Modelling of heat and moisture induced strain to assess the impact of present and historical indoor climate conditions on mechanical degradation of a wooden cabinet

To assess the risk of present and future indoor climate conditions within historic buildings on mechanical degradation of wooden art objects, it is of high importance to know the climate variations that these objects might have been exposed to in the past. Historical indoor climate data can indicate climate variations that may have caused damage to objects. Avoiding these variations in the present and future may prevent new or further degradation. However, historical indoor climate data conditions are often not available and cannot be derived from recent indoor climate data as many historic buildings nowadays have climate control systems. In this study, multi-zone hygrothermal building simulation is applied to reconstruct the historical indoor climate in a 17th-century Dutch castle based on meteorological data, building properties, and user behaviour. Furthermore, a finite element model is created to analyse heat and moisture induced strain of a historic wooden cabinet. This cabinet has been located in the castle since the 18th century and shows damage caused by movement of the wood in response to climate variations. Mechanical degradation of the cabinet could have occurred when the strain exceeded the yield strain for safe, reversible deformation. The results show that combining a hygrothermal building simulation model and a finite element model can generate an adequate prediction of the microclimate around an object; though obtaining accurate data on hygroscopic and mechanical material properties can be difficult. Although the cabinet has experienced considerable tension after a conservation heating system was installed in the castle during a recent major renovation, the predicted strain was within the limits for safe, reversible deformation. This corresponds to the observation that no further damage occurred after the renovation. Damage may not be caused by the regular present or historical indoor climate in the castle, but could be indicated if the long-term average moisture content of the wood significantly deviates from the room conditions or if the vapour concentration in the room increases because of a flooding event.