The evaluation of indoor comfort requires a thorough understanding of how human occupants perceive four indoor environmental factors: visual conditions, air quality, acoustic ambience and thermal conditions. Recent studies have found that overall comfort is more than the average effects of these four parameters. Beside their main effects, their mutual interactions play an equally important role in the perception of comfort. Thus, to progress regarding our understanding of global comfort, more effort is needed to further investigate the interactions between indoor environmental factors. For this kind of perceptual evaluation, it is necessary to conduct user studies. In these, subjects' evaluations need to be recorded in addition to the physical parameters that provoke them. Therefore, the sensitivity of people to their environment is the principal parameter around which the studies should be designed. This paper presents a first evaluation of the sensitivity of people to visual and thermal parameters in real office environments to establish a groundwork for future investigations. From this cross-sectional observational study, we concluded that possible effects of interactions between factors are difficult to see when the conditions are more or less comfortable. In that case people are not enough sensitive to environmental changes.