BP ESGARD 1/2" High Density Roof Insulator or High Strength Roof Insulator are composed of interlocking wood fibers impregnated with a water-repellent petroleum wax emulsion that imparts a high resistance to water absorption. The product increases the strength and rigidity of the roof system. It has an ideal surface for the application of hot asphalt and It provides an excellent substrate for the roofing membranes.