Análise da disponibilidade de iluminação natural e artificial em salas de aula de instituição pública de ensino superior

Abstract

The classrooms are the more permanent environments at schools; therefore their thermal, visual and acoustic characteristics must be carefully considered. Visual comfort can be achieved only with daylighting; artificial lighting is necessary when the daylighting is insufficient. The artificial lighting is responsible for high energy consumption in buildings. According to Klüsener (2009), who analysed a building of UFSM in accordance with Brazilian energy efficiency standards (RTQ-C), the artificial lighting systems reached the level E (on a A-E scale). In general, simple actions could be improving the energy efficiency of the building lighting system. Considering that the university buildings have a similar performance, the adaptation of lighting systems is important for low-energy consumption. This study aims to define classrooms guidelines for visual comfort in accordance with illuminance levels available and their distribution on the work surface where tasks are performed, as well as the energy efficiency of the classrooms lighting systems. The classrooms were selected to represent the existing universe buildings. The classrooms were characterized with regard to dimensions, surface light reflections, opening systems, solar orientation, sun shading systems, external obstructions and artificial electrical lighting systems. The illuminance levels were measured in two classrooms simultaneously with Instrutherm luximeters, model LDR 225. The measurements were in accordance with the Brazilian standards (NBR 15215) and were carried out at six points on an orthogonal grid. A comparative analysis was made for the classrooms that were simultaneously measured. Additionally the partial RTQ-C lighting criteria were applied on the classrooms lighting systems and the theoretical external illuminance levels were calculated in order to generate the daylight factor (DF). The results pointed that the internal daylight distribution is affected by external obstructions that reduce the portion of visible sky and these are not considered in the windows design. For simultaneous daylighting and artificial lighting, the illuminance levels are excessive and poorly distributed; consequently they cause high energy consumption. The existence of unnecessary sun shading systems, for southern solar orientations and for windows with complete sky obstructions, contributes for the insufficient classrooms illuminance levels. The RTQ-C criteria analysis point levels E and C for the classrooms. In general, the DF do not correspond to expected values indicated by international recommendations.