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A Systematic Study for Smart Residential Thermostats: User Needs for the Input, Output, and Intelligence Level

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The development of "smart" residential thermostats-both in terms of wider connectivity and higher intelligence-has revealed great opportunity for energy conservation, as well as providing comfort and convenience. This paper focuses on the interaction design of such a novel system, and analyzed user requirements for input, output, and level of intelligence systematically through both in-depth interviews and a survey.
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buildings
Article
A Systematic Study for Smart Residential
Thermostats: User Needs for the Input, Output,
and Intelligence Level
Pei-Luen Patrick Rau *, Yun Gong, Han-Jing Huang and Jing Wen
Department of Industrial Engineering, Tsinghua University, Beijing 100084, China;
gong-y14@mails.tsinghua.edu.cn (Y.G.); huanghj15@mails.tsinghua.edu.cn (H.-J.H.); avenjing@163.com (J.W.)
*Correspondence: rpl@tsinghua.edu.cn; Tel.: +86-10-62776664
Academic Editor: Burcin Becerik-Gerber
Received: 15 January 2016; Accepted: 26 April 2016; Published: 29 April 2016
Abstract:
The development of “smart” residential thermostats—both in terms of wider connectivity
and higher intelligence—has revealed great opportunity for energy conservation, as well as providing
comfort and convenience. This paper focuses on the interaction design of such a novel system, and
analyzed user requirements for input, output, and level of intelligence systematically through both
in-depth interviews and a survey.
Keywords: smart thermostat; user needs; user interface; automation
1. Introduction
With the rapid development of smart buildings worldwide, end user experience becomes
increasingly important—it is more than technological sophistication. In the U.S., the energy for
residential heating and cooling amounts to a high of 9% of the total primary energy use [
1
,
2
].
As an attempt
to save energy, programmable thermostats have been promoted all over the world
to automatically relax temperatures at night or during unoccupied periods according to the presets.
Such programmable thermostats can theoretically reduce energy usage by 5%–15%, but a recent study
reported that users were shutting down their smart thermostats due to poor usability [
3
], as many
users complain that they are too complicated to use and the effect is limited.
The development of advanced techniques, such as machine learning, speech recognition, and
motion detection, reveal great opportunities for residential thermostats, but it is also a challenge
to integrate these techniques with old user interfaces without producing negative experiences.
Take the most popular smart thermostat as an example; Nest provides fascinating functions such
as auto-schedule and auto-away, utilizing machine learning and occupancy detection technology
to simplify control tasks. However, new usability problems emerge: people are losing a sense of
control. The heating was sometimes turned on for no reason (probably because the user had turned
it on the day before after a shower and this behavior was recognized and learned permanently).
The temperature remains unrelaxed because the movement of pets were detected. As a result, users
shut down automation [
3
,
4
]. The interaction design of smart thermostats has become a significant issue.
This study aims to provide a systematic user study on the requirements and expectations of
residential smart thermostats. Three variables are discussed: input, output, and level of intelligence.
The research questions include:
I
nput
: Via what platform? With buttons, touch screen, speech, or gesture? Should it be set-based
or satisfaction-based?
Output: What to display? How to display? Where to display?
Level of intelligence
: How do users like automation in indoor environment controls? What type
of automation is preferred?
Buildings 2016,6, 19; doi:10.3390/buildings6020019 www.mdpi.com/journal/buildings
Buildings 2016,6, 19 2 of 15
To answer these questions, interviews and a survey were conducted. The goal of the interviews
was to collect the user habits and the expectations of residential thermostats and, in general, to explore
the potential individual differences in the use of thermostats. Subsequently, the survey was conducted
to answer more specific questions about user behavior with the thermostat, user preferences for
input/output, and important elements of the user interface.
2. Related Work
2.1. Smart Home
The concept of smart home was first used by the American Association of House Builders in
1984. A Smart Home system is “a physical world that is richly and invisibly interwoven with sensors,
actuators, displays and computational elements, embedded seamlessly in the everyday object of our
lives, and connected through a continuous network,” providing ways for controlling, interacting, and
monitoring the house [5].
Since the 1990s, the ubiquitous home network became the new trend to integrate individual
electronic control devices. Compared to a traditional home, the ubiquitous home network had
the capacity of adjusting its function according to the status and needs of users, equipment, and
environment. Meanwhile, the ubiquitous home network can hide the information of the system’s
mechanism, information exchange, and user network, which was irrelevant to the user experience.
This hidden information technology provided opportunities for users to focus more on the operational
task. Equally interesting, however, users may prefer to manually control the task they were familiar
with. Rodden and Benford pointed out that the human-computer interaction in the smart home should
be evolved from the existing interactive mode [6].
By the beginning of the 21st century, the development of smart home emphasized the concept of
“Internet of Things”. The “Internet of Things” opened up a whole range of possibilities for exchanging
information between people, appliances, systems, and networks. With networks, users can control
the household appliances through the control panel, webpage [
7
], the social platform [
8
], phone [
9
],
and even the table [
10
] or the wall [
11
]. Some research claimed that the main challenge was to develop
appropriate standards and protocols for interconnectivity between multiple networks, both within
and outside the home [12].
2.2. Classification o f Smart Home Devices
To better understand the opportunities and challenges of a smart system in a home, this study
reviews several smart home control devices. This review mainly focuses on three issues: the interaction
platform, interaction modality, and automation.
There are three basic platforms to develop interactive technologies for domestic settings:
interactive appliances, augmented furniture, and information applications [
6
]. Interactive appliances
add interactive capacities to the existing household, which offers new forms of interaction. For example,
the refrigerator can be directly controlled by voice. Augmented furniture is the furniture equipped with
interactive capacities. Examples of these include the DiamondTouch interactive table [
13
]; the display
can be activated to control household devices. An information application integrates the existing
information technology equipment. For example, people can use a telephone, pad, or television to
interact with household devices.
The interaction modality mainly includes touchscreen interaction, voice interaction and gesture
interaction. Taking the thermostat as an example, the touchscreen interaction is common in the mobile
APPS and wall-mounted thermostats equipped with a touchscreen. Touchscreen interaction provides
a high level of precision [
9
]. Voice interaction often acts as an assistive function for the touchscreen
interaction [
14
,
15
]. Voice interaction is effective in situations where a user ’s hands and eyes are busy
doing other tasks. Voice interaction usually uses some keywords as user commands. However, lack of
accuracy is another problem resulting from the difference of expression habit and recognition accuracy.
Buildings 2016,6, 19 3 of 15
Gesture interaction uses a wireless sensor package with multiple accelerometers to capture the spatial
trajectory of the gesture. Gesture interaction also has obstacle of low accuracy [
10
,
16
]. Users still
need some practice to control the thermostat. People also claim that the simple gesture interaction
is not as natural as they want. Moreover, the gesture interaction requires large data processing [
17
],
transparency to user [
5
], and security issues concerning the increasing number of sensors around
users [18].
Automation control includes human sensor automation, environment-based automation, and
history-based automation. Human sensor automation applies infrared detectors to track the position,
number, and temperature of the sources of heat and directly control the temperature to the user’s need.
Environment-based automation perceives the difference between the indoor and outdoor temperature
and automatically adjusts the indoor temperature. History-based automation adjusts the temperature
according to users’ usage history. For example, Nest would learn people’s usage in the first week, and
later adjust the temperature without the users’ participation based on a weekly schedule. However,
machine learning may require more sophistication to be useful, rather than just repeat what users did.
It should distinguish which adjustment is a regular input and what is an exceptional case [3,19].
2.3. Usability of Smart Home Devices
Some usability research indicated some facts about user requirements and preferences in the use
of smart home devices.
For the interaction platform, users prefer the mobile phone for instant control and the computer
for pattern control [
20
]. For the interaction modality, people have different needs in different situations.
For voice interaction, most people accept voice control when the task is easy and error-prone, but
they also fear that the system will misunderstand their words. The negative attitude derives from
the experiences with the cumbersome voice assistant in mobile phones. For the movement modality,
people claim the simple gesture interaction is not as natural as they want. People prefer the GUI
system because they believe visible icons and buttons make the task easier.
In the acceptance of automation control, people usually show great interest in, and need for,
automation in surveys and interviews [
21
]; however, the interest in automation is lower in field
studies [
20
,
22
]. For example, in a survey of 200 people, people showed an interest in using multimodal
commands to control lights and the thermostat remotely, and open and close windows and shutters
automatically. However, a three-year field study showed participants had considerable resistance
towards the increase of proactive information technology in homes [
22
] . Another six-month study
also showed that participants did not get used to the home’s ability to “live a life of its own” [20].
Some researchers noted that trust was the important factor affecting people’s acceptance of
automation. When people do not absolutely trust automation, it can be semi-automated with some
human intervention. There are two methods: one is that people preset an automation mechanism [
20
],
the other is that automation cannot work without user permission [
23
]. Tiiu Koskela found that
participants still believed that technology cannot completely understand complicated environmental
factors. This can be another factor influencing acceptance of the smart thermostat. Additionally,
people wanted to take control and observed the effect of each operation [
20
]. A recent study showed
that automatic environmental control should not always be the same, but adaptively designed in
accordance with specific comfort-energy trade-off situations, considering different control scenarios,
personal requirements, and cultures [
24
]. Trust should be established on users’ understandings of the
automation mechanisms. For example, some research showed that the Auto-Away feature of Nest
was unpopular. Auto-Away is a feature that detects whether people are at home and automatically
goes into away mode when no one is detected. The lack of a priori knowledge about how “Auto-away“
works may make users feel less in control. To adapt to the new system, some users even changed it
back to manual mode. Due to the inconvenience in controlling the system and the limitations of the
technology, it turned out to not be necessarily energy-saving [3].
Buildings 2016,6, 19 4 of 15
Some researchers pointed out that the following system characteristics may potentially improve
the trust level of users to automation [
23
]: (1) automation technologies should be robust, fail-safe,
and non-intrusive; (2) the level of automation should be carefully chosen. The complex work can be
done by the system, but users should have the opportunity to make the most important decisions; and
(3) the design should be predictable, transparent, and with feedback.
3. Study 1: Exploring User Needs through Interviews
The target test users stem from different backgrounds and are supposed to offer insight from
different perspectives on the usage and expectation of thermostat user interface. Among these,
14 Chinese participants (eight males) aged from 25 to 71 years old were recruited in the interviews,
with their occupations including a student, teacher, programmer, retired doctor, and engineer. Their
residence statuses also varied from a single apartment or shared room to living with family members.
All interviews were conducted in the lab except for one elderly woman who failed to come; her
interview was conducted at the participant’s home. Two staff members joined the interview sessions,
one was responsible for hosting each interview and the other was in charge of audio recording. The
interviews lasted for 1 h on average.
Interview questions (Table 1) were generated in three categories: demographic information;
general questions about environmental comfort; and specific questions concerning input, output,
and intelligence.
Table 1. Interview questions.
Category Question
Demographic information
Age, living status, thermostat ownership, smart phone ownership, web
access, occupation
General questions
How do you define a comfortable environment? What is your preference
for temperature, humidity, ventilation, etc.
What is your habit when using a thermostat (when and why do you
regulate, frequently used functionality, sleep settings)?
Describe the ideal controller.
Specific questions
Input: What are the conveniences and inconveniences of current
controller? (Not limited to thermostat)
Output: What information do you expect the thermostat to display?
Intelligence: What do you want the thermostat to do for
you automatically?
The interview data were coded and analyzed using a structured process: open coding, axial coding,
and selective coding. A detailed record of each participant’s answer can be found in the Table A1.
3.1. Results
3.1.1. Input: More Accessible Access
Almost all participants (10/12) liked the idea of setting the temperature when they were away
from home. One person mentioned the scenario of controlling the automobile air conditioner. “When I
was buying my car, I wanted to buy the car with a remote controller to turn on the AC before getting
into the car.”(P7) Some participants still believed it was more convenient to use a remote control
at home. “I am using an app to control my TV, it is very convenient and I don’t have to look for
the remote control ever since.”(P1) They enjoyed adjusting settings at night without getting out of
Buildings 2016,6, 19 5 of 15
bed. “Sometimes I do feel hot at night, but I am just too lazy to look for the controller.” (P6) They
actually wanted an instant controller that would enable them to make adjustments at any place, at any
time. This finding indicated a new interaction paradigm with multiple access methods. Almost all
participants appreciated the possibility of integrating controllers into one. They had problems with
finding controllers all of the time. “I have three controllers to control the ACs in different rooms and it
always occurred that I couldn’t find them. I wish I could control all ACs with one controller.”(P3).
3.1.2. Automation: Balance the Sense of Control
It was interesting to note that the key word “automation” had the highest occurrence frequency
in the description of ideal appliances. They expressed that the full-automatic washing machine and
refrigerator were easy to use. They can simply turn the machine on with one button operation. “I like
the control of my soy milk machine. I just need to press one button to start the process and then it is
all the machine’s business.”(P5). Participants had different opinions of automation. Five participants
preferred the full-automatic thermostat: “I hope the system can learn my control habits and ultimately
replace me.”(P8) “I want to have central AC at home and it would be so great if it could keep me
comfortable all the time.”(P3) Other participants preferred the adjustable automatic thermostat. “Now
we have to turn on the AC manually, but I wish that AC could be automatically turned on when the
temperature is beyond my comfort range.”(P4) Participants also expressed their concern about system
failure. “People’s behavior is random, I am feared that the machine cannot learn well.” Some of them
were even afraid of new technology. “I don’t want it to be too advanced. It scares me.”(P9) Thus, some
participants still wanted to gain a sense of control.
This finding reflected that people expected the automatic thermostat, but they still cannot fully
trust the machine because of immature technology. Without appropriate feedback, higher level of
automation may cause some fears. However, most of fears can be addressed by the semi-control.
People can set a control rule to make the machine run as they hope. This is confirmed by other studies.
3.1.3. Output: More Information about Results of Operation
As temperature was the only data provided by current thermostats, users were concerned with
other operational conditions of the AC such as whether it was running, when they needed to change
the filter, time to the target temperature, and environmental parameters such as humidity, outdoor
temperature, weather forecast, air quality, etc. Participants also cared about how much they spent on
air conditioning. People liked to know about running history, and they appreciated recommendations
and alerts on energy saving. “I want to know how much money I can save if I raise the temperature
by 1
˝
C.”(P9) “The system should tell me how much I would pay if I turned the AC on for the whole
night.” (P7) In all, participants focused more on the direct effect of their operations, rather than the
data itself. User needs for output still varied with individual differences: older and female users
cared more about information about energy and utility; young and male users cared more about
comfort-related information. Most participants were curious about information such as the condition
of the environment they were living in, the running status of the thermostat system, difference in
power costs under different settings and feasible solutions to save energy. Moreover, people stressed
the importance of the more intuitive display of information.
3.1.4. Function: Integrate More Machines into One
Although the question was about the control of the thermostat, almost all people (10/12) naturally
talked about the need of thermostat function. It was not surprising that users liked to have more
functions integrated in one machine. The most desired functions were purifying and humidifying
air, which motivated people to replace old thermostat. However, even if some participants owned
machines to purify and humidify air, they still needed a machine with all functions integrated. “I have
an air cleaner, an air humidifier but I still want an AC with all of these functions integrated in it”. (P4)
Integrated machine can significantly save space and reduce the tasks for user.
Buildings 2016,6, 19 6 of 15
3.1.5. Older People: Fear of Change
It should be noticed that older people usually have different needs. Most of them kept the
traditional consumer behavior and lifestyle. In most cases, they preferred to use fans to save money.
Their body functions degenerate gradually, they could not clearly distinguish buttons on remote
controller. Moreover, older participants were afraid of changes to the user interface. Most of these
fears can be addressed by a good design. For example, the system can provide a special mode for the
elderly, which keeps the original interface, simplifies the function of remote control and makes the
system more stable.
4. Study 2: Exploring User Needs through a Survey
In all, 87 participants aged from 19 to 52 years old (mean age = 27.01, SD = 7.93; male: 54.02%) took
the survey. All participants were recruited through social networking applications. Their occupations
included student, teacher, programmer, doctor, and so on. Their resident statuses also varied
from single apartment or shared room or live with family members. Before the questionnaire, six
representative thermostats (Table 1) were introduced to participants in great detail. The selection
criteria for the thermostats included the following: (1) they cover most input and output modalities;
(2) most of them (except Type 6) are existing thermostats that could be bought on the market; (3) type
6 is a representative prototype of thermal-sensation control. For example, when someone feels hot,
he/she pushes the “hot” button, the thermostat would lower the inside temperature. This type of
control may be more suitable for people who do not know the operating mechanism of thermostats,
especially for old people and children. The study explores whether using thermal-sensation would be
more natural way to control thermostat.
Three sections were involved in the survey, focusing on user behavior, preferences for
input/output modalities (Table 2), and display of information, respectively.
Table 2. Descriptions of the thermostats.
Type Input Modality Output Modality Picture
Type 1: Round shape,
can be operated by
pressing and turning the
control ring
Input 1: More
intuitive, traditional,
ring-shaped thermostat
with an LCD screen
Output 1: More intuitive,
graphical information display.
For example, to show that it is
now in ENERGY SAVING
mode, a green leaf will appear
on screen
Buildings2016,6,196of15
elderly,whichkeepstheoriginalinterface,simplifiesthefunctionofremotecontrolandmakesthe
systemmorestable.
4.Study2:ExploringUserNeedsthroughaSurvey
Inall,87participantsagedfrom19to52yearsold(meanage=27.01,SD=7.93;male:54.02%)
tookthesurvey.Allparticipantswererecruitedthroughsocialnetworkingapplications.Their
occupationsincludedstudent,teacher,programmer,doctor,andsoon.Theirresidentstatusesalso
variedfromsingleapartmentorsharedroomorlivewithfamilymembers.Beforethequestionnaire,
sixrepresentativethermostats(Table1)wereintroducedtoparticipantsingreatdetail.Theselection
criteriaforthethermostatsincludedthefollowing:(1)theycovermostinputandoutputmodalities;
(2)mostofthem(exceptType6)areexistingthermostatsthatcouldbeboughtonthemarket;(3)type
6isarepresentativeprototypeofthermalsensationcontrol.Forexample,whensomeonefeelshot,
he/shepushesthe“hot”button,thethermostatwouldlowertheinsidetemperature.Thistypeof
controlmaybemoresuitableforpeoplewhodonotknowtheoperatingmechanismofthermostats,
especiallyforoldpeopleandchildren.Thestudyexploreswhetherusingthermalsensationwould
bemorenaturalwaytocontrolthermostat.
Threesectionswereinvolvedinthesurvey,focusingonuserbehavior,preferencesfor
input/outputmodalities(Table2),anddisplayofinformation,respectively.
Table2.Descriptionsofthethermostats.
TypeInputModalityOutputModality Picture
Type1:Round
shape,canbe
operatedby
pressingand
turningthe
controlring
Input1:More
intuitive,traditional,
ringshaped
thermostatwithan
LCDscreen
Output1:More
intuitive,graphical
information
display.For
example,toshow
thatitisnowin
ENERGYSAVING
mode,agreenleaf
willappearon
screen
Type2:Large
touchscreenand
virtualbuttons
Input2:
Monochromatic
touchscreenwith
virtualbuttonon
screentooperate
Output2:
Monochromatic
touchscreen
displays
informationwith
numbersandtext
Type3:Large
colortouch
screenand
virtualbuttons
Input3:Colortouch
screenwithvirtual
buttononscreento
operate
Output3:Color
displayand
display
informationwith
numbersandtext
Type4:Physical
pushbuttons
Input4:Operated
byphysicalpush
button,eachbutton
isforoneoperation
Thesameas
Output2
Type 2: Large touch screen
and virtual buttons
Input 2:
Monochromatic
touch screen with
virtual button on
screen to operate
Output 2: Monochromatic
touch screen displays
information with numbers
and text
Buildings2016,6,196of15
elderly,whichkeepstheoriginalinterface,simplifiesthefunctionofremotecontrolandmakesthe
systemmorestable.
4.Study2:ExploringUserNeedsthroughaSurvey
Inall,87participantsagedfrom19to52yearsold(meanage=27.01,SD=7.93;male:54.02%)
tookthesurvey.Allparticipantswererecruitedthroughsocialnetworkingapplications.Their
occupationsincludedstudent,teacher,programmer,doctor,andsoon.Theirresidentstatusesalso
variedfromsingleapartmentorsharedroomorlivewithfamilymembers.Beforethequestionnaire,
sixrepresentativethermostats(Table1)wereintroducedtoparticipantsingreatdetail.Theselection
criteriaforthethermostatsincludedthefollowing:(1)theycovermostinputandoutputmodalities;
(2)mostofthem(exceptType6)areexistingthermostatsthatcouldbeboughtonthemarket;(3)type
6isarepresentativeprototypeofthermalsensationcontrol.Forexample,whensomeonefeelshot,
he/shepushesthe“hot”button,thethermostatwouldlowertheinsidetemperature.Thistypeof
controlmaybemoresuitableforpeoplewhodonotknowtheoperatingmechanismofthermostats,
especiallyforoldpeopleandchildren.Thestudyexploreswhetherusingthermalsensationwould
bemorenaturalwaytocontrolthermostat.
Threesectionswereinvolvedinthesurvey,focusingonuserbehavior,preferencesfor
input/outputmodalities(Table2),anddisplayofinformation,respectively.
Table2.Descriptionsofthethermostats.
TypeInputModalityOutputModality Picture
Type1:Round
shape,canbe
operatedby
pressingand
turningthe
controlring
Input1:More
intuitive,traditional,
ringshaped
thermostatwithan
LCDscreen
Output1:More
intuitive,graphical
information
display.For
example,toshow
thatitisnowin
ENERGYSAVING
mode,agreenleaf
willappearon
screen
Type2:Large
touchscreenand
virtualbuttons
Input2:
Monochromatic
touchscreenwith
virtualbuttonon
screentooperate
Output2:
Monochromatic
touchscreen
displays
informationwith
numbersandtext
Type3:Large
colortouch
screenand
virtualbuttons
Input3:Colortouch
screenwithvirtual
buttononscreento
operate
Output3:Color
displayand
display
informationwith
numbersandtext
Type4:Physical
pushbuttons
Input4:Operated
byphysicalpush
button,eachbutton
isforoneoperation
Thesameas
Output2
Type 3: Large color touch
screen and virtual buttons
Input 3: Color touch
screen with virtual
button on screen to
operate
Output 3: Color display and
display information with
numbers and text
Buildings2016,6,196of15
elderly,whichkeepstheoriginalinterface,simplifiesthefunctionofremotecontrolandmakesthe
systemmorestable.
4.Study2:ExploringUserNeedsthroughaSurvey
Inall,87participantsagedfrom19to52yearsold(meanage=27.01,SD=7.93;male:54.02%)
tookthesurvey.Allparticipantswererecruitedthroughsocialnetworkingapplications.Their
occupationsincludedstudent,teacher,programmer,doctor,andsoon.Theirresidentstatusesalso
variedfromsingleapartmentorsharedroomorlivewithfamilymembers.Beforethequestionnaire,
sixrepresentativethermostats(Table1)wereintroducedtoparticipantsingreatdetail.Theselection
criteriaforthethermostatsincludedthefollowing:(1)theycovermostinputandoutputmodalities;
(2)mostofthem(exceptType6)areexistingthermostatsthatcouldbeboughtonthemarket;(3)type
6isarepresentativeprototypeofthermalsensationcontrol.Forexample,whensomeonefeelshot,
he/shepushesthe“hot”button,thethermostatwouldlowertheinsidetemperature.Thistypeof
controlmaybemoresuitableforpeoplewhodonotknowtheoperatingmechanismofthermostats,
especiallyforoldpeopleandchildren.Thestudyexploreswhetherusingthermalsensationwould
bemorenaturalwaytocontrolthermostat.
Threesectionswereinvolvedinthesurvey,focusingonuserbehavior,preferencesfor
input/outputmodalities(Table2),anddisplayofinformation,respectively.
Table2.Descriptionsofthethermostats.
TypeInputModalityOutputModality Picture
Type1:Round
shape,canbe
operatedby
pressingand
turningthe
controlring
Input1:More
intuitive,traditional,
ringshaped
thermostatwithan
LCDscreen
Output1:More
intuitive,graphical
information
display.For
example,toshow
thatitisnowin
ENERGYSAVING
mode,agreenleaf
willappearon
screen
Type2:Large
touchscreenand
virtualbuttons
Input2:
Monochromatic
touchscreenwith
virtualbuttonon
screentooperate
Output2:
Monochromatic
touchscreen
displays
informationwith
numbersandtext
Type3:Large
colortouch
screenand
virtualbuttons
Input3:Colortouch
screenwithvirtual
buttononscreento
operate
Output3:Color
displayand
display
informationwith
numbersandtext
Type4:Physical
pushbuttons
Input4:Operated
byphysicalpush
button,eachbutton
isforoneoperation
Thesameas
Output2
Type 4: Physical
push buttons
Input 4: Operated by
physical push button,
each button is for one
operation
The same as Output 2
Buildings2016,6,196of15
elderly,whichkeepstheoriginalinterface,simplifiesthefunctionofremotecontrolandmakesthe
systemmorestable.
4.Study2:ExploringUserNeedsthroughaSurvey
Inall,87participantsagedfrom19to52yearsold(meanage=27.01,SD=7.93;male:54.02%)
tookthesurvey.Allparticipantswererecruitedthroughsocialnetworkingapplications.Their
occupationsincludedstudent,teacher,programmer,doctor,andsoon.Theirresidentstatusesalso
variedfromsingleapartmentorsharedroomorlivewithfamilymembers.Beforethequestionnaire,
sixrepresentativethermostats(Table1)wereintroducedtoparticipantsingreatdetail.Theselection
criteriaforthethermostatsincludedthefollowing:(1)theycovermostinputandoutputmodalities;
(2)mostofthem(exceptType6)areexistingthermostatsthatcouldbeboughtonthemarket;(3)type
6isarepresentativeprototypeofthermalsensationcontrol.Forexample,whensomeonefeelshot,
he/shepushesthe“hot”button,thethermostatwouldlowertheinsidetemperature.Thistypeof
controlmaybemoresuitableforpeoplewhodonotknowtheoperatingmechanismofthermostats,
especiallyforoldpeopleandchildren.Thestudyexploreswhetherusingthermalsensationwould
bemorenaturalwaytocontrolthermostat.
Threesectionswereinvolvedinthesurvey,focusingonuserbehavior,preferencesfor
input/outputmodalities(Table2),anddisplayofinformation,respectively.
Table2.Descriptionsofthethermostats.
TypeInputModalityOutputModality Picture
Type1:Round
shape,canbe
operatedby
pressingand
turningthe
controlring
Input1:More
intuitive,traditional,
ringshaped
thermostatwithan
LCDscreen
Output1:More
intuitive,graphical
information
display.For
example,toshow
thatitisnowin
ENERGYSAVING
mode,agreenleaf
willappearon
screen
Type2:Large
touchscreenand
virtualbuttons
Input2:
Monochromatic
touchscreenwith
virtualbuttonon
screentooperate
Output2:
Monochromatic
touchscreen
displays
informationwith
numbersandtext
Type3:Large
colortouch
screenand
virtualbuttons
Input3:Colortouch
screenwithvirtual
buttononscreento
operate
Output3:Color
displayand
display
informationwith
numbersandtext
Type4:Physical
pushbuttons
Input4:Operated
byphysicalpush
button,eachbutton
isforoneoperation
Thesameas
Output2
Buildings 2016,6, 19 7 of 15
Table 2. Cont.
Type Input Modality Output Modality Picture
Type 5: Physical push
buttons with direction key
and menu key
Input 5: Operated by
physical push button.
A single button can
work with the “menu”
button to perform
various operations.
Output 4: Menu-like
information display
Buildings2016,6,197of15
Type5:Physical
pushbuttons
withdirection
keyandmenu
key
Input5:Operated
byphysicalpush
button.Asingle
buttoncanwork
withthe“menu”
buttontoperform
variousoperations.
Output4:Menu
likeinformation
display
Type6:Color
touchscreen,
virtualbuttons.
Youoperatethe
systemby
expressingyour
feelingsandthe
systemwill
makeadecision
foryou
Input6:Theinput
informationisyour
feeling,like“Ifeel
cold”,ratherthan
commands
Output5:Color
displaywithiconic
displayand
emphasisonuser’s
feelings
4.1.ResultsofUserBehavior
Table3liststhedescriptivedataforuserbehavior.Thequestionnaireforuserbehaviormainly
focusesonthreeaspects:userhouseholdactivity(UB1,UB2,UB3),regularcontrol(UB4,UB5),and
mentalmodel(UB6,UB7,UB8).Theagreementtoeachstatementwasmeasuredbyasevenpoint
Likertscalerangingfrom1—stronglydisagreeto7—stronglyagree.Meanandstandarddeviationof
theratingsaregivenasfollows.
Table3.Descriptivedataofuserbehavior.
NotationUserBehavio
r
MeanSD
UB1IalwayscarrymyphonewithmewhenI’mhome.4.991.85
UB2WhenI’mhome,Ialwaysstayinthesameroomforalongtime.5.611.54
UB3Ialwaysdisagreewithmyfamilyaboutsettingthepropertemperature.3.291.68
UB4Duringworkdays,Icontrolthetemperaturewithregularadjustmentstomy
thermostat.4.952.07
UB5Duringweekends,Icontrolthetemperaturewithregularadjustmentstomy
thermostat.5.231.68
UB6Inmyopinion,athermostatisjustaswitchtocontrolcoolingorheating.Tobe
comfortable,Ineedtorepeatedlyregulatethethermostat.3.831.98
UB7
Inmyopinion,tobecomfortable,allIneedtodoistosetapropertemperature
forthermostat,anditwillfinishtheremainingworkautomaticallytoguarantee
mycomfort.
5.361.64
UB8
Inmyopinion,settingtemperaturelowerthanneededcanspeedupcooling.
(Forexample,thecurrenttemperatureis25°C,andIwanttosetitto23°C.To
speedupcooling,Iwouldsetitto18°C.)
4.921.97
4.1.1.HouseholdActivity
Figures1–3showthedistributionofagreementtoUB1,UB2,andUB3.Figures1and2showthat
ahighproportionofuserscarrytheirphonesandstayinthesameroomwhentheyareathome.The
agreementtoUB3didnotshowasignificantmodality,whichindicatestheremaybeindividual
differencesintheoccurrenceofcomfortdisputes.
Type 6: Color touch screen,
virtual buttons. You
operate the system by
expressing your feelings
and the system will make
a decision for you
Input 6: The input
information is your
feeling, like “I feel
cold”, rather than
commands
Output 5: Color display with
iconic display and emphasis
on user’s feelings
r
4.1. Results of User Behavior
Table 3lists the descriptive data for user behavior. The questionnaire for user behavior mainly
focuses on three aspects: user household activity (UB1, UB2, UB3), regular control (UB4, UB5), and
mental model (UB6, UB7, UB8). The agreement to each statement was measured by a seven-point
Likert scale ranging from 1—strongly disagree to 7—strongly agree. Mean and standard deviation of
the ratings are given as follows.
Table 3. Descriptive data of user behavior.
Notation User Behavior Mean SD
UB1 I always carry my phone with me when I’m home. 4.99 1.85
UB2 When I’m home, I always stay in the same room for a long time. 5.61 1.54
UB3
I always disagree with my family about setting the proper temperature.
3.29 1.68
UB4 During workdays, I control the temperature with regular adjustments
to my thermostat. 4.95 2.07
UB5 During weekends, I control the temperature with regular adjustments
to my thermostat. 5.23 1.68
UB6
In my opinion, a thermostat is just a switch to control cooling or heating.
To be comfortable, I need to repeatedly regulate the thermostat. 3.83 1.98
UB7
In my opinion, to be comfortable, all I need to do is to set a proper
temperature for thermostat, and it will finish the remaining work
automatically to guarantee my comfort.
5.36 1.64
UB8
In my opinion, setting temperature lower than needed can speed up
cooling. (For example, the current temperature is 25 ˝C, and I want to
set it to 23 ˝C. To speed up cooling, I would set it to 18 ˝C.)
4.92 1.97
4.1.1. Household Activity
Figures 13show the distribution of agreement to UB1, UB2, and UB3. Figures 1and 2show
that a high proportion of users carry their phones and stay in the same room when they are at home.
The agreement to UB3 did not show a significant modality, which indicates there may be individual
differences in the occurrence of comfort disputes.
Buildings 2016,6, 19 8 of 15
Buildings2016,6,198of15
Figure1.AgreementtoUserBehavior1.
Figure2.AgreementtoUserBehavior1.
Figure3.AgreementtoUserBehavior3.
4.1.2.RegularControl
Figures4and5showthefrequencydistributionsofagreementtoUB4andUB5,respectively.
Theresultsshowthatahighproportionofusersregularlyadjusttheirthermostat,bothonweekdays
andonweekends.
Thettestresultindicatesthatfemaleusersaredoingmoreregularcontrolstothethermostat
thanmaleusersdoonworkdays(femaleuser:5.79±1.28,maleuser:4.88±1.78,P=0.017).However,
theirregularcontrolsofthethermostatonweekendsaresimilar.
Figure 1. Agreement to User Behavior 1.
Buildings2016,6,198of15
Figure1.AgreementtoUserBehavior1.
Figure2.AgreementtoUserBehavior1.
Figure3.AgreementtoUserBehavior3.
4.1.2.RegularControl
Figures4and5showthefrequencydistributionsofagreementtoUB4andUB5,respectively.
Theresultsshowthatahighproportionofusersregularlyadjusttheirthermostat,bothonweekdays
andonweekends.
Thettestresultindicatesthatfemaleusersaredoingmoreregularcontrolstothethermostat
thanmaleusersdoonworkdays(femaleuser:5.79±1.28,maleuser:4.88±1.78,P=0.017).However,
theirregularcontrolsofthethermostatonweekendsaresimilar.
Figure 2. Agreement to User Behavior 1.
Buildings2016,6,198of15
Figure1.AgreementtoUserBehavior1.
Figure2.AgreementtoUserBehavior1.
Figure3.AgreementtoUserBehavior3.
4.1.2.RegularControl
Figures4and5showthefrequencydistributionsofagreementtoUB4andUB5,respectively.
Theresultsshowthatahighproportionofusersregularlyadjusttheirthermostat,bothonweekdays
andonweekends.
Thettestresultindicatesthatfemaleusersaredoingmoreregularcontrolstothethermostat
thanmaleusersdoonworkdays(femaleuser:5.79±1.28,maleuser:4.88±1.78,P=0.017).However,
theirregularcontrolsofthethermostatonweekendsaresimilar.
Figure 3. Agreement to User Behavior 3.
4.1.2. Regular Control
Figures 4and 5show the frequency distributions of agreement to UB4 and UB5, respectively. The
results show that a high proportion of users regularly adjust their thermostat, both on weekdays and
on weekends.
The t-test result indicates that female users are doing more regular controls to the thermostat than
male users do on workdays (female user: 5.79
˘
1.28, male user: 4.88
˘
1.78, P = 0.017). However, their
regular controls of the thermostat on weekends are similar.
Buildings 2016,6, 19 9 of 15
Buildings2016,6,199of15
Figure4.AgreementtoUserBehavior1.
Figure5.AgreementtoUserBehavior1.
4.1.3.MentalModel
Figures6–8indicatethatahighproportionofusersbelievethatathermostatwillautomatically
guaranteetheircomfortaftertheysetapropertemperature.Ahighproportionofpeoplebelievethat
settingthetemperaturelowerthanneededcanspeedupcooling.
Figure6.AgreementtoUserBehavior1.
Figure7.AgreementtoUserBehavior1.
Figure 4. Agreement to User Behavior 1.
Buildings2016,6,199of15
Figure4.AgreementtoUserBehavior1.
Figure5.AgreementtoUserBehavior1.
4.1.3.MentalModel
Figures6–8indicatethatahighproportionofusersbelievethatathermostatwillautomatically
guaranteetheircomfortaftertheysetapropertemperature.Ahighproportionofpeoplebelievethat
settingthetemperaturelowerthanneededcanspeedupcooling.
Figure6.AgreementtoUserBehavior1.
Figure7.AgreementtoUserBehavior1.
Figure 5. Agreement to User Behavior 1.
4.1.3. Mental Model
Figures 68indicate that a high proportion of users believe that a thermostat will automatically
guarantee their comfort after they set a proper temperature. A high proportion of people believe that
setting the temperature lower than needed can speed up cooling.
Buildings2016,6,199of15
Figure4.AgreementtoUserBehavior1.
Figure5.AgreementtoUserBehavior1.
4.1.3.MentalModel
Figures6–8indicatethatahighproportionofusersbelievethatathermostatwillautomatically
guaranteetheircomfortaftertheysetapropertemperature.Ahighproportionofpeoplebelievethat
settingthetemperaturelowerthanneededcanspeedupcooling.
Figure6.AgreementtoUserBehavior1.
Figure7.AgreementtoUserBehavior1.
Figure 6. Agreement to User Behavior 1.
Buildings2016,6,199of15
Figure4.AgreementtoUserBehavior1.
Figure5.AgreementtoUserBehavior1.
4.1.3.MentalModel
Figures6–8indicatethatahighproportionofusersbelievethatathermostatwillautomatically
guaranteetheircomfortaftertheysetapropertemperature.Ahighproportionofpeoplebelievethat
settingthetemperaturelowerthanneededcanspeedupcooling.
Figure6.AgreementtoUserBehavior1.
Figure7.AgreementtoUserBehavior1.
Figure 7. Agreement to User Behavior 1.
Buildings 2016,6, 19 10 of 15
Buildings2016,6,1910of15
Figure8.AgreementtoUserBehavior3.
4.2.RankofInputModalities
Figure9ranksthepreferenceforsixtypicalinputmodalitiesinthesurvey(notethatlowerrank
meanshigherpreference).TheringshapedthermostatwithanLEDscreenrankedfirst,followedby
themonochromatictouchscreenandcolortouchscreen.Thesatisfactionbasedtouchscreencamein
last,partiallybecauseitwasjustaprototype.
Resultsindicatedthatuserspreferredsimpleandaccurateinputwithacolortouchscreento
physicalpushbuttons.Thepreferenceforsatisfactionbasedinputwaspolarized.Itwasthefavorite
inputstylefor14.9%participants(justlowerthantheringshapedthermostatwithanLEDscreen
andthelargetouchscreenwithcolordisplay),whileitwasalsotheleastfavoriteinputstylefor51.7%
participants.Thissuggeststhatsatisfactionbasedinputcouldbeasupplementaryinputmethod.
Figure9.Rankofinputmodalities.1Lowerrankmeanshigherpreference.
4.3.RankofOutputModalities
Fortheoutputmodalities,Figure10calculatesthemeanrankforfivetypicaloutputmodalities
(notethatlowerrankmeanshigherpreference).Graphicalinformationdisplay(mixednumbersand
text)tookfirstplace,whileoutputmodalitiesbasedonnumbersandtextfollowed.Iconicdisplay
focusingonuser’sfeelingcameinlast.
Resultsreflecteduserpreferencesforgraphicalandintuitiveoutputwithcolordisplay.Similar
totheinputmodalities,thepreferenceforsatisfactionbasedoutputwaspolarized.Itwasthefavorite
inputstylefor13.8%participantswhileitwasalsotheleastfavoriteoutputstylefor44.8%of
participants.Thissuggeststhatsatisfactionbasedinputcouldbeasupplementaryoutputmethod.
2.47
3.01
3.05
3.83
4.21
4.38
123456
RingshapedthermostatwithLEDscreen
Bigtouchscreen(Monochromaticdisplay)
Bigtouchscreen(Colordisplay)
Physicalpushbutton(Onebuttonforone
operation)
Physicalpushbutton(Menuanddirectionbutton)
Bigtouchscreen(Satisfactionbased)
Rank1ofinputmodalities
Figure 8. Agreement to User Behavior 3.
4.2. Rank of Input Modalities
Figure 9ranks the preference for six typical input modalities in the survey (note that lower rank
means higher preference). The ring-shaped thermostat with an LED screen ranked first, followed by
the monochromatic touch screen and color touch screen. The satisfaction-based touch screen came in
last, partially because it was just a prototype.
Results indicated that users preferred simple and accurate input with a color touch screen to
physical push buttons. The preference for satisfaction-based input was polarized. It was the favorite
input style for 14.9% participants (just lower than the ring-shaped thermostat with an LED screen and
the large touch screen with color display), while it was also the least favorite input style for 51.7%
participants. This suggests that satisfaction-based input could be a supplementary input method.
Buildings2016,6,1910of15
Figure8.AgreementtoUserBehavior3.
4.2.RankofInputModalities
Figure9ranksthepreferenceforsixtypicalinputmodalitiesinthesurvey(notethatlowerrank
meanshigherpreference).TheringshapedthermostatwithanLEDscreenrankedfirst,followedby
themonochromatictouchscreenandcolortouchscreen.Thesatisfactionbasedtouchscreencamein
last,partiallybecauseitwasjustaprototype.
Resultsindicatedthatuserspreferredsimpleandaccurateinputwithacolortouchscreento
physicalpushbuttons.Thepreferenceforsatisfactionbasedinputwaspolarized.Itwasthefavorite
inputstylefor14.9%participants(justlowerthantheringshapedthermostatwithanLEDscreen
andthelargetouchscreenwithcolordisplay),whileitwasalsotheleastfavoriteinputstylefor51.7%
participants.Thissuggeststhatsatisfactionbasedinputcouldbeasupplementaryinputmethod.
Figure9.Rankofinputmodalities.1Lowerrankmeanshigherpreference.
4.3.RankofOutputModalities
Fortheoutputmodalities,Figure10calculatesthemeanrankforfivetypicaloutputmodalities
(notethatlowerrankmeanshigherpreference).Graphicalinformationdisplay(mixednumbersand
text)tookfirstplace,whileoutputmodalitiesbasedonnumbersandtextfollowed.Iconicdisplay
focusingonuser’sfeelingcameinlast.
Resultsreflecteduserpreferencesforgraphicalandintuitiveoutputwithcolordisplay.Similar
totheinputmodalities,thepreferenceforsatisfactionbasedoutputwaspolarized.Itwasthefavorite
inputstylefor13.8%participantswhileitwasalsotheleastfavoriteoutputstylefor44.8%of
participants.Thissuggeststhatsatisfactionbasedinputcouldbeasupplementaryoutputmethod.
2.47
3.01
3.05
3.83
4.21
4.38
123456
RingshapedthermostatwithLEDscreen
Bigtouchscreen(Monochromaticdisplay)
Bigtouchscreen(Colordisplay)
Physicalpushbutton(Onebuttonforone
operation)
Physicalpushbutton(Menuanddirectionbutton)
Bigtouchscreen(Satisfactionbased)
Rank1ofinputmodalities
Figure 9. Rank of input modalities. 1Lower rank means higher preference.
4.3. Rank of Output Modalities
For the output modalities, Figure 10 calculates the mean rank for five typical output modalities
(note that lower rank means higher preference). Graphical information display (mixed numbers and
text) took first place, while output modalities based on numbers and text followed. Iconic display
focusing on user’s feeling came in last.
Results reflected user preferences for graphical and intuitive output with color display. Similar
to the input modalities, the preference for satisfaction-based output was polarized. It was the
favorite input style for 13.8% participants while it was also the least favorite output style for 44.8% of
participants. This suggests that satisfaction-based input could be a supplementary output method.
Buildings 2016,6, 19 11 of 15
Buildings2016,6,1911of15
Figure10.Rankofoutputmodalities.1Lowerrankmeanshigherpreference.
4.4.ImportanceThermostatDesignelements
Table4showsthetop10mostimportantdesignelementsoutofthe18designelementsinthe
informationdisplay.Theothereightdesignelementsarelocalweatherforecast,otherrelatedsystem
information,helpinformation,utilityinformation,currentenergyprice,audiotouchconfirmation,
confirmationbutton,andonebuttonoverride.
Thestronglyrequiredelementsaremainlyaboutoutputratherthaninput,andmostofthemare
outputsofcurrentstatus.Someofthemhavealreadybeenrealizedinexistingproducts,whilesome
stillhavenot,suchasachangefilteralarm,anindicationwhetherthethermostatisrunning,
malfunctionalarm,andcurrenthumidity.Forinputelements,copyschemefunctionandspeeddial
wereregardedasimportantelements.Forsmartelements,energyconsumptioninformationanda
malfunctionalarmwereregardedasimportantelements.
Table4.Top10importantdesignelementsofthermostatoutof18.
ElementsMean SD Category SubCategory
Currenttemperature5.841.15OutputCurrentStatus
Changefilteralarm5.630.98OutputCurrentStatus
Currentmode,forexample,sleepmode.5.401.06OutputCurrentStatus
Lowbatteryalarm5.401.06OutputCurrentStatus
Indicationwhetherthethermostatisnow
actuallyworking,insteadofinidlemode.5.291.17OutputCurrentStatus
Malfunctionalarm5.291.60Intelligence CurrentStatus
Copyschemefunction5.051.38InputInput
Currenthumidity5.021.25OutputCurrentStatus
Fromtheabove,thesurveygivesmorespecificresultsaboutusers’needsandpreferences.First,
mostusers’behaviorsaresimilar,andtheiruserhabitsareinfluencedbypastexperiences;for
example,mostpeoplebelievethatsettingalowertemperaturecanspeedupcooling.Second,user
needsforinputmodalitiesandoutputmodalitiesaredifferent.Fortheinput,peopleprefersimple
anddirectcontrolofthethermostat.TheringshapedthermostatwithanLEDscreenandthetouch
screenarethemostpopular.Fortheoutput,peoplepreferclearanddirectinformationdisplays
includingnumbersandtext.Peoplewanttoknowmoreinformationaboutthecurrentenvironment,
suchascurrenttemperatureandhumidity.Theyarealsoconcernedabouttimelyenergy
consumptioninformation.Moreover,thissurveyexplorespeople’sattitudestowardsanew
interactionmethodbasedonsatisfaction.Theresultsshowthatpeople’spreferenceonsatisfaction
basedinputandoutputarepolarized.Mostpeopledidnotlikesatisfactionbasedinputandoutput.
2.77
2.68
2.71
4.18
4.38
123456
Graphicalinformationdisplay(Mixedwith
numbersandtext)
Numbersandtextonly(Colordisplay)
Numbersandtextonly(Monochromaticdisplay)
Menulikeinformation
Iconicdisplayfocusonuserʹsfeeling
Rank1ofoutputmodalities
Figure 10. Rank of output modalities. 1Lower rank means higher preference.
4.4. Importance Thermostat Designelements
Table 4shows the top 10 most important design elements out of the 18 design elements in the
information display. The other eight design elements are local weather forecast, other related system
information, help information, utility information, current energy price, audio touch confirmation,
confirmation button, and one-button override.
The strongly required elements are mainly about output rather than input, and most of them
are outputs of current status. Some of them have already been realized in existing products, while
some still have not, such as a change filter alarm, an indication whether the thermostat is running,
malfunction alarm, and current humidity. For input elements, copy scheme function and speed dial
were regarded as important elements. For smart elements, energy consumption information and
a malfunction alarm were regarded as important elements.
Table 4. Top 10 important design elements of thermostat out of 18.
Elements Mean SD Category Sub-Category
Current temperature 5.84 1.15 Output Current Status
Change filter alarm 5.63 0.98 Output Current Status
Current mode, for example, sleep mode. 5.40 1.06 Output Current Status
Low battery alarm 5.40 1.06 Output Current Status
Indication whether the thermostat is now
actually working, instead of in idle mode. 5.29 1.17 Output Current Status
Malfunction alarm 5.29 1.60 Intelligence Current Status
Copy scheme function 5.05 1.38 Input Input
Current humidity 5.02 1.25 Output Current Status
From the above, the survey gives more specific results about users’ needs and preferences. First,
most users’ behaviors are similar, and their user habits are influenced by past experiences; for example,
most people believe that setting a lower temperature can speed up cooling. Second, user needs for
input modalities and output modalities are different. For the input, people prefer simple and direct
control of the thermostat. The ring-shaped thermostat with an LED screen and the touch screen
are the most popular. For the output, people prefer clear and direct information displays including
numbers and text. People want to know more information about the current environment, such
as current temperature and humidity. They are also concerned about timely energy consumption
information. Moreover, this survey explores people’s attitudes towards a new interaction method
based on satisfaction. The results show that people’s preference on satisfaction-based input and output
are polarized. Most people did not like satisfaction-based input and output.
Buildings 2016,6, 19 12 of 15
5. Discussions and Conclusions
This paper describes interviews and a survey to explore people’s needs and preferences regarding
thermostats, including control, display and intelligence.
For the thermostat user interface, people prefer a simpler, more intuitive, and convenient
thermostat control. For convenience, one suggestion is to support control through multiple access
methods. Now that most people have mobile phones with them all of the time, it is time to utilize such
devices as new controllers. The controllers of household appliances should be more integrated with
more appliances.
People need more integrative feedback about the current environment from the user interface.
A smart thermostat should provide operational status, energy consumption information, and
environmental status in greater detail. With a higher level of automation, more feedback should
be offered to enhance users’ trust in the thermostat and their feeling of involvement. In addition, one
participant was interested in comparing his energy consumption performance to that of his friends or
neighbors. This encourages the development of a sharing function that can not only make thermostat
usage fun but also encourage energy-saving behavior.
For thermostat intelligence, different people have different levels of acceptance of smart
thermostats. Female users and elderly users are afraid of changes in user interfaces and less interested
in obtaining a smart thermostat. An improved traditional thermostat may better fit the needs of such
users. Male users of approximately 30 years old were found to be the target users, as they are more
willing to pay for technology. There can be different modes for different people. People are more
concerned about energy-saving and health issues. Smart thermostats should create more functions
to promote energy-saving behavior and users’ health. This study also explores people’s acceptance
of satisfaction-based input and output, which is a new interaction method. The result showed that
people’s levels of acceptance are polarized. Most people dislike satisfaction-based input and output.
This finding indicates that the design of the new interaction paradigm should also consider the users’
different levels of acceptance and the reasons behind them.
This study also has theoretical implications for smart appliance design. Previously, little work has
discussed people’s needs and expectations of new smart appliances at home. The current study found
that current technology can realize most customer needs. Researchers and designers should focus on
the user needs for new products.
Finally, it is important to note that there are a lot of unsolved problems on hardware and
technology in the real smart thermostats. In this study, limited consideration has been given to
how to improve technology systems in thermostat. Another weakness of this study is that the research
only conducted interview and survey to explore user needs about smart thermostat. The results may
be different from user experience in real in situ conditions. More experiments should be done to verify
the results. Moreover, this study makes incremental contribution by offering some guidelines to the
design of thermostat, but this study does not propose a new subversive design.
This study hopes to raise awareness that designers should take full consideration of user needs
and try to balance users’ desire for innovative technology and the desire for a simple domestic lifestyle.
In future work, this study plans to apply “in situ” methods to explore users need. This study can
conduct some diary studies. This study also wants to learn more details about different people’s
preference for intelligent levels in different scenarios.
Acknowledgments:
This research was supported by the United Technologies Research Center. We also wish to
thank all of the participants for participating in the interview and openly discussing their opinions.
Author Contributions:
P.-L.P.R., J.W., and Y.G. conceived and designed the experiments; Y.G., J.W., H.-J.H.
performed the experiments; Y.G., H.-J.H. and J.W. analyzed the data; Y.G. and H.-J.H. wrote the paper.
Conflicts of Interest: The authors declare no conflict of interest.
Buildings 2016,6, 19 13 of 15
Appendix
Table A1. A brief record of interview results.
Participant Desired Input Desired Output Desired Intelligence
P1-30-male-apprentice of
Chinese-medicine-tenant
An integrated operation
panel on smart phone.
Automation based on indoor
and outdoor environment as
well as user behavior
Provide health-related
information, such as humidity
Automatic settings according
to indoor & outdoor status
P2-29-female(pregnant)
-engineer-tenant
Quick start
Remote control from
outside home
Running status indicator(e.g.,
whether it is running or not)
System status indicator (e.g.,
change filter alarm)
Humidity, weather forecast
Humidity sensor and control
Air purify
P3-71-female-retired
doctor-owner of house
Big buttons and texts
Remain traditional interface
Full automation
One controller controls
several facilities
Energy consumption information
Automatically set according
to tiered pricing for
household electricity
P4-63-male-retired
teacher-owner of house
Physical buttons are ok.
One controller controls
several facilities
Automation based on
user-defined algorithm
Energy consumption information
Current power fee
Air purify
Automation based on
user-defined algorithm
P5-26-female-
educator-tenant
One-button operation
Energy consumption information
Humidity
Air purify
Humidity sensor and control
P6-28-male-student-live
in the dorm with other
5 students
Full automation
Remote control on bed
One controller controls
several facilities
Running status indicator
Air quality indicator
Automatically set according
to preference
P7-25-male-postgraduate
-live in the dorm with
another student
Default setting based on
user behavior
Remote control from
outside home
System status indicator
Energy consumption information
with power fee
Automatically set according
to preference and indoor &
outdoor status
P8-25-male-postgraduate
-live in the dorm with
another student
Complete automation based
on machine learning
Energy consumption information
(compared with others)
Learnable system, realize
complete automatically
control ultimately
P9-31-female-
educator-tenant
Terms rather than icons
One-button operation
(leaving home, arriving
home etc.)
Terms rather than icons
Indoor air quality indicator
Energy consumption advice
Recommendation/ default
setting for healthy and
energy saving
P10-35-male-IT
engineer-owner of house
As simple as possible. “I
know what I want.” Time to complete operation Air purify
P11-33-male-management
consulting-owner of
house
One-button operation based
on personal preference
Graphical output such as a smiling
face stands for good condition
Humidity sensor and control
P12-33-female-
management
consulting-owner of
house
One-button operation based
on personal preference
My perception is the best
feedback information
Humidity information
Outdoor temperature
Air purify
Buildings 2016,6, 19 14 of 15
Table A1. Cont.
Participant Desired Input Desired Output Desired Intelligence
P13-28-female-
researcher-owener of
house
Simple, one-button operation
Default settings such as
sleeping mode
Clear, close
Feedback of time to get my
set-point
Information of system status
Detect the users’ skin temp.
and regulate automatically
for special users such as
pregnant woman
P14-29-male-management
consulting-owner of
house
Simple, intuitive
Need remote access
Clear, simplest
Humidity sensor and report
Information of running time and
energy usage
Simple and direct controlling
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... Heating and cooling accounts for a substantial portion of residential energy consumption, a lot of this energy is wasted due to inefficient use [22]. Programmable thermostats are generally inefficient due to poor usability design [26]. Automation-based approaches have been introduced to the market, a well-known example is the Nest thermostat, which uses machine learning and sensing technologies to control the home's temperature [37]. ...
... Expanding the capabilities and features of home appliances can cause a gap between users' mental models causing inefficient use, confusion, dissatisfaction, and abandonment system's features [37]. Increasing levels of automation will require more feedback about the system's behavior to enhance trust and feeling of involvement [26]. ...
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... There is a lack of laboratory-controlled tests, apart from those made by the manufacturers. Also, the general perception from the user's answers in the surveys and interviews shows the difficulty of knowing the real savings coming from the use of smart thermostats [9,11]. These were the original motivations of this new research. ...
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