--- title: Water Vapor Transmission of Materials, aka Permeance - 04-14-2020 description: Roy Schauffele, President and Founder of Division 7 Solutions, Inc., wrote an article on water vapor transmission of materials, aka permeance. He explains that permeance is a measurement of water vapor transmission through a material often based on testing performed in accordance to ASTM E96, either by a dry cup/desiccant ... image: https://www.chamberlinltd.com/hubfs/Imported_Blog_Media/3304-1.png --- [ Client Login ](https://www.chamberlinltd.com/articles/log-in-to-your-account) [ 877-428-1000 ](tel:8774281000) [ Report a Leak ](https://www.chamberlinltd.com/report-a-leak) [![Chamberlin_Logo_Option](https://www.chamberlinltd.com/hubfs/Logos/Chamberlin_Logo_Option.svg) ](https://www.chamberlinltd.com) # Water Vapor Transmission of Materials, aka Permeance Posted on: May 1, 2021 5 AM ![](https://www.chamberlinltd.com/hubfs/Imported_Blog_Media/3304-1.png) ![](https://www.chamberlinltd.com/hubfs/Imported_Blog_Media/3307-1.png)   Roy Schauffele, President and Founder of Division 7 Solutions, Inc., is an internationally published author and speaker in the fields of energy conservation and sustainable building envelopes. He shares his thoughts on permeance testing in an article about water vapor transmission through building envelope materials. He discusses “perm rating” testing often performed in accordance to ASTM E96. The specification itself states, in part, “A permeance value obtained under one set of conditions may not indicate the value in another set of conditions.” Based on a round-robin testing effort, ASTM reports E96 has about 20% lab-to-lab variability. Roy questions how data with that type of discrepancy can be reliable. Today’s science tells us that unimpeded air infiltration can move 32 to 64 times more moisture into a building than can water vapor transmission alone and that is why the development of air barrier technology was so critical. Though, he cautions not to place too much importance on perm ratings with the ever-growing use of CI (continuous insulation) diminishing the significance of air barrier perm ratings. ### [Read Full Article](https://www.chamberlinltd.com/articles/water-vapor-transmission-materials-aka-permeance/)   #### Subscribe Today! Stay-in-the-know and subscribe to our blog today! ## Related Articles ### [Oh Baby! Posted on: May 1, 2021 5 AM](https://www.chamberlinltd.com/blog/oh-baby) [**Chamberlin has added some new members of our family recently and we might be biased, but they are pretty cute.** ### [More of Chamberlin's Team](https://www.chamberlinltd.com/chamberlin-team/) ](https://www.chamberlinltd.com/blog/oh-baby) [### Helping the New Guy Posted on: May 1, 2021 5 AM It doesn’t matter how long you have been on the job or worked for the company, at one time or another everybody has been the “New Guy.” Most accidents occur among the least experienced workers,... ](https://www.chamberlinltd.com/blog/helping-the-new-guy) [### Plaza Decks Training Posted on: May 1, 2021 5 AM An important aspect of Chamberlin’s quality initiative is Chamberlin University. Chamberlin ‘U’ was conceived and developed in 2006 and implemented as part of our strategy to prepare Chamberlin... ](https://www.chamberlinltd.com/blog/plaza-decks-training) © 2026 | Chamberlin, Ltd.