The temperature on the thermostat may not be the only thing determining whether a room feels too hot or too cold.
A new study suggests that subtle changes in ordinary white lighting can also influence how warm or cool people feel.
Researchers led by scientists at Penn State found that changing the amount of red and blue wavelengths within white light affected people’s perception of temperature, even when the lighting looked essentially identical to the human eye.
The findings are published in the journal Energy and Buildings.
The effect was relatively small but potentially useful. Different lighting conditions changed the gap between actual and perceived temperature by as much as 1.3°F, or about 0.7°C.
That could have important implications for energy use. If people can remain comfortable across a slightly wider range of indoor temperatures, buildings may not need as much heating or air conditioning.
Even small changes to thermostat settings could add up to meaningful energy savings across large numbers of homes, offices and other buildings.
Previous research has shown that visible colors can affect how people experience temperature. Blue lighting, for example, may make a space feel cooler, while red lighting may make it feel warmer. But filling offices, classrooms and homes with strongly colored light would not always be comfortable or practical.
The Penn State researchers therefore tried a more subtle approach.
They created two kinds of white light that appeared the same but contained different combinations of wavelengths. One was enriched with shorter blue wavelengths, while the other contained more longer red wavelengths. This allowed the researchers to test whether the physical spectrum of light itself could influence temperature perception without people consciously seeing different colors.
The study involved 10 adults between the ages of 18 and 35, including five women and five men. Participants sat in a simulated office cubicle inside a climate-controlled chamber at Penn State’s University Park campus.
The room initially had a temperature of about 76°F, or 24°C. Researchers then gradually raised and lowered the air temperature while exposing participants to the two different types of white light. Throughout the experiments, participants reported how warm or cool they felt, how comfortable they were and how they responded to the changing conditions.
Under blue-enriched white light, participants were comfortable at temperatures about 1.3°F warmer than they otherwise would have tolerated. Red-enriched white light produced the opposite effect, making the room feel warmer.
The researchers caution that this was a small exploratory study involving only young adults. Larger studies will be needed to determine whether the effect also occurs among children, older adults and people from different backgrounds.
Future research will also examine how lighting works together with other environmental factors, including sound, window views and visual patterns.
Eventually, this subtle manipulation of white light could become another tool for designing comfortable, energy-efficient buildings.
Rather than relying entirely on heating and air conditioning, future buildings might use lighting to gently influence how occupants experience temperature—without them even noticing that the light has changed.
Source: KSR.
