The effects of a novel personal comfort system on thermal comfort, physiology and perceived indoor environmental quality, and its health implications ‐ Stimulating human thermoregulation without compromising thermal comfort

Abstract The classical textbook interpretation of thermal comfort is that it occurs when the thermoregulatory effort is minimized. However, stimulating human thermoregulatory systems may benefit health and increase body thermal resilience. To address this gap, we tested a novel personal comfort system (PCS) that targets only the extremities and the head, leaving the rest of the body exposed to a moderately drifting temperature (17–25°C). A randomized, cross‐over study was conducted under controlled laboratory conditions, mimicking an office setting. Eighteen participants completed two scenarios, one with a PCS and another one without a PCS in 17–25°C ambient conditions. The results indicate that the PCS improved thermal comfort in 17–23°C and retained active thermoregulatory control. The torso skin temperature, underarm‐finger temperature gradients, energy expenditure, substrate oxidations and physical activity were not affected by the PCS in most cases. Only slight changes in cardiovascular responses were observed between the two scenarios. Moreover, the PCS boosted pleasure and arousal. At 25°C, the PCS did not improve thermal comfort, but significantly improved air quality perceptions and mitigated eye strain. These findings suggest that human physiological thermoregulation can be stimulated without compromising thermal comfort by using a PCS that only targets the extremities in cold conditions.

when body temperatures are kept within a small range to minimize the thermoregulatory effort of the body. [4][5][6] Hence, in the past decades the paradigm has developed that indoor temperatures in air-conditioned buildings should be maintained within a stringent temperature range with limited permissible daily and seasonal variations. This paradigm is mainly caused by strict interpretations of the Predicted Mean Vote (PMV) model in the ASHRAE standards 3 and ISO standards, 7 which are based on the work of Fanger. 8 Indoor climate conditioning is associated with 20% of the global energy consumption. 9,10 Driven by sustainability challenges and climate change, it is worthwhile to start rethinking the current paradigm of strict indoor climate control. In this context, a highly relevant question is whether such a narrow indoor temperature range is beneficial for human health or not. Previous studies 11,12 show that several metabolic diseases may be related to permanently residing in constant thermal neutral conditions. Furthermore, literature suggests a causal link between people mostly residing in the thermoneutral zone (TNZ) and the increased prevalence of obesity. 13,14 The TNZ is defined as the range of ambient temperatures without regulatory changes in metabolic heat production or evaporative heat loss. 15 Kingma et al. 16 suggest that the thermal comfort zone in a uniform and stable condition is a subset of the TNZ. Therefore, the prevalent stable indoor climate design may keep people in the TNZ minimizing energy metabolism, which may, in combination with other lifestyle factors, tip down the energy balance to the 'gaining weight' side. 17,18 Variations outside the TNZ can increase the metabolism and reverse the 'tipping'. 19 Moreover, regularly exercising thermoregulation in mild cold/heat can benefit body glucose metabolism (increase insulin sensitivity) 20,21 and reduce the risks of cardiovascular diseases. 22, 23 Van Marken Lichtenbelt et al. 19 document the details of those health implications in their review paper.
Another concern of the current paradigm of stable indoor climate design is possible decreased body thermal resilience, that is, our ability to cope with (extreme) non-neutral conditions. The current indoor temperature design minimizes the thermoregulatory effort, which means less or no "stimulation" to the thermoregulation system, jeopardizing our thermal resilience. Thermal resilience is even more of interest in the context of global warming with increased likelihood of more extreme weather events. 24,25 Hence, another argument to rethink the current paradigm is that regularly stimulating thermoregulation in mild cold/heat increases thermal resilience, 26 mitigating physiological stress in extreme conditions.
The adaptive thermal comfort model by de Dear et al. 27 may have the potential to bridge health and thermal comfort as it allows for much more temperature variation, both diurnal and seasonal.
Based on field study data in naturally ventilated buildings, the adaptive thermal comfort model established a linear relationship between a comfortable temperature range and running mean outdoor temperature of the past few days. 27 The adaptive thermal comfort model proposes a combination of three underlying mechanisms: (i) behavioral adaptation such as clothing adjustments, (ii) physiological adaptation and (iii) psychological adaptation. 28 However, behavioral adaptation may substantially reduce thermal stress to the extent where thermoregulatory efforts are limited, and therefore physiological adaption may not occur.
Personal comfort systems (PCSs) in combination with varied ambient thermal conditions, even beyond adaptive thermal comfort limits, have the potential to provide climatic conditions near occupants that are favorable for health while fulfilling the need of thermal comfort. A PCS directly targets human body segments, such as hands, feet and the torso, using person-controlled local heating/cooling. This close-to-body conditioning provides individual thermal comfort while relaxing ambient conditions to a range of 14°C-32°C, 29,30 and, hence, paves the way for substantial building energy savings. 29,30 More essentially, a PCS can precisely eliminate the local thermal discomfort of targeted body segments while the thermal stimulus to other untargeted body segments may remain, which may activate body thermoregulation and benefit health as outlined above. However, most of the studies only address the effect of PCSs on thermal comfort and energy savings (see recent reviews by Zhang et.al. 29 and by Veselý et.al. 30 ) and the majority employs torso heating/cooling or conditioning of large body areas. [31][32][33] Thereby, the thermal stimulus to the body may be reduced substantially. This study focuses on a novel PCS concept that targets only the extremities and the head to maintain the thermal stimulus to elicit the above-mentioned health benefits. Previous literature indicates that the hands and feet are the most uncomfortable body parts in mild cold and that the head is the most uncomfortable part in warm conditions. 34,35 Therefore, the novel PCS precisely targets local thermal discomfort of the extremities and the head, to improve overall thermal comfort while maintaining the thermal excitation to the torso in mild cold/warm conditions. This may provide a solution for the future to create a healthy, comfortable and energy-efficient environment.
This study hypothesizes that human thermoregulation can be stimulated in a moderately drifting thermal environment while providing comfort using a PCS design that targets only the extremities and the head. Therefore, this study investigates the effects of the de-

Practical Implications
The designed PCS achieved an 84% comfortable rate in a drifting temperature scenario over a wide range of ambient air temperatures (17-25°C), which potentiates significant energy savings. Moreover, a positive, healthy thermal stimulus to the body can be sustained. The designed PCS, therefore, implies a great potential for the future to create a healthy, comfortable and energy-efficient built environment.

| Participants
Eighteen healthy participants were recruited (Caucasian, nine males and nine females), 18-40 years old with a BMI of 18-27.5 kg/m 2 (Table 1). Female participants were taking contraception and the measurements were conducted after their menstrual cycle to minimize hormonal influences. Smokers, individuals with Raynaud's phenomenon, and people who are taking medication that will interfere with outcome parameters were excluded.

| Personal comfort system
The PCS was designed to warm up the extremities and cool down the head. It includes a heating desk, a heating mat on the floor and two fans for ventilation ( Figure 1). Each device has four settings: off, low, medium and high (for surface temperatures and air speed rates see Table 2). The participants were able to control the devices at their desires in the PCS scenario. The settings of the PCS were monitored and recorded. In addition, the airflow direction of the ventilation fans was adjusted before the experiment, to direct the air flow on the participant's head area. It remained in that direction during the experiment.

| Study design
This study has a cross-over, randomized design, consisting of two scenarios in drifting ambient temperature conditions ( Figure 2) on two separate days -with PCS (PCS scenario) and without PCS (NOPCS scenario). Participants started either with PCS scenario or NOPCS scenario based on a permuted blocked randomization procedure. To avoid possible short-term thermal acclimation induced by the experiment's exposure, 36 the two test days were at least one day apart. To minimize the influence of long-term seasonal thermal acclimatization, 37 the two test days were scheduled within 14 days.
Throughout the study, participants were not informed about the actual ambient temperature.
An office setting was emulated in the climate chambers of the Metabolic Research Unit of Maastricht University, where participants stayed for eight hours (from 9:00 h to 17:00 h) and performed typical office work (activity level ≈ 1.2 METs). In the chamber, participants wore standardized clothing, including underwear, a longsleeved shirt, sweatpants, socks and shoes and sat on an office chair (total of 0.80 clo). Whereas most of the PCS studies were conducted in static environments, this PCS was tested in a dynamic environment to provide new insights regarding PCS's performances in dynamic environments. Moreover, a dynamic environment may reduce building energy consumption. 38 Our research group has previously demonstrated that drifting temperatures (17-25°C) stimulate humans' thermoregulations 39 and will not lead to unacceptable conditions. 40 Therefore, a dynamic profile was applied to the climate chamber's indoor temperature starting at 17°C for 30 min, followed by a 1.5°C/h ramp for 320 min, and remaining stable at 25°C for 130 min (Figure 2). The designed minimum temperature of 17°C was intended to avoid shivering. 40 The maximum temperature of 25°C fits the thermal comfort zone (PMV is around 0.5) according to ASHRAE standard 3 and ISO standard 7 . The imposed ramp of 1.5°C/h is within the ISO 7730 comfort ramp limit. 7 According to earlier studies, 40,41 thermal sensation under the imposed slow ramp should not be affected by the previous thermal experience. An up ramp was chosen as it follows the rising trend of outdoor temperatures during office hours in winter (9:00-17:00), and, hence, is in line with the drifting temperature pattern that would occur in practice to improve energy efficiency in the office buildings. The first 30 min at 17°C intended to let participants habituate to the cold environment.
The maximum temperature of 25°C lasted for two hours to achieve a stable thermal state as in step-change transient temperatures the thermal sensation stabilizes after 30 min. 42

| Standardization before test days
The participants attended a standardization session one day before every test day to acquaint themselves with the climate chamber, the standardization procedure and the test procedure. To stabilize the participants' physiological state during the test day, the lifestyles were standardized 24 h before the test day. Participants were asked to consume the same amount and kind of food as much as possible in the two standardization sessions. They were also asked to refrain from taking food and drinks after 22:00 h with the exception of water, and to stick to normal bedtimes and sleep duration in the night before the test day. Furthermore, participants were instructed

N 18
Age ( Figure 2). Once the temperature reached 25℃, these measurements were performed every 65 min (t = 415 min and 480 min, Figure 2). Skin temperature, energy expenditure, physical activity and heart rate were continuously measured. Two times during the test day, participants performed a stepping exercise for 5 min to emulate normal office walking activity.
Participants rested twice in a supine position for 30 min to measure the resting metabolic rate (RMR, Figure 2). Breakfast and lunch were standardized and provided by the researchers on both test days.
Water was consumed at libitum.

| Indoor climate measurements
Air temperature was measured during the test days at 0.1 m, 0.6 m and 1.1 m from the ground near the participants using iButton dataloggers (DS1922L, Maxim Integrated, USA). Before the test days, mean radiant temperature, air speed and relative air humidity were also measured using an Almemo 2890-9 device (Ahlborn Mess, Germany). These measurements were done during the same temperature drifts as during the actual measurements with the volunteers. The results indicated that the mean radiant temperature of the test chamber closely followed the air temperature. The air speed was constantly close to 0.2 m/s, and relative humidity remained between 40% and 55% RH.

| Participants' characteristics
The body weight, height and body fat were measured in the morning under a fasted state. Participants' fat content was determined by an air displacement plethysmograph (Bodpod, Cosmed, Italy). The body surface area was calculated according to the Du Bois formula. 43

| Thermal perception
Based on the ISO standard 10551, 44 whole-body thermal sensation, thermal comfort and thermal preference were assessed by visual analogue scales ( Figure S1). In addition, thermal acceptance was F I G U R E 1 Designed personal comfort system including two ventilation fans (yellow ovals), a heating desk and a heating mat. Since the LDF measures the relative blood flow instead of an absolute blood flow, a normalized blood flow value was determined by dividing the measured value of blood flow during the day with the measured value of blood flow during the BMR measurement.

| Perceived air quality, affective states and eye-related symptoms
For the perceived air quality and air freshness, two continuous scales were used ( Figure S2A, B). Moreover, pleasure and arousal components of affect were assessed with the self-assessment manikin (SAM) scale 49 ( Figure S2C, D). An eye-related symptoms list was adopted from Viola et al. 50 using discrete scales ( Figure S2E).

| Statistical tests
A Mixed Linear Model (MLM) was employed to compare the differences between the PCS and NOPCS scenarios, treating the participants as a random factor. The scenario, measurement timepoints and their interaction were included as fixed factors. To account for the air temperature difference between the two scenarios, the difference between the temperature protocol and actual air temperature was added as well.
To improve the accuracy and increase the power of the MLM, relevant control variables and their interaction with measurement timepoints were considered as covariates: Body surface area to mass, fat-free mass to body surface ratio, gender and age. For the resting condition, fat and muscle mass play a major role in body insulation, where muscle mass can explain up to 90% of the insulation. 51 Thus, the mass to body surface area ratio represents the F I G U R E 2 Protocol of the experiment body insulation, whose reciprocal (body surface area to mass) indicates the heat transfer coefficient (heat loss ability). On the other hand, because the fat-free mass strongly relates to the body's heat production in resting condition, 52,53 fat-free mass to body surface ratio indicates the individual heat production ability. Moreover, the thermoregulation ability is also affected by gender and age. 54 For all continuously measured variables (heart rate, energy ex-

| Ambient air temperature
The air temperature profiles of both scenarios followed the protocol ( Figure S3). A small, but statistically significant difference was observed between the two scenarios: the air temperature was, on average, slightly higher in the PCS scenario. However, the average difference (0.15 ± 0.14°C) is regarded as acceptable.

| Thermal perception
Without a PCS, local thermal sensations, whole-body thermal sensation, thermal comfort and thermal preference were in line with the temperature profile ( Figure 3). There were clear individual differences in thermal perception. The standard deviation of thermal sensation was more than 0.5 unit on the 7-point thermal sensation scale ( Figure 3G). Moreover, the individual differences in thermal sensation were more pronounced near the neutral condition while in more extreme conditions, participants' votes were more consistent ( Figure 3G).
Local thermal sensation of the extremities was significantly warmer with the use of a PCS, particularly in the colder part of the temperature ramp (p < 0.05, Figure 3A). On the other hand, local thermal sensation of the head was significantly warmer at 23°C, but was significantly lower at the end of 25°C in PCS scenario (p < 0.05, Figure 3B). In addition, the thermal sensation of the torso (nontargeted body segment) was significantly warmer at 21°C and 23°C with a PCS (p < 0.05, Figure 3C), while at 17°C, 19°C and 25°C no significant differences were present between the two scenarios ( Figure 3C).

As compared to the NOPCS scenario, a PCS resulted in sig-
nificantly warmer whole-body sensations, improved whole-body thermal comfort and lowered heating preference under the cold to neutral environments (17-23°C, p < 0.05, Figure 3). In the PCS scenario, 98% of the total votes fell in "acceptable" while in the NOPCS scenario this was 91% of the votes (Table 3). Most importantly, by applying a PCS, the overall comfort rate (equal or higher than "just comfortable") increased from 71% to 84%, where the increases in the mild cold were most prominent (23% increase at 17°C and 33% increase at 19°C, Table 3). Although the thermal comfort rate was 56% at 17°C with the PCS, the thermal acceptability rate was 89%.
In addition, the variances of the thermal preferences in the PCS scenario were significantly lower than in NOPCS scenario at 21°C (p < 0.05, Table 3) and showed a trend toward significance at 23°C (p = 0.07, Table 3). No significant benefits of the PCS in thermal perception under a slightly warm environment was found, despite the convective head cooling functionality.

| Skin temperature
The mean skin temperature, distal skin temperature, head skin temperature, torso skin temperature and underarm-finger gradient generally followed the temperature profile in both scenarios (Figure 4). As compared to the NOPCS scenario, the mean skin temperature was significantly higher in the PCS scenario at 19, 21, 23°C and at the beginning of 25°C (p < 0.05, Figure 4A). On average, mean skin temperature increased 0.26 ± 0.5°C by using a PCS.
The distal skin temperature in the PCS scenario was significantly higher at 19, 21, 23 and the first 25°C-time point ( Figure 4B) while the head skin was significantly lower at all time points at 25°C ( Figure 4C). No significant differences in torso skin temperature and underarm-finger gradient between the two scenarios were found ( Figure 4D, E).

| Cardiovascular responses
Heart rate over time shows no clear relation with the temperature ramp ( Figure 5A). However, the hand skin blood flow increased with increasing ambient temperature ( Figure 5E). The PCS significantly increased the average heart rate by 2.2 bpm (p < 0.001, Figure 5B), decreased systolic blood pressure by 1.5 mmHg (p < 0.01, Figure 5C), and diastolic blood pressure by 0.9 mmHg (p = 0.052, Figure 5D). The hand skin blood flow was significantly higher at 23°C in the PCS scenario (p < 0.05, Figure 5E) while no significant differences were found at other temperatures ( Figure 5E) between the two scenarios. Moreover, the PCS significantly elevated the average hand skin blood flow by 8% (p < 0.05, Figure 5F).

| Energy expenditure, substrate oxidation and physical activity
The energy expenditure was significantly higher at 17°C in the PCS scenario than in the NOPCS scenario (p < 0.05, Figure 6A). The average difference was 0.32 kJ/min, which is equivalent to 6% of BMR. PAI tended to be larger in PCS scenario at 17°C (p = 0.055, Figure 6B). In line, physical activity measured by accelerometry was also found to be significantly higher at 17°C (p < 0.05, Figure 6E).

Carbohydrate and lipid oxidations were similar between the two
scenarios among all temperatures ( Figure 6C, D).

| Air perception
Overall, both perceived air quality and air freshness were negatively related to the air temperature (p < 0.05, Figure 7A, C). No difference was found between the two scenarios in cold and neutral environments (17-23°C, Figure 7A, C). Interestingly, the PCS significantly TA B L E 3 Paired comparisons between two scenarios   Figure 7B) and air freshness (7.6 ± 15.4 unite increase, p < 0.05, Figure 7D) at 25°C.

| Eye-related symptoms
Most votes of the eye discomfort, eye fatigue and eye strain symptoms were no more than "Slight" (Figure 8 and Figure S4). Eye discomfort and eye fatigue appeared to be unaffected by PCS throughout time ( Figure S4A, B). However, the PCS significantly reduced average eyestrain at 25°C (p < 0.05, Figure 8B), while at 17-23°C, no significant effect of the PCS on eye strain was found ( Figure 8A).

| Affective states
Pleasure and arousal levels remained relatively stable during the day ( Figure S5A, B). However, the average votes of all measurements in the PCS scenario generally indicated more pleasure, and more arousal than in the NOPCS scenario (p < 0.05, Figure 9A, B).

| Individual differences, thermal perception and control behavior
This study indicates that individual differences in thermal perceptions are prominent, also after controlling for BMI and age. The individual differences in thermal sensation were more prominent near thermal neutrality ( Figure 3G). This finding is consistent with Luo's study, 62 indicating that the participants' thermally perceptive responses are more diverse near the neutral condition. Furthermore, our results showed that, by using the PCS, participants preferred less change in their thermal environment and the variance of the thermal preference votes was significantly smaller near-neutral conditions (21 and 23°C, Table 3). Counter-intuitively, this implies that the personal control mode can contribute more to individual differences near the neutral condition, as the participants have a larger variance in thermal demands. Figure 10 further illustrates how the individual differences in near-neutral conditions were compensated by the PCS by control behavior adjustments between two selected participants. During 17-21°C, those two participants had similar heating settings, while near the neutral condition, 21-25°C, the two participants present quite distinct control behavior.
In this study, we attempt to mitigate thermal discomfort by targeting the most uncomfortable body segments. As expected, the head did not significantly improve thermal comfort in 25°C, which is against the findings in the study by Nakamura 67 and the study by Pallubinsky. 68 The difference in environmental temperatures between our study and those two studies can possibly explain this inconsistency. The warm condition in our study was 25°C while it was 32-34°C in the other studies. 67,68 In the current study, the participants felt comfortable and preferred no change in 25°C ( Figure 3F), which suggests that there was little to improve. The fan-using behavior may be used to fulfill other desires, such as to improve air quality and air freshness, rather than improving thermal comfort.

| Physiological responses induced by the PCS
It was hypothesized that human thermoregulation can be exercised without compromising thermal comfort by using the designed PCS.
We found no significant differences in the torso skin temperature between the two scenarios ( Figure 4D). Skin temperature is an essential driver for thermoregulation, 69 especially in cold conditions. 70 The primary thermosensory body sites used for thermoregulation are the hairy skin of the torso and proximal extremities, 69 in particular the abdomen, 71 whereas the non-hairy skin sites (such as palms and soles) provide limited feedback signal to the thermoregulatory system. 69,72 The designed PCS mainly heated up the non-hairy skin (palm and sole) and resulted in no significant changes in the major hair skin (torso). Therefore, it is reasonable to assume that the whole-body thermoregulatory responses are similar between the two scenarios. The results confirm this, with the exception of the lowest temperature condition (17°C). Indeed, the PCS did not significantly change the energy expenditure, substrate oxidation, physical activity in most of the cases, and merely resulted in slight changes in the whole-body cardiovascular responses (2.2 bpm increase in heat rate, 1.5 mmHg decrease in systolic blood pressure, and 0.9 mmHg decrease in diastolic blood pressure, see Figure 5). At 17°C, energy expenditure was relatively high in the PCS scenario, possibly because of the increase in physical activity ( Figure 6A, E).
Interestingly, the hand skin blood flow significantly increased at 23°C in the PCS scenario while no significant differences were found at 17, 19, 21 and 25°C ( Figure 5E). Hand skin blood flow is modulated by local temperatures and mean body temperature, 73 where the proximal body part (core body tissue) dominates this modulation. 74,75 The effect of local heating on hand skin blood flow depends on the existing level of whole-body vascular tone. 76,77 In this study, the designed PCS did not alter the thermal state of the torso in the range of 17-21°C ( Figure 4D), therefore, the 'cool' torso still modulated the whole-body vasomotor tone and dominated the   78 If the 90% confidence interval does not contain the threshold, it can be concluded that for an alpha value of 0.05, an effect is statistically smaller than the meaningful threshold. 78 As a meaningful threshold for an effect may differ among disciplines, Table S1 provides the 90% confidence interval of the differences in physiological responses between the two scenarios, to help readers to judge the meaning of those differences.

| Health indications
Increasing human metabolism can offset the excessive energy intake combating the prevalence of obesity. Studies have shown that mild cold (16-19°C) can increase human energy expenditure. [79][80][81] In contrast, our results show an even lower energy expenditure at 17°C in the NOPCS scenario compared to 23°C ( Figure 6A). Differences in physical activity and circadian rhythm effects may explain this inconsistency. Firstly, the difference in physical activity may mask the real effect of mild cold on energy expenditure. On average, physical activity at 17°C in NOPCS scenario was lower than at 23°C ( Figure 6E).
Secondly, the circadian rhythm also plays a role. In our study, the 17°C occurred in the morning while 23°C occurred in the afternoon.  Figure 6). Therefore, using the designed PCS in mild cold conditions may retain cold-induced thermogenesis, combating the prevalence of overweight. More importantly, realistic indoor temperature conditions (17-19°C) with long-term exposures increase non-shivering thermogenesis, 84 even result in weight loss 84 and affect insulin sensitivity. 85 Our results suggest that the use of the PCS mitigated thermal discomfort and did not substantially reduce the human body's thermoregulatory effort in an ambient temperature range of 17-25°C. Therefore, the designed PCS combined with mildly cold conditions may possibly F I G U R E 11 An explanatory framework for physiological responses by using the PCS benefit metabolic health without compromising thermal comfort.
Moreover, the results also suggest other health implications of the designed PCS. The first is the improved air quality perception and air freshness perception by using the PCS under slightly warm ambient thermal conditions, which is in accordance with previous studies. 66,86 Secondly, we also show that the ventilation element of the PCS could reduce eye strain at 25°C. Finally, the designed PCS boosted pleasure and arousal over the entire ambient thermal range of 17-25°C. Besides metabolic health, those results also demonstrate that the PCS may benefit psychological health.

| Limitations
This study investigated the effects of a PCS that focuses on the ex-

| CON CLUS IONS
This paper has validated the hypothesis that human thermoregulation can be stimulated without compromising thermal comfort using a PCS design that targets only the extremities and the head. The main conclusions are as follows: 1. The designed PCS significantly improved thermal perceptions in a moderately drifting ambient temperature range of 17-23°C.
2. The designed PCS did not reduce whole-body thermoregulatory responses in the drifting temperature range from 17-25°C. The torso skin temperature, underarm-finger temperature gradients, energy expenditure, substrate oxidations and physical activity were generally similar between PCS and NOPCS scenarios in most cases.
3. The designed PCS slightly influenced cardiovascular responses Overall, the results show that in a temperature drift human thermoregulation can be stimulated without compromising thermal comfort by using a PCS that only targets the extremities in cold conditions. The designed PCS may provide a great potential for the future to create a healthy, comfortable and energy-efficient built environment.

ACK N OWLED G M ENTS
The authors acknowledge the financial support from TKI project "PERDYNKA-dynamic light and indoor climate for office", for the cooperation with developing the personal comfort system (Comfortdesk) and Almende BV for building its monitoring system.

CO N FLI C T O F I NTE R E S T
The authors have no conflict of interest to declare.

PE E R R E V I E W
The peer review history for this article is available at https://publo ns.com/publo n/10.1111/ina.12951.
[Correction added on 20 December, after first online publication: Peer review history statement has been added.]