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.
- Review the standardized testing procedures to measure vapor permeance of materials.
- Compare the testing procedures to actual performance in installed conditions.
- Discuss the theory of transient hygrothermal analysis and the effect of variable vapor permeance.
- Assess the impact of the vapor permeance of an air barrier on a defined wall assembly.
WDP & Associates Consulting Engineers, Inc.