Polyisocyanurate Foam

NOTE:See also Accepted Roof Deck Insulation products by clicking on this link.

Polyisocyanurate is a closed-cell rigid foam material. The insulation boards are manufactured with asphalt-saturated felt, glass fibre or acrylic facer sheets on the top or bottom of the foam core. In some cases the foam core is reinforced with glass fibre or acrylic to provide additional fire resistance and greater dimensional stability.

Polyisocyanurate foamboard roof insulation is presently manufactured to two standards:

• CAN / ULC S704-01 (CGSB 51-GP-21M) applies to unfaced polyisocyanurate rigid insulation boards intended for applications where the continuous use surface temperature does not exceed +110°C (+230°F). This standard establishes one type (Type 4) and three classes (Class 1, 2 or 3) of polyisocyanurate insulation. The type is determined by the physical properties of the material and the class is determined by its surface burning characteristics.

• CAN / ULC S704-01 (CAN / CGSB-51.26-M86) applies to faced polyisocyanurate rigid insulation boards intended for applications where the continuous use temperature is within -60°C to +80°C (-76°F to +176°F). This standard establishes four types (Type 1, 2, 3, or 4), four facing categories (Facing 1, 2, 3, or 4), and two surface burning characteristic classifications (surface burning characteristic “a” or “b”). The type is determined by the physical properties of the material, the facing is determined by the product the insulation is foamed between, and the surface burning characteristic is derived from the final product's flame spread classification. RoofStar Guarantee Standards require that polyisocyanurate insulation manufacturers clearly identify the manufacturing date on product labels.

Polyisocyanurate insulation provides the following properties and advantages:

• Compatible with asphalt
• Compatible with roof system components
• Resistant to the effects of moisture
• Resistant to cell deterioration
• Resistant to impact
• Resistant to thermal conductivity
• Resistant to fire
• Resistant to thermal cycling (dimensionally stable)
• Unaffected by hot asphalt
• Retains mechanical fasteners

The possible disadvantages or precautions involved in the use of polyisocyanurate foam insulation include:

• Requires an insulation overlay (fibreboard or retrofit board) to prevent potential asphalt blistering
• Aged thermal resistance Long Term Thermal Resistance (LTTR) tested to CAN / ULC -S770 should be used for design calculations.
• Felt skin may change dimensionally if exposed to weathering (provide protection prior to installation)
• Heavy equipment may compress insulation, causing deflections and de-bonding of the membrane
• Will not retain nails (requires screws and plates)

Storage and Handling

See the Technical Update for January 12, 2012 concerning an issue of moisture in packaged polyisocyanurate insulation bundles. Also consult the PIMA Technical Bulletin #109 for storage and handling guidelines.