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Learn about Polyiso Rigid Board Insulation

Polyiso Rigid Board Insulation

Polyiso rigid board insulation is made of polyisocyanurate foam, a closed-cell foam with a very high insulation value of R-6 to R-6.5 per inch. It can also be made into structurally insulated panels or foamed in place.

Polyiso insulation boards and structural panels can be used for wall sheathing and roofs. Look for products that use low-toxicity flame retardants like TCPP or better - some are even free of TCPP.

ASTM test methods for determining the R-value of a material at a mean temperature of 75°F. Unlike extruded polystyrene (XPS) and expanded polystyrene (EPS), polyiso performance degrades as temperatures dip. As an example, extruded polystyrene (XPS) is rated at R-5 per inch, yet out performs polyiso rated at R-6 in climates below 50°F. This is due to the condensing of trapped blowing-agent gases that can occur at cold temperatures. While the product performs well in warmer climates, it may not in cooler climates. You should also avoid using polyiso in damp climates due to its lack of permeability.

Polyiso is considered one of the most environmentally friendly types of rigid foam board, because it has a high insulation value and typically does not the high global warming potential HFC blowing agents in its manufacture. Many brands also use relatively low-toxicity flame retardants such as TCPP.