**1. Introduction**

Either building-integrated photovoltaic (BIPV) or double-skin façades (DSF) is widely adopted in buildings; however, few studies or real applications of the hybrid mechanism of BIPV and DSF have been implemented in either academic or industrial settings [1]. Therefore, it is worth understanding the behaviour of this novel integrated system – BIPV-DSF. As shown in **Figure 1**, the BIPV-DSF is analogous to a typical DSF, which consists of an outer façade, an inner façade and an air cavity between the two facades; and there are ventilation openings within the BIPV-DSF [2]. However, a semi-transparent PV panel serves as the external window glazing on the outer facade of the BIPV-DSF, while the window of the inner façade is composed of a normal glazing unit. The outer façade of the BIPV-DSF provides protection against the outdoor environments and the ventilation in the air cavity is driven by the stack effect through the ventilation openings to cool the indoor area down in

#### **Figure 1.** *Schematic diagram of the BIPV-DSF.*

summer, while the openings are closed to reduce heat loss in winter, hence delivers a comfortable indoor thermal condition [2]. Moreover, the energy production (electric power generated by PV panel and thermal energy from the heated air in the cavity) can be obtained from the BIPV-DSF, which contributes to the reduction of the energy consumption of buildings.

Numerical simulation modelling of buildings and building systems has been developing and carrying out for over 30 years, during which time the accuracy, depth and speed of the simulation have been widely verified and significantly improved for the design and analysis of new buildings [3]. It has been proved that numerical simulation modelling is much more cost-effective and less time consuming than experimental study, especially for those inaccessibly experimental conditions in real life [4]. In this context, the proposed chapter presents a comprehensive method of numerical simulation modelling of the novel BIPV-DSF system in buildings.

The proposed numerical BIPV-DSF model can be used to investigate the advantages of double-skin façades and building-integrated photovoltaic technology in terms of thermal and electrical performances of the entire BIPV-DSF integrated onto buildings, which are related to indoor thermal condition and energy consumption of buildings.
