Abstract: Optimal classroom acoustics enhance students' engagement and learning efficiency. In warm-humid climate, ceiling fans are used at different speeds to enhance thermal comfort in naturally ventilated classrooms. Although ceiling fans enhance thermal comfort, using fans at higher speeds significantly increases Background Noise (BGN), interfering with acoustic comfort. To achieve an optimal acoustic environment, it is important to understand the effect of BGN on acoustic comfort. Hence, focusing on ceiling fan noise in classrooms, this study investigates the effect of acoustic environment and students' noise sensitivity on acoustic comfort, productivity, and engagement. A four-month-long field study was conducted in 11 naturally ventilated classrooms, obtaining 828 responses. Sound pressure levels in active classrooms were measured to calculate BGN and Signal-to-noise ratio (SNR). Reverberation time (RT) was measured both in students' presence and absence. Acoustic comfort conditions, productivity, and engagement of students at every seat were obtained through questionnaire survey. BGN levels and RT ranged from 58.2 to 65.3 dBA and 0.7–2.1 s, respectively. A positive correlation was found between acoustic comfort and engagement level and productivity. Regression analysis showed that students with high noise sensitivity reported acoustic discomfort when the BGN exceeded 62.4 dBA, RT was above 1.7 s and SNR was below 3.7 dBA. Chi-square test involving the acceptability vote indicated that students were more likely to accept the BGN ≤61 dBA, RT ≤ 0.7 s, and SNR ≥6.5 dBA. This study establishes the relation of BGN, RT, and SNR with acoustic comfort in naturally ventilated classrooms, offering insights for classroom acoustic environment enhancement.

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Abstract: Research on thermal comfort has revealed various adaptive behaviours in a hostel room, such as changing clothing, use of windows, doors, and ceiling fans. Hostel rooms are used for various activities and are typically furnished with a wardrobe, bed, study table, and chair. Recent studies indicate that ceiling fan fixed at the centre of the room may not provide adequate air velocity for different activities occurring in different parts of a room. Although students generally arrange furniture based on their preferences and room geometry, the influence of fan-induced air on furniture layout to improve thermal comfort is yet to be established. In this context, this study investigates spatial adaptation and identifies the factors affecting furniture layout preferences in hostel rooms. In a yearlong study, patterns of furniture layout were observed in twenty-one naturally ventilated hostel buildings to find their relationship with environmental and non-environmental factors. A total of 1665 observation data was collected from single, double, and triple occupancy rooms. Influence of various factors on arranging the furniture was identified through a questionnaire survey. Throughout the survey, outdoor temperature varied between 23 and 41 °C and outdoor relative humidity varied between 32.3 % and 97.5 %. The spatial arrangement of furniture was evaluated against fan location. Results indicate that fan location and indoor temperature significantly influence the furniture arrangement. A logistic regression equation was developed to evaluate the trigger temperature when students began moving furniture towards ceiling fan. In a single occupancy room, above 34.2 °C, the probability of moving the bed towards the fan was found to be maximum. In single and double occupancy rooms, students move the bed near the ceiling fan predominantly during night-time to get sufficient air movement. A cautious design of furniture layout and adding a personalised fan for various activities may improve the thermal comfort in hostel rooms.

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Abstract: This study investigates how fan-induced non-uniform air movement affects thermal comfort conditions and productivity at different seats in different parts of a lecture hall. A four-month-long field study was conducted, involving 11 naturally ventilated lecture halls, 828 samples from the students, monitoring thermal environments, and measuring air movement at every seat. Thermal comfort conditions and productivity at every seat were obtained through questionnaire survey. During the study, outdoor temperature varied between 24.7 °C and 36.7 °C. From ANCOVA and cluster analysis, it was found that students seated farther from the fan experience less air velocity, resulting in a significant difference in comfort conditions and productivity. The thermal sensation of the students was found to be comparatively less in Zone-1 (Mean = 0.2, SE = 0.06) than Zone-2 (Mean = 0.53, SE = 0.05). In the zone near the fan, 8.1% of students voted hot sensation at 33°C–34 °C, whereas in the zone far from the fan, this number increased to 35.9%. The slope of the regression line plotted between thermal sensation and indoor operative temperature was found to be 0.368/°C. Regression analysis revealed that thermal comfort could be achieved up to 33.8 °C with an air velocity of 1.2 m/s. The acceptable temperature limit for 80% of students was between 23.4 °C and 29.7 °C. A narrower comfort band was observed compared to ASHRAE-55 and the Indian standard, indicating limited adaptive opportunities in lecture halls. An adaptive comfort model is proposed that includes the effect of air velocity.

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Abstract: A window is an inevitable element of a naturally ventilated building, and its usage improves indoor environmental conditions. Various research has presented window opening behavior models, stating that it may vary with region, climate, season, building type and many more environmental and non-environmental factors. Major studies in India relied on survey data and were not focused on continuous monitoring. Limited occupants’ behavior studies have been reported in warm and humid climatic zones, specifically in hostel buildings. Also, a realistic description of occupants’ window opening behavior is require for more accurate evaluation of building performance using energy simulation. Therefore, there is a need to study the window opening behavior to predict the indoor environment more accurately by using energy simulation tools. In this context, a one-year field research involving questionnaire survey, physical observation, and monitoring was conducted in different hostel buildings in Tiruchirappalli, India. Logistic models were developed to predict the window state in hostel buildings in warm and humid region based on physical observational and long-term monitoring data. It is found that window use is influenced by season, time of the day, weekdays, floor level, buildings’ orientation, user type, and gender. Results also showed that insects and animal menace (snakes, squirrels, lizards, mosquitoes etc.) impede window opening behavior. The study also presented a logistic model for window opening behavior based on outdoor environment conditions for simulation modeling.

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Abstract: Thermal comfort is an important factor in hostel buildings when the aim is to maximize the productivity of the students. Due to the extreme weather conditions, achieving thermal comfort in a hostel building in a hot and humid climate is even more difficult. Studies conducted in naturally ventilated hostel buildings in warm-humid climates involved the influence of outdoor air temperature only up to 34.4°C and have been conducted in a specific season. In contrast, the Tiruchirappalli climate is characterized by a higher range of environmental variables. Therefore, to understand the thermal comfort conditions and usage of the environmental controls in naturally ventilated hostel buildings at the higher range of the environmental variables, a thermal comfort field study spread over one year was carried out at the National Institute of Technology, Tiruchirappalli, India, in twenty-seven hostel buildings. This study relies on field observation and thermal comfort responses from 2028 questionnaires collected from the students between September 2019 to August 2020. The analysis revealed a neutral temperature of 29.5°C and a comfort range from 26.1°C to 32.8°C, indicating a wide range of thermal adaptation than suggested by the National Building Code of India and ASHRAE standard 55. The preferred temperature was 27.8°C, indicating that students preferred a cooler environment. Acceptability with sweating conditions extended the upper limit of thermal acceptability from 31.8°C to 32.4°C. The use of a mosquito net can increase the probability of opening a window. Results indicated that overall behavioral adjustment could extend the comfort limits. The study results would be helpful to develop guidelines and designs for naturally ventilated hostel buildings in warm and humid climates that will contribute to reducing energy demand.

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Abstract: In India, the gross electricity consumption of residential buildings has been increasing at a fast pace. This is mainly due to the increasing use of air-conditioning units in homes to achieve a thermally comfortable environment. Thermal comfort in a warm and humid climate is mainly associated with increased air velocity through natural ventilation. Natural ventilation can be implemented to reduce discomfort hours, which leads to less energy consumption. The objective of this study is to investigate the potential for natural ventilation on different floors, months, and times of the day. To this end, a low-rise residential building constructed in India's 'warm and humid climate has been selected for the investigation. Indoor thermal parameters of two living spaces were logged from July 2019 to June 2020 to evaluate the comfort hours on different floors. Further, an energy simulation model was developed and validated by monitored data, and a thermal simulation was done to evaluate the effect of different window opening scenarios. The effect of different scenarios was evaluated based on the Indian adaptive thermal comfort model. Results showed the potential of ~19.2% increase in comfort hours on top floors and ~32.4% on ground floors during the summer month by natural ventilation.

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Abstract: Architects are encouraged to follow rating methods and codes to design energy-efficient buildings. However, to work with these codes, additional skills are required, and codes offer a variety of design options rather than thumb rules. In India, climate design guidelines for hot and dry region recommend north-south orientation for building and no windows on west façade to reduce solar heat gain, whereas plots with longer west side require windows on west façade for daylight, air and view. Therefore, it is important to find out optimum window to wall ratio (WWR) that can provide adequate daylight as well as low energy consumption. This paper attempt to analyse WWR with respect to room depth, lighting power density (LPD) and glazing material to arrive at a simple thumb rule for architects. The study is performed via Ladybug and Honeybee tools which depends on Radiance and Openstudio for simulation, considering essential factors of daylight and energy, i.e., useful daylight illuminance (UDI), heating, cooling, and lighting load. Results showed that at 5 W/m2 LPD, 20-25% WWR gives the minimum energy consumption as well as adequate daylight till 9m room depth. Further studies are required to explore the effect of WWR for different climate and orientation.

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Abstract: The windows have a great influence on daylighting in the interior of the building and are considered as an important element for energy-efficient buildings. The size of the opening area, its orientation, and shading device affect the inside illumination. This study assesses the relation between heating, cooling, and daylighting and provides solutions for opening in an office building. The study focuses on the effect of changing Window Wall Ratio (WWR), sill level, window height, number of windows, glazing materials, and shading device on daylight in the built environment. The consequences of the two objectives, i.e., daylight and energy consumption are contradictory in terms of openings. Therefore, optimizing the window area is essential in low-energy buildings. Optimization has been done for the south facade by computer-generated models and simulations. This study covers the essential factors of daylight and energy, i.e., daylight autonomy, useful daylight illuminance, daylight uniformity, total load, and optimization of fenestration design.

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