Saving energy with light? Experimental studies assessing the impact of colour temperature on thermal comfort

We tested whether the colour temperature of the illumination (realised through manipulating the ceiling light) impacted on thermal comfort, based on the hypothesis that a lower colour temperature is associated with feeling warmer and a higher colour temperature with feeling cooler. If confirmed, then light might be a tool for energy-saving through allowing ambient air temperatures to vary over a wider range and hence reducing the need for space heating and cooling. Testing took place in a climate chamber. In Study 1, comfort ratings were collected using thermal comfort surveys (N = 32). In Study 2, an observational design was used, where changes in clothing level, interpreted as thermal discomfort responses, were observed (N = 32). We compared comfort ratings and changes in clothing level under light with a colour temperature of 2700 K vs. 6500 K. Results partly confirmed the hypotheses: both self-report and observation indicated higher comfort under the low colour temperature. Further research will need to replicate findings in a real-world setting to see if light might indeed be a tool to modulate thermal comfort, and hence reduce usage of heating and cooling.