In lab, white light shifts perceived temperature by 1.3°F

A room can feel warmer without the thermostat moving. In a Penn State climate chamber, 10 participants sat in a simulated office cubicle while the air temperature rose and fell from an initial temperature of approximately 76°F (24°C). The researchers changed the light, not its visible appearance: both white-light settings looked identical to the human eye.

The difference was hidden in the spectrum. One lamp was enriched in blue short-wave light, the other in red long-wave light—two parts of the electromagnetic radiation humans perceive as light. Under the blue-enriched white light, participants felt cool enough to tolerate air temperatures about 1.3°F warmer. Red-enriched white light made them feel warmer instead.

That distinction matters because colored lighting can be distracting in offices, classrooms and homes. The Penn State team, led by architectural engineering professor Julian Wang, found that changing the spectral composition inside ordinary-looking white light could influence thermal sensation without visibly changing the room. Wang said a wider comfort range could eventually reduce heating and cooling demand and produce cumulative energy savings.

And concretely? The near-term result is not a building product or a demonstrated energy saving. It is a controlled experiment suggesting that lighting systems might one day help people remain comfortable at slightly different temperatures, potentially reducing the work required from heating and cooling equipment. The study was exploratory, involved young adults aged 18–35, and needs larger, more diverse tests before the effect can be applied broadly.

The researchers plan to study how the response holds across different ages and backgrounds, as well as how lighting interacts with sound, window views and visual patterns. They also want to test the strategy under more extreme heat and cold and evaluate its use in real-world buildings, including homes, offices and space habitats.