Building Envelope Design Optimization of a Hypothetical Classroom Considering Energy Consumption, Daylighting, and Thermal Comfort: Case Study in Lhokseumawe, Indonesia

This study evaluated the building performance of a hypothetical elementary school classroom considering its annual energy consumption, daylight criteria, and adaptive thermal comfort in Lhokseumawe, Indonesia. Variations in building materials, construction, and horizontal shading features were evaluated for the most optimal design solution. The aim was to optimize the multi-performance criteria as an integrated sustainable design solution for a typical classroom in Indonesia. To achieve this objective, the study utilized a computational simulation method using Rhinoceros, Grasshopper, and Ladybug Tools platforms. The optimization was conducted with Galapagos, an engine based on a genetic algorithm. The results suggest that the optimal solution achieved 100% sDA_300/50% and more than 96% UDI_100-3000lx. The annual thermal comfort percentage was also increased to over 90%, while the energy consumption was reduced by 20% compared to the baseline design.

Design optimization; Hypothetical classroom; Integrated building design

    Designing a sustainable building is a complicated process that involves the consideration of the needs of building occupants, the building environment, aesthetics, and functional elements (Gharouni Jafari et al., 2021). A school classroom is an example of a building space where all of the performance criteria are necessary to ensure effective learning processes and outcomes among the students, particularly in elementary schools, where students are the most sensitive (Boubekri et al., 2020; Heschong et al., 2000). To achieve this goal, the performance criteria must be considered during the process of designing a classroom. Some of the most important building performance criteria are thermal comfort, annual energy requirement, and daylight availability (Konis et al., 2016).

These three aspects all influence each other. For example, in a tropical region such as Indonesia, daylight is abundantly available throughout the year. This condition may have various consequences, such as higher environmental temperature and the risk of excessive sunlight. These may contribute to more heat energy entering the building space, which means that it requires more energy to cool the internal space. Concerns about energy usage in relation to mechanical and operational costs in buildings has been previously investigated (Nwanya et al., 2016). However, to ensure that all the performance criteria are fulfilled, an integrated building design is required to obtain an optimal design solution. Some studies have attempted to optimize building design based on annual thermal comfort, energy requirements, and visual comfort with some design parameters, such as the geometric size and shape of the building and opening variations (Bakmohammadi and Noorzai, 2020; Zhu et al., 2020). Furthermore, studies have evaluated the facade shape in relation to wind infiltration, and façade retrofitting has previously been conducted (Hong et al., 2019; Darvish et al., 2020). However, building envelope materials have not been considered as a design parameter in previous studies. Clearly, building envelope materials affect thermal comfort and annual energy requirements, since they influence the heat that enters or leaves the building (Alsharif et al., 2021).

    This paper has integrated several elements of evaluating and optimizing building performance. The optimization has yielded a hypothetical sustainable classroom, which is thermally comfortable, has good annual daylight availability, and consumes a low amount of electrical energy annually. The classroom has a symmetrical bilateral opening and shading typology and is located in Lhokseumawe, Indonesia.  In the baseline condition, the building space is dominated by excessive daylight with high illuminance. This is indicated by the high sDA_300/50% value of 100% and a low UDI_100-3000lx average value of around 50-60%. Meanwhile, the adaptive thermal comfort percentage is around 67%, and the cooling energy consumption is around 40,000 kWh per annum.  Furthermore, after optimization, the building space is now dominated by useful daylight, indicated by the high UDI_100-3000lx average value of around 98% and the high sDA_300/50% value of 100%. Despite the high illuminance in the classroom, the adaptive thermal comfort percentage in the internal space has increased to around 98%. The cooling energy consumption also decreased by about 23-24% compared to the baseline condition, to around 30,000 kWh.

    This research was funded by the Institut Teknologi Bandung (ITB) 2021 Research Program, contract number 139/IT1.B07.1/TA.00/2021.

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