Predicting temperature and moisture distributions in conditioned spaces using the zonal approach

Moisture is one of the main problems in buildings. In spite of the complexity to describe moisture physical phenomena, recent technological improvements have allowed them to be incorporated into building simulation programs. However, it is still unrealistic to predict whole building hygrothermal behavior using CFD models. As a result, the available whole hygrothermal building programs assume the room air to be perfectly mixed, which is a poor assumption for conditioned spaces. To take into account the convective phenomena imposed by mechanical ventilation, we have used an intermediate approach (zonal method) to develop a model library to predict whole hygrothermal behavior in conditioned rooms. In this paper, a zonal library, which includes two models in order to consider building envelope moisture buffering effects, is proposed. It is also discussed how to take into account the dynamic aspect of jet airflow in the zonal method. The zonal library is applied to a case study to show the impact of the external humidity on the whole hygrothermal performance of a room equipped with a vertical fancoil unit.