Material Performance and Environmental Response during Conservation and Adaptive Reuse of Historic Masonry Buildings: A Multicentre Longitudinal Observational Study

Adaptive reuse can extend the service life of historic buildings, but its performance must be evaluated without assuming that more intensive intervention causes better outcomes. This multicentre longitudinal observational study compared 72 historic masonry buildings in Guangzhou, Nanjing, and Xi’an that were already managed under conservation-only, material-compatible passive-retrofit, or adaptive-reuse with reversible environmental-control strategies (24 buildings per strategy; eight per city-strategy cell). Indoor temperature, relative humidity, carbon dioxide, energy use, and wall moisture were monitored during 2025; humidity ratio was derived from paired indoor temperature and relative humidity. Material condition was assessed at baseline and month 12, and post-occupancy outcomes were collected at follow-up. Mean wall-moisture change was −0.23 ± 0.95, −2.09 ± 0.78, and −2.37 ± 0.86 percentage points in the conservation-only, passive-retrofit, and adaptive-reuse groups, respectively. In an ANCOVA that excluded strategy-defining material compatibility from the primary covariate set, strategy was associated with month-12 wall moisture (F(2,61)=40.96, P<0.001). Relative to conservation-only, adjusted differences were −1.88 percentage points for passive retrofit (95% CI, −2.40 to −1.36; Holm-adjusted P<0.001) and −2.20 for adaptive reuse (95% CI, −2.73 to −1.67; Holm-adjusted P<0.001); adaptive reuse and passive retrofit did not differ (−0.32; 95% CI, −0.84 to 0.20; Holm-adjusted P=0.222). A sensitivity model adding material compatibility produced similar estimates. Monthly humidity ratio did not show an independent strategy association in the adjusted generalized estimating equation (omnibus P=0.410). Surface deterioration, maximum crack width, and functional fit remained associated with strategy after their prespecified family-wise false-discovery-rate corrections. The heritage-authenticity model was nominally significant (P=0.039) but not after correction (q=0.059). These observational findings are consistent with a wall-drying benefit under both intervention strategies, but they do not establish causation or superiority of adaptive reuse over passive retrofit. Longer follow-up, verified assessment reliability, and complete life-cycle inventories are needed.