Behavior and comfort during floor usage in gathering activities on Indonesia apartments

In response to the development in housing needs, human habits and behavior inside the house have a decisive role, and changes in preference from landed houses to vertical houses should be considered. In correlation with body contact, every activity will involve attachment to a horizontal surface (floor surface), and the vertical surface will impact the surrounding area of human thermal comfort. In a tropical climate like Indonesia, climate, internal space, and the human body are essential interrelated things. Associated with the thermal comfort needs of the human body, direct transfer of thermal conditions and direct contact with the surface will also affect the comfort of living every day in the residential area, represented by the behavior of Indonesians in floor usage for daily activities. This part of the research will focus on describing the behavior in horizontal surface usage and comfort, for which data is collected by using multiple types of questions, such as subjective assessment questionnaires and followed by cluster analysis, to comprehend the result.


Introduction
In response to the development in housing needs from landed to vertical houses, this research was conducted on low to luxury apartments in Indonesia to make them more energy-efficient and respond to the comfort level of residents.With the theory of Francis D. K. Ching about the vertical and horizontal field of architectural objects, the plane most often in contact with the human body is the horizontal surface, in the form of the floor [1].Associated with thermal comfort to the human body, direct contact with the field will also affect the comfort of living daily in the residential area.Personal comfort systems and thermally active clothing can warm and cool the body of individual building occupants by transferring heat or cold directly to and from their body surfaces.Such systems would ideally target local body surfaces with high-temperature sensitivities.
Through diversity in Indonesia, several behaviors influence daily activities related to direct contact with horizontal surfaces in dwellings.Activities such as sitting or sleeping on the floor are widespread in Indonesia.
It is shown by the random sampling experiment that the highest percentage of people's area of sleeping is above the bed, at 80.6%.But the next highest total is utilizing floor, which is using the mattress on the floor, futon on the floor, or directly to the floor, with a total percentage of 14.6% [2].Every activity in a particular architectural object, in this case, an apartment, will involve attachment to a horizontal surface, and every vertical surface and surrounding environment will impact the human thermal body sensitivity area.Although thermal adaptations are essential to consider in relation to the physiological approach to assessing thermal comfort [3], there is a linkage between thermal assessment IOP Publishing doi:10.1088/1755-1315/1351/1/012028 2 and psychological and cultural processes [4,5].Thus, those results have not revealed the relationship between human thermal comfort and the environment.
To focus on the dynamic of urban environments in Indonesia, five major cities and areas were strategically selected based on their diverse thermal conditions, recognizing the critical role that climate plays in shaping the urban experience.Jabodetabek, Bandung, Makassar, Medan, and Surabaya were chosen as the main areas that are expected to represent the heterogeneity of community life in Indonesia.Jabodetabek is mostly located in Sub-monsoonal and Equatorial.

Aim and Scope
This research will focus on searching for the answers to the behavior of Indonesian people regarding floor usage related to body comfort by the correlation between daily activities and behavior on floor usage, including daily postures.In the future, the following research question will be regarding the energy usage of low-income apartments.Will achieving a higher body comfort level with lower energy consumption be possible?
Finding a way to optimize the utilization of thermal conditions, both interior and exterior, so that it can cause comfort for the occupants will be an advantage.In addition to thermal comfort, it is expected to reduce energy use and reduce costs.This study uses objects that have been built, but the main goal is to be a guide in planning for low-income apartment buildings with optimal utilization of thermal conditions.In the future, the following research question will be regarding the energy usage of lowincome apartments.Will achieving a higher body comfort level with lower energy consumption be possible?
Human thermal comfort can describe the state of mind that can express and increase satisfaction with the surrounding environment.It refers to several conditions in which the majority of people feel comfortable.The human body produces heat depending on the activity level and expels heat according to environmental conditions.In principle, the body will lose or gain heat in three ways: radiation, convection, and evaporation.An unpleasant sensation of being too hot or cold will affect the thermal discomfort, distract people from their recent activities, and may disturb their well-being.This condition will reduce the ability to concentrate and decrease motivation for working or doing other activities [6].
The thermal sensations received by skin surface temperatures are a primary input to our sense of the surrounding environment and to judge whether we are comfortable or not.The skin's warm and cool sensitivities determine the thermal sensations experienced at different temperatures [7].This process is essential for designing heating and cooling systems in particular architectural objects, especially with the contact of horizontal surfaces.
The values for each body part's thermal sensitivity for the foot sole, forearm, and lower leg are more sensitive to cooling, and the back side equals cooling and warming.The average sensitivity coefficients for the body part mostly in contact with the horizontal surface or floor are the chest (1.8), abdomen (1.98), back (2.02), upper arm (2.07), forearm (1.84), buttock (2.16), thigh (1.92), sole 0.75 -1.2), and foot dorsum (1.08 -1.1) [7].This part of the discussion focuses on the 2 nd phase of the questionnaire from the leading research, which aims to disclose the comprehensive results related to the behavior on floor usage.Residential conditions that support the human body's comfort are needed to improve the quality of life.Therefore, experiments with the user in a household are conducted through direct interviews with the user as a respondent by using a questionnaire with open and closed-ended questions to obtain the data on floor usage in daily behavior through observation of behavior diversity in Indonesia, which is represented by several habits that influence daily activities related to direct contact with floor contact in low-income apartments.

Methods
The research will use an Explanatory Design for the whole phase, as the two-phase Exploratory Design intends that the results of the first method (qualitative) can help develop or inform the second method (quantitative) [12].Based on the premise that exploration is needed when measures or instruments are not available, the variables are unknown, or there needs to be a guiding framework or theory.Because this design begins qualitatively, it is best suited for exploring a phenomenon [13].Subjective assessment can be used to understand the background, behavior, and human perception of thermal.
In this study,as seen in Figure 1, subjective assessment is used to observe the behavior diversity in Indonesia to seek several habits that influence daily activities related to direct contact with horizontal surfaces in dwellings to get an objective result.As a variable, studying, rest/relaxing, sleeping, mealtime, and gathering were considered the main categories of activities during daily life in Indonesia, and the questions were asked according to the category.
The site selection for this study is formed from data from a few of the largest cities in Indonesia.According to the 2010 official population data, Indonesia has 11 cities with over 1 million, although estimates from 2014 show that there are 14 cities with populations exceeding 1 million.Five big cities were chosen from this data for the questionnaire respondents.Figure 2 shows the typical body posture when encountering horizontal surfaces or floors.There are ten postures: standing, chair sitting, seiza sitting, cross-legged sitting, sideway sitting, both-knees erect sitting, leg-out sitting, lateral, supine, and prone positions [7].This posture represents the posture of sitting on the floor and sitting on the chair.

Subjective assessment: main questionnaire
The goal is to understand the behavior and preference regarding human thermal comfort and thermal sense with normal daily clothing conditions while in contact with a horizontal surface in a low-income vertical house.
The respondents are 3383 households, which are spread from Condominiums, Rusunami, and Rusunawa, and random sampling of mixed gender for all house members in 5 of Indonesia's big cities is expected to represent various ethnic groups in Indonesia, many of which may have moved to big cities.Furthermore, with three types of building type as an object study, the results represent more detail regarding the character of vertical housing in Indonesia.
Thirty-seven (37) multiple types of questions were asked directly to the respondents.This phase was conducted in June-December 2022 and carried out by the surveyor company, IPSOS, as seen in Table 1.It describes the schedule of the direct survey, from September to November.In the questionnaire, closed-ended questions and multiple answers type of questions are used to define the main posture, main foot cover, and main floor surface cover are used to describe the sitting behavior daily.

Statistical Analysis
In this stage, all activities related to the postures will be discussed first; studying, mealtime, and gathering have similar results.The preferred posture is sitting on the floor and sitting on the chair/sofa.Gathering appears as an Indonesian culture.The practice of gathering has become part of the culture and lifestyle of the Indonesian community of any age and all genders, and it is held while sitting on the floor/floor sitting posture without using modern furniture (even the furniture is available) [10].Therefore, for further discussion, it will focus on the gathering activity.Consequently, determining the appropriate number of clusters that best fit a dataset, along with evaluating the clustering outcomes, has been the focus of numerous research endeavors.This process of assessing the outcomes of a clustering algorithm is referred to as cluster validity.Three indexes were used to determine the optimal number of clustering (Figure 5).WSS (Within Sum of Squares) measures the total variance within each cluster.We aim to minimize WSS.The optimal number of clusters is at the 'elbow point' in the WSS plot.Silhouette Score measures how close each point in one cluster is to points in neighboring clusters.A high value means the point is well-matched to its own cluster and poorly matched to neighbors.From these results, the optimal cluster number was decided as 6.
Clustering methods were classified into five types: hierarchical methods, partitioning techniques, density or mode-seeking techniques, clumping techniques, and other methods not falling into the other categories [11].In this research, hierarchical methods were used because this method consistently generates a variety of solutions, spanning from n clusters to a single-cluster solution.From Figure 7, the behavior of floor cover usage during gatherings inside the vertical housing can be observed.Using carpet, the main floor cover in the gathering was strongly seen in C1, C4, and C6.Without mats are most chosen in C2 and C3, and mats are most chosen in C5.All the results strongly appear from respondents who answered a single answer.The traits evident in the clusters are as follows: C1 and C2 primarily exhibit sitting on chairs and being barefoot; C6 predominantly showcases individuals seated on chairs, with sandals/slippers as foot cover and the inclusion of a carpet.Specifically, C1 employs a carpet, whereas C2 does not use a mat.On the other hand, C3, C4, and C5 respondents prefer sitting on the floor barefoot, with C3 not using a mat, C4 using a carpet, and C5 using a mat.In Figure 8, C3, C4, and C5 are most seen in all Cities.Therefore, the highest percentage of locations from the respondents appears In Bandung in C4.In cluster composition observed from Figure 9. three apartment categories in Indonesia are used: Rusunawa, Rusunami, and Condominium.In Bandung, cluster 4 is strongly seen in all three building types.Jabodetabek's trend is increasing percentage from Condominium -Rusunami -Rusunawa for C3 and C4.Meanwhile, C1 and C6 have the opposite trend, decreasing.In Makassar, Medan, and Surabaya, C4, C5, and C6 are almost evenly distributed.In preference for sitting on the floor in C3, C4, and C5, respondents who like sitting on the floor are higher than those who dislike sitting on the floor.C5 has more than 50% of respondents who answered that they like to sit on the floor, while C3 and C4 have more than 75%.On the contrary, opposite trends are seen in C1: more than 50% dislike sitting on the floor, C2 more than 75%, and C6 around 90% respondents tend to have a preference for dislike of sitting on the floor.During the behavior of sitting, the strongest reasons to prefer sitting on the floor are comfortable and cool.Another reason for a single answer is because of habit.Meanwhile, the strongest reasons for not preferring to sit on the floor are uncomfortable and too hot.This represents the conditions of daily behavior in vertical housing.

Figure 1 .
Figure 1.Flow Chart for the Research Plan.

Figure 3 .
Figure 3. Variables Used to Discover The Indonesian Behavior on Floor Usage.

Figure 6 . 6 In
Figure 6.Main Posture in Gathering (a) and Main Foot Covering in Gathering (b).

Figure 9 .
Figure 9. Cluster Composition among Building Types is Divided into Locations.

Figure 10 .
Figure 10.Preference for Sitting on the Floor.

Figure 11 .
Figure 11.Main Posture in Gathering (a) and Main Foot Covering in Gathering (b).