A perm is simply a unit of measure for the amount of water vapor that will pass through a given area of a
material over a period of time…Laverne Dalgleish, ABAA, May 2022

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Sealant compatibility with air barriers, moisture-resistive barriers and self-adhered modified bitumen wraps and flashings is most important to long-term adhesion. Chamberlin Roofing and Waterproofing, Ben T. Hixon CCA CCS Hixon Consultants, July 23, 2020

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