Does polyiso have a high R-value?
Unlike other insulating materials, the R-value-per-inch of polyiso increases with thickness because of the unique closed-cell structure of the rigid foam boards. Because of its superior R-value and durability, buildings that use polyiso have lower heating and cooling costs. Most polyiso manufacturers have adopted the LTTR method as the exclusive means to measure thermal performance of permeable-faced polyiso roof insulation. Polyiso manufacturers, who belong to the Polyisocyanurate Insulation Manufacturers Association, have certified LTTR-value products verified by the QualityMark Program. Based on consensus standards in both the United States and Canada, Long Term Thermal Resistance (LTTR) is a scientifically supported method to calculate the 15-year, time-weighted average R-value of roof insulation. Most polyiso manufacturers have adopted the LTTR method as the exclusive means to measure thermal performance of permeable-faced polyiso roof insulation.
