Moisture Admittance Model: Measurements in a Furnished Dwelling.

The BRE method of predicting water vapour conditions in houses is based on two generalised moisture admittance parameters a and p. Previous laboratory experiments suggested that it is possible to determine these coefficients for an unfurnished room with wooden panels, using measurement periods of six hours under dynamic equilibrium conditions. The present study explores the possibility of using such conditions to determine a and P in-situ for the living-room and bedroom of a furnished flat of conventional construction. Dynamic equilibrium conditions were measured and used to calculate the moisture coefficients of both rooms. These were included in a simulation program based on the moisture admittance model developed by BRE, and compared with measurements for different scenarios: constant heat input, constant humidity input, both constant heat and humidity input. Results show that a and P can be measured in real situations with an accuracy as good as in the laboratory, despite the widely differing materials involved in the process of absorption- /desorption. The mean deviation between measurements and predictions for the admittance model is about 30% lower than for the Loudon model. In addition some guidelines concerning the experiments in-situ are derived from the mathematical theory.