Moisture Risk in Unvented Attics Due to Air Leakage Paths - Minneapolis Minnesota

Description

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 "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 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.

Resources

Name Format Description Link
55 BEopt Version 2.0.0.6. HPXML for 1ACH50 run https://data.openei.org/files/5495/to4-7.1.3beopthpxml1ach50.xml
55 BEopt Version 2.0.0.6. HPXML for 10ACH50 run https://data.openei.org/files/5495/to4-7.1.3beopthpxml10ach50.xml
0 Version 2.0.0.6 Temperature and humidity for 3 cities and 3 ACH50 values. https://data.openei.org/files/5495/to4-7.1.3beopt.beopt
33 DOE Report http://www.eere.energy.gov/buildings/publications/pdfs/building_america/moisture-risk-unvented-attics.pdf
55 BEopt Version 2.0.0.6. HPXML for 5ACH50 run https://data.openei.org/files/5495/to4-7.1.3beopthpxml5ach50.xml
53 From BEopt Version 2.0.0.6. Hourly temperature and relative humidity output for three different cities, and three different ACH50 values for each city. https://data.openei.org/files/5495/to4-7.1.3beopthoulryoutput.xlsx

Tags

  • wufi
  • cathedralized-attics
  • building-america
  • attic-air-leakage
  • multifamily
  • hygrothermal-analysis
  • buildingamerica
  • residential
  • attic-ventilation
  • moisture-risk
  • single-family
  • computational-fluid-dynamics
  • beopt
  • cold
  • closed-cell-spray-foam-insulation
  • water-vapor-flow-rate

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