What is the main advantage of PIR over PUR foam?

PIR has a more stable chemical structure, providing significantly better fire resistance and higher thermal stability. (Refer Introduction).

What is the maximum thermal conductivity allowed by IS 17533?

The maximum aged thermal conductivity is 0.023 W/(m·K). (Table 1).

What are the key fire safety requirements for PIR foam in this standard?

The Limiting Oxygen Index (LOI) must be at least 24%, and it must meet specific criteria for surface spread of flame as per IS 15061. (Table 2 and Table 3).

Which IS code should be used for testing the properties of PIR foam?

IS 17534 provides the comprehensive test methods for rigid polyisocyanurate foam for thermal insulation.

IS 17533

: 2021

Polyisocyanurate (PIR) foam for thermal insulation - Specification

CurrentFrequently UsedSpecificationBIMMEP · Insulation Materials

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This standard specifies the requirements, sampling methods, and tests for rigid polyisocyanurate (PIR) foam intended for use as thermal insulation. It covers material properties such as thermal conductivity, density, compressive strength, and fire performance for PIR supplied in boards, blocks, or other forms.

Specifies requirements for polyisocyanurate (PIR) foam used for thermal insulation.

Quick Reference Values

Maximum Thermal Conductivity (aged)0.023 W/(m.K)

Minimum Compressive Strength (at 10% deformation)150 kPa

Minimum Closed Cell Content90 %

Minimum Limiting Oxygen Index (LOI)24 %

Maximum Water Absorption2.0 % by volume

Dimensional Stability (max % change)1.5 %

Practical Notes

PIR foam offers superior fire resistance and higher service temperatures compared to standard polyurethane (PUR) foam, making it suitable for more demanding applications.

Always use the 'aged' thermal conductivity value for energy performance calculations and building compliance, as the initial value degrades over time.

The type of facing material on the PIR board (e.g., aluminum foil, glass fiber) is critical as it significantly affects fire performance, structural integrity, and water vapor resistance.