The Effect of Sorption on Airborne Moisture Movement in Dwellings

A Moisture Admittance Model, which takes into account absorption and desorption, has been developed to simulate moisture behaviour in dwellings. The model has been integrated with the BREEZE computer model used to simulate air and contaminant flow. Simulations from the combined model have been compared with predictions using the Louden model and with measurements of vapour pressure taken in a test house. The Louden model tended to over-predict experimental values but there was reasonable agreement between the MAM-BREEZE model results and measured values. The effect of sorption on the performance of a domestic ventilation system was also investigated. The Lounden model, which does not take sorption into account, can over-estimate humidity peaks. The use of such a model in the design of a ventilation system could result in over-ventilation and reduced energy efficiency.