Anyone who has suffered in an overcooled or overheated meeting room for a day or two understands the need for improved thermal comfort. Complaints about poor thermal comfort abound in occupant satisfaction studies. Yet, to date, solutions have proven elusive or only partially satisfactory.
New research, though, provides insights into the mechanisms that influence our sense of temperature and how to achieve a more sustainable balance between occupant comfort and building performance.
We each have our own "internal thermostat" that determines our tolerance for changes in temperature. Put a group of people in a room set at a moderate temperature, say around 70 degrees Fahrenheit, and inevitably some will soon perceive the room to be too cold while others will perceive it to be too warm.
This makes regulating the temperature in any building or given space difficult. The use of certain building and surface materials, especially those that do not retain heat, compound the problem. To complicate things further, researchers are discovering other factors also can affect our sense of thermal comfort.
A team of Australian researchers conducting a survey of thermal comfort in classrooms discovered students' experience with and ability to adapt to climate changes affected their thermal sensitivity "with students in locations exposed to wider weather variations showing greater thermal adaptability than those in more equable weather districts."
As reported in a recent issue of the science journal PLOS ONE, "Observing cues indicating a change in another's body temperature [especially, cues that indicate that they are cold] results in a corresponding temperature change in the observer."
In short, thermal discomfort can be contagious. If we see someone as suffering from the cold, we become colder ourselves. Similarly, another study found associations of money with coldness (both physical and social) caused subjects to experience cold when they were reminded of money.
It would appear, then, that a variety of stimuli besides the actual temperature and physical surroundings influence body temperature and perceived thermal comfort.
These and other studies suggest that providing occupants with more options for personally controlling their level of thermal comfort would result in higher levels of satisfaction. Consequently, this would reduce the negative effects of discomfort — such as decreased productivity and morale, and increased illness and absenteeism.
The problem from a building-performance perspective is how to allow for greater variation in occupant behavior without jeopardizing efficiency or energy consumption targets. A team of investigators at the Center for the Built Environment at the University of California, Berkeley, drew upon the Center's extensive research archive to examine "new ways of thinking about designing or operating buildings to optimize both comfort and energy performance."
They contend that allowing building temperatures to float over a wider range than current practice would increase comfort, improve energy performance and combat "thermal monotony" — a condition caused by uniform, static temperature levels throughout a building or space.
They propose five "new ways of thinking" to break the current paradigm:
- more personalized control (such as the use of desk fans, foot warmers and heated chairs)
- breezy air movement (which both healthy and refreshing)
- attention to thermal pleasure
- greater use of passive design (including natural ventilation)
- improved systems and occupant feedback
The results of a 2011 Center for the Built Environment occupant satisfaction survey that sampled 351 buildings and 53,000 occupants found thermal comfort ranked second to last in occupant satisfaction (just ahead of sound privacy). Based on that, the Berkeley investigators conclude, "The industry is not doing a very good job of creating thermally comfortable environments in buildings. They should welcome a thorough look at new opportunities to improve this record."
With a growing body of research to guide them, builders and designers can explore solutions for how buildings can better accommodate occupants' fluctuating levels of comfort, rather than the other way around.
