IMPACT ON CONDUCIVENESS OF CLASSROOM : AIR-CONDITIONED VERSUS NATURALLY VENTILATED ENVIRONMENT

Abstract

In Singapore, air conditioning has been extensively used to provide thermal comfort indoors. Therefore, Indoor Air Quality (IAQ) has become a concern for people who spend a large portion of their time indoors, especially that of an air-conditioned environment. Some schools have introduced air-conditioned classrooms to provide a more conducive studying environment. Thus, this study aims to evaluate the benefits and drawbacks of air-conditioned classroom from both objective and subjective perspectives to determine if air-conditioned classrooms are more conducive. Field studies were conducted to collect measurements of IAQ and thermal comfort parameters of the air-conditioned classroom, such as carbon dioxide and carbon monoxide level, Relative Humidity (RH), air velocity, Total Volatile Organic Compounds (TVOC), sound pressure level, and temperature. Students of the school in this study were also surveyed to gain understanding on their perceptions of air-conditioned classroom and to determine the presence of sick building syndrome during lessons. The analysis shows that air-conditioned classrooms are better in many aspects, especially students’ perception and its temperature and relative humidity level, but the high level of carbon dioxide accumulated can be harmful to the students in the long run. Measurement in the air-conditioned classroom presented a high level of carbon dioxide averaging around 1800ppm, over time it even exceeded 2000ppm. This will cause students to feel lethargic during lessons time. The increasing trend of the TVOC in the air-conditioned classroom shows that there is a chance for its build-up to increase to an undesirable level. The naturally ventilated classroom has lower pollutant levels. The only two undesirable parameters is the higher temperature (more than 30°C) and RH level (more than 70%), which are the main determinants of the comfort level in an indoor environment. This study concludes that air-conditioned classrooms can provide a more conducive learning environment, as long as the IAQ parameters (especially the carbon dioxide level) are in control and kept within healthy levels.