水分収支を考慮した木造外皮の耐久性評価のための木材腐朽予測モデル: 建築外皮の湿害に対する評価手法の開発　その1

摘要

木造住宅の防露設計では、壁体内部に結露が生ぜず、壁体含水 率がハイグロスコピック状態（相対湿度が90～95%RH以下）に 維持できることが望ましい。これは、壁体の内部結露による生 物劣化発生、凍害、断熱性能低下等の防止を目的とするが、結露 の許容範囲は、湿害の種類と発生メカニズムにより大きく異なる。%In order to ensure safety and sustainability of building, both appropriate design and construction practice are required. Hence, damages of building by various deterioration factors should be estimated prior to construction. An important deterioration factor is a wood decay by fungi in the case of a wooden construction. However, it is difficult to predict the occurrence and the rate of wood decay, and the risk of wood decay has not been assessed quantitatively at present. In this report, we investigated a prediction model of wood decay occurrence considering moisture balance for the durability assessment of building envelopes. In the model, mathematical expression which estimated a risk of the wood decay in consideration of hygrothermal behavior within wood components was made. The constants of degradation rate during the wood decay were obtained from a laboratory experiment under various temperature and humidity conditions, and those constants were incorporated into the mathematical expression. The effect of water occurred from the wood by the fungal decomposition was also considered in the model. The risk of wood decay under climate conditions was assessed by applying the prediction model to building envelopes. Although the prediction model was useful for the design, the improvement of reliability must be studied on some points.