Relative humidity control in historical buildings allowing the safe natural indoor-climate fluctuations

In the paper, we present a method of relative humidity control in historical buildings based on the specifications of the European standard EN 15757. The approach follows the concept of acclimatization of the objects containing hygroscopic materials to the fluctuations of historical environment, which in general should not change substantially if the control is introduced. Only large fluctuations from the natural seasonal cycles of the indoor climate should be removed by the control system. Thus, the set point for the dehumidifier and humidifier are not constant, but follow the natural (seasonal) cycles of the interior microclimate. Next to the theoretical background, simulation experiments are provided and the application issues, including implementation on a programmable controller, are discussed.