The sun’s rays are relentless, especially during the early afternoon hours. In addition to the heat, the sun is the source of ultraviolet radiation, which has been shown to degrade and accelerate the aging of the asphalt layers of the shingle. If not for the protective layer of colored granules, roofing shingles would fail very quickly. Other factors such as moisture, pollution and physical effects (roof traffic, hail, snow loads, tree limbs etc.) all contribute to the aging and degredation of roofing shingles.
Seasonal and weather changes can also play a role in the aging of asphalt roofing shingles. For example, consider the common situation in which the roof is bathed in the intense heat of the summer sun. On such a day the rooftop may reach temperatures in excess of 160 F. Now imagine a cold front sweeping through the area, bringing with it the violent thunderstorms that are a common occurence during the sweltering days of summer. Almost instantaneously the rooftop temperature drops 60-100F as it is pounded with a summer shower. Thermal shocks such as this cause the rock deck beneath to expand and contract, placing a strain on the shingles. Year after year this process is repeated, resulting in cyclic fatigue on the shingles.
In addition to all the climatic and external variables that can impact the performance of the roof, consider the internal factors that negatively influence the performance of roofing shingles. Research has confirmed that an improperly ventilated air space inhibits air movement and under most circumstances increases moisture content in comparison with properly vented attic air spaces. Heat shortens the shingle’s life and moisture causes deck movement and/or deterioration, which ultimately affects the performance of shingles.
As you can see, the roofing environment is a hostile one with many factors influencing the longevity of roofing shingles. The natural aging process begins as soon as the shingles are installed on a roof. Day after day the shingles are exposed to the elements – sun, rain, heat and cold. A roof never has a “good day.”
Asphalt is one of the primary ingredients in roofing shingles. Its purpose is to provide the waterproofing integrity for the roof. Secondarily, the asphalt holds the colored granules in place and contributes to the overall strength of the shingle. Asphalt, which is derived from petroleum, contains oils that provide ductility and pliability to the shingles. During the lifetime of the shingles these oils begin to rise to the surface, where they are washed away by rainwater. In an attempt to restore equilibrium, new oils surface and the washing process continues. Also the intense heat of the roof oxidizes or hardens the asphalt over time.