ETF-equivalent quantification of lighting-related thermal perception shifts in young Japanese women under steady-state summer conditions

Lighting conditions can alter thermal perception, but the magnitude of these shifts on a temperature-equivalent scale is uncertain when physiological state is measured concurrently. This secondary analysis re-examined climate-chamber data from 54 young Japanese women exposed at 26°C, 28°C and 30°C to 30 combinations of illuminance (100 lx to 2900 lx) and correlated colour temperature (CCT; 2800 K to 5200 K). Conduction-corrected modified effective temperature (ETF) was used to express lighting-related differences in thermal appraisal. Mean skin temperature showed no consistent lighting-related shift. At neutral visual thermal sensation, ETF-equivalent values for six illuminance levels spanned approximately 2°C, with a maximum difference of 1.7°C between 250 lx and 1700 lx; however, the values were non-monotonic and bootstrap confidence intervals were wider than the ETF range studied. CCT showed no statistically supported association with visual thermal comfort. The ETF-equivalent values therefore describe perceptual appraisal rather than a change in physical temperature or thermophysiological heat balance. Under these short, near-neutral exposures, illuminance may influence thermal appraisal, but the present data are insufficient to support specific lighting or HVAC control recommendations.