Where in a wall does water vapor condense, and does a vapor retarder or exterior foam fix it, by climate?
research/house-dewpoint
Where in a wall does vapor condense, and does a vapor retarder or exterior foam fix it? Steady-state Glaser check of a 2x6 wall in four assumed climates; winter condensation appears in Chicago and Duluth only, and only polyethylene clears Duluth. Stylised.
What it found
A steady-state Glaser check of a 2x6 batt wall (gypsum, optional retarder, OSB, optional 1 or 2 in XPS, housewrap, siding) in four assumed climates. In winter nothing condenses in Miami or Atlanta. In Chicago painted drywall gives about 6 g/m2/day at the sheathing; 2 in of exterior XPS removes it and a kraft facing cuts it to 0.05. In Duluth only polyethylene reaches zero (painted drywall about 11 g/m2/day). The summer case shows no condensation because the model has no wet-cladding reservoir. Stylised: steady state, unsourced permeances and climate values, no moisture storage, not WUFI.
A figure from its own output
Paper, code and results
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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.