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BS* + Beer

The BS* + Beer Show: Vapor Control

Learn why vapor in our buildings matters and how to think about and solve for it

Smart vapor retarder installed on the interior side of a roof assembly. Image credit: Alex Wilson

This episode of the BS* + Beer show features Christine Williamson, founder of Building Science Fight Club, talking about vapor and why we need to care about it in our building assemblies. She answers the question: What are we really trying to do when controlling vapor? Topics include products we buy vs. what we need to achieve, molecular diffusion, four ways to address condensation, the role of surface area and type, inward vapor drive, reservoir cladding, and much more. Christine is a rockstar. Tune in.

The BS* + Beer Show schedule

The next show is on February 2, 2023, from 6-7:30 p.m. ET.


Kiley Jacques is senior editor at Green Building Advisor.

One Comment

  1. [email protected] | | #1

    Are ceilings treated the same as outside walls? We are not using a vaper barrier or vaper retarder on our walls (zone4), should we also do the same for the ceiling below the attic?

    1st flr: Brick-vented air gap/older Homasote(tarboard)/NO foam(plastics and tar dont mix)/ 2x4wall/R16 roxul/DensArmer drywall/ NO VB/VR (as i need to ensure the homasote dries)
    2nd flr: siding/plywood/2x6wall/spray foam airgaps/R23 Roxul/DensArmor drywall/NO VB/VR
    Ceiling: baffles for airflow & ridge vent, R30 maybe R38, ??? No VR ?? correct?
    Interior: Geo for air/Radiant floors/ERV fresh air system

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