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Title: Moisture Risk in Unvented Attics Due to Air Leakage Paths

IBACOS completed an initial analysis of moisture damage potential in an unvented attic insulated with closed-cell spray polyurethane foam. To complete this analysis, the research team collected field data, used computational fluid dynamics to quantify the airflow rates through individual airflow (crack) paths, simulated hourly flow rates through the leakage paths with CONTAM software, correlated the CONTAM flow rates with indoor humidity ratios from Building Energy Optimization software, and used Wärme und Feuchte instationär Pro two-dimensional modeling to determine the moisture content of the building materials surrounding the cracks. Given the number of simplifying assumptions and numerical models associated with this analysis, the results indicate that localized damage due to high moisture content of the roof sheathing is possible under very low airflow rates. Reducing the number of assumptions and approximations through field studies and laboratory experiments would be valuable to understand the real-world moisture damage potential in unvented attics.
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  1. IBACOS, Inc., Pittsburgh, PA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Technical Report
Research Org:
IBACOS, Inc., Pittsburgh, PA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B)
Country of Publication:
United States
residential; Residential Buildings; IBACOS; Building America; cathedralized attics; unvented attics; hygrothermal analysis; moisture risk; closed-cell spray foam insulation; attic ventilation; attic airflow paths (cracks); attic air leakage; moisture in unvented attics; water vapor flow rate; condensation; humidity; CONTAM; WUFI; BEopt; CFD analysis; cold climate