Outdoor environmental comfort is increasingly relevant amid climate change and population ageing because it affects well-being, behaviour and public-space use. However, the relationship between microclimatic conditions, environmental perception, and public-space use among older adults remains underexplored. The novelty of this study lies in integrating environmental measurements, subjective thermal perception, microclimatic simulations and public-space use within a baseline assessment undertaken before the redevelopment of a real public space, providing an evidence-informed framework for age-friendly urban design. The study examines environmental conditions, subjective perception and reported public-space use among adults aged 55 years and over within the Barrendain intervention area (Beasain, Spain). A mixed-method approach combined seasonal field surveys (n = 117) with microclimatic simulations. Survey data included thermal sensation, environmental perception, adaptive behaviour, and reported public-space use and perceived sociability. PET distributions were simulated using ENVI-met/BIO-met simulations driven by meteorological data from an official weather station. The results indicate that thermal perception exhibited a marked adaptive character. Neutral temperatures ranged from 12.35 °C in the cold-period campaign to 19.87 °C in the warm-period campaign, reflecting seasonal adaptive thermal responses among older adults. Tree-covered areas presented lower PET values than exposed surfaces during warmer conditions, highlighting the role of vegetation in mitigating summer heat stress. The partial correspondence between simulation-derived PET and subjective thermal sensation further emphasises the importance of combining objective microclimatic assessment with user-centred evaluation in age-friendly public-space design. In addition, 55% of respondents reported using the intervention area primarily for physical activity, whereas 36% identified social encounters as a main motivation for visiting the public space. The findings indicate that environmental comfort should be understood as an enabling condition for public-space use and perceived sociability rather than as their sole determinant. The proposed methodological framework demonstrates how simulation-based and user-centred evidence can be combined to support climate-responsive and age-friendly urban regeneration.