Indoor thermal comfort under climate change and heat waves in mountainous Friuli Venezia Giulia: Archetype residential building analysis

Climate change is gradually altering environmental conditions across Europe, with increasing temperatures, changing seasonal patterns and more frequent extreme events such as heat waves. While studies have mainly focused on urban and plain areas, mountainous areas, traditionally considered climatically favorable, are increasingly experiencing conditions leading to possible heat stress. This is particularly important in the Friuli Venezia Giulia (FVG) region of northern Italy, where the historically climate-adapted buildings increase vulnerability to changing conditions. This study investigates the impact of climate change on indoor thermal comfort in the mountainous FVG, focusing on a residential building in Tolmezzo. The aim is to compare occupant comfort in the current state of the building and a refurbished scenario under current and future climate conditions, with particular attention to extremes. Dynamic simulations are used to analyze indoor thermal conditions over time. The building model is based on the TABULA webtool. Two constructions are evaluated: an existing building and a refurbished version with passive adaptation measures, including improved insulation and windows, each with and without employing a ventilator. Climate inputs include observed local data and three future scenarios (RCP 8.5) from regional climate models. Extreme temperatures are specifically analyzed to assess their impact on indoor comfort using standard thermal comfort indices for the warm months. The results show a clear deterioration of indoor comfort under future climate conditions. The existing building shows increased indoor temperatures and discomfort hours, especially during extreme events. The refurbished scenario improves conditions regarding future increasing temperature but will not solve the problem, since changes in climate models highlight some uncertainties but confirm ongoing warming trends. Overall, the findings suggest that mountainous regions are not immune to the risks of extreme heat. While passive adaptations increase resilience, they may not fully address future extreme conditions, underscoring the need for climate-tailored adaptation strategies and planning policies.