Abstract The paper introduces a novel method for risk assessment and preventive conservation of organic hygroscopic cultural heritage objects. The method is based on the analysis of the historic climate that is established in the European Standard EN 15757:2010. This new approach enables interpreting visible damage and assessing cause–effect relationships and it finds practical application in improving conservation strategies for real life buildings and objects. The paper investigates how it may be advantageous to reconstruct the historic climate back in time to obtain sound information about the target relative humidity (RH) level and the domain of RH fluctuations that can be considered safe for conservation. The method was applied to an inlaid wooden choir in the basilica of S. Giustina, Padua, Italy. The past indoor climate has been reconstructed over the whole life of the object, built in 1477, with documentary proxy data, instrumental readings and building simulation. Winter has been found to be the most critical season for the mechanical stress and wood yield. For the future, the indoor climate has been simulated until 2100 to timely devise preventive conservation measures to reduce the risk induced by climate change. Finally an evaluation of uncertainties has been considered.