An asphalt shingle is a type of roof shingle that uses asphalt for waterproofing. It is one of the most widely used roofing covers in North America because it has a relatively inexpensive up-front cost and is fairly simple to install. Two types of base materials are used to make asphalt shingles, organic and fiberglass. Both are made in a similar manner, with an asphalt-saturated base covered on one or both sides with asphalt or modified-asphalt, the exposed surface impregnated with ceramic granules, and the under-side treated with sand, talc or mica to prevent shingles from sticking to one-another before use. The top surface granules block ultra-violet light, which causes the shingles to deteriorate, provides some physical protection of the asphalt core, and provides color. Lighter shades preferred for their heat reflectivity in sunny climates, darker in cooler ones for their absorption. Self-sealing strips are standard on the underside of shingles to provide resistance to lifting in high winds. An additive known as styrene-butadiene-styrene (SBS), sometimes called modified or rubberized asphalt, is sometimes added to the asphalt mixture to make shingles more pliable, resistant to thermal cracking, and more resistant to damage from hail impacts. Most insurance companies offer discounts to homeowners for using Class 4 impact rated shingles.
Disadvantages - Organic growths such as algae and foliose lichen and woody debris which remains on the shingles will cause premature deterioration through both chemical and physical processes. These should be physically removed from the roof with a copper sulfate, zinc chloride or other solution carefully applied and thoroughly rinsed. To prevent the growth of algae and moss install zinc or copper strips or wire at the ridge and every four to six feet down the roof. Black algae growth can be cleaned with a bleach solution
Approximately 11 million tons of asphalt shingle waste is generated each year in the United States. The most common disposal method for asphalt shingles in the US is landfilling. Waste asphalt shingles do, however, offer a strong potential for recovery and recycling with uses in hot mix asphalt (HMA), cold asphalt patching, and as a fuel in cement kilns.