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Dependence of water vapor permeability on temperature and humidity

From National Research Council Canada

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Affiliation
  1. National Research Council of Canada
FormatText, Article
SubjectHeating; air moisture transfer; water vapor; permeability; building papers; temperature gradients
Abstract
The present approach to the calculation and prediction of vapor flow through materials uses a simple flow equation with vapor pressure as the potential. The corresponding coefficient of permeability is, for many materials, a function of temperature and humidity. Ways of correlating dry-cup and wet-cup permeance data to provide the necessary permeability coefficients for the isothermal case are presented and discussed. Test data obtained for two building papers over a range of temperatures and humidities are presented. The effect of a temperature gradient, in the general case of vapor flow, is not yet established, and may introduce great complication, requiring an equation which recognizes surface-film and capillary migration under a moisture content gradient combined with vapor diffusion occurring under the vapor pressure gradient.
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  • Heating, Piping, Air Conditioning, no. 3 (March 1956): 149–155.
LanguageEnglish
Peer reviewedNo
IdentifierDBR-RP-21
NRC numberNRCC 3922
NRC-IRC-474
NPARC number20358671
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Record identifier9aca41af-554a-4e2d-b8a2-a1b8e4cdffea
Record created2012-07-20
Record modified2023-12-19
Date modified: