Organic shingles are generally paper (waste paper) saturated with asphalt to make it waterproof, then a top coating of adhesive asphalt is applied and ceramic granules are then embedded. In the case of algae resistant shingles, a portion of the granules contain leachable paint ceramically coated, designed to protect against discoloration from algae on the roof.
The ceramic granules are embedded in organic shingles for two reasons. The primary reason is to protect the shingles from the sun. The sun’s UV rays are very damaging to asphalt and cause it to deteriorate prematurely. This is one of the same reasons that gravel is used on built-up roofs commonly seen on commercial buildings. The second, and more obvious reason for the granules, is aesthetics. Asphalt shingles are available in a wide variety of colors to match almost any façade or landscape.
Fiberglass shingles have a glass fiber reinforcing mat manufactured to the shape of the shingle. This mat is then coated with asphalt which also contains mineral fillers. The fiberglass mat is used for reinforcement and is not waterproof by itself. Asphalt is used to provide waterproofing properties to the fiberglass shingle. However, the asphalt itself will not stick to the mat. For this reason, “fillers” are used. The fillers in the asphalt cling to the glass fibers in the mat. The asphalt then encapsulates the glass fibers, fills all of the voids in the mat rendering it waterproof. After this cools, adhesive asphalt is used to cover the mat and the ceramic granules are then embedded.
The lifespan of asphalt shingles is highly dependent on the environment in which it is used. Shingles in cooler climates, such as the northern United States, generally last longer than those installed in warmer climates. Studies have shown that the average lifespan for a 20 year shingle in Arizona is around 14 years, in Minnesota the lifespan is 19.5 years, and in Pennsylvania the lifespan is 20.8 years. This data suggests that the hotter the environment, the shorter the service life of the shingles. Thermal shock can also greatly diminish the lifespan of asphalt shingles. Thermal Shock occurs when the ambient temperature changes dramatically within a very short period of time – usually 24 hours. For example, in areas in California, the temperatures during a summer day can often reach 100 degrees and at night they’ll often drop below 50 degrees.
The specific composition breakdown of an asphalt shingle (by weight) is as follows:
- 24% Asphalt Cement
- 4% Limestone or Silica Sand
- 20% Felt (Fiberglass)
- 2% Adhesives (Oil Based)
- 50% Granules