In industrialized countries, people spend on average 85-90% of their time indoors (1). For this reason, major efforts are being made to understand and control the factors which affect people’s comfort, health and well-being inside buildings (2). The indoor environmental quality is characterized by four main parameters, i.e., indoor air quality, acoustic ambience, visual and thermal conditions. The human senses allow people to perceive the environment and estimate their comfort and acceptability with respect to these four indoor environmental factors. For this reason, the evaluation of indoor comfort requires a thorough understanding of how humans (intended as beings characterised by a body and mind) perceive and respond to these environmental parameters (3). Over the last century, studies have considered only one single factor at a time of the indoor environment with the aim to identify relationships between the single component and human comfort. These studies resulted in comfort models (e.g., thermal comfort) (4), standards, guidelines (5–8) and quantitative indices (9) which provided threshold values for light, temperature, noise and air quality. Current building design and technologies devoted to control the indoor environment are designed on supposedly independent effects of visual, thermal and other factors (10). Yet, human sensory systems are not modular, but integrate and respond to environmental factors simultaneously. Moreover, such environmental factors commonly occur in combination. It becomes clear that no single parameter of the indoor environment can be evaluated on its own. Thus, to improve our understanding of the influence of environmental parameters on human responses and perceptions in indoor environments, it is necessary to study their combined effects. Predicting the integral building performance in terms of comfort is a complex task. For this reason, to progress with global comfort knowledge it is necessary to start with the study of the interactions of two factors at a time (11). This Ph.D. research focuses on the interaction between visual and thermal stimuli on comfort perception and performance by means of experiments in an office-like test room in EPFL campus and validation in field studies. In particular, it analyzes the effect of visual variables on the perceived thermal comfort and of thermal variables on the perceived visual comfort, beside their interactive influence on performance. Three different experiments are planned, analyzing the mutual influence of the following parameters on thermal and visual comfort perception: (i) coloured daylight and temperature, (ii) illuminance level and temperature (iii) glare and temperature. The first experiment about the influence of coloured daylight on thermal comfort perception and of temperature on colour acceptability and preference has started in November 2016.