The Relationship of Indoor and Outdoor Thermal Variables to Create an Energy-Efficient Modern House in the Tropical Mountains of Indonesia

Instrumentation

Digital hygrometer: The indoor temperature and relative humidity were continuously measured using an Extech RHT20 Digital Hygrometer (Extech Instruments, USA, Version 2022). This device was selected due to its accuracy in measuring both temperature and humidity over extended periods. The device was placed in five key locations within the house: terrace, living room, family room, bedroom, and kitchen. The hygrometer was programmed to log data every 10 min for 24 h a day, continuously for 30 days. 

Materials used

Data recording and analysis: The temperature and humidity data collected by Extech RHT20 were stored and analyzed using Microsoft Excel (Version 2021). Data analysis was focused on identifying patterns and trends in indoor climate conditions in various rooms. Graphs were plotted to depict temperature and humidity fluctuations throughout the measurement period. Regression analysis was done to assess the relationship between indoor and outdoor temperatures.

Methodology for data analysis

Regression analysis: A regression model was used to quantify the relationship between outdoor air temperature (Ta_Outdoor) and indoor temperature for each room. The regression equation used was Y = a + bXY = a + bXY = a + bX, where:

• Y is the dependent variable (indoor temperature),

• X is the independent variable (outdoor temperature),

• a is the regression constant,

• b is the regression coefficient. This method helps in identifying how outdoor environmental changes affect the indoor thermal comfort, and its significance was evaluated using statistical tests.

Environmental conditions

Climatic data: The climatic conditions during the data collection period were monitored to contextualize the thermal performance of the building. Average daily outdoor temperatures fluctuated between 15 °C and 30 °C, with significant variation between day and night temperatures due to the tropical highland climate.

Study site specifications

This study was conducted in Wonosobo, located in the tropical mountains of Central Java, Indonesia (latitude −7.3569° and longitude 109.8959°). The region experiences a wet tropical climate with heavy rainfall during the rainy season (November to March), which significantly influences the indoor temperature and relative humidity levels.

Survey site and climatic conditions

The field investigation was conducted in Wonosobo, a mountainous region in Central Java, Indonesia, at an elevation of approximately 850–1,200 m above sea level, categorized under a tropical highland climate (Af/Cfb - Köppen classification). During the rainy season, which typically spans from November to March, the region experiences heavy precipitation with average monthly rainfall exceeding 300 mm, high relative humidity averaging 75%–95%, and daily temperatures fluctuating between 15 °C at night and 28 °C during the day. The average annual temperature is approximately 22 °C, with cooler nights and warmer days due to highland diurnal variation. These climatic characteristics significantly influence indoor thermal comfort and building envelope performance, thus making Wonosobo a suitable location for assessing thermal behavior in residential architecture during the rainy season.

Data collection

Data collection for this study was accomplished over a 30-day period, from March 1st to March 30th, 2022, during the rainy season. The climatic conditions during the data collection period were characterized by high humidity levels, averaging 75%–95%, and daily temperature fluctuations ranging from 15 °C at night to 28 °C during the day. The region experienced frequent rainfall, which contributed to the elevated indoor humidity and cooler temperatures, especially during the night. These climatic factors were considered during the data collection process, as they directly influence the indoor thermal comfort of the residential spaces being studied.

House characteristics

The house had a hipped roof with a terrace using a wide concrete slab. The roof covering used glazed tiles. The walls were made of plastered bricks and the floor used ceramics. The house had a large front yard measuring 5 × 12.3 m². Several plants were arranged in the yard. Part of the front yard floor used ceramics, and the rest was soil for planting plants. The front yard was not covered by a roof and was bordered by a fence with a door wide enough for vehicles to enter the yard. The fence used the attached stone material with a black iron door. The house had a large terrace measuring 2.5 × 12 m², supported by two columns with a diameter of 0.4 m in green (Figure 1).

The house was divided into two areas, namely the main house and the back house. The main house consisted of a living room, family room, one master bedroom with a bathroom inside the room and a child’s bedroom (Figure 2). The main house had one master bedroom with a bathroom inside the bedroom. One bedroom was located inside the main house with a different size. Both bedrooms did not have bathrooms inside the room. The other two bedrooms were in the back house facing the fishpond. The back area of the main house had a void so that air could move more easily. The kitchen was in the back house with a size of 4.8 × 3 m². The dining room was the one with the kitchen. The void made it easy for smoke from the kitchen to escape. The laundry area was located next to the back bathroom. The garage was located next to the house with an elongated shape that was large enough to accommodate three cars.

The living room was not too spacious with a size of 3.3 × 3.0 m². The furniture in the living room consisted of two long chairs and one small chair with a table in the middle. The ventilation in the living room was located on the left and front sides. The left side of the living room had a window that could be opened with a glass panel. The front side of the living room had a window which could not be opened (dead window) using glass (Figure 3).

The main bedroom was the bedroom used by parents. The bedroom had an area of 3 × 5 m². The furniture in the main bedroom consisted of a mattress, wardrobe, filing cabinet, television. The bedroom had a bathroom measuring 1.5 × 1.5 m². Ventilation in the bedroom was a dead glass window that had an area of 1.5 × 2 m² (Figure 4).

Family room was a place to watch television. Family room had the largest size compared to other rooms, which was 5 × 5.5 m². Furniture in the family room consisted of a bed, a television rack with a television, a wardrobe, a desk, a sofa and a table. Ventilation in the family room was the most compared to other rooms. Windows were placed on the side and behind the room. The size of the side windows was 2 × 2 m² and 1.5 × 2 m² (Figure 5).

The kitchen had a semi-open space. The kitchen measured 4.6 × 3.5 m². The kitchen did not have a special door. Air circulation in the kitchen was unhindered, easy to enter and exit from the outside. In front of the kitchen there was a fishpond without a roof. Wind and light could easily enter the kitchen. The furniture in the kitchen was quite full, consisting of a dining table and chairs, a table for placing the stove, a cupboard, a sink and a cupboard. Full furniture did not interfere too much with air circulation and lighting (Figure 6).

Room temperature

The temperature in the four interior rooms showed differences but not too large. The temperature in the bedroom was on average higher than the temperature in the other three interior rooms. The temperature in the kitchen fluctuated and was not constant. At certain times it appeared to be the highest compared to the temperature in other rooms, but at other times it appeared to be the lowest compared to the temperature in other rooms. The temperature in the family room and living room merged indicating that the temperature in the family room and living room was not much different (Figure 7). All rooms showed a periodic up and down pattern, which most likely reflected the daily cycle of air temperature. The bedroom had a temperature higher than the other rooms throughout the time, in accordance with the results of the higher average temperature in the study. The kitchen showed greater temperature fluctuations, with higher peak temperatures than the other rooms, especially during the day till evening. This could be attributed to cooking activities that increased the heat in the room. The family room and living room had relatively stable temperatures and were lower than the bedroom and kitchen. Compared to the living room (Ta_Living Room), the family room had a slightly more stable temperature, as this room was located deeper in the house and had fewer openings to the outside.

Compared to the bedroom (Ta_Bedroom), the temperature of the family room was lower because the bedroom was more often closed and has better insulation. Compared to the family room (Ta_Family Room) and living room (Ta_Living Room), the bedroom had a more stable and more comfortable temperature. Compared to the kitchen (Ta_Kitchen), the bedroom had smaller temperature fluctuations because it is not affected by cooking activities that produced heat. Compared to the bedroom (Ta_Bedroom), the kitchen had larger temperature fluctuations due to cooking activities. Compared to the living room or family room, the kitchen had a higher average temperature due to the heating effect of cooking appliances. The kitchen temperature remained more stable than the outside temperature, indicating that the building has good thermal insulation.

Compared to the bedroom (Ta_Bedroom) or living room (Ta_Family Room), the terrace temperature varied more because it was more exposed to the outside environment. Compared to the kitchen (Ta_Kitchen), the terrace temperature followed the outside temperature pattern more, while the kitchen temperature was more influenced by cooking activities. The terrace acted as a transition zone between the inside of the house and the outside environment, so its temperature was between the indoor and outdoor temperatures.

At certain times (night or early morning), the temperatures of all rooms were lower. The bedroom temperature was more stable and closer to the comfortable temperature than other rooms. The kitchen temperature had a sharp spike, indicating the influence of activities in the room. The temperature in the house was influenced by time and activity factors in the room. The bedroom was the most comfortable room, while the kitchen had the most extreme temperature variations. The living room and family room had more stable temperatures but were still lower than that of bedroom in terms of thermal comfort.

Comparison of outdoor and indoor temperatures

Outdoor and living room temperatures were very distinct. Outdoor temperature (Ta_Outdoor) showed large fluctuations, up and down with a wide range, especially during the day and night. The living room temperature (Ta_Living Room) was more stable than the outdoor temperature. This shows that the living room had better insulation, so that the indoor temperature was not too affected by the outdoor temperature. During the day, the outdoor temperature was higher than the indoor temperature, which indicates that the building material was able to absorb heat from the outside. At night, the outdoor temperature tends was lower than the indoor temperature, indicating that the building maintained warmth indoors (Figure 8). The living room had a more stable thermal condition compared to the outdoor environment. This shows the effectiveness of the building in maintaining indoor thermal comfort. Significant outdoor temperature fluctuations indicate a large difference in day and night temperatures in the highlands. This is in accordance with the climate characteristics of the area, where temperatures can drop drastically at night. Architectural design with good insulating materials can help maintain thermal comfort indoors, especially during the rainy season or when there are extreme temperature changes.

Outdoor temperatures fluctuated widely, with a temperature range of around 15 °C–35 °C. The living room temperature was more stable than the outside temperature, indicating that it had good insulation. During the day, the outside temperature increased significantly, while the living room temperature remained lower. At night, the outside temperature dropped drastically, but the living room temperature remained stable (Figure 9).

The living room is generally located inside the house and is not directly exposed to sunlight like the outside room, so the temperature is more stable. The wall, roof, and floor materials used in the living room play a role in keeping the temperature from changing too quickly according to the outside temperature. The living room has good cross ventilation, so the temperature will adapt more easily to the environment without extreme changes. If this room is more closed or located in the middle of the building, the temperature will be more stable because it is affected by the heat from other rooms. Outside temperatures in the highlands experience quite extreme differences between day and night. The stable temperature in the living room indicates that the house design is quite good at maintaining thermal comfort.

The living room has a more stable temperature than the outside temperature, indicating that the house design is effective in reducing the influence of environmental temperature. The outside temperature fluctuates greatly, especially between day and night, which emphasizes the need for good building materials to maintain thermal comfort. The design of ventilation and house materials greatly affect the comfort of the occupants, especially in frequently used rooms such as the family room. The bedroom has the most stable thermal conditions compared to the outside temperature. This shows that the bedroom is well designed to maintain the comfort of the occupants. The significant fluctuation of the outside temperature emphasizes the need for good insulation materials in house construction, especially in highland areas. The bedroom is more comfortable than other rooms, because the temperature remains close to the ideal temperature for sleeping (around 24 °C), even though the outside temperature changes drastically.

The temperature in the bedroom is more stable than the outside temperature, with smaller changes over time. During the day, the outside temperature increases significantly to nearly 35 °C, while the inside temperature remains lower. At night, the outside temperature drops drastically to around 15 °C, but the inside temperature remains more stable and does not drop as drastically. The bedroom uses thicker and more insulated materials than other rooms, which helps maintain temperature stability. Materials such as plastered brick or wood that have high thermal capacity can absorb heat during the day and release it at night, so the temperature remains more stable (Figure 10). Bedrooms that are in the interior of the house or have windows with limited openings tend to have more stable temperatures. Fluctuating outside temperatures indicate that this area has a large temperature difference between day and night, which is typical of highlands. The stability of the bedroom temperature indicates that the house design is quite effective in maintaining thermal comfort.

The temperature in the kitchen (blue) follows a fluctuating pattern but is more stable than the outside temperature. During the day, the outside temperature increases significantly, but the kitchen shows a more controlled pattern with a slight increase. At night, the outside temperature drops drastically, while the kitchen temperature is more stable and does not experience extreme changes. The temperature in the kitchen tends to be higher than other rooms when cooking is taking place. Temperature fluctuations in the kitchen may be sharper than in the living room or bedroom but are more stable than the outside temperature. • The kitchen has sufficient open ventilation or windows, so the heat from cooking can be quickly dissipated, keeping the temperature stable (Figure 11).

Kitchens with brick walls or materials with high heat absorption can maintain their temperature longer than other rooms. Ceramic kitchen floors can absorb heat and have little effect on the room temperature. The kitchen temperature shows a more stable pattern than the outside temperature but still has significant fluctuations due to cooking. The kitchen is warmer than other rooms, especially when cooking is taking place, but still does not experience temperature changes as extreme as the outside environment. A well-ventilated kitchen design is essential for maintaining thermal comfort, especially to avoid overheating due to cooking. Kitchen materials and layout play a role in controlling the temperature of the room, so choosing the right materials can help reduce the heat effects of cooking activities.

The temperature on the terrace almost follows the pattern of the outside temperature, but with a slight difference in stability. During the day, the outside temperature rises sharply, and the temperature on the terrace also rises, but is slightly more muted. At night, the outside temperature drops sharply, and the temperature on the terrace also decreases, but with a smaller fluctuation than the outside temperature (Figure 12).

Because the terrace is a semi-open area, its temperature is more affected by the outside temperature than the interior of the house. If the terrace has a roof or additional protection, the temperature will be more stable than the completely open outdoor area. The ceramic terrace floor can absorb heat during the day and release it slowly at night, which makes the temperature more stable than the outside temperature. The walls around the terrace, if there are any, can also help reduce direct temperature fluctuations. If the terrace has a roof or is on the shadier side, the temperature will be more stable than the outside environment.

The temperature on the terrace is more similar to the outside temperature, but with a slight damping, indicating that the design of the house provides some protection from environmental fluctuations. The temperature fluctuation on the terrace is greater than that of the interior of the house, but remains more stable than the outside temperature, especially if there is a roof or protection from direct sunlight. A well-designed terrace (with a roof or suitable heat-absorbing material) can help reduce the impact of extreme temperature changes, so that it remains comfortable to use throughout the day. The terrace is a semi- open area whose air temperature is greatly influenced by the outside temperature but still has better stability than the outside temperature completely.

The bedroom had the highest mean temperature (24.17 °C), indicating that this room tends to be warmer than the other rooms. The kitchen had the lowest mean temperature (22.85 °C), but the difference was not significant compared to the living room and family room. The kitchen had the lowest minimum temperature (18.40 °C), which is more likely to occur at night or early morning when cooking is not taking place. The bedroom had the highest minimum temperature (20.70 °C), indicating that this room remains warmer even when the ambient temperature is at its lowest. The bedroom had the highest maximum temperature (29.00 °C), indicating that this room warms up more quickly than the other rooms, perhaps due to limited ventilation or building materials that retain heat longer. The kitchen also had a high maximum temperature (27.80 °C), which is more likely to occur during cooking (Table 1). The bedroom was the room with the highest mean temperature (24.17 °C) but also had the highest maximum temperature (29.00 °C), indicating that this room tends to be warmer overall. The kitchen shows quite large temperature fluctuations, with the lowest minimum temperature (18.40 °C) and a high maximum temperature (27.80 °C). This is influenced by cooking activities that can increase the temperature significantly. The family room and living room have more stable temperatures, with less extreme fluctuations than the bedroom and kitchen. Ventilation design and building materials play an important role in the stability of room temperature. Rooms with good ventilation will have a more stable temperature, while rooms with high insulation tend to be warmer.

Regression analysis of outdoor and indoor temperatures

Table 2 shows the results of the regression test with outdoor temperature (Ta_Outdoor) as an independent variable and indoor temperature (Ta_LivingRoom, Ta_FamilyRoom, Ta_Bedroom, and Ta_Kitchen) as dependent variables. The dependent variable is predicated on the outdoor temperature (Ta_Outdoor), namely the indoor temperature in several different rooms. Unstandardized Coefficients are regression coefficients that show how much influence Ta_Outdoor has on each indoor temperature. Constant is a regression constant that shows the indoor temperature value when Ta_Outdoor is zero. The analysis uses the t Statistical Test which is used to test the significance of the relationship between outdoor temperature and indoor temperature. The Sig. value is the significance value (p- value), which determines whether the relationship between the independent and dependent variables is statistically significant.

Linear regression models formed for each space are: (Table 2)

1. Living Room

Ta_LivingRoom = 198.361 + 0.038 × Ta_Outdoor

It can be inferred that for every 1 °C increase in the outdoor temperature (Ta_Outdoor), the living room temperature increased by 0.038 °C.

2. Family Room

Ta_FamilyRoom = 198.039 + 0.037 × Ta_Outdoor

The living room temperature increased by 0.037 °C for every 1 °C increase in the outside temperature.

3. Bedroom

Ta_Bedroom = 205.221 + 0.046 × Ta_Outdoor

The bedroom had a temperature increase of 0.046 °C for every 1 °C increase in outside temperature.

4. Kitchen

Ta_Kitchen = 184.623 + 0.102 × Ta_Outdoor

The kitchen showed the largest temperature increase, namely 0.102 °C for every 1 °C increase in outside temperature.

All p-values (Sig.) in the table are less than 0.05, which indicates the relationship between outdoor temperature and indoor temperature is statistically significant. The highest t-value is for the kitchen (t = 8.370), indicating that the kitchen temperature had a stronger relationship with outdoor temperature than other rooms. The living room and family room have similar regression coefficients, indicating that their temperature responses to changes in outdoor temperature were similar. Indoor temperature was affected by outdoor temperature, but the degree of influence varied depending on the type of room. The kitchen had the highest sensitivity to changes in outdoor temperature (regression coefficient 0.102), while the family room had the lowest sensitivity (regression coefficient 0.037). All relationships between outdoor temperature and indoor temperature are statistically significant.

Indoor relative humidity

Relative humidity showed clear daily fluctuations, with a regular up-and-down pattern. The kitchen had the highest humidity value compared to other rooms most of the time. The bedroom had a lower humidity value than other rooms, especially with some sharp drops. The living room and family room showed similar patterns and were more stable than that of kitchen and bedroom (Figure 13).

There are daily fluctuations that are most likely caused by changes in ambient temperature and indoor activities. At some points, humidity increases significantly (e.g. around August 25–26), which may be caused by more humid weather or changes in ventilation conditions. The kitchen tends to have higher humidity than other rooms. This can be caused by cooking activities that produce water vapor. The bedroom often experiences a drastic decrease in humidity due to ventilation. The family room and living room have similar humidity patterns, with less extreme fluctuations than the bedroom.

Indoor relative humidity fluctuates significantly throughout the day, most likely influenced by human activities and changes in ambient temperature. The kitchen has the highest humidity, which may be caused by cooking activities and water vapor. The bedroom had the most unstable humidity, with several points where the relative humidity dropped sharply. The family room and living room showed a more stable pattern, indicating relatively constant environmental conditions. The increase in humidity around August 25–26 could be an indication of changing weather conditions or ventilation in the house.

Comparison of outdoor and indoor relative humidity

Outdoor humidity fluctuates much more than living room. Outdoor humidity changes drastically throughout the day, with very rapid up-down cycles. This can be caused by changes in weather, rain, sunlight, and other factors. Living room humidity is more stable than Outdoor, indicating that conditions in the living room tend to be more controlled and less affected by direct weather changes (Figure 14). Outdoor humidity is generally higher than Living Room humidity, although there are some points where the values are almost the same. There is a pattern of humidity decreasing slightly slowly in late August to early September, which could indicate a change in season or drier weather conditions. Daily fluctuations are obvious in Outdoor, while Living Room only changes slightly over time. Outdoor humidity is more dynamic than Living Room, indicating that indoor conditions have a better control influence on humidity, such as ventilation or air conditioning systems. Living Room humidity has a narrower range of values, indicating that the indoor environment is more stable than outdoor. During certain periods, Outdoor humidity is higher than that of Living Room, especially when the outside humidity experiences a large spike that can be caused by rain or certain environmental conditions.

Outdoor humidity fluctuates significantly throughout the day, while the humidity in the living room is more stable. The outside environment is more humid than the living room most of the time, which is likely due to weather factors such as rain or natural air humidity. The living room has better humidity control, indicating the possibility of a humidity control system such as air conditioning, ventilation, or good insulation. Large fluctuations outdoors indicate significant external environmental influences, while the living room maintains humidity within a smaller range.

Outdoor Humidity shows very large and rapid fluctuations over time. This reflects the natural changes in outdoor humidity due to environmental factors such as daily temperature changes, rain, or sunlight. Family Room humidity is more stable than RH_Outdoor, indicating that the humidity in the living room tends to be more controlled. Outdoor humidity is higher than indoor humidity most of the time, although there are some points where the values are almost the same (Figure 15).

The daily fluctuations in Outdoor Humidity are very clear, showing a pattern of ups and downs every day. This is most likely related to the day-night cycle and changes in ambient temperature. Family Room humidity has a narrower and more stable humidity range, indicating that indoor conditions are more controlled than the outdoor environment. There is a more significant drop in outdoor humidity at several points around mid to late August, which could indicate changing weather conditions, such as drier air or reduced rainfall.

Outdoor Humidity is more dynamic and experiences large fluctuations, while Family Room is relatively stable. Outdoor Humidity is usually higher than Family Room, especially when the ambient conditions are more humid, such as after rain. The difference in humidity between the living room and outside indicates that indoor conditions are better maintained, possibly due to humidity control through ventilation. Outdoor humidity is very volatile, influenced by weather factors such as changes in temperature, rain, or natural air humidity. The humidity in the living room is more stable than outdoors, indicating that indoor conditions are better maintained and less dependent on external changes. Outdoor humidity is generally higher than the Family Room, but at some points the values are almost the same. The decrease in outdoor humidity in late August may indicate a change in season or drier weather conditions.

Outdoor Humidity fluctuates greatly and rapidly throughout time, with significant changes every day. This reflects a highly dynamic environment, likely influenced by day-night cycles, weather, or rainfall. Bedroom Humidity is more stable than Outdoor Humidity, indicating that the humidity in the bedroom tends to be more controlled than the outdoor environment. Outdoor humidity is higher than the bedroom most of the time, although there are some points where the two are almost the same (Figure 16). Outdoor humidity is more dynamic and fluctuates greatly, while bedroom humidity is more stable. Outdoor Humidity is generally higher than Bedroom Humidity, indicating that the outdoor environment is more humid than the bedroom, especially at night or in the morning. Outdoor humidity is highly fluctuating, with significant up-and-down patterns every day, likely influenced by weather factors such as temperature changes, rain, or natural air humidity. Bedroom humidity is more stable than outdoor, indicating that indoor conditions are more controlled and less dependent on changes in the external environment. Outdoor Humidity is generally higher than Bedroom, but at some points the values are almost the same.

Outdoor humidity fluctuates greatly and rapidly throughout time, with significant changes occurring daily. This reflects the highly dynamic outdoor environment, influenced by daily temperature changes, rainfall, and other weather factors. Kitchen humidity is more stable than Outdoor, indicating that the humidity conditions in the kitchen are more controlled than the outdoor environment. Outdoor humidity is higher than the kitchen most of the time, but there are some periods where the two values are almost the same (Figure 17). Kitchen humidity has a more stable humidity range, indicating that the kitchen conditions are more controlled than the outdoor environment. A more significant decrease in outdoor humidity around the end of August may indicate a change in the weather to drier or less rainfall. Outdoor humidity is more dynamic and fluctuates greatly, while humidity in the kitchen is more stable. Outdoor humidity is generally higher than Kitchen, indicating that the outdoor environment tends to be more humid than the kitchen. Kitchen humidity remains within a narrower range. Kitchen humidity is more stable than Outdoor, indicating that the indoor conditions are more controlled and less affected by changes in the external environment. Outdoor humidity is generally higher than Kitchen, but at some points the values are almost the same.

The humidity of the Terrace is more stable than the Outdoor but still has slight fluctuations because the terrace is a semi-open area that is still affected by the outside environment. The humidity of the Outdoor is higher than the humidity on the terrace most of the time, although at some points the two are almost the same. The humidity of the Terrace has a similar pattern to the Outdoor, but with a smaller amplitude of change, indicating that although the terrace is still affected by the outside environment, it has little protection from the weather elements (Figure 18).

The humidity of the Outdoor is more dynamic and experiences greater fluctuations than the Terrace, which is more stable because it is somewhat protected from direct exposure to wind and rain. The humidity of the Outdoor tends to be higher than the Terrace, but at some points the values are almost the same, indicating that the conditions on the terrace are still quite close to the outside environment. The difference in humidity between the Terrace and Outdoor shows that although the terrace is affected by the outside weather, there are factors such as a roof or ventilation that help maintain humidity stability.

The humidity of the Terrace is more stable than the outside environment but still experiences fluctuations due to its semi-open nature. The humidity of the Outdoor is generally higher than the Terrace, but at some points the values are almost the same. Terrace humidity can be maintained more stable with good roof design and sufficient ventilation, to maintain the comfort of residents in the area.

The kitchen had the highest average humidity (77.93%), which was most likely due to cooking activities that produce water vapor. The Bedroom had the lowest average humidity (74.97%), which could be attributed to the use of air conditioning or better ventilation for sleeping comfort. The Family room and Living room had almost the same average humidity values, namely 76.15% and 75.68%, indicating that the conditions of these two rooms were quite uniform in terms of humidity (Table 3).

The highest minimum humidity occurred in the kitchen (58.00%), indicating that despite the decrease in humidity, the kitchen still maintained a relatively high humidity level. The lowest minimum humidity occurred in the bedroom (45.10%), indicating that the bedroom was the driest area compared to other rooms. The family room and living room had higher minimum humidity than the bedroom, namely 57.90% and 56.50%.

The kitchen had the highest maximum humidity (95.30%), supporting the hypothesis that cooking activities produce an increase in humidity. The bedroom has a lower maximum humidity (90.60%), which is still quite high, but more controlled than the kitchen. The family room and living room had maximum humidity of 87.80% and 90.30%, which were between the humidity values of the kitchen and bedroom. The kitchen has the highest humidity compared to other rooms, both in terms of average, minimum, and maximum. This is natural because cooking activities produce water vapor which increases humidity. The bedroom had the lowest humidity, especially at the minimum value (45.10%). The family room and living room had similar humidity patterns, with humidity tending to be stable between the kitchen and bedroom. The highest humidity fluctuation occured in the bedroom, with a fairly large difference between the minimum humidity (45.10%) and maximum humidity (90.60%). This may be attributed to the windows being opened and closed periodically.

Regression analysis between oudoor and indoor humidity

Table 4 presents the results of the Regression Test to see the relationship between outdoor humidity as an independent variable with indoor humidity in various areas of the house, namely Living Room, Family Room, Bedroom, and Kitchen as dependent variables. Dependent Variable is one that depends on outdoor humidity, namely Living Room, Family Room, Bedroom, and Kitchen Humidity. Constant is a Constant in the regression model, which shows the indoor humidity value when outdoor humidity is zero. Unstandardized Coefficients are regression coefficients that show how much influence outdoor humidity has on indoor humidity. The t Statistical Test was used to test the significance of the relationship between outdoor humidity and the dependent variable. Sig. is the significance value (p-value), which determines whether the relationship between the independent and dependent variables is statistically significant. The linear regression model formed for each room is shown in Table 4.

1. Living Room

RH_LivingRoom = 623.715 + 0.088 × RH_Outdoor

It can be inferred that for every 1 °C increase in outdoor humidity, the living room humidity increased by 0.088 °C.

2. Family Room

RH_FamilyRoom = 648.326 + 0.067 × RH_Outdoor

For every 1 °C increase in outdoor humidity, the living room humidity increased by 0.067 °C.

3. Bedroom

RH_Bedroom = 621.403 + 0.099 × RH_Outdoor

The humidity in the bedroom increased by 0.099 °C for every 1 °C increase in outdoor humidity, which was the highest compared to other rooms.

4. Kitchen

RH_Kitchen = 653.477 + 0.074 × RH_Outdoor

For every 1 °C increase in outdoor humidity, kitchen humidity increased by 0.074 °C.

All p-values (Sig.) in Table 4 are 0.000 (p < 0.05), indicating that the relationship between RH_Outdoor and indoor humidity is statistically significant. The highest t-value was seen in the bedroom (t = 8.523), indicating that bedroom humidity has a stronger relationship with outdoor humidity than other rooms. The living room and family room had lower regression coefficients, indicating that indoor humidity in these rooms was less affected by outdoor conditions than the bedroom. Indoor humidity was affected by outdoor humidity, but the degree of influence varied depending on the type of room. The bedroom had the highest sensitivity to changes in outdoor humidity (regression coefficient 0.099), while the family room had the lowest sensitivity (regression coefficient 0.067). The kitchen had the highest regression constant (653.477), which indicate that humidity in the kitchen was naturally higher than other rooms. All relationships between outdoor and indoor humidity were statistically significant.

If the humidity in the bedroom is easily affected by outside humidity, it is better to use good ventilation settings or a humidity regulator (humidifier/dehumidifier) to maintain comfortable sleep. The kitchen is significantly influenced by outside humidity, so a good ventilation system (such as an exhaust fan) is needed to avoid the accumulation of water vapor that can cause mold or unpleasant odors. The family room and living room have a lower correlation to outside humidity, indicating that the design or indoor conditions help maintain humidity stability. To predict indoor humidity based on outside humidity, then the bedroom is the most important factor to consider because it has the greatest influence.