Roof Insulation Comparison Analysis EPS vs. PUR

The analysis focused on two main issues: insulation value and flammability. Insulation value is a critical factor in determining the effectiveness of roof insulation. EPS has an average R-value of 4 per 1 inch thickness, depending on the manufacturer. Styropax, a manufacturer of EPS, indicates an R-value of 5. In contrast, PUR has an average R-value of 7 to 8 per inch, depending on the manufacturer. However, no manufacturer's data was submitted to verify the PUR R-values from the National Scientific Corporation of Pakistan. The use of a foil-faced surfacing with PUR can achieve higher R-values, eliminating thermal drift and acting as a radiant barrier. This adhered reflective foil can add R=2 to the total insulating value. Flammability is another critical factor in determining the suitability of roof insulation materials. EPS ignites at around 200 degrees F and reverts back to a liquid state when on fire. In contrast, PUR, being a thermoset material, ignites at a much higher temperature and self-extinguishes when the heat source is removed. For this reason, PUR is recommended. Code-related issues also need to be considered when selecting roof insulation materials. The drawing does not indicate a thermal barrier, such as a deck board or gypsum board, as required by the IBC code (2009) Section 1508 ROOF INSULATION and Section 2603.4 THERMAL BARRIER. However, an exception exists for the deletion of the thermal barrier, provided the roof assembly with the foam plastic insulation satisfactorily passes FM4450 or UL1256. In the event of a fire inside the building, this thermal barrier would help to protect the foam from the fire. The analysis concludes that PUR is recommended based on its higher R-value per inch thickness and its self-extinguishing properties. However, the use of a foil-faced surfacing with PUR can further enhance its insulating value.