Application of synthetic indices for thermal discomfort assessment in historical buildings according to the adaptive approach

This paper presents a novel methodology that combines thermal modelling, free-floating energy simulation and the use of synthetic comfort indices for assessing potential discomfort issues in buildings. The research methodology includes detailed modelling in TRNSYS, supported by extensive surveys and on-site measurement of indoor environmental variables such as air temperature and relative humidity. Suitable synthetic indices are introduced such as FTD (Frequency of Thermal Discomfort), ITD (Intensity of Thermal Discomfort) and FD (Fluctuation of thermal Discomfort). These indices are adaptable to different thermal comfort theories, in line with major thermal comfort standards such as ASHRAE-55 and EN 16798-1. The methodology is tested in a historical office building in Catania (Italy); the results show that significant thermal discomfort issues can be identified in the zones more exposed to solar gains and located on the upper floors, particularly during summer months. The combined implementation of non-invasive mitigation strategies (such as internal shading, free cooling by nighttime ventilation) led to a reduction in the Intensity of Thermal Discomfort (ITD) by up to 95% in the critical zones. The proposed methodology proves to be a versatile tool for assessing thermal discomfort and evaluating the effectiveness of possible mitigation strategies for reducing indoor overheating and improving indoor conditions in historical buildings.