Asphalt shingle

Asphalt shingles are an American invention by Henry Reynolds of Grand Rapids, Michigan. They were first used in 1903, in general use in parts of the United States by 1911 and by 1939 11 million squares () of shingles were being produced. A U.S. National Board of Fire Underwriters campaign to eliminate the use of wood shingles on roofs was a contributing factor in the growth in popularity of asphalt shingles during the 1920s. The forerunner of these shingles was first developed in 1893 and called asphalt prepared roofing, which was similar to asphalt roll roofing without the surface granules. In 1897 slate granules were added to the surface to make the material more durable. Types of granules tested have included mica, oyster shells, slate, dolomite, fly-ash, silica and clay. In 1901 this material was first cut into strips for use as one-tab and multi-tab shingles. All shingles were organic at first with the base material, called felt, being primarily cotton rag until the 1920s when cotton rag became more expensive and alternative materials were used. Other organic materials used as the felt included wool, jute or manila, and wood pulp. In 1926 the Asphalt Shingle and Research Institute with the National Bureau of Standards tested 22 types of experimental felts and found no significant differences in performance. In the 1950s self-sealing and manually applied adhesives began to be used to help prevent wind damage to shingle roofs. The design standard was for the self-sealing strips of adhesive to be fully adhered after sixteen hours at . Also in the 1950s testing on the use of staples rather than roofing nails was carried out showing they could perform as well as nails but with six staples compared with four nails. Also in the 1960s research into hail damage found that it occurs when hail reaches a size larger than . The Asphalt Roofing Manufacturers Association (ARMA) formed the High Wind Task Force in 1990 to continue research to improve shingle wind resistance. In 1996, a partnership between members of the U.S. property insurance industry, the Institute of Business and Home Safety, and the Underwriter's Laboratory (UL) was established to create an impact resistance classification system for roofing materials. The system, known as UL 2218, established a national standard for impact resistance. Subsequently, insurers offered discounted premiums for policies on structures using shingles that carried the highest impact classification (class 4). In 1998, Texas Insurance Commissioner Elton Bomer mandated that Texas provide premium discounts to policyholders that installed class 4 roofs. ==Types==

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 slate, schist, quartz, vitrified brick, stone, Fiberglass Fiberglass reinforcement was devised as the replacement for asbestos in organic mat shingles. Fiberglass shingles have a base layer of glass fiber reinforcing mat made from wet, random-laid glass fibers bonded with urea-formaldehyde resin. The mat is then coated with asphalt containing mineral fillers to make it waterproof. Such shingles resist fire better than those with organic/paper mats, making them eligible for as high as a class "A" rating. Area density typically ranges from . Fiberglass shingles gradually began to replace organic felt shingles, and by 1982 overtook them in use. Widespread hurricane damage in Florida during the 1990s prompted the industry to adhere to a 1700-gram tear value on finished asphalt shingles. Per 2003 International Building Code Sections 1507.2.1 and 1507.2.2, asphalt shingles shall only be used on roof slopes of two units vertical in 12 units horizontal (17% slope) or greater. Asphalt shingles shall be fastened to solidly sheathed decks. Shallower slopes require asphalt rolled roofing, or other roofing treatment. Architectural or three-tab Asphalt shingles come in two standard design options: architectural (also known as dimensional) shingles, and three-tab shingles. Three-tab are essentially flat simple shingles with a uniform shape and size. They use less material and are thinner than architectural shingles, and are therefore lighter and lower cost for both the material and the installation. They also do not last as long or offer manufacturer's warranties as long as good architectural asphalt shingles. Three-tab are still the most commonly installed in lower-value homes, such as those used as rental properties. However, they are declining in popularity in favor of the architectural style. Dimensional, or architectural shingles are thicker and stronger, vary in shape and size, and offer more aesthetic appeal; casting more distinct, random shadow lines better mimics the appearance of traditional roofing materials such as wood shake shingles. The result is a more natural, traditional look. While more expensive to install, they come with longer manufacturer's warranties, sometimes up to 50 years - typically prorated, as virtually all asphalt shingle roofs are replaced before such an expiration could be reached. While three-tab shingles typically need to be replaced after 15–18 years, Dimensional typically last 24–30 years. ==Qualities==

Asphalt shingles have varying qualities which help them survive wind, hail, or fire damage and discoloration. • The American Society of Testing Materials (ASTM) has developed specifications for roof shingles: ASTM D 225-86 (Asphalt Shingles (Organic Felt) Surfaced with Mineral Granules) and ASTM D3462-87 (Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules), ASTM D3161, Standard Test Method for Wind-Resistance of Asphalt Shingles (2005), • Many shapes and textures of asphalt shingles are available: 3-tab, jet, "signature cut", Art-Loc, t-lock, tie lock, etc. Architectural (laminated) shingles are a multi-layer, laminated shingle which gives more varied, contoured visual effect to a roof surface and add more resistance for water. These shingles are designed to avoid repetitive patterns in the shingle appearance. Hip and ridge lines can have standard three-tab shingles cut to fit. Manufacturers also make specialized shingles for these areas. Starter shingles are also required and, because they are not visible after installation is complete, the use of extra shingles (commonly referred to as 'waste') are used here. However, manufacturers also make a specialized starter row shingle. The use of specialized ridge/hip shingles and the use of specialized starter row shingles, results in decreased labor expenses in exchange for an increase in material cost. Laminated shingles are heavier and more durable than traditional three-tab shingle designs. • Solar reflecting shingles help reduce air conditioning costs in hot climates by being a better reflective surface. • Wind damage: Asphalt shingles come in varying resistance to wind damage. Shingles with the highest fastener pull through resistance, bond strength of the self-seal adhesive, properly nailed will resist wind damage the best. Extra precautions can be taken in high wind areas to fasten a durable underlayment and/or seal the plywood seams in the event the shingles are blown off. UL 997 Wind Resistance of Prepared Roof Covering Materials class 1 is best Wind Resistance roof standard and ASTM D 3161 class F is best for bond strength. • Hail damage: Hail storms can damage asphalt shingles. For impact resistance UL 2218 Class 4 is best. This increases survivability from hailstorms, but the shingles become more susceptible to hail damage with age. Shingles tend to last longer where the weather stays consistent, either consistently warm, or consistently cool. Thermal shock can damage shingles, when the ambient temperature changes dramatically within a very short period of time. "Experiments...have noted that the greatest cause of asphalt shingle aging is thermal loading." Shingles should not be applied when temperatures are below 10 °C (50 °F), as each shingle must seal to the layer below it to form a monolithic structure. The underlying exposed asphalt must be softened by sunlight and heat to form a proper bond. The protective nature of asphalt shingles primarily comes from the long-chain hydrocarbons impregnating the paper. Over time in the hot sun, the hydrocarbons soften and when rain falls the hydrocarbons are gradually washed out of the shingles and down onto the ground. Along eaves and complex rooflines more water is channeled so in these areas the loss occurs more quickly. Eventually the loss of the heavy oils causes the fibers to shrink, exposing the nail heads under the shingle flaps. The shrinkage also breaks up the surface coating of sand adhered to the surface of the paper, and eventually causes the paper to begin to tear itself apart. Once the nail heads are exposed, water running down the roof can seep into the building around the nail shank, resulting in rotting of roof building materials and causing moisture damage to ceilings and paint inside. ==Maintenance==

Cycles of wet and dry environmental conditions, as well as 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. Performed regularly, physical removal of debris, and physical or chemical removal of organic growth (for example, using a copper sulfate, zinc chloride, or other solution carefully applied and thoroughly rinsed), can prolong the life of asphalt roofing materials. ==Disposal and recycling==

Disposal methods According to a 2007 study conducted for the United States Environmental Protection Agency (EPA), approximately of asphalt shingle waste is generated each year in the United States, with the most common disposal method being landfilling. Waste asphalt shingles, however, can be recycled. Recycling Reclaimed asphalt shingles (RAS) can be broken down and incorporated into asphalt concrete mixtures, which are used to form pavements and road surfaces. RAS are an attractive component in recycled asphalt mixes, primarily due to their relatively high content of asphalt cement, which acts as the binding element in asphalt concrete. There are two forms of RAS: post-manufacturer shingles that are reclaimed from factory waste, and post-consumer shingles that are reclaimed at the end of their service life (also referred to as “tear-offs”). The majority of asphalt shingle waste is post-consumer. When RAS binder is combined with low-grade virgin binder, it has been demonstrated to provide some beneficial properties, such as increased resistance to rutting. Health and safety concerns The use of RAS in recycled asphalt mixes is entirely prohibited in 10 states, and the majority of states that allow the use of RAS restrict it to certain sectors and pavement types. Asphalt also naturally contains polycyclic aromatic hydrocarbons (PAHs) which may leach out of RAS stockpiles or be emitted when RAS are heated. Some PAHs are carcinogenic and may put workers at risk. The recycling of RAS may lead to PAH emissions, however, there is no evidence to show that PAH emissions are lower when virgin asphalt is used in place of RAS. ==See also==