In Knoxville, two types of base materials are used to make asphalt shingles: a formerly living organic base and fiberglass base. Both types are made in a similar manner with asphalt or modified asphalt applied to one or both sides of the asphalt saturated base, covered with slate, schist, quartz, vitrified brick, stone, or ceramic granules and the back side treated with sand talc or mica to prevent shingles from sticking to each other before use.
The top surface granules block ultra-violet light which causes the shingles to deteriorate, provides some physical protection of the asphalt and gives the shingles their color. Some shingles hav e copper or other material added to the surface to prevent the shingles from being blown off by high winds. This material is typically limestone or fly-ash modified resins, or polymer-modified bitumen.
American Society of Civil Engineers ASCE 7-05 is the standard most United States residential building codes use as their wind load standard with the top class ratings; Class D – passed at basic wind speeds up to and including 90 mph; Class G – Passed at basic wind speeds up to and including 120 mph; and Class H – Passed at basic wind speeds of up to and including 150mph.
An additive known as SBS, sometimes called modified or rubberized asphalt, is sometimes added to the asphalt mixture to make shingles more resistant to thermal cracking, as well as more resistant to damage from hail impacts. Most insurance companies offer discounts to Knoxville homeowners for using impact-4-rated shingles.