• IEQC3-PSC2: the unconcerned extrovert

The unconcerned extrovert profile is considered as a large profile size that consists of 59 students (14%), of which the female students' percentage (58%) is higher than the male students' percentage (41%). These students recorded the highest percentage of feeling neutral while they were completing the questionnaire (28%). They are the second lowest profile to experience recently positive events (24%). Furthermore, they rated the lowest positive affect (16.9). It can be noted that this profile has the least students that suffered from both depression (15%) and anxiety (19%). In terms of IEQ preferences, the unconcerned extrovert students are the least concerned with artificial light in their study places (5.5). Nonetheless, temperature (7.9) is the most important IEQ preference. With regards to IEQ perception, the unconcerned extrovert students reported the least dissatisfaction percentage with air freshness (50%). Pertaining to the IEQ-related items, these students rated both personal ventilation and fresh air the least important (6.2) and headphones (6.6). Nevertheless, control of shading (7.2) and control of room ventilation (7.0) are the most important items for them. Regarding the psychosocial preferences, this profile rated of lowest importance cleanliness (6.8) in their study places. However, the unconcerned extrovert profile is one of the profiles that rated the highest importance for the presence and company of others (6.3).

• IEQC3-PSC3: the unconcerned non-perfectionist

The unconcerned non-perfectionist profile has the same profile size as the unconcerned extrovert profile, with 59 students (14%), of which the percentage of male students (54%) is higher than the percentage of female students (46%). Students within this profile rated the lowest negative affect score among other profiles (10.9). Regarding health, this profile is the second highest group that suffered from depression (29%). Pertaining to IEQ perception, this profile that is dissatisfied the most with air freshness (75%). In terms of IEQ preferences, the unconcerned non-perfectionist students are the least concerned with artificial light (5.5), view to the outside (6.4), daylight (6.6), and ventilation and fresh air (7.1). On the other hand, they are only concerned about temperature (8.1). With regards to IEQ-related items, they rated the least importance for the presence of plants (4.0), control of room ventilation (6.0) and headphones (6.6). Nonetheless, they are concerned about the control of shading (7.3) and surrounding sounds (7.0). Regarding the psychosocial preferences, this profile of students is the least concerned with the presence and company of others (3.6) and the size of the room (4.0). While amenities (7.4) and cleanliness (6.8) are the most important for these students, they are rated the least important among other profiles.

#### **4. Discussion**

#### *4.1. Comparison with Previous Studies*

The majority of students (74%) within this study spent most of their studying time at their homes. A previous study indicated that a home can be considered as an off-campus informal study place, and that most students studied at home as well before the COVID-19 outbreak [33].

Students in this study were generally concerned with three IEQ preferences: daylight, view of the outside, and temperature in their study places. Furthermore, they rated high importance levels for two psychosocial aspects: amenities and cleanliness. Previous studies found similar findings with regards to these preferences. For example, temperature [34] and daylight [3,25] (which is also known as natural lighting) were found to be important criteria by university students in informal study places. Due to the development of the information and communication technologies (ICT), amenities including PCs and laptops were considered important aspects by students in informal study places [3]. In addition, the presence of windows, which also refers to the view to the outside, was also preferred by university students for their study places at the library [35]. Cleanliness has also been affirmed to be an important aspect for students in informal study places such as university libraries [36] and university campus facilities [37]. While students in the current study

rated a high importance score for the view to the outside, university students in another study rated a low importance score for the window view in the university library [36]. Yet, in another two studies [38,39], university students tended to choose their study places in the campus library that is close to the window. The latter outcome is similar to the findings of the current study: students generally preferred to have a view to the outside in their study places, whether at home or on campus. A previous study concluded that window views of the natural environment outside (e.g., green spaces) have a positive psychological impact on university students in terms of recovery from attentional fatigue [40]. During COVID-19 lockdown, the poor view to the outside negatively affected the mental health of university students while they were staying at home [41]. Hence, these preferences have a significant role in fulfilling students' preferences, as well as promoting their health.

In a study conducted by Zhang et al. [12], six profiles of primary school children based on their IEQ preferences and needs in classrooms were determined. While the most important three environmental aspects for these children were "hearing the teacher", "fresh air", and "air temperature", university students from the faculty of architecture were mainly concerned with visual aspects including "daylight" and "view to the outside". In both studies, one IEQ profile was concerned with light or visual aspects, although the primary school children were mainly concerned with artificial light and the university students with natural light. Furthermore, in both studies, one profile was concerned with all IEQ aspects and one profile was not concerned with any of the IEQ-aspects. The difference can be seen in the additional profiles concerned with sound, thermal and air quality aspects. These differences could be associated with the population. In other words, the respondents in this study were all bachelor students of the faculty of Architecture studying to become an architect, a profession in which visual aspects are important. On the contrary, primary school children comprise pupils that are yet to choose their profession or field of study.

#### *4.2. Students' Profiles Based on the Overlap between the Two Cluster Models*

While previous studies on office workers [26] and outpatient staff [27] conducted the cluster analysis separately based on IEQ preferences/perception and psychosocial preferences, the present study explored the overlap among the IEQ preferences and psychosocial preferences clusters. This resulted in several advantages. For instance, the number of variables that were significantly different among the profiles was higher than in the separated cluster models. In this study, health (e.g., depression) was not significantly different among both cluster models (IEQ and psychosocial preferences). However, this variable was found to be significantly different among the nine profiles resulting from the overlap. According to the study of office workers [26], the health variables such as anxiety were only significantly different among the IEQ clusters, while not found to be significantly different among the psychosocial preferences clusters. Similarly, in the study on outpatient staff [27], some variables only varied significantly among the IEQ clusters (e.g., preference for control of temperature), while it was not significantly different among the psychosocial clusters. Therefore, the overlap facilitates a more detailed understanding of the distinct characteristics among the profiles. IEQ, as well as psychosocial preferences, is also important to support comfort; combined profiles contribute to more realistic insights.

Students that had similar IEQ preferences within IEQC1, who were mainly concerned with all IEQ aspects, showed differences in various psychosocial aspects. The results showed that concerned perfectionist students were concerned with all IEQ preferences (specifically sounds and smells), as well as all the psychosocial preferences, except the presence and company of others. On the contrary, the concerned extroverts rated similar importance scores for IEQ preferences as the concerned perfectionists, but they were the most concerned cluster in terms of the presence and company of others in their study places. Additionally, the concerned extrovert students belonged to the profile that had the least personal control over IEQ aspects in their most used study places. Furthermore, both the concerned perfectionists and the concerned extroverts experienced the most recent positive events. In contrast, the concerned non-perfectionist students who were concerned with

all IEQ aspects (specifically ventilation and fresh air) scored the highest negative affect compared to the other clusters. In addition, this profile scored the least importance for bonding or identifying with the place, ability to adapt or control the place, and size of the room. However, this profile rated the highest importance score for headphones as a significant IEQ-related item that helps them to study better.

Students within cluster IEQC2 that were generally concerned with daylight scored different in their psychosocial preferences. The overlap between IEQC2 and the three psychosocial preference clusters showed a significant difference in several characteristics. Visual concerned perfectionist students were the most concerned with daylight and the view to the outside. However, the students in this profile experienced the least positive events, while they scored the highest positive affect. Additionally, they were more concerned with a lamp on their desks to study better than the visual concerned-extrovert students, who were the least concerned with privacy in their study places. While the visual concerned perfectionists were the most concerned with amenities, the visual concerned non-perfectionists were the least concerned with amenities. In terms of health, the visual concerned non-perfectionists suffered the most from anxiety.

IEQC3 students were the least concerned with both artificial light as well as ventilation and fresh air. They showed different characteristics in the overlap between IEQC3 and the three psychosocial preferences profiles. While both the unconcerned extroverts and unconcerned non-perfectionists suffered the most from depression, the unconcerned extroverts suffered the least from depression. In addition, the unconcerned extroverts suffered the least from anxiety. It is interesting to note that all three profiles were the least concerned with having personal desk ventilation and fresh air in their study places. However, only the unconcerned non-perfectionists reported the highest dissatisfaction with air freshness in their most used study places, while both the unconcerned introverts and the unconcerned extroverts reported the least dissatisfaction with air freshness. Additionally, the unconcerned introverts were the least dissatisfied with the smell in their most used study places. While the unconcerned introverts rated the highest importance score for control of room temperature, both the unconcerned extroverts and the unconcerned non-perfectionists rated low scores for this IEQ-related item. Additionally, the unconcerned introverts had the highest control level over IEQ aspects in their study places (specifically, ventilation, shading from the sun, and lighting). Furthermore, while the unconcerned introverts rated the highest importance for cleanliness, both the unconcerned extroverts and the unconcerned non-perfectionists were the least concerned with cleanliness. Furthermore, although the unconcerned introverts were the most concerned with privacy in their study places, both the unconcerned extroverts and the unconcerned non-perfectionists were not very concerned with privacy.

#### *4.3. Differences in Preferences of Profiles in Relation to Design Implementations*

In general, there were significant differences among the profiles in terms of IEQ and psychosocial preferences, which means that generalizing the preferences of the whole study sample is not appropriate. For example, while privacy was indicated as highly preferred by students in their study places [34], this study reveals that there are two opposite profiles in terms of the importance of privacy in the study places: one of them (the unconcerned introvert) was highly concerned with privacy, while the other one (the visual concerned extrovert) rated privacy in their study places as less important. This result is similar to the findings of a previous study [23] in which the outcome showed that students' characteristics (birthplace and current educational level) have an influence on students' preferences, such as privacy and interaction.

While all the nine profiles were found to be statistically different in all IEQ preference aspects, their mean importance scores were higher than the mid-scale point (5.0). Nonetheless, there were profiles for which their mean importance scores for sounds from the outside (visual concerned extroverts and visual concerned non-perfectionists), sounds from the inside (visual concerned perfectionists), and smells (visual concerned non-perfectionists) were less than the mid-point scale (5.0). This means that there are profiles of students which are not highly concerned about sounds in their study places. The current study found that three profiles are not concerned about the sounds (from the outside or the inside) at their study places. This is in line with another study, conducted by Cunningham and Walton [20], which indicated that the preferences of university students to study in a quiet environment (e.g., university library) vary. In contrast, Beckers et al. [2] found that most university students prefer studying in quiet learning spaces.

The overlap among the IEQ and psychosocial models contributed to understanding indepth students' profiles based on their different preferences in their study places. Different approaches can be applied to fulfil the different preferences of each profile. For instance, soundscape approach considers the individual's sound preferences in a certain environment. According to ISO 12913-1 [42], the soundscape is defined as: "acoustic environment as perceived or experienced and/or understood by a person or people in a context". This approach can understand the sound preference of each profile at study places. Additionally, the soundscape is mainly focused on using the sound as a resource that fulfils the sound preference rather than focusing on quiet spaces [43]. For instance, Shu and Ma [9] concluded that natural sound sources, such as birdsongs and stream sounds, had restorative effects on classroom children after performing a cognitive task, while the quiet condition did not show an effect. In addition, a study conducted by Topak and Yılmazer [44] found that students' sound preferences differ based on the context of the space, classroom or computer laboratory. They also found that natural sounds (e.g., birdsongs) were preferred by students to hear in their learning environments. Moreover, Xiao and Aletta [45] concluded that the soundscape approach could facilitate architects and interior designers to understand the students' experiences to provide high-quality sound environments or study places, such as libraries, by identifying different types of users. Accordingly, soundscape can be accounted for during the design process to understand the sound preferences of each profile of students at their study places. Another approach that can be applied to fulfil the different preferences is the application of customized (i.e., personalized) designs. These applications can match the preferences of each profile and could provide comfort for them, such as customized and personalized shading [46], ceiling fans [47], and heating [48], which allow users to have control over the surrounding environment based on their preferences.

#### *4.4. Limitations*

The sample of this study is limited to bachelor university students (specifically of the faculty of Architecture and the Built environment), whose mean age was 20 years old. The questionnaire was also completed at the time of the COVID-19 outbreak, which may have influenced students' preferences during this situation. It was sent to students during the fall and spring (October and March) seasons in the Netherlands, which could have had an impact on students' responses such as whether they scored high importance for both daylight and temperature. Furthermore, the IEQ and psychosocial preferences were asked within the context of studying at study places in general, while the learning activities/styles (e.g., individual, collaborative) were not investigated in the present study. The nine profiles in this study were identified based on the preferences (IEQ and psychosocial preferences) of bachelor students at the faculty of Architecture and the Built Environment in the Netherlands. Hence, further studies could validate these nine profiles with students from other faculties, as well as other universities with a different cultural background. As this study is based on a survey (questionnaire) with 451 students who were studying either at their homes or in educational buildings, space geometry and physical measurements of IEQ factors were not included in this study.

#### **5. Conclusions**

In conclusion, students with similar IEQ preferences have different psychosocial preferences, and vice versa. This was affirmed by determining nine profiles of university students based on the overlap between the IEQ and psychosocial preferences. These profiles showed significant differences among them in terms of various variables, including perception, lifestyle, health, and gender. It is worthwhile to note that the number of variables that were significantly different between the profiles is higher within the overlap between the IEQ and psychosocial preferences than clustering the students based on these preferences separately. The outcome of this study provides insight into different profiles of university students, each with their own preferences of study places. For instance, the concerned perfectionists are highly concerned with sounds (from the outside and inside) of their study places, while the visual concerned non-perfectionists are not highly concerned with sounds. These findings show the need for designing study places for more than one profile and not just for the "average" student.

The novelty of this study lies in the overlap of the IEQ and psychosocial preferences models that resulted in nine profiles, which showed significant differences among a number of variables. Therefore, it is recommended for future studies to determine the profiles of occupants (e.g., students, office workers, home occupants) within different scenarios (e.g., classrooms, study places, offices, homes) by the analysis of the overlap between the two sets of clusters.

Since this study is based on a survey in which physical measurements were not considered, it is suggested for future research to investigate these study places in-depth. For instance, field studies such as exploring the soundscapes of these study places can be investigated by measuring the sound pressure level (SPL), identifying sound sources as well as space geometry, and conducting in-depth interviews with the students from different profiles.

**Author Contributions:** Conceptualization, A.H., A.E. and P.M.B.; methodology, A.H., A.E., and P.M.B.; formal analysis, A.H.; investigation, A.H. and P.M.B.; data curation, A.H.; writing—original draft preparation, A.H., A.E. and P.M.B.; writing—review and editing, A.H., A.E. and P.M.B.; supervision, A.E. and P.M.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (HREC) of DELFT UNIVERSITY OF TECHNOLOGY (31 January 2022).

**Informed Consent Statement:** Informed consent was obtained from all students involved in the study.

**Data Availability Statement:** The data are not publicly available due to restrictions regarding the privacy of the participants of this study.

**Acknowledgments:** The authors would like to thank the first-year bachelors students (2021 and 2022) of the Faculty of Architecture and the Built Environment at TU Delft for completing this questionnaire.

**Conflicts of Interest:** The authors declare no conflict of interest.


#### **Appendix A. Sections and Sub-Sections of the Questionnaire**




#### **Appendix C. Psychosocial Preferences Clusters**



\* N < 5, thus chi-squared test not performed.
