Accurately predicting indoor illuminance from daylight during the early stages of building design is an important factor in saving energy and the costs associated with lighting. The objective of this study was to predict sky luminance distribution using the Commission Internationale de l’éclairage (CIE) standard sky model, and propose a method that can be used to predict indoor illuminance. Results obtained from the proposed prediction method were compared and verified with simulation values obtained by Desktop Radiance. From the CIE overcast sky, the zenith/horizon ratio was 3:1. From the CIE clear sky, the luminance value was highest around the sun. In contrast, the luminance value was lowest in the opposite direction of the sun when the angle between the sun and sky elements was 90°. In addition, this study suggested an indoor illuminance prediction method by applying the effects of sky luminance, direct sunlight, and wall reflection elements. When the proposed equation’s calculation results were compared with Desktop Radiance simulation’s value in overcast and clear sky, all statistically analysis (R², MBE, Cv(RMSE), t-value, p-value) satisfied each standard and showed high correlations. Consequently, it was established that the predicted indoor illuminance obtained from the proposed prediction method was accurate and can be used to predict the level of indoor illuminance. The results further revealed that it is possible to calculate indoor illuminance when installing blinds, by substituting variable values of visible light transmittance (VLT).

This study aims to suggest a basis for the selection of technologies for developing high-performance buildings to reduce energy consumption and greenhouse gas emissions. Energy-saving technologies comprising 15 cases were categorized into passive, active, and renewable energy systems. EnergyPlus v8.8.0 was used to analyze the contribution of each technology in reducing the primary energy consumptions and CO₂ emissions in the Korean climate. The primary energy consumptions of the base model were 464.1 and 485.1 kWh/m²a in the Incheon and Jeju region, respectively, and the CO₂ emissions were 83.4 and 87.4 kgCO₂/m²a, respectively. Each technology (cases 1–15) provided different energy-saving contributions in the Korean climate depending on their characteristics. The heating, cooling, and other energy-saving contributions of each technology indicate that their saving rates can be used when selecting suitable technologies during the cooling and heating seasons. Case 15 (active chilled beam with dedicated outdoor air system + ground source heat pump) showed the highest energy saving rate. In case 15, the Incheon and Jeju models were reduced by 189.4 (59.2%) and 206.2 kWh/m²a (57.4%) compared to the base case, respectively, and the CO₂ emissions were reduced by up to 32.7 (60.8%) and 35.6 kgCO₂/m²a (59.3%), respectively.

In many office buildings, an air-handling unit (AHU) in a variable air volume (VAV) system is operated using discharge air temperature (DAT) simply fixed at a particular set point. However, this simply fixed control causes a variety of inefficiencies related to cooling energy. Therefore, this study compares the cooling energy consumption of the fixed-control strategy, which fixes the AHU DAT at a specific temperature, and the cooling energy consumption of an AHU DAT set point reset strategy based on the outdoor air (OA) temperature, which proportionally controls the AHU DAT according to the change of the OA temperature. Commercially available software was used to compare the AHU DAT control methods of fixed control and the AHU DAT set point reset strategies. The comparison results show that the effect of reducing the total cooling energy consumption in summer (June to August) is negligible; however, in spring (March to May) and autumn (September to November), it was found to be significant compared with the single-fixed-control method. Therefore, if a method of proportionally controlling the AHU DAT is implemented, as in the case of the AHU DAT set point reset based on the OA temperature, it could be an advanced control scheme to improve energy efficiency, especially by reducing the energy consumption of the chiller, which accounts for the highest proportion of the total cooling energy consumption.