can reach temperatures that are nearly
100°F above the ambient temperature. A cool roof, by contrast,
stays at or near the ambient temperature due to the characteristics
of its outer layer. There are many benefits to keeping a roof's
surface cooler, including air-conditioning energy and demand
savings, monetary savings, increased human comfort both indoors and
outdoors, and other positive impacts on urban environmental
quality.
Although the actual benefits of a cool roof on a particular
building will depend on many factors, including building type,
load, season, and climate zone, cool roofs can significantly reduce
summer electrical energy usage. A reasonable energy savings
expectation for a typical low-rise commercial building is 10% to
20% of the air-conditioning electricity usage. The energy savings
achieved through cool roofing translate into monetary gains for
building and facility owners, as well as helping to reduce
emissions of atmospheric pollutants and greenhouse gases.
Under the 2005 California Title 24 standards, cool roofs are
assumed as a baseline in the model buildings that establish the
required energy performance for non-residential buildings with
low-slope roofs. However, installing cool roofs is not mandatory
for new construction. Although not mandatory, cool roofing is often
the least expensive option to achieve the required energy
performance; consequently, cool roof technology is gaining more
attention in the building industry. Owners, designers, contractors,
and other stakeholders need to have a better understanding of how a
cool roof can be successfully applied to new construction projects
and re-roofing projects.
This design brief provides information about how a cool roof
works, focusing on the benefits of commercial and industrial
low-slope roof applications. Design considerations are discussed,
and the methods of applying cool roof technology to comply with
California Title 24 building requirements are described. Finally,
examples of two cool roof applications are provided.
