Abstract
A mock-up test was conducted with a one-story test house (3.64m by 3.64m) with eaves ventilation in the suburb of Tokyo to examine the hygrothermal conditions in an attic space. A series of measurements were carried out to clarify the effect of the vent opening area, an air stopper insulation in the partitioning, and the vented cavity of outer wall on the hygrothermal conditions. Main findings from the experiments are as follows; 1. The absolute humidity in the attic space is hardly changes from midnight to early morning. Condensation on the surface of sheathing roof board occurs because the nocturnal radiation and outdoor temperature reduces the surface under dew-point. 2. The surface absolute humidity of the lower part of the north facing sheathing roof board gradually decreases in the afternoon, with keeping higher values than those of the central part and the attic space air. This is probably because the moisture content in the lower part is higher than that at the central part. 3. Occasionally, the absolute humidity in the attic is lower than outdoors. 4. The attic space-connected vented cavity contributes to keeping low humidity in the attic air since the influx air is drier than the outdoor air. This contribution ratio is not low, so the inclusion of its effect is necessary for examining ideal ventilation areas.
