ENERGY FACT: 173,000 TERAWATTS OF SOLAR ENERGY STRIKES THE
EARTH CONTINUOUSLY – MORE THAN 10,000 TIMES THE WORLD’S
Will a Broader Range of Indoor Temps Silence Occupant Complaints?
➙According to ASHRAE Standard 55: Thermal Environmental Con-
ditions for Human Occupancy, no
more than 20% of a building’s occu-
pants should be dissatisfied with indoor
temperatures in their building. Would at
least 80% of the humans in your building
report that they are satisfied?
If not, you have a lot of company. One
study found that 41% of workers are
dissatisfied with their thermal environment. A major culprit may be thermal
boredom, according to researchers at the
Center for the Built Environment (CBE)
at the University of California.
In a paper entitled “Evolving Opportunities for Providing Thermal Comfort,”
the researchers describe the futility of
trying to design indoor environments
to static, uniform conditions with no
perceptible air movement. They liken the
resulting monotony to eating the same
foods at every meal and experiencing unchanging light and weather conditions.
Not only do individuals have varying
preferences, but also those preferences
change through the day. Different activities – typing, reading, making phone
calls that boil the blood – affect occupants’ sense of what is comfortable.
approach also incurs a huge energy
penalty. The solution, the researchers believe, is to provide more individual control with personal devices. In turn, that
would allow FMs to let setpoints float
over wider and more energy-efficient
levels and alleviate thermal boredom.
Measuring the Impact of
Personal Comfort Systems
The CBE is developing so-called
personal control systems (PCS) designed to reduce energy and improve
individual thermal comfort satisfaction. The PCS devices allow occupants
to adjust thermal conditions to their
personal preferences over a wider range
of ambient temperatures. In this sense
they function much like task lighting,
which the individual can control at the
workspace while ambient lighting levels
The first generation of devices involved a desktop fan using 1-4 watts and
an underdesk footwarmer using up to 30
watts. Both have integrated occupancy
sensors that turn the devices off when
the workspace is not in use. They also
have USB ports for cables that transmit
use patterns to the central system.
Field study showed that the footwarmers were effective over the winter
heating season, allowing ambient
temperature settings to be reduced by
4 degrees (from 70 to 66 F.) without decreasing thermal comfort. The average
additional 20 watts consumed by each
footwarmer were offset by a 500-watt
reduction per occupant in HVAC consumption. A similar comfort correction
of 4 degrees was recorded during the
summer cooling season.
The second-generation PCS is a chair
with a paired fan and heating element
in the chair back and another pair in the
seat. A control box with a knob is located
on the side of the seat. The chair con-
sumes 3. 6 watts in cooling mode and 14
watts in heating mode. Its rechargeable
batteries are recharged at night. Pre-
liminary results suggest that the chair is
more effective than the fan/footwarmer
combination, although more testing is
The research suggests that people
favor a perceptible level of air move-
ment when they feel warm or cool. The
researchers theorize that occupants may
like the air movement for its freshening
effect, not only its thermal compensation.
INDIVIDUAL TEMPERATURE CONTROL via personal devices helps relieve thermal boredom while
allowing FMs to maintain energy-efficient HVAC setpoints.
Heated element (seat)
Heated element (back)