Field of the Invention
The present invention relates to an air-conditioning
control system.
Background of the Invention
In a house, there is available an air-conditioning
control system that turns off air conditioning devices such
as an air conditioner to seek energy saving when a dweller
is absent within a home or turns on the air conditioner
pursuant to a command from a cellular phone to maintain the
home as a comfortable space before the dweller comes back
home (see, e.g., Japanese Patent Application Publication No.
2008-138902).
The conventional air-conditioning control system
essentially controls home appliances, and there has
disclosed no system that can effectively use natural energy
such as an ambient air to provide a comfortable indoor space
to a home-coming family member while seeking energy saving.
In some cases, a dweller is absent within a home for a
short time period, e.g., about two or three hours. In other
cases, a dweller does not exist within a home for a long
time period, e.g., about two or three days. In the event
that natural energy is used to provide a comfortable indoor

space to a home-coming family member while saving energy, an
air conditioner needs to be differently controlled depending
on the length of absence time period. However, the
conventional air-conditioning control system remains silent
on this point.
Summary of the Invention
In view of the above, the present invention provides
an air-conditioning control system capable of providing a
comfortable indoor space to a home-coming family member
while using natural energy to seek energy saving.
In accordance with an aspect of the present invention,
there is provided an air-conditioning control system
including a ventilating device for performing ventilation
between an indoor space and an outdoor space; an absence
detecting unit for detecting absence of a human within the
indoor space; and an air conditioning controller adapted to
operate, when the absence of the human is detected by the
absence detecting unit, the ventilating device during at
least a part of an absence period to control a thermal
environment within the indoor space.
The system may further include an air conditioning
device for cooling or heating the indoor space. The air
conditioning controller may be adapted to operate, when the
absence of the human is detected by the absence detecting

unit, the ventilating device during at least a part of the
absence period such that, when operating the air
conditioning device next time, the thermal environment
within the indoor space is controlled in such a way as to
reduce a power consumption of the air conditioning device.
With this configuration, it is possible to provide a
comfortable indoor space to a home-coming family member
while using natural energy to seek energy saving.
The absence detecting unit may be adapted to, when the
absence of the human is detected by the absence detecting
unit, make determination whether the absence period is a
long period equal to or longer than a predetermined time
period or a short period shorter than the predetermined time
period, and the air conditioning controller is adapted to
control the ventilating device in different control patterns
depending on whether the absence period is the long period
or the short period.
With this configuration, the air conditioning control
throughout the absence period can be adaptively performed
depending on whether the absence period is the long period
or the short period.
The absence detecting unit may determine whether the
absence period is the long period or the short period by
comparing the length of the absence period with a threshold,
and the threshold .may be varied with at least one of year,
month, day and hour at which the determination is made.

With this configuration, it is possible to set the
threshold in accordance with the life pattern of family
members which varies depending on the seasons and the time
zone.
The absence detecting unit may determine whether the
absence period is the long period or the short period by
estimating an end time of the absence period, and the air
conditioning controller may be adapted to continuously
operate the ventilating device throughout the absence period
if the absence period is the short period, and start an
operation of the ventilating device a specified time earlier
than the end time of the absence period if the absence
period is the long period.
With this configuration, if the absence period is the
long period, the ventilating device is not operated
throughout the entire absence period but is operated for a
minimum period immediately before a family member comes home.
This makes it possible to prevent an unnecessary power
consumption through the absence period and to effectively
perform the control of the thermal environment within the
home using the ventilating device.
The system may further include a photovoltaic power
generating device for generating electric power by using
sunlight to supply the electric power to the air
conditioning device and the ventilating device. The air
conditioning controller may be adapted to operate the air

conditioning device and the ventilating device throughout
the absence period if the absence period is the long period
and the electric power generated by the photovoltaic power
generating device is equal to or greater than a
predetermined value, and operate the ventilating device a
specified time earlier than the end time of the absence
period regardless of the magnitude of the electric power
generated by the photovoltaic power generating device.
With this configuration, if the electric power
generated by the photovoltaic power generating device is
equal to or greater than a predetermined value, the air
conditioning device and the ventilating device are operated
to control the thermal environment within the home
beforehand in such a way as to make the home comfortable.
This makes it possible to more effectively operate the
ventilating device immediately before a family member comes
home .
The system may further include a photovoltaic power
generating device for generating electric power by using
sunlight to supply the electric power to the air
conditioning device and the ventilating device; a battery
for storing the electric power generated by the photovoltaic
power generating device and supplying the electric power to
the air conditioning device and the ventilating device; and
a reverse power flow control unit for reversely supplying
the electric power generated by the photovoltaic power

generating device to a commercial power supply system. The
air conditioning controller may be adapted to control, if
the absence period is the long period, the reverse power
flow control unit to reversely supply the electric power
generated by the photovoltaic power generating device to the
commercial power supply system instead of supplying the
electric power to the battery.
With this configuration, the DC power generated by the
photovoltaic power generating device is charged to the
battery throughout the absence period. However, if the
absence period is the long period, the power loss is
increased due to the discharge of the battery. In this case,
the DC power generated by the photovoltaic power generating
device is reversely supplied and sold to other consumers,
whereby the generated power can be effectively used in case
of the long-term absence.
The absence detecting unit may estimate an end time of
the absence period and make determination whether the
absence period is a short period shorter than a first
predetermined time period, a first long period equal to or
longer than the first predetermined time period but shorter
than a second predetermined time period, or a second long
period longer than the second predetermined time period, and
the air conditioning controller may be adapted to
continuously operate the ventilating device throughout the
absence period if the absence period is the short period, to

start an operation of the ventilating device a specified
time earlier than the end time of the absence period if the
absence period is the first long period or the second long
period, and control the reverse power flow control unit to
reversely supply the electric power generated by the
photovoltaic power generating device to the commercial power
supply system instead of supplying the electric power to the
battery if the absence period is the second long period.
With this configuration, it is possible to more
carefully perform the reverse power flow control and the
control of the ventilating device throughout the absence
period.
As stated above, the present invention is capable of
providing a comfortable indoor space to a home-coming family
member while using natural energy to seek energy saving.
Brief Description of the Drawings
The objects and features of the present invention will
become apparent from the following description of
embodiments, given in conjunction with the accompanying
drawings, in which:
Fig. 1 shows the configuration of an air-conditioning
control system in accordance with first and second
embodiments.
Fig. 2 shows the configuration of an air-conditioning

control system in accordance with a third embodiment.
Fig. 3 shows the configuration of an air-conditioning
control system in accordance with a fourth embodiment.
Detailed Description of the Embodiments
Embodiments of the present invention will now be
described in detail with reference to the accompanying
drawings which forms a part of the subject specification.
Identical or similar components throughout the drawings will
be designated by like reference symbols and will not be
described repeatedly.
(First Embodiment)
Fig. 1 shows the configuration of an air-conditioning
control system for houses in accordance with the present
embodiment. The air-conditioning control system includes an
air conditioning controller 1 for performing an air
conditioning control within a home; an air conditioning
device 2 having an air conditioner and designed to cool or
heat the home; a ventilating device 3 for performing
ventilation between the home and the outside; a human sensor
4 for detecting a human existing within the home; a setting
unit 5 operated by a family member; a temperature sensor 6
for measuring a temperature within the home; a photovoltaic
power generating device 7 for generating an electric power
with sunlight; a battery 8 for storing the electric power

generated by the photovoltaic power generating device 7 and
supplying the electric power to the air conditioning device
2 and the ventilating device 3; and a heat accumulator 9 for
accumulating heat using the electric power generated by the
photovoltaic power, generating device 7.
The air conditioning controller 1 includes an absence
detecting unit la serving as an absence detecting unit for
detecting the absence of a human within the home, the human
sensor 4 and the setting unit 5 being connected to the
absence detecting unit la; a control pattern determining
unit lb for determining operation control patterns of the
air conditioning device 2 and the ventilating device 3, the
temperature sensor 6 being connected to the control pattern
determining unit lb; and a control signal transmitting unit
lc for transmitting control signals to the air conditioning
device 2 and the ventilating device 3 pursuant to the
control patterns. determined by the control pattern
determining unit lb.
Description will now be made on the cooling operation
in summer by way of example.
First, if a human exists within the home, the human
sensor 4 transmits a human sensing signal to the air
conditioning controller 1. In response to the human sensing
signal, the absence detecting unit la of the air
conditioning controller 1 determines that a human exists
within the home and outputs an existence signal to the

control pattern determining unit lb. Responsive to the
existence signal, the control pattern determining unit lb
determines, e.g., a control pattern in which the air
conditioning device 2 is operated, if necessary, in
combination with the ventilating device 3. Upon receiving
the control pattern, the control signal transmitting unit lc
transmits control signals corresponding to the control
pattern to the ventilating device 3 and the air conditioning
device 2, thereby controlling the startup operations of the
ventilating device 3 and the air conditioning device 2. In
this manner, the air conditioning controller 1 performs an
air conditioning control to cool the home.
In the air conditioning control, the measured
temperature of the temperature sensor 6 is feedback
controlled to become equal to a target temperature (26°C in
the present embodiment) set by a user through the use of the
setting unit 5.
Next, if a human goes out and does not exist within
the home, the human sensing signal outputted by the human
sensor 4 is cut off. The absence detecting unit la of the
air conditioning controller 1 determines that a human does
not exist within the home and outputs an absence signal to
the control pattern determining unit lb. Responsive to the
absence signal, the control pattern determining unit lb
determines, e.g., a control pattern in which the air
conditioning device 2 is stopped throughout an absence

period and the ventilating device 3 is operated to ventilate
the home during at least a part of the absence period. Upon
receiving the control pattern, the control signal
transmitting unit lc transmits control signals corresponding
to the control pattern to the ventilating device 3 and the
air conditioning device 2, thereby controlling the startup
operations of the ventilating device 3 and the air
conditioning device 2. In this manner, the air conditioning
controller 1 performs an air conditioning control.
In this air conditioning control, the ventilating
device 3 performs"ventilation throughout the absence period
by which the indoor air heated to a high temperature within
the closed home is exchanged with the outdoor air having a
temperature lower than that of the indoor air. Thus, the
thermal environment is controlled in such a way as to reduce
the indoor temperature. The power consumption of the
ventilating device 3 is lower than the power consumption of
the air conditioning device 2 that performs cooling. As
compared with a case where the air conditioning device 2 is
operated throughout the absence period, it is therefore
possible to save energy.
Next, when a family member who went out comes back
home, the human sensor 4 transmits a human sensing signal to
the air conditioning controller 1. In response to the human
sensing signal, the air conditioning controller 1 performs
again an air conditioning control to cool the home using the

air conditioning device 2, if necessary, in combination with
the ventilating device 3. In this manner, throughout the
absence period, the thermal environment within the home is
controlled in such a way as to make the home comfortable
(e.g., to reduce the indoor temperature in summer) using the
outdoor air as natural energy. Thus, with a reduced power
consumption, the air conditioning device 2 restarted by a
home-coming family member can perform a cooling operation to
make the indoor temperature equal to a target temperature.
In the present embodiment, as described above, it is
possible to provide a comfortable indoor space to a home-
coming family member by using the outdoor air as natural
energy to seek energy saving.
In addition to the afore-mentioned detection method in
which the absence of a human within the home is detected
pursuant to the human sensing signal from the human sensor 4,
it may be possible to use a detection method in which the
setting unit 5 is operated by a family member to set one of
the existence and the absence and, then, the absence of a
human within the home is detected pursuant to the setting in
the setting unit 5.
(Second Embodiment)
Just like the first embodiment, the air-conditioning
control system of the present embodiment is shown in Fig. 1.
The same components as those of the first embodiment will be
designated by like reference symbols and will not be

described.
In the air conditioning controller 1 of the present
embodiment, the absence detecting unit la serves not only as
an absence detecting unit but also as an absence period
determining unit for estimating the end time of the absence
period (i.e.,, the home-coming time) and then determining
whether the absence period is a long period equal to or
longer than a predetermined time period or a short period
shorter than the predetermined time period.
The process of estimating the home-coming time and the
process of determining the long period or the short period
are performed based on the settings inputted by a family
member through the setting unit 5 before the family member
leaves home. For example, the setting unit 5 includes a
unit for inputting the length of the absence period or the
expected home-coming time. The home-coming time is
estimated from the length of the absence period or the
expected home-coming time thus inputted. The absence period
equal to or longer than the predetermined time period is
determined as the long period. The absence period shorter
than the predetermined time period is determined as the
short period. The threshold used in determining whether the
absence period is the long period or the short period varies
depending on the air conditioning characteristics of a
building and the capacity of the ventilating device 3. As
an example, the threshold is set equal to about two hours.

Alternatively, the absence detecting unit la may store
a history of past absence periods. The absence detecting
unit la may estimate the length of the absence period based
on the absence occurring time and day in the absence period
history and may perform, pursuant to the length of the
absence period, the process of estimating the home-coming
time and the process of determining whether the absence
period is the long period or the short period.
The threshold, which is compared with the length of
the absence period to determine whether the absence period
is the long period or the short period, may vary with at
least one of the year, month, day and hour indicating the
seasons and the time zone at which the determination is made.
This makes it possible to set the threshold based on the
life pattern of family members which varies depending on the
seasons and the time zone.
Depending on whether the absence period is the long
period or the short period, the control pattern determining
unit lb changes the control pattern of the ventilating
device 3 throughout the absence period. In other words, the
air conditioning control throughout the absence period can
be adaptively performed depending on whether the absence
period is the long period or the short period.
If the absence period is the short period, the control
pattern determining unit lb performs, throughout the entire
absence period, the air conditioning control by which the

air conditioning device 2 is stopped and the ventilating
device 3 is operated to ventilate the home as in the first
embodiment.
If the absence period is the long period, the control
pattern determining unit lb stops the operations of the air
conditioning device 2 and the ventilating device 3 after
detecting the absence state. The air conditioning device 2
is kept stopped throughout the entire absence period.
However, the ventilating device 3 is controlled to start its
operation a specified time (e.g., two hours) earlier than
the home-coming time of a family member. In other words, if
the absence period is the long period, the ventilating
device 3 is not operated throughout the entire absence
period but is operated for a minimum period immediately
before a family member comes back home. This makes it
possible to prevent unnecessary power consumption throughout
the absence period and to effectively perform the control of
the thermal environment within the home using the
ventilating device 3.
(Third Embodiment)
In the air-conditioning control system of the present
embodiment, the control relying on the electric power
generated by the photovoltaic power generating device 7 is
added to the thermal environment control of the second
embodiment. The same components as those of the second
embodiment will be designated by like reference symbols and

will not be described.
Referring to Fig. 2, the air conditioning controller 1
of the present embodiment includes a power measuring unit 1d
for measuring the electric power generated by the
photovoltaic power generating device 7. The value of the
generated power measured by the power measuring unit 1d is
outputted to the control pattern determining unit lb. As in
the second embodiment, the control pattern determining unit
lb changes the control pattern of the ventilating device 3
throughout the absence period, depending on whether the
absence period is the long period or the short period.
If the absence period is the short period, the control
pattern determining unit lb performs, throughout the entire
absence period, the air conditioning control by which the
air conditioning device 2 is stopped and the ventilating
device 3 is operated to ventilate the home.
If the absence period is the short period, the control
pattern determining unit lb controls the operations of the
air conditioning device 2 and the ventilating device 3
depending on the value of the generated power measured by
the generated power measuring unit 1d, for example.
Specifically, if the value of the generated power is smaller
than a predetermined value, the control pattern determining
unit lb stops the air conditioning device 2 and the
ventilating device 3. If the value of the generated power
becomes equal to or greater than the predetermined value,

the control pattern determining unit lb operates the air
conditioning device 2 and the ventilating device 3.
In an alternative example, the surplus power of the
photovoltaic power generating device 7 is measured. If the
generated power has no surplus, the control pattern
determining unit lb stops the air conditioning device 2 and
the ventilating device 3. If the generated power is surplus,
the control pattern determining unit lb operates the air
conditioning device 2 and the ventilating device 3 through
the effective use of the surplus power and controls the
thermal environment within the home beforehand in such a way
as to make the home comfortable.
The surplus power of the photovoltaic power generating
device 7 referred to herein means the electric power
excluding the power charged to the battery 8, the power
supplied to the heat accumulator 9 and the power used in
operating the home appliances. The power measuring unit 1d
can measure not only the value of the generated power but
also the power charged to the battery 8, the power supplied
to the heat accumulator 9 and the power used in operating
the home appliances. Accordingly, it is possible to
calculate the surplus power.
Regardless of the magnitude of the generated power of
the photovoltaic power generating device 7, the operation of
the ventilating device 3 is started a specified time (e.g.,
two hours) earlie-r than the home-coming time of a family

member. Regardless of existence of the surplus power, the
thermal environment within the home is controlled by the
ventilating device 3 in such a way as to make the home
comfortable immediately before the home-coming of a family
member. If the generated power of the photovoltaic power
generating device 7 is surplus immediately before the home-
coming of a family member, the air conditioning device 2 is
also operated in combination with the ventilating device 3.
Accordingly, in the event that the air conditioning
device 2 and the ventilating device 3 were operated by the
surplus power throughout the absence period, it is possible
to more effectively operate the ventilating device 3
immediately before the home-coming of a family member.
Moreover, immediately before the home-coming of a family
member, the air conditioning device 2 can be operated
through the effective use of the surplus power so as to
effectively improve the thermal environment.
(Fourth Embodiment)
In the air-conditioning control system of the present
embodiment, the reverse power flow control of the
photovoltaic power generating device 7 is added to the
thermal environment control of the second embodiment. The
same components as those of the second embodiment will be
designated by like reference symbols and will not be
described.
In the present embodiment, as shown in Fig. 3, the

air-conditioning control system includes a power conditioner
10 for converting the DC power generated by the photovoltaic
power generating device 7 to an AC power. The air-
conditioning control system has a function (a reverse power
flow unit) of causing the generated power to reversely flow
toward a commercial power supply system. The air
conditioning controller 1 includes a reverse power flow
control unit 1e for controlling the reverse power flow
operation of the power conditioner 10.
Depending on the length of the absence period, the
absence detecting unit la assorts the absence period into
three patterns, e.g., a short period corresponding to the
absence period of less than one hour, a first long period
corresponding to the absence period of not less than one
hour but less than two days, and a second long period
corresponding to the absence period of not less than two
days. The thresholds (i.e., one hour and two days), which
are compared with the length of the absence period to assort
the three patterns, may vary with at least one of the year,
month, day and hour indicating the seasons and the time zone
at which the determination is made. The control pattern
determining unit lb changes the control pattern of the
ventilating device 3 throughout the absence period,
depending on whether the absence period is the short period,
the first long period or the second long period.
If the absence period is the short period, the control

pattern determining unit lb performs, throughout the entire
absence period, the air conditioning control by which the
air conditioning device 2 is stopped and the ventilating
device 3 is operated to ventilate the home.
If the absence period is the first long period or the
second long period, the control pattern determining unit lb
stops the operations of the air conditioning device 2 and
the ventilating device 3 after detecting the absence state.
The air conditioning device 2 is kept stopped throughout the
entire absence period. However, the ventilating device 3 is
controlled to start its operation a specified time earlier
than the home-coming time of a family member.
If the absence period is the second long period, the
reverse power flow control unit 1e operates the power
conditioner 10 to reversely supply the DC power generated by
the photovoltaic power generating device 7 to the commercial
power supply system instead of the battery 8 and the heat
accumulator 9. In other words, the DC power generated by
the photovoltaic power generating device 7 is charged to the
battery 8 and thermally accumulated in the heat accumulator
9 throughout the absence period. However, if the absence
period is the second long period, i.e., the longest period,
the power loss is increased due to the discharge of the
battery 8 or the heat dissipation of the heat accumulator 9.
In this case, the DC power generated by the photovoltaic
power generating device 7 is reversely supplied and sold to

other customers, whereby the generated power can be
effectively used during the long-term absence.
In the first through fourth embodiments, a summer
cooling operation has been taken as an example to describe
the configuration of providing a comfortable indoor space to
a home-coming family member while using the outdoor air as
natural energy to seek energy saving. In a winter heating
operation, it is equally possible to obtain the same effect
by using the outdoor air having a temperature higher than
the indoor temperature.
An outdoor temperature measuring unit may be provided
to measure the outdoor temperature. The ventilating device
3 may be operated if a human does not exist within the home
and the indoor temperature measured a specified time earlier
than the expected home-coming time is higher than or lower
than the manually-set target temperature and the outdoor
temperature. The ventilating device 3 may not be operated
in other cases. This is to keep the ventilating device 3
stopped when the indoor temperature is lower than the
outdoor temperature in summer or when the indoor temperature
is higher than the outdoor temperature in winter. It may
also be possible to stop the ventilating device 3 when the
indoor temperature reaches a target temperature.
In the embodiments described above, the ventilating
device 3 is a ventilating fan. The ventilating device 3 may
include other devices capable of introducing the outdoor air

into the home, e.g., an electric window.
In the embodiments described above, the air-
conditioning control system is installed in a house by way
of example. However, the air-conditioning control system
may be installed in any place where the indoor space and the
outdoor space are divided, e.g., in a residential complex,
an apartment, an office, a shopping arcade and a factory.
While the invention has been shown and described with
respect to the embodiments, it will be understood by those
skilled in the art that various changes and modifications
may be made without departing from the scope of the
invention as defined in the following claims.

We claim:
1. An air-conditioning control system, comprising:
a ventilating device for performing ventilation
between an indoor space and an outdoor space;
an absence detecting unit for detecting absence of a
human within the indoor space; and
an air conditioning controller adapted to operate,
when the absence of the human is detected by the absence
detecting unit, the ventilating device during at least a
part of an absence period to control a thermal environment
within the indoor space.
8. The system of claim 1, further comprising:
an air conditioning device for cooling or heating the
indoor space,
wherein the air conditioning controller is adapted to
operate, when the- absence of the human is detected by the
absence detecting unit, operate the ventilating device
during at least a part of the absence period such that, when
operating the air conditioning device next time, the thermal
environment within the indoor space is controlled in such a
way as to reduce a power consumption of the air conditioning
device.
3. The system of claim 2, wherein the absence detecting

unit is adapted to, when the absence of the human is
detected by the absence detecting unit, make determination
whether the absence period is a long period equal to or
longer than a predetermined time period or a short period
shorter than the predetermined time period, and the air
conditioning controller is adapted to control the
ventilating device in different control patterns depending
on whether the absence period is the long period or the
short period.
4. The system of claim 3, wherein the absence detecting
unit determines whether the absence period is the long
period or the short period by comparing the length of the
absence period with a threshold, and the threshold is varied
with at least one of year, month, day and hour at which the
determination is made.
5. The system of claim 3 or 4, wherein the absence
detecting unit determines whether the absence period is the
long period or the short period by estimating an end time of
the absence period, and the air conditioning controller is
adapted to continuously operate the ventilating device
throughout the absence period if the absence period is the
short period, and start an operation of the ventilating
device a specified time earlier than the end time of the
absence period if the absence period is the long period.

6. The system of claim 5, further comprising:
a photovoltaic power generating device for generating
electric power by using sunlight to supply the electric
power to the air conditioning device and the ventilating
device,
wherein the air conditioning controller is adapted to
operate the air conditioning device and the ventilating
device throughout the absence period if the absence period
is the long period and the electric power generated by the
photovoltaic power generating device is equal to or greater
than a predetermined value, and operate the ventilating
device a specified time earlier than the end time of the
absence period regardless of the magnitude of the electric
power generated by the photovoltaic power generating device.
7. The system of claim 3 or 4, further comprising:
a photovoltaic power generating device for generating
electric power by using sunlight to supply the electric
power to the air conditioning device and the ventilating
device;
a battery for storing the electric power generated by
the photovoltaic power generating device and supplying the
electric power to the air conditioning device and the
ventilating device; and
a reverse power flow control unit for reversely

supplying the electric power generated by the photovoltaic
power generating device to a commercial power supply system,
wherein the air conditioning controller is adapted to
control, if the absence period is the long period, the
reverse power flow control unit to reversely supply the
electric power generated by the photovoltaic power
generating device to the commercial power supply system
instead of supplying the electric power to the battery.
8. The system of claim 7, wherein the absence detecting
unit estimates an end time of the absence period and
makes determination whether the absence period is a
short period shorter than a first predetermined time
period, a first long period equal to or longer than
the first predetermined time period but shorter than
a second predetermined time period, or a second long
period longer than the second predetermined time
period, and
wherein the air conditioning controller is adapted to
continuously operate the ventilating device throughout the
absence period if the absence period is the short period,
start an operation of the ventilating device a specified
time earlier than the end time of the absence period if the
absence period is the first long period or the second long
period, and control the reverse power flow control unit to
reversely supply the electric power generated by the
photovoltaic power generating device to the commercial power
supply system instead of supplying the electric power to the
battery if the absence period is the second long period.

ABSTRACT
In an air-conditioning control system, a ventilating
device performs ventilation between an indoor space and an
outdoor space, and an absence detecting unit for detecting
absence of a human within the indoor space. An air
conditioning controller adapted to operated, when the
absence of the human is detected by the absence detecting
unit, the ventilating device during at least a part of an
absence period to control a thermal environment within the
indoor space.