Long-term indoor climate evolution in historic churches under climate change: a decadal study of the basilica di Sant’Andrea, Mantova

Preventive conservation safeguards the material and cultural value of historic buildings; however, climate change increasingly challenges indoor environmental stability, particularly in large churches that rely on passive buffering by massive envelopes. This study examines whether such buildings can continue to absorb external climatic changes without generating localized moisture-related risks. The research analyses the decadal evolution of the indoor climate of the Basilica di Sant’Andrea in Mantova, Italy, by comparing two monitoring campaigns conducted in 2007-2014 and 2024-2025. The methodology applies the EN 15757:2010 framework to evaluate relative humidity (RH) stability, integrates dew point analysis to assess condensation risk, and examines indoor-outdoor thermal coupling to quantify buffering capacity and response lag. The results indicate a clear increase in mean outdoor temperature during the recent period, while overall indoor RH variability remains within its historical range. However, seasonal clustering of RH deviations and a higher frequency of near-condensation conditions at specific locations reveal localized vulnerability during transitional months. Lag analysis confirms a delayed indoor thermal response, which reflects the buffering effect of the building envelope. Overall, the Basilica retains substantial microclimatic stability, yet progressive warming may gradually influence indoor equilibrium and increase moisture-related risks.