Evaluating the Effects of Air Barriers with Variable Vapor Permeance in Hygrothermal Analysis

Track 3: Testing & Inspection

Wednesday, March 27, 11:00 – 12:00pm

With the ever-expanding number of materials being incorporated into the building envelope, understanding the impacts of how vapor will diffuse through the wall can have a significant impact on the long-term performance of the wall assembly.  ASTM E96, “Standard Test Methods for Water Vapor Transmission of Materials,” is the standardized test that outlines different methods to determine the vapor permeance of materials.  However, these methods generally only test materials under certain conditions and do not incorporate a range of conditions that will be encountered when installed in the wall assembly.  Hygrothermal analysis is becoming an important tool to evaluate the long-term performance of wall assemblies and relies on the material data in order to accurately predict the vapor diffusion through the wall over time.  This session aims to evaluate different wall assemblies and the impacts of air barriers with variable vapor resistance.

Learning Objectives:

  1. Review the standardized testing procedures to measure vapor permeance of materials.
  2. Compare the testing procedures to actual performance in installed conditions.
  3. Discuss the theory of transient hygrothermal analysis and the effect of variable vapor permeance.
  4. Assess the impact of the vapor permeance of an air barrier on a defined wall assembly.
Level of content:
Design Professionals
Testing & Inspection

Jodi Knorowski

WDP & Associates Consulting Engineers, Inc.

Jodi joined WDP in 2013 and has experience providing professional design and construction administration services for post-occupancy failures of existing buildings related to the building envelope.  She has performed numerous field investigations for air and moisture related issues ranging from bulk water infiltration to air leakage to hygrothermal performance.  Jodi has completed a certificate course for WUFI and is an NFRC Certified Simulator, both tools that are used to model performance of existing buildings and to make recommendations for new construction projects.  Jodi is also a member of ASTM and participates on subcommittees for Historic Preservation and Thermal Insulation and has been actively involved in the development of the ASTM Standard 3069-17 which provides guidance for historic preservation of existing mass masonry walls when changing the thermal or moisture properties of the wall.  Her experience in evaluating existing wall assemblies includes deploying data logging instrumentation devices and subsequently analyzing the data acquired to determine how heat, air, and moisture are moving simultaneously through building assemblies and ultimately understand the performance and behavior of a building component.