Field Survey of Hygro-Thermal Characteristics in an Experimental House

Abstract

Most exterior walls of wooden residential buildings in Japan have a vented air space between the exterior cladding and the insulation.This air space is designed to dehumidify exterior walls by discharging humidity to the outside and taking outdoor air into the walls, in order to decrease the risk of condensation on exterior walls in winter. Many studies have been carried out on 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 the field have not been clarified. Our previous study clarified the characteristics of ventilation volume through the vented air space based on field measurements. This study continues that work by reporting on the hygro-thermal characteristics of vented air space. The field measurement and numerical simulation have been carried out on the vented air space and it was pointed out that absolute humidity of the vented air space is lower on the average than the outdoor air due to absorption and desorption of the exterior cladding and the daily variation in ventilation volume through the vented air space.