Polyisocyanurate (PIR) is a highly efficient closed-cell rigid foam insulation material, widely used in construction and industrial applications. To further enhance its performance, PIR boards are often laminated with one or more facing materials, with aluminum foil being one of the most common choices.

Selecting the appropriate type of Aluminium foil used for PIR is crucial as it directly impacts the overall effectiveness and durability of the insulation system. The primary roles of aluminum foil in PIR boards include providing a radiant heat barrier, enhancing water vapor resistance, and improving structural stability and fire performance.
Firstly, the reflective property of aluminum foil is its core advantage. High-purity, bright-surfaced aluminum foil possesses a very low emissivity, capable of reflecting up to 95%-97% of radiant heat. This means in summer, it helps prevent external heat from entering the interior, and in winter, it reduces indoor heat loss to the outside, thereby significantly increasing the overall thermal resistance (R-value) of the PIR insulation board.
Secondly, aluminum foil is an excellent water vapor barrier. While PIR foam itself has some moisture resistance, laminating it with aluminum foil greatly reduces its water vapor permeability. This is vital for preventing moisture ingress into the insulation layer, avoiding performance degradation and material damage due to condensation, especially in high-humidity environments or applications with significant temperature differentials.
Regarding the specific type of aluminum foil, industrial-grade foil with a certain thickness and strength is typically used. The thickness generally ranges from 6 microns to 50 microns, depending on application requirements and the PIR board manufacturing process. Thinner foils might be more susceptible to damage during installation, while thicker foils offer better mechanical strength and durability.
To enhance the mechanical properties of the aluminum foil and its adhesion to the PIR core, manufacturers often use composite or laminated aluminum foils. For example, aluminum foil can be laminated with materials like Kraft paper, glass fiber scrim, or polyethylene (PE) film. Such composite structures, like FSK (Foil-Scrim-Kraft) facers, not only improve the foil's tear strength and dimensional stability but also facilitate better bonding with the foam core during the PIR foaming process.
Surface treatment is also a consideration. Some aluminum foils are coated to enhance their corrosion resistance or improve their adhesion with adhesives. For PIR board production, the aluminum foil surface typically needs to be clean and suitable for reacting and bonding with polyurethane chemicals.
Furthermore, the purity of the selected aluminum foil will affect its reflectivity and corrosion resistance. Typically, aluminum foil used for insulation applications has a high purity to ensure optimal radiant heat reflection and long-term stability.
In terms of fire performance, aluminum foil itself is a non-combustible material. When used as a facing for PIR boards, it can, to some extent, improve the fire rating of the entire board and limit flame spread. Of course, the flame retardant properties of the PIR core itself are also key.
In summary, aluminum foil suitable for PIR insulation materials is typically industrial-grade foil with high reflectivity, low emissivity, and good water vapor barrier properties. Its thickness, whether it's a composite with reinforcing materials (like glass fiber scrim or Kraft paper), and its surface treatment are determined by specific application scenarios and the performance requirements of the PIR board. Choosing the right aluminum foil facing can significantly enhance the thermal performance, durability, and overall reliability of the PIR insulation system.