Dive Brief:
- Slightly changing the light can change how warm or cold a room feels to people, even if the difference isn’t visible, according to research from the Pennsylvania State University.
- Those in blue-enriched light waited longer before asking for relief as the building temperature rose, while red-enriched light made subjects feel warmer even as the room cooled. Building energy simulations suggest that pairing these lighting adjustments with small thermostat adjustments could cut cooling energy use by 5.2% to 11.4%, depending on climate zone, according to the paper, which was published in Energy and Buildings on Aug. 1.
- “Together, these results identify a human-mediated pathway for HVAC-lighting synergy, demonstrating how spectral lighting can support energy-efficient and decarbonized building operation through coordinated perceptual and thermal control strategies,” the researchers say.
Dive Insight:
Although wavelength differences are invisible to the human eye, they can influence the gap between perceived and real temperature by as much as 1.3 degrees Fahrenheit, found the researchers, led by Julian Wang, professor of architectural engineering at Penn State.
People in the U.S. spend approximately 90% of their time indoors, making indoor environmental quality, or IEQ, a crucial factor influencing work performance, comfort, satisfaction, health and well-being, the researchers say.
IEQ is defined as a combination of environmental factors — temperature, thermal radiation, humidity and air speed — personal factors like activity and clothing and personal comfort preferences that vary from one occupant to the next, according to ASHRAE/ANSI Standard 55, Thermal Environmental Conditions for Human Occupancy.
Because thermal comfort, a key component of IEQ, is maintained through HVAC systems and other strategies that impact energy consumption, there is increasing interest in finding ways to maintain thermal comfort while reducing heating and cooling energy consumption.
Tweaking lighting controls to improve HVAC performance is one such method, according to the paper.
“By leveraging such synergy, buildings may maintain thermal comfort while reducing heating and cooling consumption, offering a low-energy pathway to support energy-efficient and decarbonized building operation,” the researchers say.
An HVAC specialist commenting on the research agrees. “Understanding thermal comfort through these lenses should shout out to industry: setpoint requirements in building codes and load calculations do not represent the human experience; they serve design objectives, not the subjectivity of perception,” Robert Bean, fellow, distinguished lecturer and member of the Center of Excellence for Indoor Environmental Quality at ASHRAE, says in a LinkedIn post.
Standard 55 was recently updated to place increasing focus on these interplaying factors. In 2023, it provided major improvements and simplifications to core sections that covered determining a satisfactory thermal environment in occupied spaces and compliance documentation.
“We can create the environmental conditions, but the perception lies within the mind,” Bean said. “Thus the formal definition of thermal comfort is a ‘condition of mind’ … not a ‘condition of space’. That's why the title of ASHRAE 55 is ‘Thermal Environmental Conditions for Human Occupancy,’ not ‘How to Make People Comfortable,’ ‘Making Spaces Comfortable,’ or ‘Delivering Thermal Comfort Through Psychrometrics.’
