Fire protection for facades

Key takeaways

Flamro’s Firebreather® technology offers trustworthy, instant fire protection for modern ventilated façades.

By combining state-of-the-art cavity barriers with proven fire safety strategies, Flamro provides a robust, multi-layered system that stops flames immediately, maintains necessary ventilation, and ensures effective compartmentation.

This comprehensive guide explains the challenges of façade fire safety, the science behind cavity barriers, and the critical advantages of Flamro’s solutions, all in line with international testing standards and regulatory requirements.

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The fire safety challenge in modern façades
How does fire spread in the façade?
Ventilated façades: benefits and considerations
Fire compartmentation of the façade
Fire resistance is an integral part of the building envelope
Cavity Barriers: the cornerstone of façade compartmentation
The science behind cavity barriers
Key considerations when selecting a cavity barrier
Advantages of Flamro’s Firebreather® technology
Test methods and standards
Conclusion
FAQs

The fire safety challenge in modern façades

Ventilated façades include protective cladding, a ventilated cavity, and an inner structural wall. This design provides excellent thermal insulation and weather resistance while allowing for creative architectural expression. However, the free airflow behind the cladding, which is essential for preventing moisture buildup, can also serve as a route for fire spread.

The “chimney effect” is a significant concern. In the event of a fire, hot air within the cavity rises rapidly, accelerating flame propagation to speeds of up to 8 meters per minute. When fire enters these concealed spaces, it can quickly travel upward and re-enter the building through windows and other openings. Known as the “Leap-Frog Effect,” this rapid vertical spread makes early containment critical.

Effective passive fire protection, as the Firebreather® Cavity Barrier, is therefore essential. Relying solely on active systems like sprinklers or detectors is inadequate; the façade must incorporate intrinsic safety features to prevent unchecked fire propagation. In this article we will explore everything you need to know about passive fire protection for façades.

How does fire spread in the façade?

Fire spreading only on the outside of cladding is often not that critical, while fire that spreads in the air gap behind the cladding can travel 5-10 times faster in the same time frame due to the rapid buoyancy of hot air in the air gap compared to fire on the outside. Fire spread behind the cladding makes it difficult for firefighters to extinguish.

Chimney effect

Why is fire in cavities and air gaps in facades so dangerous?

Due to the “chimney effect, ” fire in the air gap behind the cladding can spread very quickly. As the oxygen in the air gap is used, the fire seeks more oxygen and moves rapidly upward.

A: Fire bypasses the fire compartment through the perimeter wall-deck joint.

B: Fire bypasses fire compartments via air gaps and breaks windows.

C: Fire spread on the outside of the façade.

Green dotted circle: Fire spread is contained due to use of Firebreather® Cavity Barrier.

The “Leap-frog”effect

A flashover occurs in a room, causing fire to break out of a window. Flames and hot gases escape through the window and spread upwards. The fire discovers gaps and penetrations and breaks into the room above. This fire spread mechanism can potentially repeat.

Even if the cavity itself is fully non-combustible, the extended length of flames created in the “chimney” still allows the flames to reach the next floor level, where windows and other wall penetrations will allow the fire to re-enter the building and maintain the spread of fire.

Ventilated façades: benefits and considerations

Ventilated façades offer many key benefits:

Thermal efficiency: The air cavity significantly reduces heat transfer, leading to lower energy consumption.

Weather protection: The outer cladding shields the building from wind, rain, and other environmental elements.

Design flexibility: Architects enjoy a wide range of materials and finishes that can be adapted to any aesthetic.

Economic value: Long-term savings on energy and maintenance costs enhance overall building value.

Despite these advantages, the very features that make ventilated façades desirable, specifically the open air gap, can also facilitate rapid fire spread.

Without integrated fire safety measures, these systems risk transforming an isolated incident into a catastrophic event.

One effective mitigation strategy is façade compartmentation, which subdivides the façade into smaller, manageable fire compartments.

This approach contains any fire that occurs, protecting the overall structure and providing essential time for emergency response.

The 2017 Grenfell Tower fire in London, which resulted in 72 deaths, heightened the focus on fire safety in façades, particularly in high-rise buildings. An independent review of UK building regulations led to studies and a ban on combustible cladding, increasing global attention on fire protection for façades.

Fire compartmentation of the façade

Just like fire cells inside a building, façade compartmentation prevents fire from spreading in the facade and eventually to the entire building.

A façade can be divided into fire compartments by using ventilated cavity barriers at floor level, ensuring that normal ventilation of the façade is maintained and at the same time ensuring effective fire protection. Cavity compartments are designed to limit the extent of hidden fire in a façade to an area where fire can self-extinguish, or to give a more controlled access for firemen either through the cladding panels, or through the insulating wall from the inside of the building.

A cavity compartment usually coincides with the extent of fire compartmentation of rooms inside. It is cavity barriers that make cavity compartmentation possible. Typically 25 or 50mm deep, they cover the cross section of a fire compartment inside. Cavity compartments can be fairly small, or span vertically from the bottom sill to the top of the wall, depending on the fire strategy. They typically cover from 10 square meters up to a few hundred square meters.

Effective façade compartmentation is essential for limiting the spread of fire and protecting the building’s overall integrity. By subdividing the façade into smaller compartments using cavity barriers, the risk of a hidden fire escalating into a building-wide disaster is dramatically reduced.

Analogous to fire cells within an interior layout, façade compartments are created by:

Horizontal Subdivision: Installing ventilated cavity barriers at each floor level to separate different fire cells.
Vertical Isolation: Employing non-ventilated fire stops at critical junctions to further restrict flame propagation.

This strategy not only confines the fire to a limited area but also provides firefighters with a more manageable scenario during emergency responses.

Fire resistance is an integral part of the building envelope

Based on the compartement requirements, a façade must neither propagate fire, nor allow fire or heat to travel from one area to another. The facade should also remain structurally intact for a reasonable amount of time when exposed to fire. That ultimately means that:

The separating function between fire cells must be maintained.

Spread of flame within the wall must be stopped

Spread of fire along the surface of the building façade should be limited.

Cavity Barriers: the cornerstone of façade compartmentation

What are cavity barriers?

Cavity barriers are passive fire-stopping devices installed within the façade cavity. They serve several critical functions:

Fire Containment: By sealing off the cavity, they prevent flames and hot gases from spreading laterally or vertically.
Structural Compartmentation: They divide the façade into smaller fire compartments—akin to internal fire cells—limiting the potential spread of a hidden fire.
Passive Safety: Operating continuously without mechanical activation, these barriers rely on their intrinsic material properties to resist fire.

By permanently subdividing the façade, cavity barriers play an essential role in isolating fire incidents, maintaining the building’s integrity, and providing a vital line of defense during emergencies.

Types of ventilated cavity barriers

There are two primary types of cavity barriers used in modern façade systems:

Open state cavity barriers

Open state cavity barriers are engineered to maintain normal ventilation by leaving an air gap during non-fire conditions. Typically, these barriers are made from intumescent strips, sometimes wrapped in plastic or combined with mineral wool.

Under normal conditions, they allow the façade to breathe and maintain energy efficiency. However, during a fire event, they depend on the intumescent material to expand and seal the gap—a process that can take several minutes. This delay may allow flames and hot gases to infiltrate the cavity before full closure is achieved.

Open state fire resistant rated cavity barriers

Open state fire resistance-rated cavity barriers provide immediate and continuous protection without compromising normal ventilation. These advanced systems are designed to prevent the passage of flames, hot gases, or embers from the very first moment a fire is detected.

Flamro’s Firebreather® Cavity Barrier exemplifies this approach, incorporating a flame-arresting element, a heat-absorbing component, and an intumescent strips that seals the cavity instantly. This multi-layered design ensures that the barrier functions effectively from the first second of fire exposure, eliminating delays and mitigating risks associated with conventional systems.

This video compares the performances of the Firebreather® Cavity Barrier with a competing product. When products are exposed to a high fire density, the Firebreather® Cavity Barrier stops the flames immediately, while the competing product allows the flames to pass for several minutes. In a real situation, the risk of fire spread to the entire building is real.

The science behind cavity barriers

Intumescent technology and flame arresting

At the heart of every effective cavity barrier lies an intumescent material, a substance that dramatically expands when exposed to high temperatures. This expansion is critical for several reasons:

Rapid Sealing: Upon exposure to fire, the intumescent material swells quickly to fill the cavity, closing off any gaps that could allow fire spread.
Thermal Insulation: The expanded material acts as an insulator, minimizing heat transfer to the unexposed side of the barrier.
Flame Arresting: In advanced systems such as Firebreather®, the intumescent material works alongside specialized flame arresting elements to ensure that fire cannot breach the barrier even momentarily.

This combination of rapid expansion and thermal protection provides a robust defense against the rapid propagation of fire in ventilated façades.

How cavity barriers function in real-world conditions

In practice, cavity barriers are mechanically fixed within the façade cavity to ensure they remain in place even under intense thermal stress. Their continuous installation along horizontal and vertical joints prevents any gaps through which flames or hot gases might escape. Critical performance metrics include:

Integrity (E): The barrier must prevent any flame transmission to the unexposed side.
Insulation (I): The temperature increase on the unexposed side should stay within safe limits, typically averaging no more than 140°C and never exceeding 180°C at any single point.

Open state fire resistant cavity barriers provide the precious seconds required to contain the fire by sealing the cavity almost instantly. This preserves the integrity of the overall façade and allows firefighters to intervene effectively.

Key considerations when selecting a cavity barrier

Choosing the right cavity barrier is crucial for balancing ventilation and fire protection. When evaluating products, it is important to consider:

Performance ratings

Look for robust integrity (E) and insulation (I) ratings. An EI rating of at least 30 minutes is typically required to ensure reliable performance.

Air gap maintenance

The barrier must preserve the necessary air gap and vertical ventilation under normal operating conditions to maintain the façade’s energy efficiency.

Immediate closure

The ideal product must prevent any flame penetration from the very first moment of fire exposure.

Resistance to direct flame impingement

The barrier must be capable of withstanding direct flame contact without degrading.

Ember and droplet prevention

Effective systems must stop burning droplets and embers from entering the cavity, reducing the risk of secondary fires.

Secure installation

Proper mechanical fixing is essential to ensure that the barrier remains effective throughout the building’s lifespan.

Third-party certification

Products should be rigorously tested and certified under recognized standards such as EN 1366-4 and ASTM E2912.

Comprehensive documentation

Detailed technical specifications and product documentation are essential for ensuring regulatory compliance and instilling confidence among fire safety professionals.

Flamro’s Firebreather® Cavity Barrier is meticulously designed to meet all these criteria, offering a state-of-the-art solution that balances exceptional ventilation performance with unparalleled fire protection.

Advantages of Flamro’s Firebreather® technology

100% passive. Our products are passive, meaning there are no moving parts, detectors, activation, or cabling.

Application areas. The Firebreather® technology can be applied in different configurations, and application areas. Our ventilated fire stopping solutions can be implemented and customized in construction, offshore installations, shipping, batteries, industry, and more.

View our Firebreather® Cavity Barrier

Instant flame arrest. The Firebreather® technology and products have key advantages including stopping flames instantly, from the first second.

Multiple Fire ratings. The minimum fire rating (EI) requirement for cavity barriers is 30 minutes. Firebreather® Cavity Barrier is available in EI30, 60, and 90.

Test methods and standards

Ensuring that façade fire safety systems adhere to rigorous regulatory standards is critical for both safety and market acceptance. Flamro’s Firebreather® products comply with international standards and have undergone extensive third-party testing. Key certifications include:

EN 1366-4: This European standard governs the fire resistance of linear joint seals, ensuring that cavity barriers effectively block flames and heat.
ASTM E2912: An American standard that tests the performance of fire dampers under sudden flame impingement.
Large-Scale Façade Tests (SP105, BS8414, Lepir2): These comprehensive tests simulate real-world conditions, confirming that the entire façade system performs reliably during a fire.

These certifications assure fire safety engineers, architects, and building professionals that Flamro’s Firebreather® solutions not only meet but often exceed the most stringent safety requirements.

Integrated fire safety solutions for modern buildings

At Flamro, we understand that achieving comprehensive fire safety in modern buildings requires an integrated approach. Our portfolio of solutions not only addresses cavity protection but also includes:

Firebreather® Eaves Vent: Engineered to ensure necessary ventilation to cold attics while preventing the ingress of flames and hot gases through the eaves.
Firebreather® Air Transfer Grille: Engineered to maintain safe air circulation through fire compartment boundaries inside the building without compromising the fire rating of the structure.

Together, these products form a cohesive fire safety system that meets the needs of architects, fire safety engineers, and building contractors. Our solutions are designed to integrate seamlessly into your project from the design phase through installation and maintenance, ensuring long-term safety and performance.

Conclusion

Modern architectural design demands solutions that are as innovative as they are safe. Ventilated façades offer tremendous benefits in energy efficiency, aesthetics, and structural flexibility, yet they also present unique fire safety challenges. Flamro’s commitment to advanced fire protection through our Firebreather® technology ensures that every façade is equipped to meet these challenges head-on.

Our integrated approach, combining instant flame arrest, multi-layered protection, and robust compartmentation, delivers unparalleled fire safety for modern buildings. Flamro’s Firebreather® Cavity Barrier, along with complementary products like the Firebreather® Eaves Vent and Firebreather Air Transfer Grille, forms a comprehensive fire safety strategy that not only meets but exceeds international standards.

For fire safety engineers, architects, and building professionals, Flamro provides an authoritative resource on façade fire safety protection. Our solutions provide peace of mind by protecting lives, property, and the future of modern architecture through advanced, rigorously tested fire safety systems.

Discover how Flamro’s innovative solutions can enhance the safety and performance of your next project by exploring our Firebreather® products and reviewing detailed technical information on Flamro’s Firebreather® Technology.

References

European Commission – Construction Products Regulation: Information on harmonized standards and regulatory requirements. Available at: European Commission
ASTM International – ASTM E2912: Standard Test Method for Fire-Test-Response of Non-Mechanical Fire Dampers Used in Vented Construction. Available at: ASTM International
EN 1366-4 – Fire Resistance Tests for Linear Joint Seals: Published by the European Committee for Standardization (CEN).
Fire Safe Europe – Fire Safety in Façades: An overview of fire safety challenges and solutions in façade construction. Available at: Fire Safe Europe

Questions about cavity barriers in façades? We have the answers.

What is the difference between “open state” and “open state fire resistance rated” cavity barriers?

There are two types of ventilated cavity barriers: “open state” cavity barriers and “open state fire resistance rated” cavity barriers. “Open state” cavity barriers provide ventilation of the façade cavity thanks to a gap that allows air flow. They are commonly either plastic-wrapped intumescent strips, or a combination of mineral wool slab and some intumescent. These can take several minutes to fully close the cavity in case of a fire. “Open state fire resistance rated” cavity barriers do not let flames nor heat pass at any time in case of a fire, while ensuring ventilation in normal time. Flamro provides “Open state fire resistance rated” cavity barriers are made of arresting elements that will keep flames and heat from entering the air gap during the first couple minutes in addition to some intumescent material that will fully close the cavity during that time.

What is a ventilated façade? What are its benefits?

A ventilated façade is a light construction fitted on the external wall of a building. The façade aims at insulating the building from heat, cold, and unwanted weather events. While ventilated façades are perceived economically and aesthetically advantageous to a growing number of architects and builders, they need special attention regarding risk of fire. Therefore, compartmentation of the façade cavity and the use of ventilated cavity barriers are required. Flamro offers “Open state fire resistance rated” cavity barriers do not let flames nor heat pass at any time in case of a fire, while ensuring ventilation in normal time.

What is cavity barrier?

Cavity Barriers are passive fire-stopping pieces of fire-stopping material used in building cavities. They are used to close concealed spaces and prevent penetration of flames, thus restricting the movement of fire within a building. Compartmentation of the façade cavity and the use of cavity barriers are essential to stop fire from spreading to other parts of a building. Installed horizontally at each floor and vertically at wall level, they prevent the spread of fire accentuated by the chimney effect. Cavity barriers can be solid cavity barriers or ventilating cavity barriers. In the ventilating cavity barriers category, we find “open state”, and “open state resistance rated” cavity barriers. The key difference is that the latter do not let flames or heat pass at any time in case of a fire, while allowing ventilation in normal time.

What to consider when selecting a cavity barrier?

There are several considerations when selecting a cavity barrier. Depending on the requirements, the cavity barrier should: - Have integrity (E) and insulation (I) ratings. - Maintain air gap and vertical ventilation as in open state. - Provide full closure. Note that the test standard does not test for closure of the air gap until 5 minutes into the test, the product should not let flames pass at any time. - Withstand direct flame impingement. - Keep embers from entering the air gap. - Be mechanically fixed so it will not fall out during a fire. - Have no loss of expanded intumescent. - Stop burning droplets from spreading fire downwards in the construction. - Maintain performance for the life span of the building. - Have an openly available product documentation and be tested according to a relevant test standard. - Preferably be third-party tested, by means of a full-scale façade test, for example by cladding producers.

How do cavity barriers work?

One of the most important parts of a cavity barrier is the intumescent that will swell and increase in volume when exposed to high heat. Intumescent materials are most typically utilised within construction products to maintain or reinstate the fire resistance of buildings. For example, within walls, floors, and ceilings. In a fire, an intumescent product will swell until completely closing-off the gap or cavity and block further spread of fire in the construction. Cavity barriers should restrict fire in the air gap so that the only fire strain comes from the outside, instead of both sides of the cladding. This will keep the temperature and the fire load on the facade much lower, and greatly reduce the risk of fire spreading to other compartments.

Are cavity barriers needed if the materials in the cavity are non-combustible?

Even if materials in the cavity are non-combustible, the extended lengths of flames enabled by the chimney effect can spread to other storeys and re-enter the building’s windows and penetrations. Therefore, the use of cavity barriers able to withstand direct flame impingement are crucial to stop the fire from spreading, also in façades with only non-combustible materials.

Difference between reaction to fire and resistance to fire?

A material's reaction to fire is an indication of how it responds to fire – whether it flares or contributes to the spread of fire. By contrast, a material's resistance to fire measures how well it performs in containing the fire, preventing it from spreading elsewhere.

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Fire protection for facades: trustworthy passive fire protection with the Firebreather® technology