How does haildamage occure?
Hail forms when water droplets are frozen at high altitudes and are lifted in turbulent updrafts. The longer the frozen droplets stay in the air, the larger these balls of ice become. They eventually become too heavy for the updraft to sustain their flight and they fall as hail. Hail stones vary in size from pea size (1/4 inch diameter, little roof damage), through marble size (3/4 inch in diameter, threshold damage to roof materials) to golf ball size (11/2 inch in diameter, typically severe damage to roofing materials). The amount of damage that a roof receives depends on several factors including wind speed and direction, roof pitch, and roof material. A direct impact of hail on a shingle is more damaging than that of a glancing blow.
Figure 1a illustrates the dynamics of hail impact on two different roof pitches. The home on the left would sustain more roof damage than that on the right, because of the more direct impact of the hail hits as opposed to the less damaging, glancing blow to the house on the right. Wind driven hail can cause a different result.
Figure 1b shows a home on the right with a steep windward facing slope on the left. The slope on the right of this house is protected and most likely undamaged. Both houses may also have siding damage on the windward side.
Figure 2A shows deformation to condensing unit fins on an a/c system, as a result of a wind diven hailstorm. This damage causes reduced air flow through the fin, which leads to higher refrigerant temperatures, lost performance, and lost reliability.
Figure 3A shows siding that has been hit with wind driven hail. The cedar itself is undamaged, but repainting is required.
Hail damage to asphalt shingles includes severe granule loss, material removal at the edges of the shingles, and penetration. Bruising of the substrate my also occur if the hail is large enough. Figure 4A shows a gutter filled with shingle granules that were ejected during a hail storm. The newer the shingle, the more hail resistant it is since asphalt become brittle with age. Warmer shingles are more compliant and more resistant to fracture from hail when compared with colder shingles because they are more pliable. However, warmer shingles release granules easier.
Most hail related damage is cosmetic and does not affect the water shedding capability of a roof, but may reduce the life span of a shingle making a typical 25yr shingle, for example, loose 8 yrs of its effective life. Significant granule loss, penetration of the shingle, and fracture may require shingle replacement.