Asphalt shingles come in two basic types: glass fiber (a.k.a. fiber glass) and organic. Organic shingles consist of an organic felt material which is generally paper saturated with asphalt to make it waterproof. A top coating of adhesive asphalt is then applied and the ceramic granules are then embedded. Organic shingles contain around 40% more asphalt per square (100 sq. ft.) than their glass fiber counterpart which makes them weigh more and gives them excellent durability and blow-off resistance.

Glass fiber shingles have a glass fiber reinforcing mat manufactured to the shape of the shingle. This mat is then coated with asphalt which contains mineral fillers. The glass fiber mat is not waterproof by itself. It's purpose is for reinforcement. What makes the glass fiber shingle waterproof is the asphalt. 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 little holes and voids in the mat rendering it waterproof. After this cools a bit, an adhesive asphalt is used to cover the mat and the ceramic granules are then embedded.

The ceraminc granules are there 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. 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 facade or landscape.

So which type is better? By far, the more popular shingles are the glass fiber ones. This may be attributed to the fact that they are cheaper and easier to manufacturer than organic shingles making them more cost effective to the homeowner, or it may be that they are easier to work with, or they may simply be a personal preference of the roofing contractor.


The lifespan of asphalt shingles depends highly upon the environment. Shingles in cooler climates such as the northern United States seem to last longer than those installed in the warmer climates. Studies have shown that the average lifespan for a 20 year shingle in Phoenix, Arizona is around 14 years. In Minneapolis, Minnesota the lifespan was 19.5 years. And in Reading, Pennsylvania, the lifespan was 20.8 years. From this data it seems obvious that the hotter the environment is, the shorter the service life of the shingles. One thing that's very damaging to shingles is Thermal Shock. Thermal Shock is what roofing materials experience when the ambient temperature changes dramatically within a very short period of time - usually 24 hours. For example, in Yreka, California, the temperatures during a summer day can often reach 100 degrees and at night, they'll often drop below 50, sometimes as low as 40. Roofing materials are unable to expand and contract to accommodate such a dramatic temperature change in such a short period of time so cracks and splits in the materials start occurring. Water can then enter the materials and damage them further in two ways. One is the damage water does to asphalt materials in general. It's not that water hurts asphalt, but algae and fungus do and the continuous presence of water will permit algae and fungus to grow on asphalt materials. Another way water damages is the freeze-thaw cycle. In the cold months, water will get into the cracks and then freeze at night. Water expands as it freezes so the more this occurs, the bigger the cracks or splits become. This is why most roofing contractors and consultants are such big advocates of sloped roofs. The better the roof sheds water, the less problems it will usually experience.

Still another factor affecting asphalt shingle roofs is attic ventilation. Proper roof ventilation has been known to extend the service life of a roof. Whether it is because it has a direct effect on the shingle themselves or on the other components such as the roof deck is uncertain.