Fire Resistance of Metal Sandwich Panels?

What Are Metal Sandwich Panels?

Metal sandwich panels, officially known as "metal-faced thermal insulation sandwich panels for construction," are self-supporting composite panels consisting of two metal faces and an insulating core bonded between them. The core materials commonly include expanded polystyrene (EPS), extruded polystyrene (XPS), rigid polyurethane foam, rock wool, slag wool, and glass wool. The metal faces are often color-coated steel sheets, and the core can also be foam-applied on site. These panels are widely used in building envelopes due to their lightweight nature, ease of installation, and thermal insulation properties. However, their fire performance varies significantly depending on the core material and structural behavior under fire conditions.

Fire Performance of Metal Sandwich Panels

The fire performance of metal sandwich panels is determined primarily by two factors: the combustibility of the core material and the structural stability of the panel as a whole. For fire walls and fire compartment walls, the core material must be non-combustible because these walls are required to have a fire resistance rating of 1.0 to 3.0 hours or more, evaluated based on load-bearing capacity, integrity, and thermal insulation. Since EPS, XPS, and rigid polyurethane foam are all combustible materials, sandwich panels containing these cores cannot be used as fire walls or fire compartment walls. These materials readily spread flames, produce large amounts of toxic smoke, and are difficult to extinguish. Even with non-combustible cores like rock wool, the panels are self-supporting rather than structurally integrated into the building's primary frame. Under fire exposure, the steel faces soften, the bonding between layers breaks down, and the panel can sag, delaminate, or collapse prematurely. This collapse not only fails to contain fire spread but also hinders evacuation and may cause casualties. For non-load-bearing exterior walls, partition walls, or roof panels where sandwich panels are permitted, the core material must be non-combustible, but this requirement alone does not qualify them for fire separation applications.

In conclusion, metal sandwich panels, regardless of core type, are not suitable as fire walls or fire compartment walls in permanent structures. Combustible cores are clearly prohibited, and even non-combustible cores cannot guarantee the structural stability and integrity required for fire-rated walls. Their self-supporting nature makes them prone to premature collapse under fire conditions, creating additional risks to life safety. The only permissible application is in temporary construction site buildings, provided that the core material meets Class A non-combustible standards and strict fire prevention measures are enforced. Fire incidents in temporary site buildings have been numerous and well documented, serving as a stark reminder that fire safety should never be compromised for the sake of convenience or cost.

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