THE INFLUENCE OF AMBIENT LIGHTING ON PUPILS IN CLASSROOMS

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1 THE INFLUENCE OF AMBIENT LIGHTING ON PUPILS IN CLASSROOMS CONSIDERING VISUAL, BIOLOGICAL AND EMOTIONAL ASPECTS -AS WELL AS USE OF ENERGY Govén, Tommy 1) Laike, Thorbjörn 2) Raynham, Peter 3) Sansal, Eren 4) ABSTRACT This poster reports the initial findings of a yearlong study into the impact of the lit environment on school children. The study is based on a group of four classrooms in a primary school with children aged eight to nine years. A total of 56 children divided in four classes took part in the study which was carried out during the school year 2008/2009. All the children attended the same educational program in the junior school. Two classrooms served as controls and two classrooms had enhanced lighting. Initial results have been analyzed and the paper presents findings in terms of energy consumption, biological* and psychological parameters and measures of academic performance. *the biological data are under analysis and will be added. 1. INTRODUCTION The school is the workplace for both children and teachers. Lately there has been a discussion about the environment in the school. Signals that children under-perform, behave in a bad manner and are tired are now being recognized. One part of the environment is the physical environment and several studies show that physical environmental factors may have an impact on the abovementioned factors. Lighting conditions is considered as an important part in the physical environment. This report covers the findings of our study from October 2008 till March The study is ongoing and full results will be published in due course. 2. BACKGROUND Correlations may exist between the physical parameters of light and the diverse biological and psycho-physiological effects. Both the intensity, spectral composition, spatial and temporal distribution of the lighting, may be of relevance. A major step was taken when in a study on rat, showed that neither rods nor cones were needed to modulate the circadian pacemaker; instead retinal ganglion cells with the photo pigment called melanopsin innervating the SCN were intrinsically photosensitive. During the last three years several convincing studies have shown that the human circadian rhythms are affected by these retinal ganglion cells also today mentioned as the third receptors. Due to the fact that more elaborated knowledge about the details of the circadian photoreceptors were established, the research on how specific wavelengths within the light spectrum affected the physiological responses rapidly grew. It has been shown that certain wavelengths have peak melatonin suppression on humans. 3. AIMS OF THE STUDY One aim of the study was to explore in what way the ambient light may have an impact on the children s emotional status, achievement and well-being described both subjectively and physiologically considering both daylight and artificial light. A second aim was to investigate the behavior in use of controls. A third aim was to investigate in which way different lighting control systems affect the use of energy in classrooms. The presentations of results are divided into different parts according to elements of the VBE-model which takes visual, biological and emotional aspects into consideration. 1

2 4. SUBJECTS A total of 56 children aged 8-9 years of age divided in four classes took part in the study. All the children attended the same educational program in the junior school. The achievements between the four classes were even regarding the grades from the previous year. They were allocated to their classrooms at the beginning of the semester by the school authority? Distribution of the children in the four classrooms Gender C1 E1 C2 E2 Total Boys Girls Total DESIGN OF THE STUDY Pickhurst Junior School. The experimental classrooms to the left, the control rooms to the right. The study was carried out in a junior school located in the south of London. For ethical reasons the only children taking part in the study were those whose parents provided positive consent. About 50 % of the children in the school year took part in the study. Four classrooms of the same size were investigated. Two experimental classrooms (E1 & E2) were equipped with a new lighting design based on an increased horizontal and ambient light in relation to two control classrooms. The two control classrooms (C1 & C2) were equipped with an existing lighting system based on general lighting. E1 & C1 were situated on ground floor with daylight penetration from one side, south. E2 & C2 were situated on the 1st floor with daylight penetration from two sides, north and south. Blinds installed on south facing windows. In order to have the same light emission in all classrooms, the luminaries in the control classrooms were changed to new luminaires equipped with high frequency ballasts. In the four classrooms the luminaries were equipped with the same type of tri-phosphor fluorescent tubes with a colour temperature of 4000 K and a Ra of STATISTICS The initial treatments of the data were carried out by one-way analysis of variance with posthoc analysis. Also t-tests were applied for some analyses. The further treatment of data was carried out mainly by means of analysis of variance with a repeated measures design. 2

3 This is a factorial design involving the following four independent factors; 1. General lighting vs. increased general lighting and increased ambient lighting. 2. Daylight penetration in one direction vs. daylight penetration I two directions. 3. Increased ambient lighting vs. increased ambient lighting at a higher amount at certain times of the day (algorithmisch scene-setting). 4. The periods of the school year (four times). The independent factors, a) to c), were tested between subjects as well as their interaction, while factor d) was tested within subjects. In most analyses, data were grouped in six blocks corresponding to the six measurement occasions during the school year. SPSS 15.0 statistical package was used for the analyses. 7. DAYLIGHT AVAILABILITY Daylight factor, DF Daylight factor DF, blinds Daylight factor with blinds closed on south facing windows. There is significantly more daylight available in the top floor classroom (C2 & E2) as they have windows on both sides of the room and they are less shaded by the trees outside. Moreover, the north facing windows in the top floor rooms do not have blinds fitted and so when the daylight factor in the rooms never drops very low. 8. LIGHTING SYSTEMS Control room Experimental room 3

4 Tommy Govén, The influence of ambient lighting on pupils in classrooms Surface mounted lighting system with direct light distribution in the control classrooms. Lighting system with a combination of direct/indirect light distribution in the experimental rooms. Illuminance values in the classrooms. Eh, Average horizontal illuminance on working plane (lux) Ev Average vertical illuminance (lux) Ec Average ceiling illuminance (lux) Eve Vertical illuminance at eye (lux) The experimental classrooms (E1 & E2) had a general lighting system adjusted to an illuminance level at working plane of approximately 500 lux. Luminaires for general lighting were suspended from the ceiling and had a direct/indirect light distribution. Additional wall-washers were installed to achieve an increased ambient light level on the walls. Furthermore E1 & E2 were equipped with an absence detection and daylight control 4 system. In one of the experimental rooms (E2) an algorithmic scene-setting system was installed in order to achieve an increased illuminance during the first lesson in the morning and the first lesson after lunch each school day for the whole school year. The both control classrooms had a general lighting system with an illuminance level at working plane of approximately 300 lux without any additional wall-washers. All luminaires were ceiling mounted. The control classrooms were both manually controlled.

5 9. RESULT Energy measurements In order to measure the energy consumption, presence, use of daylight and the use of controls a data-logger were installed at the school. All the parameters were continuously measured over the whole school year. Rooms C1 and C2 have manually controlled lighting and thus it is the preferences of the teachers that determine if the lighting is switched on or off. In room C1 the energy consumed for the week was 13.7 kwh and in C2 it was 9.5 kwh. It is assumed the difference is explained by the greater daylight availability in C2 allowing the teacher to turn off the lights more often. 5

6 In room E1 the benefits of the automatic control system are seen with an energy use of only 10.7 kwh for the week. Whilst E1 has the same amount of daylight as room C1 the automatic dimming system ensures that this is fully exploited to reduce the power of the lighting, also the absence detection system ensures that the lighting is not on when the room is empty. Weekly use of energy (kwh) Given that the lighting system in room E1 can deliver almost twice the light of the one in C1 this is a remarkable result. The use of energy lighting is in average approximately 20% higher during the dark period versus the brighter period of the year. Use of energy C1 E1 C2 E2 Typical week commencing November/December Typical week commencing March/April Academic performance All of the academic performance test scores like reading, writing and math, showed a steady progress between the tests. However, there appears to have been a slightly higher rate of improvement in the experimental classes. Typical of these results are the reading tests of which are shown in below. The progress in academic performance in reading -, writing and math grades between the control room C1 and experimental room E1 are shown in graphs below. 6

7 Graphs on academic performance Mood Cortisol The analysis of the monthly trend of the overall mood at 09:50 revealed a significant difference between the classes on the ground floor and those on the 1st floor. The analysis of the monthly trend of the cortisol levels at 09:50 revealed a significant interaction between different months and the two floors. On the ground floor the analysis of the monthly trend of the overall mood at 09:50 revealed a significant difference between control room (C1) and the experimental room (E1) on the ground floor. On the ground floor the analysis revealed a tendency that the pupils in the experimental room (E1) showed higher levels of cortisol over the whole school year than in the control room. 7

8 On the first floor the analysis of the monthly trend of the overall mood at 09:50 revealed a minor difference between the control room and the experimental room. On the first floor there was a significant interaction between classrooms revealing that children in the experimental room (E2) showed higher levels of cortisol, especially during the darkest period than in the control room (C2). 10. DISCUSSION It should be stressed that the findings presented in this paper are interim in nature and further results of analyses of the data will be published as they become available. However there are certain key trends that have already been spotted in the data. There seem to be a general trend that there are differences between the experimental rooms and the control rooms. Improved ambient lighting may have an impact on both the progress in academic performance and on the children s mood. The improved ambient lighting showed a positive impact on the children s mood at 09:50 in the morning. The cortisol levels are also higher in the rooms with improved ambient lighting, both on the ground floor and on the first floor. Furthermore, in three of the four rooms we also found an increase of cortisol in February, which also have been shown in earlier studies. All together we have now found several indicators pointing in the same direction, namely the improved ambient light affect individuals cognitive, emotional and biological. The study also shows that the use of lighting controls has a major impact on use of energy without harming the quality of light in classrooms. Further analyses of visual aspects will be published. 1) Fagerhult, Lighting Technology Dept, Stockholm, Sweden, tommy.goven@fagerhult.se 2) Lund University, Faculty of Engineering, Lund, Sweden, thorbjorn.laike@arkitektur.lth.se 3) University College London, The Bartlett School of Graduate Studies, London, UK, p.raynham@ucl.ac.uk 4) University College London, The Bartlett School of Graduate Studies, London, UK, k.sansal@ucl.ac.uk Author Tommy Govén AB Fagerhult Lighting Technology Manager Tegelviksgatan 32 SE Stockholm, Sweden Phone Direct Mobile Fax tommy.goven@fagerhult.se 8