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ASTM Selected Technical Papers
Roofing Research and Standards Development: 10th Volume
Editor
Sudhakar Molleti
Sudhakar Molleti
Symposium Chair and STP Editor
1
National Research Council Canada
,
Ottawa, ON,
CA
Search for other works by this author on:
Walter J. Rossiter, Jr. Jr.
Walter J. Rossiter, Jr. Jr.
Symposium Chair and STP Editor
2
W.J. Rossiter & Associates
,
Clarksburg, MD,
US
Search for other works by this author on:
ISBN:
978-0-8031-7747-5
No. of Pages:
254
Publisher:
ASTM International
Publication date:
2023

Since the early 2000s there has been a surge of U.S. cities adopting “cool” roofing (e.g., high-reflectivity roof coverings) initiatives and mandates with the intent of improving energy efficiency. For many years, “cool” roofing (e.g., use of high-reflectance roof coverings) was predominantly restricted to warmer climates, but it has become more prevalent in mixed and heating climate zones within the last five years. However, improperly placed or configured insulation in “cool” roofs in these mixed and heating climate zones can lead to condensation and associated biological growth, air quality concerns, and structural deterioration. The model code requirements for roofs, particularly for reroofing and recover projects, do not provide adequate guidance on how to prevent condensation for “cool” roofing in mixed and heating climate zones. Reroofing and recover projects are particularly susceptible to condensation-related failures because they are less likely to have a qualified designer or consultant involved. The authors of this paper have observed the harmful effects of an improperly configured “cool” roof assembly on projects in various climate zones. However, hygrothermal modeling can be used to mitigate the condensation potential by evaluating the performance of a proposed cool roofing system to ensure long-term durability. This paper discusses the current model code deficiencies, describes several case studies exhibiting the deterioration that can be caused by condensation in a cool roofing assembly, provides hygrothermal modeling case studies that demonstrate this phenomenon, and provides design solutions to common issues. In addition, this paper discusses how local industry professionals worked with the city of Denver when the city adopted a “cool” roofing mandate to author location-specific provisions that would protect Denver's “cool” roofs from the deleterious effects of condensation. The holistic approach developed in Denver could be considered for future “cool” roofing provisions in other jurisdictions as this trend continues across the country.

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