Builders and designers continue to push towards higher levels of airtightness, raising new questions about the impact of different materials and design choices. At passive house levels, every decision can feel critical. Well-designed research and testing can help sort out what really matters, bringing the big picture into focus and supporting evidence-based decision-making.

In this presentation, we’ll take a look at an example of a real-world observation and the question it raised: does the air permeance of sheathing material matter for airtightness? Join us to find out how we got to an answer, focusing on typical assemblies for low- to mid-rise wood-framed buildings.

Learning Objectives:

1. Discuss the difference between airtight materials and airtight assemblies and identify key requirements for passive design and other high-performance approaches.
2. Review why concerns have been raised about the air permeance of some sheathing materials.
3. Describe how field observations can be tested to evaluate their relative impact on assembly or whole-building airtightness.
4. Discuss the impact of sheathing air permeance vs other sources of airflow through the enclosure.

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Jonathan Smegal, M.A.Sc.

Based in Waterloo, Jonathan is an Associate and Senior Project Manager at RDH, leading projects related to laboratory research, forensic analysis of building failures, hygrothermal modeling, and field monitoring of building enclosure performance. As a researcher, he is an author on multiple peer-reviewed papers and has frequently shared his work through industry publications, webinars, and speaking events.