VISUAL AND THERMAL COMFORT EVALUATION OF SCHOOL CLASSROOMS FOR FENESTRATION DESIGN

Abstract

The schools are first place where children begin their formal education and develop their skills through learning in classrooms. The overall environment of classrooms affects comfort level of children, which further has an impact on their learning, performance and other activities. The environment of classrooms is mainly of two types i.e. first is physical environment (includes classrooms design – size and shape, layout, opening, visual and thermal conditions) and second is psychological environment (mainly depends upon internal issues, stresses, learning skills and interest of the students). The natural light and thermal comfort in classrooms play an important role in affecting the psychology or behavior of the students. The increase in temperature, improper daylight and low ventilation rate not only has a negative impact on the student’s performance but also affect their physical health and concentration (Bako-Biro, 2012; Healey, 2012; Gado, 2009). The large variations in temperature and other parameters in composite climate of India has challenges in maintaining the comfort level, which needs to be addressed properly while designing the building envelope components like fenestrations (Almas, 2011). This research is an attempt to assess the role of fenestrations design in naturally ventilated school classrooms and evaluate the visual and thermal comfort in them using a survey cum case study research method. The case studies for field survey were conducted in Roorkee region located in composite climate zone of India. The data through manually operated instruments and responses from students were collected, processed and analyzed for the interpretation of actual classroom conditions. An evaluation method was proposed to assess the visual and thermal comfort in classroom spaces using validated simulation on fenestration design iterations. This thesis concludes with development of design guidelines for fenestrations in classrooms with reference to visual and thermal comfort. Literature was extensively reviewed through different databases in the domain of school building design aspects in relation to the indoor environment of classrooms. The Indian education system has need of more than two lakhs of school with good infrastructure due to increasing demand of new schools to meet the population figure of children in the age group of 0-14 years. India has second highest population in the world with literacy rate of around 73% in 2011 and as per 12th five-year plan (2012-2017) and the aim is to reach nearly 100 % by 2020 (IBEF, 2017; Technopak, 2012). The gaps and challenges were identified for designing buildings in Indian climatic conditions, specifically for composite climate (Ali, 1993; Krishan, 1999; Attri, 2010). The comfort level in classrooms is highly affected by the variations in climatic conditions. The current condition of schools in composite climate needs to be evaluated for different seasons. The perspectives of school building design and their classroom spaces were described in respect ii of various design determinants of building envelope and fenestration design (Srivastava, 1991; Garg, 1991). The academic performance of children has a direct linkage with visual and thermal comfort conditions of classrooms (Heschong, 2002; Higgins, 2005; Choyimanikandiyil, 2013). Students in naturally ventilated school classrooms have to adapt for a wide range of diurnal and annual variations (Edwards, 2002; Brager, 2004; Baruah, 2014; De Giuli, 2014). The impacts and role of these determinants were found important in affecting visual and thermal comfort for indoor spaces in buildings (Singh, 2010; Indraganti, 2010; Oral, 2004; Thomas, 2002). The majority of researches were conducted on visual and thermal comfort assessments with reference to the office or commercial buildings. Therefore, a huge gap and scope of work was identified to assess the comfort and design conditions of school buildings in India (Choyimanikandiyil, 2013). The major national standards and IS codes as well as international standards and ISO codes were reviewed with reference to the design requirements in school classrooms (BIS NBC, 2005, BIS SP41, 1995; BIA, 2007; IS 10894, 2005; ES ISO, 15099, 2012). However, very limited information was found for fenestration design requirement in classroom spaces to achieve the optimum comfort level. Therefore, the evaluation tools and techniques were reviewed from the previously published researches, current standards and ISO codes for design and measurement to assess the existing conditions of school classrooms in India (Khan, 2012; Haddad, 2012; ISO 7730, 2005; CBRI, 1978). Inferences from the review have helped in the development of a methodological structure to assess the visual and thermal comfort in classroom spaces. This study seeks to assess the visual and thermal comfort in classroom spaces while considering the impact and role of fenestration design. A survey cum case study based methodology was adopted to conduct this work in Roorkee (study area) which lies in a composite climate zone of India. It was selected considering its proximity to collect and observe the data during the different months. The months from May to January were identified as critical period for survey. For interpretive case studies, eight schools were selected in the study area to understand the classrooms design and their visual and thermal conditions. Therefore, interpretive case studies with background knowledge from literature had helped in developing a methodological structure for data collection from the final four evaluative case study of schools in study area. The evaluative case studies were selected based on stratified random sampling considering proximity for data collections and covering all types of classrooms and school designs. iii Data collection tools and methods were examined through pilot survey on four classrooms of a school. The visual and thermal comfort parameters were observed by considering the protocols of design standards. The daylight and thermal comfort data was observed by using manually operated data loggers in classrooms (like Digital Luxmeter for daylight illumination, Thermo-Hygrometer for temperature and relative humidity, and Anemometer for air speed). Daylight readings in units of lux were observed in a 3 x 3 grid (from nine locations) at a height of 0.75 m and other parameters (temperature, relative humidity and air speed) for thermal comfort were observed at center location at height of 1.1m. Thermal comfort was calculated by using Tropical Summer Index (TSI) for its assessment in classrooms. A sample of 53 classrooms were selected from four schools for final data collection. The selection of the sample classrooms was done by using the stratified random sampling process to cover all variations in design typologies. Survey schedule was prepared to collect data from each sample classroom during every month from May to January. The data was collected from sample classrooms and processed for the analysis of daylight and thermal comfort variations in them. A total of 28 sample classrooms were selected for students’ feedbacks by using questionnaire (i.e. from ninth and above classes having age group of 13 to18 years). The response for daylight quality, thermal sensation and thermal preference from the students with their seating locations were recorded. A 5-point scale was used by modifying ASHRAE 7-point scale and Nicol Scale for taking feedbacks (Haddad, 2012). The student’s responses were analyzed to compare and validate the daylight and thermal comfort data, which were measured at the same time for each classroom. The format for data processing of daylight measurements was developed to present nine observations of all classrooms. This also enabled a basic assessment of Glare index calculated through identification of maximum and minimum illumination ratio in classrooms (Szokolay, 2002). Similarly, the responses from the students from each classroom were tabulated. The subjective response for daylight and thermal comfort was tabulated with the measured data recorded at the same time. A data process format was developed for detailed analysis and interpretations. All sample classrooms in each school were categorized into groups based on their fenestration opening orientation. The time-index graphs for daylight and TSI values were plotted to analyze variations in them. Some pattern in variation of daylight and TSI were identified for each category of fenestration orientation. This reveals the impact and role of different orientation on daylight and thermal comfort in classrooms. Similarly, the variations due to floor level were also noticed for TSI value as well as on daylight levels. Further, students’ responses were analyzed in comparison to measured data for validation of visual and thermal comfort in iv classrooms. The corroboration was found with moderate relationship of students’ response with measured daylight illumination as well as with TSI. This assessment was made for the overall perception of students for daylight and thermal comfort in classrooms. Further, classrooms were categorized based on their visual and thermal comfort performance to identify the critical cases where extremely low level of daylight and uncomfortable thermal conditions were found. The measured data from the field survey limits the fenestration design recommendation due to limited / insufficient variations of fenestration design in sample classrooms. Therefore, Design Builder as a simulation tool was employed to conduct the design evaluation of fenestration designs in classrooms through simulation analysis. The simulation models for all four schools were developed and validated using field based measured data. However, most of the sample classrooms in all schools were designed in required size limits except few sample classrooms. Hence, a base case model of classrooms (size 7m x 7m) was developed for simulation. The iterations for fenestration design were developed based on their determinants (like window wall ratio (WWR), opening area, window’s height and width, sill height and number of opening). These iterations grouped into four categories based on WWR (i.e. 30%, 40%, 50% and 60%) and run for four major opening orientations (i.e. north, south, east and west facing) in the base case. The results from the simulation of design iterations of the base case were compared within respective orientations and best design option(s) were identified for each orientation. Further, these best design options were validated for implementations by using it on some of the critical sample classrooms through simulation. The fenestration design guidelines were proposed for different opening orientations with suitable design recommendations.