Abstract
The successful application of modern hygrothermal simulation models to building envelopes requires accurate values of moisture permeability. Unfortunately, the generation of reliable data is sometimes not possible using the currently-applied gravimetric test methods, because of the extremely long test periods which can be involved. In addition, these test methods are incapable of separating the total mass flow into its vapour and liquid components, the individual transfer coefficients which are required for the complete description of the moisture transmission process. This paper introduces a new approach to permeability measurement, which has been developed to overcome these deficiencies. It involves testing under reduced barometric pressures, which allows a rapid evaluation of permeability, together with the identification of the separate vapour and liquid fluxes. The new approach is validated through the presentation of experimental results for five building materials, which are compared with benchmark data on the same materials obtained from standard tests.
Résumé
Une application résussie des modèles hydrothermiques modernes de simulation aux enveloppes de bâtiment exige des valeurs précises de perméabilité à l'humidité. Malheureusement, la génération de données fiables n'est parfois pas possible lorsque l'on utilise les méthodes d'essai gravimétriques actuellement appliquées, en raison des périodes extrêmement longues d'essai qui peuvent être impliquées. En outre, ces méthodes d'essai sont incapables de vapeur et liquides, les différents coefficients de transfert étant exigés pour la description complète du processus de transmission de l'humidité. Cet article présente une nouvelle approche à la mesure de perméabilité, qui a été développée pour surmonter ces insuffisances. Ceci implique un examen sous des pressions barométriques réduites, permettant une évaluation rapide de perméabilité, ainsi que l'identification de la vapeur séparée et des flux liquides. Cette nouvelle approche est validée par la présentation de résultats expérimentaux pour cinq matériaux de construction, qui sont comparés aux données de repère sur les mêmes matériaux obtenus à partir d'essais standard.
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Editorial note The Building Research Establishment (BRE), UK, is a RILEM Titular Member.
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Galbraith, G.H., Kelly, D.J. & McLean, R.C. Moisture permeability measurements under reduced barometric pressures. Mat. Struct. 37, 311–317 (2004). https://doi.org/10.1007/BF02481677
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DOI: https://doi.org/10.1007/BF02481677