Scientists from the University of Pennsylvania in the United States have discovered that the spectrum of room lighting affects a person's perception of the temperature of the surrounding environment.
According to the journal Energy and Buildings, changes in the spectrum of white light, invisible to the naked eye, can create a subjective feeling that a room is "cooler" or "warmer." The difference between the actual and measured temperature can be as much as one degree Celsius.
The researchers conducted an experiment involving ten volunteers aged 18-35. They were placed in a room simulating an office inside a climate-controlled chamber. The initial room temperature was approximately 24 degrees Celsius. During the tests, the researchers gradually raised and lowered the air temperature, recording the participants' reactions.
In separate sessions, scientists exposed participants to two types of white light that appeared identical but differed in the dominant wavelengths of their spectrum. One type of light was enriched with short-wavelength blue light, while the other was enriched with long-wavelength red light. Throughout the experiments, researchers monitored participants' thermal sensation, comfort levels, and behavioral responses.
The researchers found that when participants were exposed to white light enhanced with blue light, they felt noticeably cooler. This allowed them to tolerate air temperatures about 0.7 degrees Celsius higher than usual. Red light, on the other hand, had the opposite effect, making them feel warmer more quickly. Thus, variations in standard white light may alter our perception of climate.
It should be noted that previous studies have shown that colored lighting may affect thermal perception. However, using bright blue or red light is impractical in everyday spaces such as offices or classrooms, as colored lights can be distracting and cause visual clutter, hindering the performance of routine tasks.
The results of this study show that using seemingly identical white light with a modified composition, the body's response is determined by the spectral composition of the radiation, not by conscious color perception. If specific lighting conditions allow individuals to feel comfortable within a wider range of temperatures, this offers practical benefits. Applying this technique could reduce the heating and cooling needs of buildings. Even a slight change in perceived temperature can lead to significant energy savings.
The researchers plan to expand the study in the future by recruiting participants from other age groups. They also intend to investigate the interaction of lighting with other environmental factors, including ambient sound, views from windows, and visual patterns in interior designs. The long-term goal of the project is to develop lighting strategies suitable for extreme heat and cold conditions.
