Author: Sze, Chun-keung
Title: Indoor environment control in primary and secondary schools in Hong Kong
Degree: M.Sc.
Year: 2002
Subject: Hong Kong Polytechnic University -- Dissertations
School environment -- China -- Hong Kong
Classroom environment -- China -- Hong Kong -- Evaluation
Department: Multi-disciplinary Studies
Department of Building Services Engineering
Pages: xiii, 134, [56] leaves : ill. ; 30 cm
Language: English
Abstract: Up to the academic year 1999/2000, there were 480 secondary schools and 819 primary schools in Hong Kong providing the venue for education of 945,000 students. The indoor environment of classrooms has been a concern for many years and improvement work is being made to provide a better study environment by the government, through the Noise Abatement Schema or efforts of the schools themselves to install air-conditioning systems for thermal comfort and noise control. The building layout and the building services provisions for most classrooms are standardized. For those existing classrooms entitled for air-conditioning, they are typically equipped with window type air-conditioners and propeller ventilation fans. The classroom indoor environment, however may still not be comfortable and healthy. New classrooms will be installed with split-type air-conditioners and fresh air pre-conditioners to increase the cooling capacity and fresh airflow rate according to the new design standard of the Architectural Services Department, leading to increased energy consumption and installation cost. Therefore, the objectives of this study were to investigate the actual indoor environment in existing classrooms and the performance of MVAC equipment, and to explore ways of reducing MVAC energy consumption. On-site indoor environmental measurements were performed in the classrooms of two schools. The results indicate that even in cases where air-conditioning was provided to maintain thermal comfort in summer, the measured indoor relative humidity was higher than the comfort level due to the limited dehumidification performance of window type air-conditioners. The ventilation rates maintained in those classrooms by the window mounted propeller fans were insufficient for maintaining an acceptable carbon dioxide concentration. The recorded values from a sample classroom were over l000ppm during the air-conditioning period with full occupation density. Besides, the recorded indoor suspended respirable particle concentration was close to the outdoor value due to the poor filtering efficiency of the air-conditioners. As a result, instead of improving the indoor air quality, the air quality was degraded when air-conditioners were run. The quality of the visual environment in the classrooms was found to be acceptable based on the measured illuminance data. Closing windows with air-conditioners operating could reduce the indoor noise level in one sample classroom but the measured indoor noise level in the other classroom was higher than the outdoor noise level due to the noisy and aged air-conditioners. Results of energy simulations demonstrate that classroom air-conditioning provision would be capable of handling the sensible load but not the latent load. The indoor air temperature and relative humidity of a classroom could be up to 34oC and 95% without providing air-conditioning according to the simulation predictions. Using tinted glazing could reduce MVAC energy consumption with a reasonable payback period while the provisions of side fins and proper orientation designs are also good alternatives for new school projects. Installing fresh air pre-conditioners can save the largest amount of MVAC energy consumption although the installation cost will be relatively high.
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