Evaluating Ventilation for Thermal Comfort in Two Classrooms Types in Malaysian Secondary Classrooms

A variety of research methods were employed to address the research questions in this study. Specifically, simulation and survey methods were used to compare results for designing secondary schools in one single- and one double-loaded-corridor design model in Malaysia. To collect data, the researchers used DesignBuilder software to simulate exterior and interior airflow, temperature, and humidity for various times of the year. The data collected from the simulations were then analyzed using the online CBE Thermal Comfort Tool to determine the thermal comfort performance based on adaptive approach to thermal comfort. The simulations were conducted for the same locations, on the same dates, and under the same environmental conditions to ensure comparable results. The entire research process is depicted in Figure 1.

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Figure 1. The research process

2.1 Study area

Historically, school designs in Malaysia have followed the Public Works Department and Economic Planning Unit guidelines, in terms of layout design and materials selection. The case studies selected to represent two different school designs in Malaysia were the Sekolah Menengah Kebangsaan (SMK) Seri Serdang (single-loaded corridor) (Figure 2), and the SMK Taman Desaminium (double-loaded corridor) (Figure 3), both examples of designs recently used by the Public Works Department for new schools.

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Figure 2. SMK Seri Serdang (single-load design)

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Figure 3. SMK Taman Desaminium (double-load design)

The SMK Seri Serdang is located in Seri Kembangan, Selangor, in a flat, low-rise urban area. The school originally had two buildings, but with additional blocks added later. Its single-loaded-corridor design features a corridor on one side of the classroom. The classrooms are oriented in linear east-west blocks, which enhance wind movement between the blocks. The classrooms have natural ventilation from four large windows (three on the exterior wall and one looking onto the corridor) to create a cross-ventilation system that cools the entire space.

The SMK Taman Desaminium is located in Seri Kembangan, Selangor, on slightly sloping land in an open rural area surrounded by trees. The school hosts primary- and secondary-level students, with nine blocks for each. The corridor divides two rows of classrooms, which feature a courtyard configuration that limits the flow of wind between the blocks. The cross-ventilation system in these classrooms comprises one large window, divided into six vertical sections with multiple horizontal panes of glass, on the outer wall and one long and narrow window looking onto the corridor.

Both schools have three floors. A classroom on the second floor was selected from each, where the effects of solar radiation and the heat energy absorbed by the bricks and concrete were less pronounced compared to the heat energy transmitted to the top floor by direct solar radiation. The same was true for choosing the location of the case-study classrooms, with the external walls able to absorb high thermal energy from their partial exposure to direct sunlight. Thus, the classrooms were chosen from the middle of a block of rooms and were situated on the north side of the school, facing the wind and getting the best ventilation.

2.2 Simulation

A computer simulation uses software to build a model with conditions that mimic a real-life situation in order to experiment or explore the behaviour of the model under specific conditions that are not possible to achieve in real life. Here, DesignBuilder software (https://designbuilder.co.uk/) was used to create the simulation because it provided the easiest workflow coupled with the latest approved calculations and building regulations compliance checks for Malaysia. DesignBuilder was designed to create different types of simulations, such as lighting, heat, comfort, cost and energy. Two dates were selected for the simulations, representing months in which the highest and lowest temperatures and wind speeds of the year occurred--15 May, 2021 (lowest temperature and highest wind speed) and 15 September, 2021 (highest temperature and lowest wind speed). On the 15th of the month, the average space humidity, wind speed, operative temperature and outdoor temperature were measured every 5 min for 12 h in order to provide the most accurate data. The following assumptions were used in the simulations for each school: 1) the models were oriented east-west because this was the most appropriate for the climate; 2) the same wind conditions applied to both models; 3) all of the windows were open at the same level; 4) natural ventilation contributed to the overall operative temperature of the classrooms; and 5) thermal comfort was achieved through natural ventilation facilitated by the open windows.

The data extracted from the simulations were these environmental variables: humidity, indoor air temperature, radiant air temperature, operating temperature, outdoor air temperature and wind speed. These data were extracted at a rate of every 5 min of 5 h per day, distributed as follows: 7:00-8:00 am, 10:00-11:00 am, 1:00-2:00 pm, 4:00-5.00 pm and 7:00-8:00 pm. The data were averaged for each hour and plotted on a chart (see Appendices A and B).

The thermal comfort module included air velocity and humidity for calculating the operative temperature. The data collected from the simulations were fed into and analysed through the online CBE Thermal Comfort Tool (https://comfort.cbe.berkeley.edu/) in order to determine the thermal comfort performance.

2.3 Questionnaire survey

A survey was employed to determine the success of each classroom plan in achieving natural ventilation by assessing the users’ perceptions. The survey contained two sections with 12 categories in total. Section A was about the users’ demographic background and included four categories--name, school grade, gender, and age. Section B involved the level of thermal comfort in the classroom and included eight categories aimed at understanding the perceptions and comfort of the students in terms of temperature at different times of the day as well as their satisfaction with the airflow and the elements available for controlling the temperature and airflow in the classroom (windows, air- conditioning, adjustable air vents, ceiling fans, portable fans, and window shades or blinds). To measure the satisfaction with temperature and airflow, a seven-point thermal sensation scale (hot, warm, slightly warm, neutral, slightly cool, cool, cold) was used. The survey was devised from Shaari and Ahmad [3] and modified to simplify the questions for the secondary school students. Permission for access to the students to conduct the surveys was sought from the Selangor Ministry of Education, but the management bodies in both schools would not allow us direct access to the students. Therefore, the questionnaires were handed to the management bodies on 13 April, 2021 and then personally collected on 15 April, 2021.

The students were surveyed from one classroom in each school. There was a total of 67 respondents--30 students and three teachers from the SMK Seri Serdang and 31 students and three teachers from the SMK Taman Desaminium.

We assessed two features of school design in Malaysia that had an impact on natural ventilation--the single- and double-loaded corridor. The former was represented by the SMK Seri Serdang school and the latter by the SMK Taman Desaminium school. We used objective data analysis to describe the environmental conditions of the two classrooms, coupled with a subjective analysis via questionnaire to record and evaluate the thermal sensations felt by the students. Comparisons were made through computer simulation analysis and a thermal comfort analysis was performed by plotting the internal classroom conditions on adaptive thermal comfort charts. Thus, we put forward a concept for implementing virtual reality environments to address design challenges, rather than relying on building designer intuition. Our results were found to be consistent with those of Al-sharaa et al. [21].

The linear design of the SMK Seri Serdang allowed for better wind flow between the blocks compared with the courtyard design of the SMK Taman Desaminium. The enhanced air movement between the school blocks led to overall better ventilation and interior air quality. There were more windows in the SMK Seri Serdang. This difference in layout and windows promoted better wind flow and ventilation in the SMK Seri Serdang than in the SMK Taman Desaminium.

From the simulations and survey, we discovered that the single-loaded-corridor design offered overall greater thermal comfort in May. In comparing the simulations, the single-loaded-corridor classroom resulted in 100% of the day being in the comfort zone in May, compared with 60% of the day within the 80% comfort zone and 20% of the day within the 90% comfort zone for the double-loaded-corridor classroom design in May. However, both classroom designs were completely outside the thermal comfort zone 100% of the day in September. To overcome this, ceiling fans were used to increase the air speed in the classrooms, which achieved a better thermal comfort experience. This shows that, even though using a single-loaded-corridor design to improve the thermal comfort level in the classroom, this is not enough to achieve year-round thermal comfort in Malaysian weather. The lack of thermal comfort in the hotter months implies the lack of a comfortable temperature, deleterious effects on the occupants’ health and higher energy consumption [22]. These findings were supported by the user’s preferences, which showed a higher rate of satisfaction in the single-loaded-corridor classroom. The low comfort rate in the double-loaded-corridor design has potentially led to decreased student performance and motivation, based on studies that have found that, regardless of the fact that the human organism is very adaptive, students cannot perform well when their environment is uncomfortable [8, 23].

Future Malaysian schools are recommended to be built to the single-loaded-corridor design, as used for the SMK Seri Serdang Secondary School. This would provide improved air circulation and overall natural ventilation. However, other methods of cooling might still be needed during the hotter months, such as ceiling fans. A school’s layout must also take into consideration enhanced wind movement between the school blocks, which also leads to better interior ventilation. Windows in classrooms should be maximised in size and be placed on both the exterior wall and the corridor wall, allowing for enhancing air circulation and lowering the interior temperature. Improving the ventilation and thermal comfort levels in future classrooms would lead to higher student performance, which could improve the level of Malaysian education.