## 2 Literature Review
Through fenestration, both beam and diffuse solar irradiation heat the room air as well as the internal thermal masses, increasing both sensible and latent cooling loads. A common way to restrict the heat gain from the window is to reduce the window-to-wall ratio. However, this method also blocks the view of the occupants and reduces the efficiency of natural ventilation. Another way to reduce the heat gain from the window is to use glazing with higher performance, such as tinted glasses and low-E glazing etc. This glazing can restrict the heat gain from the window. [PERSON] et al. [45] compared clear, tinted, reflective and low-e glazing for their energy-saving in regard to both HVAC and artificial lighting electricity use in Hong Kong. Low-e glazing is the most energy efficient due to its good thermal performance and high visible light transmittance, reducing both HVAC energy and lighting energy use. Though considered as an energy-saving measure, tinted glazing was the less favorite as it reduces visible light transmittance thus consuming more energy to maintain an environment with good lighting. Low-e glazing would be an appropriate passive technique for a good-performance building in Hong Kong. Two types of devices (fixed or movable) can be installed as external shading devices, and internal shading devices are commonly used to control the solar radiation in the conditioned space [46]. These devices partially block solar radiation and reflect it to the outdoor environment. Additionally,they can control glaring from the outdoors when used properly. Popular fixed shading devices in Hong Kong include horizontal overhangs and vertical side fins outside windows. Both devices can block the direct solar beam radiation from certain angles. Their characteristics are defined by overhang projection factor (OPF) and side-fin projection factor (SPF) (Equation (1) and (2)), which are at an average of 0.34 and 0.31, respectively, in Hong Kong [38]. Devices with larger factors can block direct sunlight from more angles and achieve low solar heat gain. However, the devices can also block the view from inside, affecting the visual comfort [47]. A fixed external shading device may block solar energy from entering and heating up rooms, subsequently increasing the heating load in winter. \[OPF=\frac{L_{o}}{H_{win}} \tag{1}\]  
where _OPF_--overhang projection factor; \(L_{o}\)--length of overhang; \(H_{win}\)--height of window (assuming overhangs are directly above the top of windows). \[SPF=\frac{L_{f}}{W_{win}} \tag{2}\]  
where _SPF_--side-fin projection factor; \(L_{f}\)--length of overhang; \(W_{win}\)--width of window (assuming side fins are directly on both sides of windows). Ventilation and infiltration are also important parts of the cooling load to buildings. Infiltration largely increases the total cooling load by 9.4%, where 56% is latent load. In the summer cooling condition, the outdoor air entering a building from both paths leads to a large cooling load increase. The satisfactory infiltration rate for a passive-designed building should be less than 0.6 ach (i.e., air changes per hour) [36]. Natural ventilation is one of the most efficient and traditional approaches to achieve indoor comfort [48]. It can provide good indoor quality without energy consumption and increase thermal comfort by increasing air movement in summer [49]. In modern buildings, natural ventilation can also be used to reduce energy consumption. The most common types are free cooling and night ventilation. Free cooling happens when the outdoor air can be used to directly offset the indoor cooling demand without affecting thermal comfort. Night cooling uses air with a lower temperature to offset the cooling demand at nighttime.