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Why EPS Cladding is Potentially Far More Dangerous than Aluminium Composite Panels


By CCN Editor | 23th October 2023

In recent years, the dangers posed by cladding materials in the construction industry have come into sharp focus. High-profile incidents such as the Grenfell Tower fire in London have underscored the importance of choosing cladding materials carefully. One such material that has garnered more recent attention is Expanded Polystyrene (EPS) cladding. In this article, we explore why EPS cladding is considered far more dangerous than Aluminium Composite Panels (ACP) and the risks associated with its use.

Understanding EPS Cladding

Expanded Polystyrene (EPS) is a lightweight construction method wherein polystyrene is attached to a framework and then rendered, creating an outer layer on a building’s facade. It has gained popularity in construction due to its cost-effectiveness, lightweight nature, and insulating properties. However, it also possesses inherent flammability risks that have raised concerns within the industry.

The Flammability of EPS

The primary reasons EPS cladding is considered highly dangerous is its high flammability. Polystyrene, the core material of the EPS cladding, is derived from petroleum and is highly combustible. When exposed to elevated temperatures, EPS can quickly shrink, melt, or ignite. This rapid ignition capability increases the likelihood of fire spreading swiftly, posing a significant risk to both occupants and property.

Styrene Gas Emissions During Thermal Degradation

When subjected to sufficient heat to degrade EPS it undergoes a depolymerization transformation that releases styrene monomer—a highly flammable gas. This gas can fuel and intensify fires, making it challenging for firefighters to control and contain the blaze. Furthermore, styrene gas can create a toxic environment, posing health hazards to those exposed to it.

Dense Smoke Production

EPS cladding contributes to fire hazards not only due to its flammability but also because of the thick, black smoke it produces when burning. Unlike some materials such as PE that burn more cleanly like a paraffin candle, EPS burns with a heavily carbonizing flame, resulting in dense, obscuring smoke. This can hinder evacuation efforts, endangering lives and complicating firefighting operations.

Regulatory Actions

Recognizing the severe risks associated with EPS cladding, regulatory authorities have taken action to mitigate these dangers. In Victoria, Australia, where EPS was widely used in construction over the past two decades, its use as external wall cladding in Class 2-9 buildings of Type A and Type B construction was prohibited as of February 1, 2021.

Identifying EPS Cladding

Identifying EPS cladding on a building can be challenging due to its render covering, which can make it appear similar to rendered concrete. If you tap on a building’s rendered surface and hear a hollow sound, it may indicate the presence of lightweight building materials covered by the render. A small drilled hole can be use to extract a sample for infra-red analysis by a testing laboratory such as ExcelPlas Labs.

Reducing Risks Associated with EPS Cladding

To reduce the risks associated with EPS cladding, the following measures can be taken:

  • Limit the overall use of EPS in construction.
  • Regularly inspect EPS panels for damage and repair them immediately to prevent exposed cores.
  • Store flammable items away from areas where EPS has been used.
  • Raise awareness among occupants and property owners about the associated risks and necessary housekeeping measures to reduce the likelihood of a fire.
  • Contain electrical items near or running through EPS with suitable conduits to reduce the risk of combustibility.
  • Implement a “Hot Works Permit” program to ensure that construction works capable of creating sparks, heat, or flames are carried out safely.
  • Expand the use of fire suppression systems, smoke alarms, and thermal detectors in the vicinity of EPS installations.

Expanded Polystyrene (EPS) cladding presents a significant fire risk due to its high flammability, styrene gas emission, and dense smoke production. The dangers associated with EPS have led to regulatory actions and prohibitions on its use in certain building types. It is crucial for the construction industry and property owners to remain vigilant and take appropriate measures to mitigate the risks associated with EPS cladding, ensuring the safety of occupants and the protection of property.

There are three main reasons why EPS cladding poses greater fire risk than ACP cladding:

-EPS has far thicker sections of the polymer (many centimetres) than the relative thin PE layer (a few mm) in ACP thus EPS presents more fuel load

-The smoke from PS is thick and black since EPS burns with a carbonizing flame unlike PE which burns similar to paraffin candle wax.

-Testing of rendered EPS has shown it results in rapid vertical fire spread and pool fires when exposed to a large fire source, such as from a window opening or an external fire source.

Expanded polystyrene (EPS) could “completely undermine” a building’s ability to stop a fire spreading, Richard Hull, a professor of fire science and chemistry at the University of Central Lancashire has said.

“I’ve seen tests on EPS where it simply melts away behind the [building’s external] render, forming pools of molten polystyrene, which burn like spilled fuel oil, that can run off in different directions,” says Hull, who contributed to a series of reports for the Grenfell Tower inquiry.

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