Evaluation of strategies that improve the thermal comfort and energy saving of a classroom of an institutional building in a tropical climate

Abstract

The unsatisfactory thermal performance of buildings belonging to higher-education institutions in Brazil causes discomfort in classrooms and affects student performance. It is thus necessary to use mechanical systems that cool environments (e.g., air conditioners) to reduce the indoor air temperature, which increases the energy expenditure of the building by about 50%. This study analyses thermal comfort at the School of Civil and Environmental Engineering, Federal University of Goiás, by making in situ measurements, recording the perceptions of users, and conducting a computer simulation to develop an energy savings plan. The methodology involves: a) analysis of the architectural design; b) field measurements of the summer air temperature and humidity within the classroom and recordings of the views of users in three different situations (i.e., the use of an evaporative cooler with open windows and doors, natural ventilation with open windows and doors, and air conditioning with closed windows and doors); c) data processing in which thermal comfort is evaluated by the indices of the predicted mean vote and operative temperature; d) comparing the collected results and the perceptions of users; and e) evaluating thermal comfort in a computer simulation. We interviewed 200 users. Approximately 69.52% of respondents were dissatisfied with natural ventilation, 60.67% with evaporative cooling, and 70.18% with air conditioning. The neutral temperature was 25.90 °C. Although results show that the situation of the evaporative cooler was the most comfortable during morning, the number of users who felt uncomfortable was high in all situations and did not meet levels recommended by ISO 7730 (2005).