Secondary school classrooms daylighting evaluation in Negeri Sembilan, Malaysia

Natural daylight is a renewable energy source that is important in photobiology study which looks into the effect of light to living organism. Students’ visual comfort satisfaction due to efficient daylight in a classroom are highlighted in the physical of the building and learning space such as windows and openings. One of the factor that influences the design of classrooms environmental condition. Environmental condition consideration includes the daylighting requirement for classrooms. Various standards and guidelines on daylighting consideration have been developed in Malaysia including the recommendation on Window-to-Floor Ratio (WFR) and illuminance level. However, the recommended WFR may not achieve the recommended illuminance level. This paper evaluates whether the recommended WFR design achieve the recommended acceptable illuminance level. Two classrooms in Kolej Permata Insan, Nilai, Negeri Sembilan with different orientation were selected for the study. Integrated Environmental Solution (IESVE) simulation software is used for daylight evaluation. The WFR of the two selected classrooms were set to the recommended 20%. Simulation results shows that the illuminance level for both classrooms are higher than recommended. The simulation also shows that the daylight distribution in the classrooms are not uniform, thus creating inefficient daylight condition. Therefore, the WFR recommends further studies with additional of daylighting design strategy considerations.


Introduction
Learning spaces design has evolved throughout the years due to various reasons such as construction technology, educational systems, government's policies, space requirement and environment condition. Throughout the classroom design development, a concept of 'open-air design' was popularized. This concept shifted the focus of classroom design towards daylighting considerations because the concept allows too much daylight amount in the classroom that causes visual discomfort to the students [1]. Various research proven that sufficient daylight in a classroom is required due to its positive effect towards the students including improvements on learning performance, alertness, cognitive skills, behavior, mood, circadian rhythm, dental strength and productivity [2,3,4]. Thus, various standards and guidelines were introduced all around the world.  Malaysian Standard 1525 (MS1525) highlighted the recommended illuminance level for learning spaces, while Uniform Building by Law (UBBL) recommends the Window-to-Floor Ratio (WFR) for learning spaces. An interview with JKR personnel shows that the classroom design standards and guidelines still follows a standard introduced by British colonial government before Malaysia's independence [5] and may not suited to the recommended illuminance level that is currently being referred to by architects and designers. Therefore, this study will focus on the evaluation of daylighting performance in an existing classrooms of a public school in Malaysia. By identifying the daylighting performance of these classrooms via simulation software, it can show whether the recommended WFR can achieve the recommended illuminance level.

Literature Review
Efficient daylighting can improve students' optimal education performance such as visual comfort, subjective mood, cognitive performance, physical activities, sleep quality, attention and alertness in classroom [6,7]. Furthermore, visual discomfort causes inefficiency in executing learning tasks, thus decreases the students' performance [8]. However, providing more daylight illumination level does not increase the visual acuity, but creates glare and visual discomfort as well [9]. Learning space that receive high daylight intensity with low glare, added with high quality artificial light source improves the visual comfort, which improves the learning space environment [10]. Proven that students learn to read 26% faster in a classroom with efficient daylight [11]..
The importance of daylight in classrooms are highlighted in various standards and guidelines. Illuminating Engineering Society of North America (IESNA) recommended 300 lux to 500 lux of illuminance level for learning tasks [12]. Others such as Malaysian Standard 1525 (MS1525), Public Works Department (JKR) and ZUMTOBEL Handbook recommends the same illuminance level of 300 lux to 500 lux for common reading task in general teaching spaces [13,14]. Table I below shows the illuminance level recommended by few standards and guidelines. It Most of the recommendations are between 300 lux to 500 lux. Therefore, the recommended 300 lux to 500 lux will be the reference for the study. Uniform Building by Law (UBBL) 2013, Section 39(3) stated that any room or space that serve the purpose of learning and education space should be designed with a minimum of 20% of Wall-to-Floor Ratio (WFR) for natural lighting and natural ventilation. Not less than 10% openings the WFR should be open-able for uninterrupted natural airflow [15]. A research shows that a public school in Ipoh, Perak that follows JKR design standards received recommended illuminance level [5]. Therefore recommendation of 20% WFR will be referred for this study.

Methodology
Measuring the illuminance level in an existing classroom requires the use of data loggers. Biesel (1953) introduced a method to measure illuminance level by considering the average, maximum and minimum illumination level of the space. These considerations are sufficient in measuring the illumination level [1], which is applicable for learning spaces such as classrooms. Measuring illuminance level at task level by luminance spot measurement on grid of 1m x 1m in the classroom [16,17] was simulated to identify the uniformity of the daylight distribution during Malaysia intermediate sky condition [5].        Figure 3 shows the wall elevations for Zone B and Zone C respectively. Both side of the windows are facing the outdoor and the corridor respectively. No external shading device and internal blinds were installed. Glass windows on both side are positioned 900mm height from floor level and not glazed. The existing Wall-to-Floor Ratio (WFR) are between 14.5% to 15.5%, lower than recommended. However, the windows for simulation will be set at 20% of WFR recommended to test the illuminance level and daylight performance. Integration Environment Solution Virtual Environment (IESVE) is a software that is used in the study. The function Radiance in IESVe is a raytracing software to estimate daylight accurately. Figure 4 below shows the result of the simulations based on recommended 20% WFR. The results show that both classrooms received average illuminance level higher than recommended, thus an inefficient daylighting. The highest illuminance level of 1413 lux and 1246 lux respectively occurs within 2m from both side of Zone B and Zone C windows. A few scattered point measurement shows recommended range of illuminance level, mainly 2m away from the windows. This shows that the daylight quality are not uniformly distributed.

Conclusion
The result of the simulations shows that independent from the orientation of the classroom, both received illuminance level higher than recommended by MS1525 of 300 lux to 500 lux, even though the WFR used were 20% as recommended by UBBL. Therefore, the recommended WFR should be furthered study to identify the suitable range so that the recommended illuminance level can be achieved. To achieve the recommended illuminance level in schools, architects and designers shall provide different designs due to the aspect of daylighting performance and the physical of the classroom such as the layout, orientation, and size of the opening.