H.B.Gunay et al.Building and Environment 70(2013)31-47 37 Instead of time-lapse photography.sensors (e.g.contact and setpoint indoor illuminance is reached;or ventilation systems that proximity sensors in windows or roller blinds)have also been provide fresh air for a set number of occupants and for a set occu- employed to acquire window opening behavior at a finer resolution pancy schedule.These set values are static assumptions published in (i.e.one to fifteen measurements per minute).For example,Yun various comfort standards [13.14.94]to address the conservative and Steemers (41]investigated the window opening behavior using design needs;however they neglect individual variations amongst the sensors in a naturally ventilated office building in parallel with occupants'preferences,behaviors,and habits.In fact,in many cases a questionnaire survey to confirm the occupancy and to estimate findings of the research on occupant control of blinds and lighting the ASHRAE [14]predicted mean vote (PMV)during a cooling [57,65 do not match with the design practices to automate the season.Use of sensors is less prone to human error and more blinds and lighting [20.64.68,90].For example,to avoid occupant efficient in data acquisition and post-processing [24].Also,longer complaints due to glare,blinds automation systems typically use studies can be performed with this technique such as Haldi and conservative setpoint values less than 2 klux [20].However,it was Robinson [39].who used a data record for six years for a naturally reported that occupants rarely close their blinds at workplane illu- ventilated office building.However,the size of sample group in minances less than 2 klux [57.651.This conservativeness,to avoid these studies was usually smaller than 50 [28,39,41,46,50.57,65.86] occupant complaints due to glare,resulted in occupant overrides to which was notably less than the large-scale surveys carried out on preserve their view and connection to the outside.This suggests that up to 1200 windows[85]using the time-lapse photography tech- occupants'preferences can be wildly different and questions the nique [32,36,38,51,53,55,82].In some of these studies [32.50]. existence of a standard indoor climate which can make every occu- hand-held sensors,instead of permanent sensors,were used in pant happy.This is also implicitly acknowledged in the current parallel with questionnaires and visual investigations.This ASHRAE comfort standard 14.As reported in Olesen and Brager approach gives immeasurable insights(e.g.rattling blinds)24]into 95].ASHRAE [14]defines conditions acceptable to a majority of a a smaller scale research group for a shorter and an irregular dura- group of occupants,whereby the majority is defined as 80%Instead tion and may become useful if coupled with other techniques such of trying to sustain a standard indoor environment,controllers in the as time-lapse photography. building automation systems can be used to run a self-adaptive al- gorithm to learn occupants'customized indoor climate preferences 2.1.8.Automated/manual controls from their behaviors.Guillemin96 showed that occupant overrides To reduce occupants'energy impact,building systems with can be reduced from 25%to 5%of the automated control actions by which occupants widely interact to adapt their indoor environments training a self-adaptive occupant-learning algorithm in the individ- (e.g.windows,window shading devices,lights,thermostats)have ual controller level. been automated in many applications.However,evidence from these applications suggest that occupants frequently override these 2.1.9.Reversal of an adaptive behavior automation systems indicating their dissatisfaction;and these It is known that occupants adapt their environment to preserve frequent overrides deemed many automation applications poorly their comfort.However the reversal of the same adaptive behaviors functioning.For example,Reinhart and Voss [57]reported that in are not fully understood [56.Only a small group of the reviewed 1263 out of 1432 attempts(88%)to close the blinds automatically. studies reported that the reversal of adaptive occupant behaviors, the control algorithm was overridden by the occupants.Reinhart such as closing a window.opening a shade,or switching-off the explained this as "You'd have a prized window seat,then Zoop!The lights,take place after the source of discomfort dissipates [97.This shades go down.There was a realization that occupants don't accept arises because the incentives of an adaptive behavior are different that".In line with this.Leaman and Bordass (87]stated that auto- than the incentives to reverse it,as shown in Fig.3.For example mation systems that exclude occupants from the control-loop(e.g. occupants open a window to improve the IAQ and thermal comfort closing blinds before glare conditions exist for occupants)can but acoustic discomfort (e.g.noise)or thermal discomfort motivate infuriate occupants.Other studies [37,88-90]confirmed these ob- them to close it.Similarly,occupants lower a window shading de- servations;many of such cases with automated blind and lighting vice to satisfy their visual and thermal comfort and privacy,but the controls were deactivated due to complaints or needed to be preference to get more daylight and to have better view to the improved/customized to meet individual preferences with a post- outside motivates them to raise it.This effect is expected to be even occupancy commissioning process.Even more surprisingly,Carter. more significant if electrical and mechanical systems provide et al.[91]reported that manually controllable lighting fixtures alternative means for comfort.Therefore,it is expected that the which do not even meet the lighting standards were perceived more predictive models for adaptive behaviors and their reversals are satisfactory than the daylight linked automated lighting controls. different.For example,Reinhart and Voss [57]reported that blinds Two different explanations have been suggested in the literature were manually closed at external facade illuminance of 50 klux and to explain occupants'discontent with the automation applications: opened at 25 klux.On the other extreme,it was observed that some (1)Desire for ability to control:Leaman and Bordass92]showed that occupants did not raise their blinds for multiple months once they there is a strong relationship between occupants'perception of were closed [54,551.Similarly,it was observed that occupants do control over their environment and productivity.In fact,a common not notice,or perhaps simply ignore,the availability of daylight and industry practice was reported as placing dummy (ie.placebo) failed to switch-off their lights at the indoor daylight level that is controllers (e.g.thermostats)so that occupants overestimate their equivalent to the artificial lighting [57.Sutter et al.[50]confirmed control on their offices,i.e.illusion of control [931.Galasiu and Veitch these observations that occupants raise their blinds at illuminance 26]interpreted this as the occupants'preference to have the capa- levels lower than at which they are lowered and defined this as a bility to choose their environment rather than being obligated to "hysteresis phenomenon".This concept was later adopted by others accept the environment chosen for them.(2)Desire for a customized [10,39,42,46,65.These studies observed the window,window indoor climate:Controllers in building automation systems are shading,or light switch actions,not as mere adjustments.They decision-makers such that they train logics to control a device.For rather classified these adjustments as opening/closing,lowering/ example,if the temperature is above the setpoint,the controller tells raising,and switching on/off.Therefore,observations that involve the air-conditioner to turn-on.Similar setpoint-based deterministic adaptive occupant behaviors should be distinguished as actions to building automation strategies are commonplace in practice.For mitigate discomfort and as the reversal of these actions after the example,automated blinds that close or lights that turn on,when the source of discomfort fades.Instead of time-lapse photography, sensors (e.g. contact and proximity sensors in windows or roller blinds) have also been employed to acquire window opening behavior at a finer resolution (i.e. one to fifteen measurements per minute). For example, Yun and Steemers [41] investigated the window opening behavior using the sensors in a naturally ventilated office building in parallel with a questionnaire survey to confirm the occupancy and to estimate the ASHRAE [14] predicted mean vote (PMV) during a cooling season. Use of sensors is less prone to human error and more efficient in data acquisition and post-processing [24]. Also, longer studies can be performed with this technique such as Haldi and Robinson [39], who used a data record for six years for a naturally ventilated office building. However, the size of sample group in these studies was usually smaller than 50 [28,39,41,46,50,57,65,86], which was notably less than the large-scale surveys carried out on up to 1200 windows [85] using the time-lapse photography tech￾nique [32,36,38,51,53,55,82]. In some of these studies [32,50], hand-held sensors, instead of permanent sensors, were used in parallel with questionnaires and visual investigations. This approach gives immeasurable insights (e.g. rattling blinds) [24] into a smaller scale research group for a shorter and an irregular dura￾tion and may become useful if coupled with other techniques such as time-lapse photography. 2.1.8. Automated/manual controls To reduce occupants’ energy impact, building systems with which occupants widely interact to adapt their indoor environments (e.g. windows, window shading devices, lights, thermostats) have been automated in many applications. However, evidence from these applications suggest that occupants frequently override these automation systems indicating their dissatisfaction; and these frequent overrides deemed many automation applications poorly functioning. For example, Reinhart and Voss [57] reported that in 1263 out of 1432 attempts (88%) to close the blinds automatically, the control algorithm was overridden by the occupants. Reinhart explained this as “You’d have a prized window seat, then Zoop! The shades go down. There was a realization that occupants don’t accept that”. In line with this, Leaman and Bordass [87] stated that auto￾mation systems that exclude occupants from the control-loop (e.g. closing blinds before glare conditions exist for occupants) can infuriate occupants. Other studies [37,88e90] confirmed these ob￾servations; many of such cases with automated blind and lighting controls were deactivated due to complaints or needed to be improved/customized to meet individual preferences with a post￾occupancy commissioning process. Even more surprisingly, Carter, et al. [91] reported that manually controllable lighting fixtures which do not even meet the lighting standards were perceived more satisfactory than the daylight linked automated lighting controls. Two different explanations have been suggested in the literature to explain occupants’ discontent with the automation applications: (1) Desire for ability to control: Leaman and Bordass [92] showed that there is a strong relationship between occupants’ perception of control over their environment and productivity. In fact, a common industry practice was reported as placing dummy (i.e. placebo) controllers (e.g. thermostats) so that occupants overestimate their control on their offices, i.e. illusion of control [93]. Galasiu and Veitch [26] interpreted this as the occupants’ preference to have the capa￾bility to choose their environment rather than being obligated to accept the environment chosen for them. (2) Desire for a customized indoor climate: Controllers in building automation systems are decision-makers such that they train logics to control a device. For example, if the temperature is above the setpoint, the controller tells the air-conditioner to turn-on. Similar setpoint-based deterministic building automation strategies are commonplace in practice. For example, automated blinds that close or lights that turn on, when the setpoint indoor illuminance is reached; or ventilation systems that provide fresh air for a set number of occupants and for a set occu￾pancy schedule. These set values are static assumptions published in various comfort standards [13,14,94] to address the conservative design needs; however they neglect individual variations amongst occupants’ preferences, behaviors, and habits. In fact, in many cases findings of the research on occupant control of blinds and lighting [57,65] do not match with the design practices to automate the blinds and lighting [20,64,68,90]. For example, to avoid occupant complaints due to glare, blinds automation systems typically use conservative setpoint values less than 2 klux [20]. However, it was reported that occupants rarely close their blinds at workplane illu￾minances less than 2 klux [57,65]. This conservativeness, to avoid occupant complaints due to glare, resulted in occupant overrides to preserve their view and connection to the outside. This suggests that occupants’ preferences can be wildly different and questions the existence of a standard indoor climate which can make every occu￾pant happy. This is also implicitly acknowledged in the current ASHRAE comfort standard [14]. As reported in Olesen and Brager [95], ASHRAE [14] defines conditions acceptable to a majority of a group of occupants, whereby the majority is defined as 80%. Instead of trying to sustain a standard indoor environment, controllers in the building automation systems can be used to run a self-adaptive al￾gorithm to learn occupants’ customized indoor climate preferences from their behaviors. Guillemin [96] showed that occupant overrides can be reduced from 25% to 5% of the automated control actions by training a self-adaptive occupant-learning algorithm in the individ￾ual controller level. 2.1.9. Reversal of an adaptive behavior It is known that occupants adapt their environment to preserve their comfort. However the reversal of the same adaptive behaviors are not fully understood [56]. Only a small group of the reviewed studies reported that the reversal of adaptive occupant behaviors, such as closing a window, opening a shade, or switching-off the lights, take place after the source of discomfort dissipates [97]. This arises because the incentives of an adaptive behavior are different than the incentives to reverse it, as shown in Fig. 3. For example, occupants open a window to improve the IAQ and thermal comfort, but acoustic discomfort (e.g. noise) or thermal discomfort motivate them to close it. Similarly, occupants lower a window shading de￾vice to satisfy their visual and thermal comfort and privacy, but the preference to get more daylight and to have better view to the outside motivates them to raise it. This effect is expected to be even more significant if electrical and mechanical systems provide alternative means for comfort. Therefore, it is expected that the predictive models for adaptive behaviors and their reversals are different. For example, Reinhart and Voss [57] reported that blinds were manually closed at external facade illuminance of 50 klux and opened at 25 klux. On the other extreme, it was observed that some occupants did not raise their blinds for multiple months once they were closed [54,55]. Similarly, it was observed that occupants do not notice, or perhaps simply ignore, the availability of daylight and failed to switch-off their lights at the indoor daylight level that is equivalent to the artificial lighting [57]. Sutter et al. [50] confirmed these observations that occupants raise their blinds at illuminance levels lower than at which they are lowered and defined this as a “hysteresis phenomenon”. This concept was later adopted by others [10,39,42,46,65]. These studies observed the window, window shading, or light switch actions, not as mere adjustments. They rather classified these adjustments as opening/closing, lowering/ raising, and switching on/off. Therefore, observations that involve adaptive occupant behaviors should be distinguished as actions to mitigate discomfort and as the reversal of these actions after the source of discomfort fades. H.B. Gunay et al. / Building and Environment 70 (2013) 31e47 37