Adaptive Ventilation Strategy for Climate Control in an Unheated Cathedral in Northern Italy

Unheated historic churches often contain objects of significant historical and cultural value, such as organs and paintings. Such buildings, with their features (massive envelope, dimensions, etc.) can often mitigate external climate fluctuation, providing a more stable indoor environment. However, although artefacts and visitors can often acclimatize to indoor conditions, the alterations caused by climate change might induce stressful events for the preserved materials and worsen the comfort levels of visitors and worshippers. In this context, the main goal of this study is to assess the implementation of an adaptive ventilation system, in a relevant religious building in Milan, through the re-adaptation of existing ventilation ducts distributed in the vaults to mitigate the indoor climate conditions, without jeopardizing valuable artworks. In particular, the proposed solution includes the replacement of existing Knapen atmospheric siphons, installed in the ventilation ducts, with fans that allow the increase of the air exchange with outside during specific occasions. Simulation analyses have shown that the proposed system might provide an average reduction in internal temperatures up to 1.7–2 ℃ in summer, while for relative humidity, it has been observed that the system can effectively reduce the excessive moisture content, without leading risk of deterioration for the artworks.