Black asphalt shingles fade over time due to prolonged exposure to the elements. This gradual process of aging and weathering affects the roof’s aesthetic appeal, often turning deep black to a duller, washed-out gray. While fading is not a sign of immediate failure, it indicates the slow degradation of the shingle’s protective components. Understanding this process helps homeowners make informed decisions about maintenance and material selection.
The Mechanism of True Color Loss
The main cause of true color fading is the sun’s ultraviolet (UV) radiation. UV rays break down the chemical bonds within the asphalt and the pigments coloring the protective ceramic granules on the shingle surface. This photochemical degradation causes the color to lighten, similar to how sunlight fades other outdoor materials.
The second factor is the physical loss of these colored granules. As the roof ages, the asphalt binder dries out and becomes brittle, weakening the bond holding the granules in place. Weathering, such as rain and wind, washes these granules away, exposing the underlying, uncolored asphalt and fiberglass mat. This exposure results in a lighter, faded appearance.
Fading vs. Biological Discoloration
Homeowners often confuse true color fading with biological discoloration, but they are distinct issues with different causes and visual effects. True fading results in the shingle color becoming uniformly lighter, shifting from a rich black to a charcoal or dull gray across the sun-exposed surface. This represents a loss of color pigment and protective material.
Biological discoloration makes the roof look darker, characterized by dark streaks or patches. This staining is caused by Gloeocapsa magma, an airborne cyanobacteria that thrives in warm, humid environments. The bacteria feed on the limestone filler in asphalt shingles and produce a dark pigment to shield themselves from UV light, creating the black streaks. Solutions for true fading involve material protection, while biological growth requires specific cleaning or antimicrobial treatments.
Factors That Accelerate Fading
The rate at which black shingles fade is influenced by environmental and material factors. Roof slopes with a south or west orientation receive the most intense and prolonged direct sunlight, causing them to fade faster than north-facing slopes. This uneven exposure often leads to a patchy, inconsistent appearance across the roof surface.
Climate also influences fading, as regions with a high UV index or extreme temperature fluctuations accelerate the breakdown of asphalt and the loss of granules. Black shingles naturally absorb more solar heat than lighter colors, increasing the material temperature. This heat retention accelerates the drying and oxidation of the asphalt base, making the shingle brittle and prone to premature granule loss. Lower-quality products may also use less durable pigments and fewer protective granules, leading to faster color loss.
Protecting Your Black Shingle Roof
Homeowners can take several steps to minimize or slow the fading and discoloration of a black shingle roof. When selecting new materials, choosing high-quality shingles that incorporate UV-resistant coatings or reflective granules can slow fading. Some manufacturers offer “cool roof” technology, which uses specialized granules to reflect solar energy and reduce absorbed heat.
Proper attic ventilation is important, as it reduces heat buildup under the roof deck. Lowering the shingle temperature from the underside slows the rate at which the asphalt binder deteriorates and releases granules. To combat biological discoloration, select algae-resistant (AR) shingles, which contain copper or zinc granules that inhibit Gloeocapsa magma growth. Installing strips of copper or zinc metal near the roof ridge provides a similar preventative effect as rain washes the metal ions down the surface.