ASHRAE Journal - September 2019 - 82

COLUMN IEQ APPLICATIONS

often two to ﬁve times higher indoors than outdoors.3
Thus, it is critical to ensure both appropriate outdoor
air ventilation rates in addition to ﬁltration of indoor
air, in order to protect residents from harmful exposure to airborne pollutants.
A wellness smart home endeavors to maximize health
and well-being beneﬁts for its residents as its primary
goal. Traditionally, smart homes consider energy savings and equipment life in determining demand optimization for HVAC systems. A wellness smart home,
however, would also consider air quality, operationalized as the levels of potentially harmful airborne
pollutant concentration, to be important as well. As
one example of how a wellness smart home could be
driven by a health priority of reducing exposure to
pollutants, a connected sensor network could monitor
pollutant levels, and the system could then turn on air
ﬁltration or ventilation when it detects that pollutants
reach and stay above programmed thresholds that are
known to pose risks to residents' health. The ﬁltration
or ventilation would then turn off once pollutant levels
have been reduced to an acceptable level. Smart sensors could also help protect residents' health by going
beyond accessing data about air quality, to inform
them of whether the air quality may pose a health
risk and to suggest tips for residents to protect their
health (e.g., using kitchen exhaust fans). The wellness
smart home concept focuses on human health beneﬁts, but also includes energy saving features, such as
occupancy-based products and systems that are able to
detect when residents are not home and reduce energy
use at those times.

Thermal Comfort

Indoor temperature has important effects on resident comfort as well as beneﬁcial physiological and
cognitive outcomes. For example, core body temperature decreases in preparation for sleep and conversely
increases in preparation for waking. Sleep is critical for physiological and mental function, yet 35% of
Americans do not achieve the recommended amount
of sleep per night.4 Fluctuations in daily ambient
temperature-with lower ambient temperature when
going to sleep, and warming temperature close to wake
time-support a healthy sleep cycle by sending cues
to help keep the body's circadian clock aligned, and
facilitating thermoregulation to reach the appropriate

core body temperature for the sleep cycle.5,6 As another
example of how temperature can affect well-being, a
slightly cooler temperature has been associated with
higher productivity7 and a warmer temperature with
relaxation.8
Traditionally, smart homes offer residents the ability to
adjust and program the temperature, but residents may
not be aware of health-based temperature standards.
Wellness smart homes can help provide optimized temperatures for health and well-being through default
settings, while still maintaining residents' ability to
adjust the temperature to their comfort. For example,
devices could reduce the temperature before an individual's scheduled bedtime to help align the body to
circadian rhythms and prepare for sleep, or could warm
the temperature when residents come home to help
them decompress after a long day at work. They can also
include setback strategies that reduce energy use during
unoccupied periods.

Lighting

Light is the most potent environmental signal
impacting the human circadian clock.9 As noted earlier, the body has circadian rhythms synchronized to
the Earth's 24-hour cycle that govern the timing of
physiological functions like sleep, physical activity,
and energy intake. Emerging research over the last
few years has found that the eye not only perceives
visibility effects from light, but also receives nonvisual signals that regulate these functions.9 Bright
light with a cool blue-white temperature during the
day stimulates alertness and activity, while dimmer
and warmer light in the evening and before bed supports sleepiness. Indeed, inappropriate exposure
to light - such as insufﬁcient light in daytime or too
much light at night-has been linked to a range of
health and well-being outcomes, from depression
and impaired cognitive function, to diabetes and
obesity.9-11
Smart homes offer advanced functionality with
customizable lighting intensity and spectrum (correlated color temperature), as well as ability to control
lights remotely and program them for energy savings.
However, given the novelty and technical nature of
research on lighting's health effects, residents may
not know how to independently program healthbased settings. Wellness smart homes can optimize
S E P T E M B E R 2 0 19

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