An oft-quoted definition from a sustainable low-slope roofing workshop held by Oak Ridge National Laboratory (ORNL), Oak Ridge, Tenn., describes a sustainable roof system as one that is "designed, constructed, maintained, rehabilitated and demolished throughout its life cycle with an emphasis on using natural resources efficiently and preserving the global environment." Quality asphalt low-slope roof systems, including built-up and polymer-modified bitumen roof systems, perform well with regard to these sustainability aspects.
Various factors related to built-up and polymer-modified bitumen roofing contribute to sustainability. The Asphalt Roofing Manufacturers Association (ARMA) has formed a sustainability council to examine these factors in greater detail. But much work remains to fully understand and quantify this complex subject.
A valuable byproduct
The asphalt used in roofing products is a byproduct of petroleum refining. This byproduct, known as asphalt flux, is the residue remaining after high-value fuels such as gasoline, kerosene, aviation fuels and furnace oils have been released from crude oil through atmospheric and vacuum distillation or fractionation. Asphalt flux is further processed into materials for the manufacture of asphalt shingles, mopping asphalt, asphalt-saturated roll roofing and polymer-modified bitumen membranes.