The relationship between wind, hailstone velocity, and impact energy is based on an understanding of fundamental physics. Over a half century of laboratory research and field studies have determined that the severity of hail damage to a roofing material is contingent on the kinetic energy at the point of impact and the roofing material's resistance to that impact energy. These studies have found that a hailstone must be of a certain mass (i.e., size), and it must be traveling at a certain speed (velocity) to result in functional damage to the roofing material. The kinetic energy is a composition of mass and velocity, defined by the following equation:
In our October 2010 newsletter, Bob Whelan, P.E., discussed how to approach a roof hail study by using the scientific method. In summary, one should perform a collateral study of the property, or neighboring properties, to gather information about the particular hailstorm in question.