Thermal comfort and visual interaction: a subjective survey

A sustainable building design should be compliant with the even more pressing en-ergy saving requirements - as in NZEB - and high levels of Indoor Environmental Quali-ty. In this context, despite it is accepted that different facets of IEQ could have antago-nistic effects on building energy demand, relatively few studies are aimed at investigat-ing the mutual interaction among its four components (thermal, acoustic, visual and in-door air quality). From this point of view, the hue-heat hypothesis is based on the idea that light and colours can affect the thermal perception. Particularly, spectral power dis-tributions of light shifted to short wavelengths seem to promote a cooler thermal percep-tion and the vice-versa. To verify this hypothesis, the object of this paper is the analysis of preliminary results obtained by a subjective investigation carried out in a special me-chanically conditioned test room provided with white-tuning LED sources. The first sample of subjects has been exposed to two different lighting scenarios characterized by warm (3000 K) and cool lights (6000 K) at a fixed illuminance value (300 lx) at the task area and typical winter thermohygrometric conditions. Preliminary results seem to con-firm that cooler light induces a shift of the thermal sensation toward cold. The percent-age of people under warm conditions decreased from 24 to 6% with an increase of sub-jects under thermal neutrality conditions from 32 to 49% (from 32 to 55% for females) in case of cold light.