Building codes require minimum R-values for all buildings, and
the codes typically provide a prescriptive table that details the
R-values required for specific climate zones. However, the R-values
listed are based on laboratory test procedures and do not take into
consideration field performance of insulation. Seldom does
insulation perform in the laboratory as it does in the field, but
advances in building-envelope technology and test procedures have
given roofing professionals an opportunity to address many factors
that can contribute to the total energy performances of building
One example of this is spray polyurethane foam (SPF).
During the past 30 years, a great deal of scientific research has
been conducted to identify factors other than R-value that affect
thermal performances of roof and insulation systems. The Spray
Polyurethane Foam Alliance (SPFA) has been active in promulgating
research to put real numbers behind these concepts. During the past
two years, SPFA has conducted thermal performance research in
attics and wall assemblies with coordination and input from Oak
Ridge National Laboratories (ORNL), Oak Ridge, Tenn.; R&D
Services, Cookeville, Tenn.; National Association of Home Builders'
Research Center; Syracuse University, Syracuse, N.Y.; and
Architectural Testing Inc., York, Pa.
During the summer of 2006, SPFA asked Mark Bomberg, a building
scientist at Syracuse University and principal of TI Research, a
consulting company in Syracuse, to analyze the relative energy
performances of SPF roof systems. The goals of the research were to
evaluate the factors affecting energy performances of SPF roof
systems in the field, review existing data from building-envelope
research that relates to these factors, and develop a matrix that
could be used by contractors to provide a more accurate estimate of
the effective field performances of SPF roof systems in various
climates and building scenarios.
The research also reviewed published scientific papers about the
factors that affect thermal performances of roofing materials,
including thermal drift (aging of gas-filled foam insulation),
thermal bridges created by mechanical fasteners, effects of air
movement on energy performance and moisture gains in roofs, and
reduction of surface temperature on cool...
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