flames on the exterior facade include poor installation, inadequate joint detailing, weak mechanical detailing in insulation and facade paneling, and insufficient railing systems.

A recent report by the Grenfell Tower Inquiry highlighted the dangers of cladding, and how inadequate installation and detailing can exacerbate the spread of fire, leading to catastrophic consequences. These factors emphasize the importance of designing and constructing buildings that are resistant to external fires, which can be much more challenging for firefighters to manage.

Ensuring the safety of building occupants is of utmost importance in the construction industry. While regulations have become stricter in many countries, it is still essential to take further steps to improve fire safety in facades. Facades are a system, and it is crucial to understand the fire performance of different materials and the fire reaction of the entire system.

To achieve safer facades, it is recommended to consult with a proper technical team that can help select materials and systems that provide adequate fire resistance while meeting functional and aesthetic requirements.

Non-combustible materials like glass and metal provide both fire resistance and aesthetic appeal. Fire-resistant weatherproofing barriers and insulation should also be used to enhance the safety of building exteriors.

The Future of passive fire protection in building facades is dependent on the combined efforts of various stakeholders, including architects, engineers, manufacturers, regulators and building owners.

By working together, embracing new technologies and materials, and prioritizing education and awareness, we can create a safer built environment that protects lives and assets.

Fire Safe Build India (FSBI) the 2 days conference on passive fire protection has been the Indian Industry’s first effort in spreading awareness & knowledge among the stakeholders of Building design & Construction Industry.