## 1 Introduction
### Daylight for Indoor Illumination  
The Heating, Ventilation and Air Conditioning (HVAC) system and lighting system are the two largest energy consumers in a building [3; 4; 5]. Many efforts have been put into improving thermal performance of buildings for energy reduction. However, how to make a proper building design to optimize the indoor lighting environment and saving energy still needs to be discussed. Daylight, which best matches the human visual response, is considered as the best substitution for artificial light in the indoor environment. It provides better color rendering and a visual environment in which occupants can properly see objects [6]. Apart from that, daylighting is a more environmentally-friendly approach compared to artificial lighting. [PERSON] et al. [7] found that at least 10% of building energy can be saved using daylight alone. As such, using daylight to effectively create a comfortable indoor light environment is necessary for both occupant health [8; 9] and building energy conservation [10]. A good building design, particularly the envelope design, is the basic solution for getting good use of daylight. By adjusting the parameters of design factors, sufficient daylight can be led into the room to take place for artificial light, thus that a part of the energy consumed by artificial lighting will be saved, and the indoor visual comfort will be improved as well [11]. [PERSON] et al. [12] developed a simplified energy estimation model to analyze the energy reduction by daylighting. The model considered four parameters: Building geometry, glazing types, window areas, and geographic locations. Results showed that glazing type and window area had more significant impacts on energy conservation. [PERSON] et al. [13] investigated the thermal and visual performance of buildings with different window sizes, to search for a design that can achieve the objectives of low energy consumption and high visual comfort. Although the key design factors are confirmed, it is difficult to decide the parameter value of each factor to achieve the optimal lighting performance. The direct way is the trial-and-error method. Researchers tried every possible parameter value to search for the one which can take the best performance [14; 15; 16]. This type of methods performs well in the cases of small-scale buildings or in which only a few design factors are considered. When the building scale becomes larger, they cannot afford the large amount of computations. Then simulation tools are applied for lighting performance prediction to reduce the calculative burden [17; 18; 19; 20]. Simulation tools can largely shorten the calculation time and improve the accuracy of the results, thus designers can quickly make a good design with an optimized lighting environment. Actually, a good design must be well performed on not only the lighting aspect, but also others such as the thermal environment and energy consumption. Besides, for the project owners, project cost is a crucial factor to be carefully controlled during the design. Therefore, some other methods are required to find a balance in the problems with multi-objectives. [PERSON] et al. [21] tried a graphic optimization method to search for the designs with the minimum annual lighting energy demand and to fulfill the indoor visual requirement. Evolutionary multi-objective optimization algorithms, such as NSGA-II and PSO-HJ, are more popularly applied to achieve the win-win goal of both the energy-efficiency and visual comfort of buildings [22; 23; 24]. These optimization methods are usually combined with thermal and lighting simulation engines, e.g., EnergyPlus, Radians, and Daysim, thus that the calculation speed and the result precision can be promoted to an all-time high. A lighting control system is another way to improve the illumination environment. There are mainly three kinds of lighting control modes, i.e., manual light switching (MLS) (on/off), automatic light switching (ALS) (on/off), and automatic light dimming (ALD) (on/off) [25].