STUDY ON THE MOISTURE CONDENSATION PROOF PERFORMANCE IN THE VENTED AIR SPACE OF EXTERIOR WALLS

Field survey on the ventilation volume in the experimental house

Abstract

Most exterior walls of wooden residential buildings in Japan have vented air space between the exterior cladding and the insulation, which is designed to dehumidify the exterior walls by discharging humidity to the outside and taking outdoor air into the walls, with the purpose of decreasing the risk of condensation in exterior walls in winter. Several studies have been carried out on the vented air space, and the most effective thickness for dehumidification has been determined. However, most of these studies have only investigated the performance of vented air spaces under laboratory conditions, and the characteristics of vented air spaces in a field environment have not been clarified. The driving forces of the airflow in the vented air space are the buoyancy force due to the temperature difference between the outdoor air and the vented air space and the wind pressure. However, few studies have dealt with the influence of wind pressure. Since the velocity and the direction of the wind change irregularly, it is difficult to estimate the ventilation volume due to the wind. The objective of this study is to survey the ventilation volume through the vented air space and to investigate the effect of the driving force of the ventilation, which are buoyancy force and wind. Measurements have been carried out on the vented air space in an experimental wooden house that has several types of vented air spaces. The correlation between the ventilation volume and the driving force was discussed.