Moisture Risk in Unvented Attics Due to Air Leakage Paths

Stacey Rothgeb, D. Prahl, M/ Shaffer, Stacey Rothgeb (NREL Technical Monitor)

Research output: NRELSubcontract Report


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, correlatedthe CONTAM flow rates with indoor humidity ratios from Building Energy Optimization software, and used Warme und Feuchte instationar 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 highmoisture 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.for applying a predetermined stress to a wafer. The wafers are carried on a belt through a chamber that illuminates the wafer with an intense light of a predetermined intensity distribution that can be varied by changing the power to the light source. As the wafers move under the light source, each wafer undergoes a dynamic temperature profile that produces a preset elastic stress. If thisstress exceeds the wafer strength, the wafer will break. The broken wafers are separated early, eliminating cost of processing into cell/module. We will describe details of the system and show comparison of breakage statistics with the breakage on a production line.
Original languageAmerican English
Number of pages37
StatePublished - 2014

Bibliographical note

Work performed by IBACOS, Inc., Pittsburgh, Pennsylvania

NREL Publication Number

  • NREL/SR-5500-63048

Other Report Number

  • DOE/GO-102014-4526


  • attic air leakage
  • attic airflow paths (cracks)
  • attic ventilation
  • BEopt building energy optimization software
  • Building America
  • C
  • cathedralized attics
  • closed cell polyurethane spray foam insulation (CCSPF)
  • condensation
  • humidity
  • hygrothermal analysis
  • moisture in unvented attics
  • moisture risk
  • residential
  • residential buildings
  • unvented attics
  • water vapor flow rate
  • WUFI


Dive into the research topics of 'Moisture Risk in Unvented Attics Due to Air Leakage Paths'. Together they form a unique fingerprint.

Cite this