Cool Roofing

A cool roof is defined as a roof surface that has both high reflectivity and high emissivity. High reflectivity requires the surfacing material to reflect solar energy away from the surface. High emissivity requires radiating heat energy away from the surface. Roofs undergo significant expansion and contraction as they heat and cool throughout the day. Heat absorbed by the roof can also accelerate degradation by ultraviolet rays and water. A reflective roof can reduce the amount of thermal shock that occurs on the roof surface and make the roof last longer and possibly reduce energy bills through less use of HVAC.

CRRC

The Cool Roof Rating Council (CRRC) is an independent, non-profit organization that maintains a third-party rating system for thermal emittance properties of roof surfacing materials. Created in 1998 to develop accurate and credible methods for evaluating and labeling the solar reflectance and thermal emittance (radiative properties) of roofing products and to disseminate the information to all interested parties.

Elongation

The ability of a membrane or coating to be stretched and lengthened by force to accommodate movement. Roofing membranes have forces exerted on them from the building movement and the membrane must be able to accommodate these movements. If a 100 foot building expands by 3%, the walls would need to move 3 feet. This would increase the stresses on the building to the point of structural failure. The United States Army Corp of Engineers estimates that buildings move less than 1%.

sources: The Garland Company, Inc.®