Numerical study on the effects of macro climate and detailing on the relative decay hazard of Norway spruce

The durability of wood depends on its in-use environmental conditions. The aim of this study was to estimate the effects associated with macro climate and detail design as well as their interdependence. A numerical moisture model and two different decay prediction models were utilized for assessing the decay risk of a horizontal member and a joint exposed at 300 sites scattered across Europe. In general, the results obtained with both decay models exhibited strong similarities to the Scheffer climate index. Distinct discrepancies were however observed in regions with much precipitation where one model stood out as less dependent on precipitation and more dependent on relative humidity. The projected decay rate of the joint was about two to four times higher than that of the horizontal board, depending on the model employed. One of the models indicated that the relative difference between the horizontal member and the joint decreased with increasing amounts of precipitation. Due to lack of reliable experimental data, no inference regarding the model accuracy could be made. Future studies should focus on collecting empirical data on relative decay risk in different climates, preferably focusing on regions where the difference in projected decay depends on the model employed.