Transfer function method to calculate moisture absorption and desorption in buildings

A transfer function approach has been described to calculate dynamic moisture absorption and desorption by building materials in the hygroscopic range, and the dynamic moisture absorption and desorption processes hare been theoretically modeled. Their surface vapor pressure and moisture absorption and desorption flux can be evaluated by this approach. It has turned out mathematically that the material surface attains instantaneous moisture equilibrium with the surroundings at high Biot number (Bi --> infinity), and that the material moisture behavior can be described through a lumped-parameter modeling at low Biot number (Bi --> 0). For building materials at intermediate Biot number, comparisons with experimental results and numerical solutions have shown satisfactory agreement with the proposed approach. Using this approach, the dynamic response of moisture absorption and desorption in interior building materials to the variation of indoor air humidity and the dynamic effect of moisture absorption and desorption by building interior materials on indoor air humidity and space latent cooling load can be simultaneously calculated. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.