A data-driven method to assess indoor climate response to outdoor conditions in heavy-weight buildings for adaptive reuse

Assessing the suitability of unconditioned buildings for adaptive reuse as archival storages, particularly with respect to their microclimate behaviour, remains a complex and evolving methodological challenge. This study proposes a data-driven method using indoor and outdoor climate data to assess whether unconditioned buildings can be adaptively reused for specific functions (e.g., archival), based on their microclimate behaviour. The multi-step approach includes quality check, stationarity analysis, temporal decomposition, and buffering capacity analysis. This is applied to 5 years (2020-2024) of air temperature (T) and relative humidity (RH) data (approximately 14 600 observations) from 10 thermohygrometers in the "Library Section for Special Collections (LSSC)" within "Dora I" (Trondheim, Norway), where conservation conditions of paper-based objects are considered satisfactory. Results indicate a very stable indoor climate with no significant trends or abrupt changes, with a mean temperature (T) and mixing ratio (MR) values of 17 ± 2 °C and 6 ± 1 g/kg respectively, and very low short-term variability, suggesting consistent conservation conditions and reduced need for active climate control. Indoor T and MR show delayed responses to outdoor conditions (up to 70 and 50 days), and buffering factors of 0.2 and 0.4, respectively, reflecting thermal inertia and moisture buffering. The proposed method captures the limited impact of site management on indoor climate and reveals structure-specific dynamics often overlooked in commonly applied evaluations.