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Environmental comfort and energy use in public school buildings: case study in Campinas, Brazil

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Environmental comfort and energy use in public school buildings: case study in Campinas, Brazil
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  Proceedings of Conference:  Air Conditioning and the Low Carbon Cooling Challenge , Cumberland Lodge, Windsor, UK, 27-29 July 2008. London: Network for Comfort and Energy Use in Buildings, http://nceub.org.uk. Environmental comfort and energy use in public school buildings: case study in Campinas, Brazil Labaki, Lucila C.; Kowaltowski, Doris; Nogueira, Flavia E. A.; Pizarro, Paula R. Department of Architecture and Building School of Civil Engineering, Architecture and Urban Planning University of Campinas, Brazil E-mail: lucila@fec.unicamp.br   Abstract Thermal and luminous comfort considerations are usually neglected when dealing with school environment in Brazil. School buildings are not air-conditioned so that energy economy considerations are seldom taken into account. The design of public schools does not consider aspects of extreme importance in thermal comfort such as high temperatures in the classrooms in most of the year. Furthermore, appropriate illumination levels in the rooms and in the covered courtyards, possible glare conditions, direct sunshine incidence in the students are not considered. This work presents results of the evaluation of three public municipal schools in the city of Campinas, Brazil. The field research consisted of collecting the variables associated with the local thermal and luminous environment in periods covering distinct climatic seasons. Observations were done of design elements that affect the thermal and visual performance, such as orientation, opening areas, façades and external and/or internal shading devices. The methodology also included gathering of information among teachers and administrative staff of the schools about the environmental control of classrooms and the building as a whole. Data about monthly electrical energy consumption were collected. The analyses of the results lead to defining the ranges of the building constructive aspects related to the efficient energetic school consumption and the thermal and luminous comfort. Keywords: environmental comfort,   energy efficiency, school buildings 1. Introduction 1.1 Comfort in the school environment The school environment and the local comfort for users, pupils and staff, can be studied by more than one approach. The appropriate literature encompasses studies of design and of environmental comfort in its various aspects: thermal, illumination, acoustics, functionality, correlation between environment and learning efficiency and physical plant situation and the behavior of users. The performance of school buildings in relation to energy efficiency is also analyzed (Becker et al., 2007 and Erhorn et al, 2007). Post-occupancy evaluations frequently produce useful information (Kowaltowski et al., 2001). Post-occupancy evaluations of school buildings in Brazil have systematically indicated that good comfort conditions were not contemplated in the srcinal projects (Ornstein & Borelli Neto, 1996; Kowaltowski et al., 2001, Ornstein, 2005). It is known that various aspects of comfort are interrelated. Choices associated to one aspect have significant influence on other aspects. For instance, the use of daylighting affects ventilation, due to the necessity of   drawing courtains at certain times of the day to avoid excessive sunshine incidence on pupils or unwanted glare from the blackboard. According to Graça & Kowaltowski (2004), in a school building it is not possible to obtain a maximum comfort quality in all aspects. This led them to propose a method they called multicriterial optimization for the design of schools. Other researchers reached similar conclusions from studies of school buildings in hot climates, independent of region and specific building details. Most schools were considered hot in the summer with insufficient ventilation. This results from inadequate orientation of windows in classrooms as well as insufficient protection elements thus allowing excess sunshine. The paper by Labaki & Bueno-Bartholomei (2001) presents basic recommendations appropriate to the climate of the Southeast region of Brazil that if followed will result in quite adequate thermal comfort. Even when the orientation is inadequate sunshading devices can be installed to avoid direct sunshine on the pupils resulting in better thermal comfort. Post-occupation evaluations of schools in Campinas (Kowaltowski, et al. 2001) have indicated that problems with thermal comfort can be mitigated at a low cost. As for luminous comfort, artificial lighting is very frequently used as a complement to natural lighting and if adequately designed and maintained will solve most of the detected problems. Associated with design details it is important to convey to pupils and teaching staff the importance of an environment consciousness therefore leading to the adequate use of solar protection devices and of artificial lighting. 1.2 Energy efficiency The relevance of properly dealing with environmental comfort factors in school projects on learning and energy saving has been pointed out by Monteiro et al, 1993; Gifford, 1997, Yannas, 1995. In spite of the high sunshine incidence in Brazil artificial lighting is widely employed due to the inadequate use of daylighting. In the subtropical Southeast region where this research was done adequate illumination, winter heating and summer cooling can be achieved through passive conditioning strategies that should as a rule be incorporated in the architectural project. This is important in Brazil where low budgets do not allow the use of heating and cooling systems in public schools. 2. Methodology The study began by choosing typical school buildings in the city of Campinas with its subtropical climate. In each case the building architecture details and environmental comfort parameters were registered. Campinas is situated at 22°54’S latitude and 43°3’W longitude at an altitude of 854 m. The temperatures are higher in January and February with average maximums at respectively 29.9ºC and 29.7ºC. The average lowest temperatures occur in June, 12.5ºC, and in July, 12.4ºC. The South façades receive direct sunshine only in summer during the whole day. The North façades receive abundant solar radiation during most of the year and from March to September for the whole day long. 2.1 Choosing the Samples A survey of technical documentation of all public schools belonging to the municipality of Campinas was made. It was then possible to select a few that are each characteristic of the several groups that were identified. The first criterion was to choose EMEFs, an acronym for Municipal School of Fundamental Education, basically because of age span of the students   (from 11 to 15 years of age), rooms equipped with computers and accessibility to the controls of equipment, basically lighting and ventilation, for staff and students. There are 42 EMEFs in Campinas of which 15 were chosen for detailed study. They were photographed in many details. Existing architecture projects were examined and user opinions were registered. In five schools a more detailed survey was possible by additionally interviewing their principals and part of the teaching staff. Furthermore, thermal and lighting parameters were measured and the energy consumption of the last three years was registered. Openings, façades, materials employed in the pavements, the use of artificial lighting and the presence of vegetation were characterized. The fifteen schools are situated in regions that present different social, cultural and economical characteristics. As was observed, this seems to cause marked differences in attitudes related to the conservation of buildings, the economy of energy and sensibility related to the adequate use of thermal and lighting devices. This work presents results referring to EMEFs Raul Pilla, Lourenço Belocchio and Ângela Cury Zákia, three schools with three different socio-cultural environments. 2.2 Measurements of environment parameters Data collecting in the three schools extended from August to December 2006, a period that encompasses the last month of winter to the beginning of summer. Measurements were taken three times, typically in the morning, at noon and in the afternoon, from 8 am to 5 pm, on week days. Flexibility was necessary not to interfere with ongoing teaching activities. Images were taken from the sunshine angle of incidence on transparent openings, the position of students and solar protection devices both inside and outside the classrooms. Air temperature, globe temperature, relative humidity and air speed were measured, both inside and outside by the classroom. Inside the classrooms the measuring station was placed at the central position of the floor 1.50m above it. The equipment consisted of digital anemometer Testo model 405 V-1, Instrutherm model TH-090 digital thermometers and globe thermometers. The operative temperature was chosen as a parameter for thermal comfort. According to Brazilian standards acceptable values for thermal comfort are 22.5ºC    t o      25.5ºC for 65% relative humidity, and 23.0ºC    t o      26.0ºC for RH 35%, for sedentary activities and 0.5 clo (summer conditions). Since most of measurements were done in warm or hot days, the summer conditions were considered. These values agree with the results obtained by Labaki & Bueno-Bartholomei (2001), in a thermal comfort evaluation of a school building in Campinas, when 25ºC ambient temperatures were considered comfortable. In the present research no meaning differences were found between ambient and operative temperatures. Horizontal illumination at the height of the top of the desks, 0.70m, was determined with a Minolta T-10 illuminance meter. This was performed in 9 internal points shown in Figure1 .    Figure1- Measurement points in classroom The IES recommendations of artificial illumination levels are followed in the Brazilian norm. This was the reference for the studies of visual comfort. The uniformity of illuminance levels and the presence of glare were studied. Therefore the measured values were classified according to Table1. Table1: Illumination criteria Illuminance level (lux) Classification < 150 Insufficient 150 to 250 Adequate 250 to 750 Ideal conditions 750 to 1000 Excessive illuminance > 1000 Possibility of glare  EMEF Raul Pilla This school is situated on the East section of Campinas, in a poor district. The building is frequently vandalized. Some of its young students are in a process of social reintegration and rather difficult to deal with. Students attend classes at four time shifts. The various buildings that form this school are scattered (Figure 2) making it difficult to monitor students out of the classrooms. All classrooms are built according to a pattern due to FDE 1  that positions windows in an upper position on the wall opposite to the main entrance. Two classrooms in the main building referred to as rooms 1 and 2, and two other rooms near the main hall referred to as room 3 and multipurpose room were the places chosen for all measurements. The multipurpose room was supposed to lodge a science laboratory, however, due to lack of teaching space is being used as a classroom. Details of the buildings are given in Table 2. 1  Fundação para o Desenvolvimento da Educação do Estado de São Paulo (Foundation for the Development of Education of the State of São Paulo)    Figure 2: Layout of EMEF Raul Pilla Table 2 - Data referred to EMEF Raul Pila Characteristics Classrrom 01 Classrrom 02 Classrrom 03 Multipurpose room Window-wall ratio 52.5 % 52.5% 58.4 % 21.05 % Wall materials Bricks Bricks Bricks Bricks Roofs Ceramic tiles Ceramic tiles Ceramic tiles Ceramic tiles Orientation of the façade NW SE NW NE Ceiling Concrete slab Concrete slab Concrete slab Concrete slab Floor area 42 m² 42 m² 46.20 m² 82.84 m² Roof edge 1.50 m 1.20 m 2.00 m 1.20 m Curtains Yes Yes No No Area of the façade 24.00 m 24.00 m 23.10 m 34.20 m Ventilators Yes Yes Yes Yes  EMEF Lourenço Bellochio EMEF Lourenço Bellocchio is also situated in a poor neighbourhood from where come most of its students. Students attend classes at two time shifts. The terrain is not leveled. There are nine nearly identical classrooms, that differ only by orientation (Figure 3) .  Measurements were performed in four rooms, two with SE orientation and two with opposite orientation. There is no solar protection in the windows, only the roof edge slightly mitigates the sunshine. The courtyard has roofing. Ceramic tiles cover all floors. Originally the roofs were made of ceramic tiles which later were substituted by metallic sheets. Table 3 contains details of the building.
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