There are many similarities between polyiso products for roof and wall applications, but there are also some important differences when it comes to facer performance and product testing. Polyiso wall products are typically made with facers such as foil or coated glass. These facers can often be used as barriers to air, vapor or bulk water when the seams and penetrations are treated properly. Although these facers are available for polyiso roofing products, the most commonly used facer for roofing applications is a glass-reinforced fiber (GRF) facer. This facer is not intended to mitigate moisture; the primary benefits are low cost and widespread availability. There are additional differences when it comes to testing. Polyiso roof and wall products both fall under the umbrella of ASTM C1289 but they are subjected to different product and assembly testing outside of that, such as NFPA 285 (walls) or uplifting testing (roof).