Moisture Management of High-R Walls (Fact Sheet)

Wyatt Metzger, R. LePage, C. Schumacher, A. Lukachko

Research output: NRELFact Sheet


The following report explains the moisture-related concerns for High R-value wall assemblies and discusses past Building America research work that informs this study. Hygrothermal simulations were prepared for several common approaches to High R-value wall construction in six cities (Houston, Atlanta, Seattle, St. Louis, Chicago, and International Falls) representing a range of climate zones(2, 3, 4C, 4, 5A, and 7, respectively). The simulations are informed by experience gained from past research in this area and validated by field measurement and forensic experience. The modeling program was developed to assess the moisture durability of the wall assemblies based on three primary sources of moisture: construction moisture, air leakage condensation, and bulk water leakage. Thepeak annual moisture content of the wood based exterior sheathing was used to comparatively analyze the response to the moisture loads for each of the walls in each given city. Walls which experienced sheathing moisture contents between 20% and 28% were identified as risky, whereas those exceeding 28% were identified as very high risk. All of the wall assemblies perform well under idealizedconditions. However, only the walls with exterior insulation, or cavity insulation which provides a hygrothermal function similar to exterior insulation, perform adequately when exposed to moisture loads. Walls with only cavity insulation are particularly susceptible to air leakage condensation. None of the walls performed well when a precipitation based bulk water leak was introduced to thebackside of the sheathing, emphasizing the importance of proper flashing details.
Original languageAmerican English
Number of pages2
StatePublished - 2013

NREL Publication Number

  • NREL/FS-5500-60488

Other Report Number

  • DOE/GO-102013-4267


  • BSC
  • Building America
  • high-R
  • high-R value
  • hygrothermal
  • moisture
  • moisture management
  • residential
  • residential buildings


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