A roof insulation system that virtually eliminates ponding water. EnergyGuard™ Ultra Tapered Polyiso Insulation provides a logical and economical answer for roofs that do not permit adequate positive drainage, like low-slope roofs. When correctly installed, tapered insulation helps eliminate problems due to ponding water and can extend the longevity of your low-slope roofing system. It is readily available in the two most popular and efficient tapers, 1/8" (3.18 mm) per foot (305 mm) (1%) and 1/4" (6.35 mm) per foot (3.18 mm) (2%).